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Next leap in battery performance for ebikes?

In 2013, Bosch released the 400Wh battery. It was a 40 cell battery, and it was their biggest battery for a few years. Already in 2015, the lithium batteries were drastically improved. So Bosch launched the 500Wh battery for 2016. It was still a 40 cell battery. And pretty much nothing has happened since.

When I talk about battery improvement in this context I’m talking about “energy density”, how many Watt-hours we get per kilo battery. Even the new 625 and 700Wh batteries have pretty much the same energy density. So when will we see the next significant increase in energy density? I share my thoughts in this video.

  1. Any increase in capacity should also be coupled with increased motor efficiency, thus will we need bigger heavy battery’s, or just make the the batter smaller and lighter, and increase bike efficiency?
  2. Awhile ago I got pronged on a post here for saying that the 700wh Levo battery was due to 21700 cells…..it’s really the only thing that made sense and I always thought it odd that Spec and the others that are using the same cells to increase their wh’s are not advertising the fact? Not a huge gain but significant enough especially in regard to C rate.
  3. Bike manufacturers should care about standard formfactors for their batteries. Customers should get batteries for 10 years for their bikes. Does anyone know of laws or regulations (EU, US,…)? thx
  4. Any increase in capacity should also be coupled with increased motor efficiency, thus will we need bigger heavy battery’s, or just make the the batter smaller and lighter, and increase bike efficiency?

    I guess there is some gain to be made by improving motor efficiency, but the biggest gain is in battery tech. When we get new battery tech, the ebike-motor/battery manufacturers can decide if they want to increase capacity or reduce weight. Up until now, they have mostly picked range over weight, but that might change in the future. With an energy density of 310Wh/kg, the Bosch 625 battery would be about half a kilo lighter.

  5. Awhile ago I got pronged on a post here for saying that the 700wh Levo battery was due to 21700 cells…..it’s really the only thing that made sense and I always thought it odd that Spec and the others that are using the same cells to increase their wh’s are not advertising the fact? Not a huge gain but significant enough especially in regard to C rate.

    The 21700 cells have higher charge and discharge rate as you say. But they didn’t necessarily have to use the 21700 cells. Greyp has a 700Wh battery too, it’s made by 60 pieces of 18650 cells! That should indicate a weight of over 4kg, but I weighed it to just 3,58kg, which is lighter than the Spesh 700Wh. And it is really small. I’m not sure what they have done, but I have a theory. To get 700Wh from 60x 18650 cells, they must have cells of about 3300mAh cells. A less energy dense cell will typically have better charge+discharge rate. Even though the 18650 cells has lower charge+discharge rate than the 21700, Greyp makes up for it by using the lower density cells in a 10s6p config, meaning 6 cells in parallell. This increases the charge and discharge rate. The power draw will be spread over several cells, so the cells will be nowhere near their limit. This means less heat developing, so Greyp could pack the battery thighter with a lighter case. No need for internal vents/ducts/etc.

    Hopefully I didn’t misunderstand your post completely!? :)

  6. what about 48V systems belonging efficency? thx

    48V is more efficient because of lower current draw compared to a 36V – at the same power output. But this is usually only an issue when the batteries are being pushed close to their maximum discharge capacity. I think the biggest advantage of the 48V is the ability to put out a decent amount of power in the mild (low power) emtbs, shuch as the Levo SL. The small range extender would most likely not work in a 36V system, it would have just 10 cells in series and wouldn’t be able to deliver enough current. But with a 48V system it does work, even if it’s on the limit.

  7. 48V is more efficient because of lower current draw compared to a 36V – at the same power output. But this is usually only an issue when the batteries are being pushed close to their maximum discharge capacity. I think the biggest advantage of the 48V is the ability to put out a decent amount of power in the mild (low power) emtbs, shuch as the Levo SL. The small range extender would most likely not work in a 36V system, it would have just 10 cells in series and wouldn’t be able to deliver enough current. But with a 48V system it does work, even if it’s on the limit.

    Another advantage of higher voltage battery packs is the ability to be charged faster without stressing the cells, as I understand it. Certainly my 48V pack charges quickly in comparison to 36V times.

  8. Another advantage of higher voltage battery packs is the ability to be charged faster without stressing the cells, as I understand it. Certainly my 48V pack charges quickly in comparison to 36V times.

    Yeah, that’s right. It works both ways. Charging a 48V battery with 4A will create about as much heat loss as charging a 36V battery with 4A. But the 48V battery is charging at higher power.

  9. 48 V systems are also more efficient at each step after the battery: wiring; connectors; motor windings; due to lower I*squared*R losses. At some point the regulations require greater protection, I do not know at what voltage this comes in.
  10. The 21700 cells have higher charge and discharge rate as you say. But they didn’t necessarily have to use the 21700 cells. Greyp has a 700Wh battery too, it’s made by 60 pieces of 18650 cells! That should indicate a weight of over 4kg, but I weighed it to just 3,58kg, which is lighter than the Spesh 700Wh. And it is really small. I’m not sure what they have done, but I have a theory. To get 700Wh from 60x 18650 cells, they must have cells of about 3300mAh cells. A less energy dense cell will typically have better charge+discharge rate. Even though the 18650 cells has lower charge+discharge rate than the 21700, Greyp makes up for it by using the lower density cells in a 10s6p config, meaning 6 cells in parallell. This increases the charge and discharge rate. The power draw will be spread over several cells, so the cells will be nowhere near their limit. This means less heat developing, so Greyp could pack the battery thighter with a lighter case. No need for internal vents/ducts/etc.

    Hopefully I didn’t misunderstand your post completely!? :)

    Certainly you can add more cells to achieve what you say. My point was that Specialized and others than GreyP are making cell packs that fit into the same integrated frames with increased wh’s and the reason they can do so is by using 21700 cells. It’s a smart move and I think more will come in the future. As well as upping voltage which is starting at appear from the major manufacturers for reasons as noted above.

    I have 4 bikes w/ 21700 cell batteries that reside in external cases that total about 2900wh’s between them that cost me $2000. Aside from one 52v the rest are 48v. So using that as a metric I can’t see that 21700 battery packs should cost significantly more to produce either.

