Battery Capacity

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Bobj183

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My new bike, a 2021Trek Powerfly 7, has a 625wh battery. A big improvement over the last Powerfly I had with a 500wh battery. Or is it? The 625wh battery weighs over 4kg, a good 1.5kg more than the 500wh battery and a good 2kg more than the 400wh Shimano battery on my wife's bike. I always use the minimum amount of power I need so have never come close to running out of juice. I'm wondering if, like on some super light ebikes, there is a place in the market for a battery option of say 350wh which would weigh in at somewhere under 2kg? My new bike's all up weight is about the same as the old one so without the battery it's quite a bit easier to lift onto the bike rack. It's seems a shame that all the work that's gone into making the motor / bike lighter is offset by battery capacity that I don't need.
Does anyone have any opinions on this? Go on I bet you must have :)
 
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My bike's battery has deteriorated over 3 years to the point that it predicts that I get 37 miles from a full battery in eco. It used to predict closer to 50 miles when it was new.

Use your ebike as a weight for resistance training, while waiting for ride companions to get ready. Hammer curls?
 
I agree - if you compare a Shimano e8000 bike with 504wh external battery like the last gen Vitus or Merida which came in at 22kg ish to the current versions with EP8, 630wh internal batteries that come in around 24kg the range difference isn’t that great.

I also have the new 630wh external battery, this is 600g more than the 504wh external, but the bike isn’t significantly heavier.

I suspect I would get more range out