  11. 48 V systems are also more efficient at each step after the battery: wiring; connectors; motor windings; due to lower I*squared*R losses. At some point the regulations require greater protection, I do not know at what voltage this comes in.

    Yeah, it’s the Amps that is the limiting factor. Increased current means increased heat loss due to increased resistance. That’s why a battery works fine at high state of charge, and gets really warm at low charge. Voltage is higher in the beginning and current draw is lower. And, as you say, this happens in the entire circuit. But it it shouldn’t be much weight or cost added having power wires big enough so there is no significant increase in resistance at max current draw.

    As you say there are stricter regulations at some point. The IEC (International Electrotechnical Commission) has a classification called ELV (Extra Low Voltage). A device cannot exceed 50V to be classified as ELV. But not all agree. The IEC defines ELV as sub 50V AC and sub 120V DC!. And the EU commission don’t talk about ELV, they have a Low Voltage classification that starts at 50V AC and 120V DC.

    So it seems there could be complications when servicing a 48V system, as this will exceed 50V at full charge. But I’m not sure how the various regulations apply in this case.

  12. Certainly you can add more cells to achieve what you say. My point was that Specialized and others than GreyP are making cell packs that fit into the same integrated frames with increased wh’s and the reason they can do so is by using 21700 cells. It’s a smart move and I think more will come in the future. As well as upping voltage which is starting at appear from the major manufacturers for reasons as noted above.

    I have 4 bikes w/ 21700 cell batteries that reside in external cases that total about 2900wh’s between them that cost me $2000. Aside from one 52v the rest are 48v. So using that as a metric I can’t see that 21700 battery packs should cost significantly more to produce either.

    The reason brands like Specialized can fit bigger batteries into existing frames is that the old 500Wh battery was made bigger than necessary. The 500Wh Specialized battery is way bigger than the Shimano BT-E8035 released last year. Shimano is sort of doing the same thing for 2021. Their new 630Wh battery is longer than last year’s 504Wh battery. So for 2021 Shimano introduces the 504Wh BT-E8035L. This is the same size as the 630Wh battery, so they will both fit the same frames.

    That being said, I agree with you. Specialized might not be able to stack 60 cells in a battery and fit it into their frame, certainly not with the layout used by Greyp. And yeah, the 21700 based batteries doesn’t have to be more expensive. It’s still the same chemistry.

  13. the 21700 based batteries doesn’t have to be more expensive

    Very true in fact theoretically they should & may already be less expensive per kWh.

    The extra 5 mm of length and 3 mm of diameter means almost 50% more volume for anode, cathode, and electrolyte in every unit of production. The benefits cascade – from cost of production and distribution as well as energy densities, runtimes & mass. Also less complexity and failure modes in higher capacity battery packs.

  14. This is all just variables on the technology we have today.
    I want to see what the future will look like.
    Already Tesla have introduced a new way of making the batteries for their cars using dry anodes.
    This process gives a significant improvement on charging speed, battery life, power and weight.
    It will be the car manufacturers that will push the science that we will all reap the benefits of later.
  15. Graphene based Batteries will be a massive advancement, or Silicon-Graphene Anode as a discreet application.
  16. This is all just variables on the technology we have today.
    I want to see what the future will look like.
    Already Tesla have introduced a new way of making the batteries for their cars using dry anodes.
    This process gives a significant improvement on charging speed, battery life, power and weight.
    It will be the car manufacturers that will push the science that we will all reap the benefits of later.

    Well it’s variation in format that will have most impact on the next bikes we buy. Variation in chemistries will follow.

    Tesla acquired Maxwell & along with it their dry electrode tech. The most obvious advantage is the manufacture of electrodes without hazardous solvents and complex expensive equipment. Apparently allows for higher electrode lithium content which extends expected lifespan & improves capacity. Of course new chemistries & formats usually take quite a while to appear in bikes.

  17. Here in NZ, as I understand it, up to 80Vdc is okay to work with but over 80Vdc and any AC system requires a certified electrician. I’m not sure if any of you watch Robert Murray-Smith’s channel on Youtube, he is a chemist who works with graphene batteries amongst other graphene products. I’ve learned much from watching his videos.
  18. This is all just variables on the technology we have today.
    I want to see what the future will look like.
    Already Tesla have introduced a new way of making the batteries for their cars using dry anodes.
    This process gives a significant improvement on charging speed, battery life, power and weight.
    It will be the car manufacturers that will push the science that we will all reap the benefits of later.

    Yeah, as I said in the video, several companies are developing the current battery tech. I set out to find what would give us ebikers the next leap in, well, energy density. And as far as I can tell, that has to be an improved lithium-ion battery. I also mentioned the Maxwell dry electrode technology. And the tabless patent. It is really interesting, I’m excited to see if they exceed 300Wh/kg. We might get the answer in a couple of months.. But the problem is Tesla is the worlds largest consumer of batteries. So I assume they will use all they can produce for their cars and energy storage products. I believe the NCM811 will be the first improved battery tech to reach ebikes.

  19. Graphene based Batteries will be a massive advancement, or Silicon-Graphene Anode as a discreet application.

    Graphene batteries could be in mass production in a couple of years. It’s expected to be an anode using "few layers" graphene. Or "nano platelets" , which is close to graphite. So they won’t be using the true, single layer graphene. This is expected to improve charge rate and lifespan, but not energy density. And the complicated process of producing graphene means the cells will be more expensive.

    I’m excited about graphene, and it seems it’s finally becoming a reality. But I think it will have bigger impact in other areas than batteries. I might of course be wrong.

  20. Another example that may be more interesting is to compare the same 36V pack to a 48V. A 48V pack has 13 series groups which will not divide evenly into 40 cells but will with 39 cells. Comparing a 40 cell 36V pack to a 39 cell 48V is pretty close to the same (2.5% difference).

    Assuming a cell resistance of 36 mOhms, the 36V pack will have a resistance of 90 mOhms (10 * 36/4) and the 48V pack will be 156 mOhms (13 * 36/3). The 48V pack will have 73% more resistance and generate 73% more heat at the same charge current. Now, it will charge faster because of the higher charging power, but it will get a lot hotter doing so and may suffer reduced cycle life.

    Also, because of the higher voltage the 48V battery will deliver less current for the same power and heat losses due to the reduced current will only be 59% of the 36V pack, but the 36V pack has only 58% of the resistance so the I2R losses are essentially the same (difference is due to 39 vs. 40 cells).

    This is all because the only thing that matters is the type and number of cells you have and not how they are wired within the pack.

  21. The small range extender would most likely not work in a 36V system, it would have just 10 cells in series and wouldn’t be able to deliver enough current. But with a 48V system it does work, even if it’s on the limit.

    This is also not true. The range extender in the SL is a 13s1p configuration that uses a 3.4 Ah 18650 cell. There are a several possible cells that could be used that have the required 7 – 10 A rating which that battery is capable of.

    Now, if you delete 3 cells to make a 36V battery, you’d have to up the current draw to 9A for equivalent power. 9A is still doable but worse because of the smaller battery, but if Spec had simultaneously switched to a 2170 cell (5 Ah Samsung 50E) they would have added 10% more capacity and had arguably more current headroom than the existing product.

    Again, this conclusion is wrong because you compare different sizes of packs and attribute the result only to voltage. Also, there are a whole host of power tools that deliver more power out of smaller lower voltage packs than the range extender. That should tell you whether a 36V pack could be made to work.

  22. Are there any graphs/data showing what the max amp draw is for each brand motor?

    Once you have that then you build a battery to those specs that will be the most efficient etc.

  23. @csj I’m talking specifically ebike batteries using 18650 and 21700 cells, so we’re limited to these cells and 10s or 13s configs. Not sure why they’re not using other formats, like the 20650 etc. Therefore there are situations where the 48V system has an advantage. I still believe the Specialized range extender battery wouldn’t be possible in a 10s1p config, based on my experience with it. The battery seems to be at its limit at low SOC, and the motor power ramps down. Sure, they could make it 10s1p, but it would have to ramp down way sooner. And at lower cell temperatures, the current output would be further reduced. Sure, it’s unfair comparing a 13 cell battery with a 10 cell. But the range extender would be completely different in a 10s2p config. Chances are it would be too big/heavy for what they want to build, and it couldn’t be brought on planes. I do of course agree that lower current output can be made up for by using more cells, like I wrote regarding 21700 Spesh (10s4p) vs 18650 Greyp (10s6p) batteries.

    Here’s my understanding of the advantages of using higher voltage. One advantage of a higher volt system is the ability to put out the same amount of power while drawing less current. This allows for a weight/cost saving using thinner cables/wires. But the distance between battery and motor is so short in an ebike, so this is a non issue. The higher voltage becomes more interesting when there’s a limit to how much current you can draw. Like for EVS. A lot of 300A fast chargers are being put up now. They are rated at 150kW at 500V. But these support up to 1000V. The Porsche Taycan is an 800V system that should be able to hit 300kW. Now cable dimensions is a real concern too.

    But I have been thinking about the effects of the rest of the system, and completely forgot about what happens when we connect cells with internal resistance in series. The internal resistance of the battery does of course increase.

  24. I’m talking specifically ebike batteries using 18650 and 21700 cells, so we’re limited to these cells and 10s or 13s configs. Not sure why they’re not using other formats, like the 20650 etc. Therefore there are situations where the 48V system has an advantage.

    What situations? Why are we limited to 10s or 13s configs? Are you ignoring my 10s/13s example?

    I still believe the Specialized range extender battery wouldn’t be possible in a 10s1p config, based on my experience with it. The battery seems to be at its limit at low SOC, and the motor power ramps down.

    What is your experience with that pack that leads you to make these claims? Are you an engineer? You make claims that require technical knowledge of the system that I doubt you have.

    Sure, they could make it 10s1p, but it would have to ramp down way sooner. And at lower cell temperatures, the current output would be further reduced. Sure, it’s unfair comparing a 13 cell battery with a 10 cell. But the range extender would be completely different in a 10s2p config.

    Never suggested a 10s2p config but a 10s1p config with a 2170 cell. That would be superior to the current pack in power and capacity and only about 70g heavier. As for flight regulation differences, that’s off-topic and unrelated to voltage. It’s also trivial to address.

    Here’s my understanding of the advantages of using higher voltage. One advantage of a higher volt system is the ability to put out the same amount of power while drawing less current.

    I already addressed this. A higher voltage system has higher battery IR that negates the advantages. If you disagree, then where is my explanation wrong?

    As for the "thinner cables", you’ve already admitted that is irrelevant to ebikes. Yes, it matters for electric cars but that’s not the topic.

    But I have been thinking about the effects of the rest of the system, and completely forgot about what happens when we connect cells with internal resistance in series. The internal resistance of the battery does of course increase.

    At the voltages and currents involved here, the external effects of different configurations are negligible. All that matters is what is happening within the battery, and that is literally nothing.

    Different configs have different voltages and currents but also different IR and this different IR completely, mathematically negates any apparent benefit of different voltages and currents external to the pack. That’s the entire point. You’ve recognized now that pack IR varies but you are still asserting benefits without considering IR. Why?

    Finally, I believe no electrical engineer would make your arguments. Also, I am an electrical engineer.

  25. Are there any batteries by any of the usual manufacturers (Bosch, Brose, etc) that are not a 10s or 13s config? Or in other words, are any of these batteries not 36V or 48V?

    I make those claims based on my experience with it, which I discussed with Marco Sonderegger. He confirmed the battery being on it’s limit and ramping down at low SOC. He said they didn’t go 21700 because they couldn’t make it fit the water bottle shape. My intention of bringing up this example was not to prove that 48V is superior, but to say it can have advantages in some situations. It allowed Specialized to build a battery as small as possible while still being powerful enough.

    I explained how I understand things, seems you interpreted it as me contradicting you. As I’ve said from the beginning, advantages from using thinner cables doesn’t mean anything in this case. That’s not something I’m suddenly admitting.

    I’ve had electrophysics classes but my engeneering degree is not electrical.

  26. Are there any batteries by any of the usual manufacturers (Bosch, Brose, etc) that are not a 10s or 13s config? Or in other words, are any of these batteries not 36V or 48V?

    That depends on your definition of "usual manufacturers". A more interesting question is why you think that matters? Limiting it to only one of two voltages helps your argument none, and further limiting it to "usual manufacturers" doesn’t help either. There are, however, voltages other than 36V and 48V, but again that’s not relevant.

    I make those claims based on my experience with it, which I discussed with Marco Sonderegger. He confirmed the battery being on it’s limit and ramping down at low SOC.

    Unless your "experience with it" is technical and involves actual product knowledge, and you are capable of understanding those issues better than you’ve demonstrated here, your experience doesn’t matter.
    As for Marco Sonderegger, what you claim he "confirmed" does not support your assertion (that a 10s battery couldn’t be made to work). Also, my understanding is that he’s a product manager. Is he an engineer? Does he know inner working details?

    He said they didn’t go 21700 because they couldn’t make it fit the water bottle shape.

    If he said that then he’s disqualified from commenting. My eMTB uses 24 2170 cells arranged in a water bottle shape and attached to the frame using a water bottle cage. That’s just absurd. Also, I sincerely doubt he claimed 2170 wouldn’t fit in a 10s config which is the topic here. 10 cells are easier to fit than 13.

    My intention of bringing up this example was not to prove that 48V is superior, but to say it can have advantages in some situations. It allowed Specialized to build a battery as small as possible while still being powerful enough.

    Yes, that’s what you’ve said, but it’s wrong and I’ve explained why it’s wrong. I’ve also refuted any claim that 48V has added a capability to the SL that you couldn’t otherwise get.

    I’ve had electrophysics classes but my engeneering degree is not electrical.

    I would suggest, then, that you determine how IR of the pack is affected by configuration, then reconsider your positions based not only on voltage and current but IR (which is responsible for the heat you’ve errantly characterized) and see where things are different than you’ve assumed. What I’ve presented is first semester EE course stuff and is not at all controversial. What you’ve presented only makes sense when you increase voltage by increasing cell count. I understand your position, I’m trying to explain where it is wrong. Take away the extra cells and all the advantages you think you see suddenly disappear.

  27. And no one has any idea on amp draw these motors max draw is ?

    The Dyname 3.0 motor has an advertised 1200W peak power. The pack fully charged is 54V, so allowing for voltage sag under load, say, 48V, that would be a short term current draw of 25A or thereabouts. This is one way to make 108Nm of torque :cool:. It is also a way to make the rear wheel step out sideways at inopportune moments lol.

  28. Hey Knut7, Thanks for your videos! I enjoy the thoughts and opinions of a fellow eMTB enthusiast. About the agressive comments above from @csj I understand what you are saying and agree that a 48v system will be more efficient and the battery will charge quicker at the rated 4 amp output of the charger than a 36v system. This guy is an antagonist…

    Keep up the good work and looking forward to your next videos.

  29. We are using the Samsung 35E batteries in a 13S2P and 14S2P config and are finding that they won’t perform to the manufacturers spec sheets at lower cell voltages. The rated 8A is like all manufacturers documentation, in a laboratory test under ideal conditions, but in the field that 8A draw is a limitation as the battery voltage falls away really to quickly towards the end of the battery’s charge and under load will trip the BMS cell low voltage levels. We are getting typically only 280 – 290 Wh with the 14S2P packs.

    However we have just gone over to the Samsung INR21700-40T which each cell has a 35A output, have to say these batteries really do pack a punch and do not drop voltage levels under power levels we are using ( we limit the engines we are using to about 15A ), on the first few rides these batteries are looking really good, at 4000mah per cell, they don’t hold the highest of density but the length of time the battery will hold there voltage above 2.9V is really impressive.

    Yes, but 40T’s don’t offer the same energy density that high energy cells like the 35E do, so packs with satisfactory range weigh considerably more. Cells like the 40T are more popular among the higher power DIY crowd.

    Modern high energy cells are rated at 2C – 3C maximum current draw but should not be used at greater than 1/2C average draw. For higher currents, other chemistries work better, as you’ve just said. This is why the Spec range extender is not really a well designed pack, it is intended to be used at 1C – 2C draws but uses a cell specifically not designed to work well in that application.

  30. @csj I’m claiming 10A for a 10s1p system, right? That’s 6,25A for 48V, so I am slightly under-estimating the current draw at 36V. We can forget about using the 18650 cells in a 10s1p config. And Spesh claim they couldn’t do it with 21700 cells, so they had to go 13s1p 18650 cells. Which was my original claim. Neither of us know what limitations they had to work with in this project. So you are free to claim they’re lying.

    I mention outside temperature because it’s relevant to the IR / max discharge current.

  31. You guys are forgetting about voltage, low voltage means a sluggish and poor performing motor, so do you pack a battery with Samsung 35E’s that has some of the best density ( W/h’s ) that can only hold its best voltage levels to 2/3rds of its rated density at the voltage level we use, or do you use the same identical 18650 size battery that can pull higher voltages 9/10th’s of its rated capacity, which is less than the 35E’s. On paper you would think that the 35E’s would be best, in the field we are finding the old Samsung 30Q cells as good if not better, but have a lower rated capacity.

    As a get me home battery you could build a 18650 battery as a 10S1P but you would have to select the battery to have probably a minimum 15 – 20 A draw rather than the 8A as the 35E’s, they are available but at about only a bit over 100Wh’s the cost would be prohibitive. Anyway you can get a 13S2P battery giving about 300W’h’s into a small case 190mm x 70mm x 80mm, why does it have to be bottle shaped. The old argument of lighter bike ( to lift over sytles sorry umm to lift over trees ) with 2 small batteries ( one in your rucksack ) is coming back full circle from where we started, certainly the sub 20kg bikes we are using ( including a 300W/h battery ) are just so much more versatile for what we do than the 25kg monster trucks that we seem to be being offered.
    There is another emerging cell format, 20700, such as the Sanyo NCR20700B 4250mAh – 15A its a tad smaller and has a pretty good draw off rating. Its only 1 mm smaller but ?

  32. That depends on your definition of "usual manufacturers". A more interesting question is why you think that matters?

    Jeez @csj do you think it could be possible to climb any further up your own arse ? You literally troll around just waiting for a moment when your primary school knowledge of battery technology can be used, in your mind, to demonstrate that you are all mighty and actually right about something (again, in your mind). You present your evidence and knowledge in it’s most primitive state and clearly show that you only have a basic understanding of the subject, but just enough to convince yourself you know what you’re talking about.

    You then go on a rampage of aggressive bullshit to try to demean another user in the hope of improving your own self esteem.

    Do you actually read what you write ? Can you understand the time you’ve wasted of Knut’s bothering to reply to your small minded bullcrap.

    Unless your "experience with it" is technical and involves actual product knowledge, and you are capable of understanding those issues better than you’ve demonstrated here, your experience doesn’t matter.

    Maybe not to you, but to the rest of us it does. From your long time trolling with just "crap post" until the forum upgrade meant you actually had to type words to be offensive … Into your birth as a user with a keyboard where all you’ve done is be aggressive and self righteous. Somewhere inside I keep hoping you might be a decent person, I even thumb up your posts to demonstrate how easy it is to be positive and maybe give you some self esteem that way rather than you just being a twit constantly. But it seems it doesn’t work.

    Ignoring that you’ve deliberately misstated the current draw

    So now you think he’s sitting there like an evil bond villain (or modern day politician…) manipulating it just to make himself look correct ..?? But you know, because you’re in his mind ?? Mind reader and worlds foremost expert on batteries.

    Also, I will note that in your contrived example

    Yes you can get further up your own arse ! you must have an arsehole ladder or hand grips ? Impressive ! Is it Yoga ?

    If he said that then he’s disqualified from commenting.

    It’s impressive that you know more than the whole specialized design team ! They must be crying that they don’t have you on-board. It’s good to know that you are judge and jury on who’s view point and knowledge is valid though. Thanks again for your help making it easier for us to understand by deciding that anyone else view doesn’t matter … this is starting to demonstrate that you might even have an arse winch ?

    Finally, Knut, it’s clear at this point that this isn’t about getting to the facts but rather about maintaining your image of expertise despite evidence to the contrary.

    Ah yes, because you know better and despite Knut being patient and trying to explain real world scenarios to you .. which don’t conform to your cereal box laboratory – yes, he’s wrong .. you’re right .. goes without saying – you’ve done and said so much to earn respect of your knowledge and view point … That must hurt though, I think your head just worked it’s way so far up your own arse it actually emerged from your own mouth ?

    I think you might have entered a state of permanent arse loop .. christ that must hurt.

    If providing correct information is antagonistic, I’m proud to be an antagonist. Nothing isn’t improved with some blind tribalism though, right?

    You continue to excel yourself. So anyone who disagrees with you is a blind tribalist ? But if they agreed with you ???? they’d be ?? What ? Clear sighted ? Or at one with the enteral arse loop arse loop arse loop arse loop arse loop ….

    Well. That’s enough time wasted reading your junk.

    @knut7 keep up the good work and don’t be put off by one moron. Or any others for that matter. Also, don’t feel the need to reply and explain yourself. You’re wasting your time. You’re not the first and won’t be the last.

  33. Umm but the real world is showing what both Knut and CSJ are saying to be true, that the 35E battery isn’t up to snuff for a single 10S1P. You can’t get around bad design but now if Spec hadn’t been suckered into the max density loop ( yep I did as well, bought over 200 over the little ferkers ) and had selected a different battery with a better C rating, they would have had success but with a trade off of lower W/H’s.

    Why the ferkin big tirade that took all of probably an hour to write, far better to be off on the bike.

  34. Why the ferkin big tirade that took all of probably an hour to write, far better to be off on the bike.

    True… :) I just keep getting fed up with CSJ jumping on everyone …. but you are correct.

    Edit. Deleted my post, my opinion is my opinion, who cares if I think CSJ is a dick 🤪

    I still think @knut7 is wasting his time communicating with him.

  35. Umm but the real world is showing what both Knut and CSJ are saying to be true, that the 35E battery isn’t up to snuff for a single 10S1P. You can’t get around bad design but now if Spec hadn’t been suckered into the max density loop ( yep I did as well, bought over 200 over the little ferkers ) and had selected a different battery with a better C rating, they would have had success but with a trade off of lower W/H’s.

    Why the ferkin big tirade that took all of probably an hour to write, far better to be off on the bike.

    I’d say observations & from what I’ve read from csj, I’d say accurate ones. If you want to communicate your expertise & be a credible voice, a friendly & respectful approach is effective. Self-righteousness – really not. Batteries become secondary when you’re being a dipwad.

  36. I’m claiming 10A for a 10s1p system, right? That’s 6,25A for 48V, so I am slightly under-estimating the current draw at 36V.

    It’s hard to tell what you’re claiming, but 10A for a 10s pack would not 6.25A for a 13s, it would be 7.7A.

    We know the SL draws 7A max. That means a 10s1p, for the same power, would require 9A. Yes, that would be worse for 18650 cells, but there’s no reason larger cells couldn’t be used, regardless of what some marketing guy told you. I’ve shown that’s the case, and have a pack that proves it is, but you aren’t interested in considering that, you seem only interested in finding some argument you can win.

    What’s interesting here, though, is that this particular argument that you focus on proves my original point, that it’s the difference in cell count that accounts for the entire difference in performance. You want to hang your hat on the fundamental difference between 13 cells and 10 as though that proves that higher voltage offers performance advantages. It does not; only more, or larger, cells does. The fact is that Spec could have dropped the voltage to 7s and used a 14 cell pack, resulting in still better performance in the same bottle cage form factor despite a lower system voltage. Also, you could actually consider the bulk of my original post(s) rather than focus on this range extender sideshow.

    We can forget about using the 18650 cells in a 10s1p config. And Spesh claim they couldn’t do it with 21700 cells, so they had to go 13s1p 18650 cells. Which was my original claim. Neither of us know what limitations they had to work with in this project. So you are free to claim they’re lying.

    No we can’t and you saying so doesn’t mean it’s true. Furthermore, "neither of us know" why "they had to go" 13s. I would wager it wasn’t because of the range extender at all.

  37. Umm but the real world is showing what both Knut and CSJ are saying to be true, that the 35E battery isn’t up to snuff for a single 10S1P. You can’t get around bad design but now if Spec hadn’t been suckered into the max density loop ( yep I did as well, bought over 200 over the little ferkers ) and had selected a different battery with a better C rating, they would have had success but with a trade off of lower W/H’s.

    Why the ferkin big tirade that took all of probably an hour to write, far better to be off on the bike.

    No one is using a 10s1p configuration so your point is moot. Spec uses a 13s1p config which is arguably also inadequate. For all other packs with at least 20 cells and low power usage, you should rethink your position on 35E-type cells.

  38. I’d say observations & from what I’ve read from csj, I’d say accurate ones. If you want to communicate your expertise & be a credible voice, a friendly & respectful approach is effective. Self-righteousness – really not. Batteries become secondary when you’re being a dipwad.

    It’s not clear who you are directing this to, or why you think it doesn’t demonstrate that you are the "dipwad". Why you think "respect" is the issue, or that it isn’t present, says more about you than it does about the topic. Engineers don’t play politics and people who want to learn do not benefit from deference to wrong answers. The ultimate respect is respect for knowledge, something you think should "become secondary" based on your personal feelings.

  39. No one is using a 10s1p configuration so your point is moot. Spec uses a 13s1p config which is arguably also inadequate. For all other packs with at least 20 cells and low power usage, you should rethink your position on 35E-type cells.

    Yup we worked that out some years back, the 35E’s work really well in the 3P 39 cell packs which we originally built, where the amperage can be drawn across all three batteries, we just built some smaller packs for a get me home battery of the 35E’s to put in our rucksacks and were a little disappointed by their performance over similar packs built with 30Q’s. It wasn’t until we put a logger on the packs to see why they were kicking out the BMS voltage shut downs that we realised the 35E’s were not living up to specs, not by much and if you accept that, the packs still have a larger W/hs than the older batteries, you just have to dial back how much ooomph you are asking of the battery in the last part of their use, if its get me home slow or not have assistance or just dial back the assistance level, its a no brainer.

    We also know we are probably getting less charge discharge cycles by abusing them this way, but battery design is changing so fast that the reduced to 500 charge / discharge cycles we are expecting, is a fair trade off.

    Why 48 volts, that is a whole different subject and one that should be discussed, its very technical, but for the less technical among us, it is to get efficiency of the engine at higher cadence levels. There’s a whole myriad of technicalities in there of +’s and -‘s and way way above my pay grade, but the way forward is 48 volts and perhaps 52 volts ( the real Ebike gurus are now using 72volts but if you put your fingers across the terminals at that voltage then we are into a hearts stopping moment ), which is what we are using on the TSDZ2 engines we are running. The firmware on these motors now calculate total W/h’s of the battery you are using ( counting Coulombs ) and have a cunning plan that when you are getting near the end of the battery, it will automatically restrict the Watts to eek out the max life of the battery, its quite cool.

  40. …the 35E’s were not living up to specs…

    Not so much missing specs but being used in manner for which they are not intended. The 2 – 3 C rating is the thermal limited continuous current draw, but they are not promising anywhere near capacity (or lifecycles) at that draw! So yeah, what you observe is right, if you want sustained high draw you need another cell like the 30Q. That’s not just true of the 35E but all the high energy cells. Also, I made this point in the Francis SL weight-weenie thread, the range extender is a terrible choice for full time operation of the bike for exactly the reasons you’re discussing.

    Why 48 volts, that is a whole different subject and one that should be discussed, its very technical, but for the less technical among us, it is to get efficiency of the engine at higher cadence levels.

    Yes, kind of. The manufacturer needs to decide how to build the motor, including how to construct the windings. High turn counts have some benefits to motor and controller construction but require higher battery voltages to support high cadences. This is almost certainly what drove the 48V decision in the SL, not anything Knut is arguing about the battery. The tail doesn’t wag the dog.

    The value of specific voltages, like 52, is esoteric and involves specific electrical devices. Such voltages aren’t important to low power ebikes like are discussed here. No reason to avoid them either, of course, but 36V vs. 48V vs. 52V are just different design tradeoffs, they are meaningless to the consumer.

    …and have a cunning plan that when you are getting near the end of the battery, it will automatically restrict the Watts to eek out the max life of the battery, its quite cool.

    It’s a neat feature but likely one that manufacturers are implementing already. Coulomb counting is effective, but you can trigger such a feature based solely on battery voltage under load, too.

  41. The value of specific voltages, like 52, is esoteric and involves specific electrical devices. Such voltages aren’t important to low power ebikes like are discussed here. No reason to avoid them either, of course, but 36V vs. 48V vs. 52V are just different design tradeoffs, they are meaningless to the consumer.

    It’s a neat feature but likely one that manufacturers are implementing already. Coulomb counting is effective, but you can trigger such a feature based solely on battery voltage under load, too.

    Sorry should have said we already are coloumb counting.

    I agree that gearing can change cadence and spin the motor in the sweet spot, but as soon as you use a lot of gearing then efficiency over all drops, computer controlled FOC changes that again, so many parameters to choose from, but then we are all learning about these great little fun machines of ours.

  42. It’s hard to tell what you’re claiming, but 10A for a 10s pack would not 6.25A for a 13s, it would be 7.7A.

    We know the SL draws 7A max. That means a 10s1p, for the same power, would require 9A. Yes, that would be worse for 18650 cells, but there’s no reason larger cells couldn’t be used, regardless of what some marketing guy told you. I’ve shown that’s the case, and have a pack that proves it is, but you aren’t interested in considering that, you seem only interested in finding some argument you can win.

    What’s interesting here, though, is that this particular argument that you focus on proves my original point, that it’s the difference in cell count that accounts for the entire difference in performance. You want to hang your hat on the fundamental difference between 13 cells and 10 as though that proves that higher voltage offers performance advantages. It does not; only more, or larger, cells does. The fact is that Spec could have dropped the voltage to 7s and used a 14 cell pack, resulting in still better performance in the same bottle cage form factor despite a lower system voltage. Also, you could actually consider the bulk of my original post(s) rather than focus on this range extender sideshow.

    No we can’t and you saying so doesn’t mean it’s true. Furthermore, "neither of us know" why "they had to go" 13s. I would wager it wasn’t because of the range extender at all.

    I specifically wrote 10s1p. I did not know the max current draw was 7A ( 48V). I estimated 300W which translates to 10A at cutoff voltage for a 36V system. And based on that assumption, you’re right, at cutoff voltage (39V) that’s 7.7A for the 48V. 6,25Ah is at 48V.

    So you assume Marco is just a marketing guy that is lying, while I can’t see what he has to gain with such a lie, so I believe him. I believe his statement is reason good enough to claim Spesh had to go 48V and you don’t. I never said it’s impossible to build a battery based on 21700 cells that will fit a bottle cage, I said Spesh tried and couldn’t do it. Chances are there are obstacles or priorities we’re not aware of.

    But there is no need to discuss the extender further, if you didn’t wanna discuss it you probably shouldn’t have brought it up.

    As I’ve said before. You’re right, I forgot about the added resistance in a 13s config. And sure, they could have built a 24V system. Noone does that though, for whatever reason. I don’t know if it’s because of the stator windings… getting as much copper as possible in the smallest possible motor? Never looked into that. Regardless, it seems we are currently limited to 36V and 48V systems, which has been my premise all along.

  43. I specifically wrote 10s1p. I did not know the max current draw was 7A ( 48V). I estimated 300W which translates to 10A at cutoff voltage for a 36V system. And based on that assumption, you’re right, at cutoff voltage (39V) that’s 7.7A for the 48V. 6,25Ah is at 48V.

    So we’ll just gloss over that I stated the 7A vs. 9A current draw up front and you presented alternative information which was wrong. How do you not know the SL is limited to 7A? You otherwise assert yourself as quite the insider on the SL batteries.

    So you assume Marco is just a marketing guy that is lying, while I can’t see what he has to gain with such a lie, so I believe him. I believe his statement is reason good enough to claim Spesh had to go 48V and you don’t. I never said it’s impossible to build a battery based on 21700 cells that will fit a bottle cage, I said Spesh tried and couldn’t do it. Chances are there are obstacles or priorities we’re not aware of.

    I can’t even verify that Marco said that. This is private information you are claiming that no one can verify and conveniently suits your narrative. There’s no need, though, for any lie to have been told. I’ve seen Marco speak on video and I have no reason to believe he knows anything. He’s a marketing guy and they claim stuff that’s wrong all the time. Their job is to push their stuff, not to inform anyone of reasons their product sucks and could be better. 21700 fits easily in water bottle form factors, end of story.

    I will point out, though, that Spec is willfully dishonest when it comes to SL marketing, claiming the same range as much more powerful bikes despite achieving that by having radically different levels of assist. By that standard every unassisted bike has unlimited range. Specialized is as dishonest as it gets with SL marketing, so by all means quote them to make your case.

    As I’ve said before. You’re right, I forgot about the added resistance in a 13s config. And sure, they could have built a 24V system. Noone does that though, for whatever reason. I don’t know if it’s because of the stator windings… getting as much copper as possible in the smallest possible motor? Never looked into that. Regardless, it seems we are currently limited to 36V and 48V systems, which has been my premise all along.

    No, you’re "premise all along" is that 48V is superior in efficiency, power delivery and charge rate, as literally anyone can verify from a simple reading of your comments that motivated my initial posts. If anyone wonders why I’m not more "respectful", it’s this deliberate dishonesty on your part.

    There have been and are 24V Ebike systems but there’s a business reason why they aren’t so common. One motor with multiple voltage ratings covers more ground but makes the 24V application pretty undesirable. Don’t take my word for it, go search Amazon or Google for "24V Ebike" and brace yourself. Geesh. For a custom design, there’s no reason to use 24V, and also no reason not to.

    The fact is that from a packaging standpoint, series packs that have only factors of 2 and 3 are better than what’s currently used. 5 and 7 are pretty bad options when it gets down to it, and 13 takes the cake for bad packaging. Low voltages, though, lead to higher currents and lower inductances, both of which can make controller design trickier. There are a number of factors that might drive choice of system voltage, none of which you seem to know.

  44. I’ve learnt a lot of valuable battery information in this thread. It’s great to be able to read different opinions.
    Would be awesome if people could keep their claws away so I can keep learning more.
  45. who cares if I think CSJ is a dick

    Is that fair?

    I don’t get the impression that CSJ is uninformed on the subject, and he’s right about something else, too: forums like this serve as a long-term repository of knowledge (or, sometimes, "knowledge", unfortunately): I agree with his assessment that it’s important to remember people who might read these threads long after the current readership has moved onto other things, and make them useful repositories.

  46. I’d say observations & from what I’ve read from csj, I’d say accurate ones. If you want to communicate your expertise & be a credible voice, a friendly & respectful approach is effective. Self-righteousness – really not. Batteries become secondary when you’re being a dipwad.

    You’re reading a "tone" into comments that really isn’t there.

  47. The ultimate respect is respect for knowledge

    I absolutely agree – equal to the respect for others participating in the discussion.

    something you think should "become secondary" based on your personal feelings.

    I don’t think it should – it just does when the tone gets personal. So I apologise for including the term ‘dipwad’ – whatever it means. It was unnecessary and unhelpful.

  48. Is that fair?

    It’s my opinion. I am entitled to my opinion.

    In my opinion it’s also fair. Nearly everything he’s written previously has been erased {by the moderators, wasting hours of their time (when they also could have been out riding) cleaning up after this dick} because it’s aggressive, ill informed or just abusive with the sole intention of improving his self esteem at the expense of others.

    Just because some of what he says is technically correct at its simplest level, doesn’t mean it’s correct in every real world application – far from it ! It also does not give him the right to demean another user. He’s accusing Knut of lying, purposefully using incorrect facts and only posting to preserve his integrity. As usual he’s trolling and bullying. If you or anyone disagree with him, your opinion isn’t valid (he even eliminated Marcus from spesh as being valid in the conversation) and anything Knut says is not valid because he doesn’t agree with him.

    I’m sorry you feel as you do. But I feel more sorry for Knut has has been unreasonably abused and felt the need to waste his time responding.

    And yes, the forum is a vast source of present and future knowledge. Because people like Knut create threads like this. Because people who have knowledge are willing to be here and share it to help others and answer people’s questions.

    Not because idiots who give nothing are abusive and disrespectful (like me).

    Personally, I’d rather have Knut giving than CSJ taking away. But each to their own.

    All the time you have people like this it pushes people away who are actually helpful. Each time I’ve seen CSJ sprout his bullsh1t on every different subject he suddenly decides he’s an expert in, we lose 3 or 4 helpful and giving people from the forum because they no longer feel comfortable here and the balance between giving and receiving is tipped too far for people to tolerate it.

    For me, someone who spent their first few months only using the old "crap post" reaction to anything they didn’t like and only started actually writing when the forum upgrade meant they couldn’t do that anymore, is a dick. Yes, he sat on the side lines and trolled, giving nothing but "crap post" reactions for 6 months ! = DICK ! (it’s simple math……..) Maybe others think thats cool, helpful, positive, giving, creative, informative ?

    No. Sorry. My opinion still stands . He’s a troll and a dick.

    I’m done here. I’m not giving anything to this thread. I only wanted to support @knut7 .

    If you don’t like what I’ve put, please, just click ignore on me.

    Thanks to the others who’ve shown support for a giving member of our community.

    If it helps you understand more, I think I’m a dick too (as is proved by my wasting my time even responding). As a dick and an expert on CSJ’s forum activities I think I’m in a perfect situation to identify someone else as a dick.

  49. No, my premise was 36V and 48V, for good reason I think. I have built an ebike with 24V years ago, so I won’t be bracing. Yeah, I could be lying about talking to Marco, I forgot about that, should have included that in my previous post.

    I said in my first response I forgot about the increased IR when going from 10s to 13s. That affects the charge and discharge rate negatively for the 48V system.

  50. No, my premise was 36V and 48V, for good reason I think. … I said in my first response I forgot about the increased IR when going from 10s to 13s. That affects the charge and discharge rate negatively for the 48V system.

    It would be nice if you could simply acknowledge that what matters is the number, and type, of cells and not how they are wired.

    Even in your acceptance of IR as an issue, you/re missing the point. When you go from 10s to 13s by adding cells, charge and discharge currents are unaffected but power is increased (because there are more cells). When you then normalize the cell count but keep the voltage difference, IR negatively effects charge and discharge in the 13s pack making the current less and power equal (because equal cell count). The only thing that matters is cell count, as I said in the beginning.

    Finally, I appreciate those who have said that having the right information is what matters. That’s all I care about, not who is right or wrong. People will come here and we don’t want them to learn dogma, we want them to have good answers.

    This is a thread about future battery technologies and there is one clear takeaway, battery chemistry improvements happen gradually. We haven’t seen much in a long time and it could be years before we get anything meaningful, despite promises. That leaves us understanding that how well our bikes work is mostly dependent on how many cells our batteries have, and an important thing that some people fail to realize is that there isn’t going to be any genre-busting bike with a teensy battery and big performance because low cell counts can’t do that. Increasing voltage is a dream that says that we can get better performance out of fewer cells by rearranging some wires. That is false.

  51. Finally, I appreciate those who have said that having the right information is what matters. That’s all I care about, not who is right or wrong. People will come here and we don’t want them to learn dogma, we want them to have good answers.

    I understand the motivation – it’s not about being right, it’s about making things right.

    Why it provokes such hysterical, excessive reaction in some people mystifies me.

    I’m neither pro nor anti either of the parties engaged in this discussion (I grew out of "sides" when I was still at school) – it’s just a difference of opinion, FFS – and the tone of some of the tantrums on here is embarrassing.

  52. But I feel more sorry for Knut has has been unreasonably abused and felt the need to waste his time responding.

    But what if CSJ’s right?

    Taking into account my admittedly limited "lay" understanding of the subject matter, nothing he has said leaps out as being glaringly off the mark: but 20-odd years of legal training and experience do allow me to recognise a strong, well-argued position when I see it…

  53. Even in your acceptance of IR as an issue, you/re missing the point. When you go from 10s to 13s by adding cells, charge and discharge currents are unaffected but power is increased (because there are more cells). When you then normalize the cell count but keep the voltage difference, IR negatively effects charge and discharge in the 13s pack making the current less and power equal (because equal cell count).

    The only thing that matters is cell count, as I said in the beginning.

    That leaves us understanding that how well our bikes work is mostly dependent on how many cells our batteries have, and an important thing that some people fail to realize is that there isn’t going to be any genre-busting bike with a teensy battery and big performance because low cell counts can’t do that. Increasing voltage is a dream that says that we can get better performance out of fewer cells by rearranging some wires. That is false.

    To put this into perspective and for all our nit picking here on quite infinitesimally small gains of battery capacity, the real story is power to weight ratios. Sure you can have your latest 102Nm motor running on increasingly efficient computer controlled motors, but the minute you put that combo in a 25kg bike with my lardy 92kgs parked astride it, then my mates converted 1998 Turner running on 26" wheels weighing all of 19kgs with his svelte 70kgs astride it, needs probably 2/3rds the battery capacity to do the same speed over the same ground.

    Far far better to stop going to the pub for a month, stop eating fatty hamburgers on the way home from work and your last years battery technology is still going to get you further than this years latest and greatest.

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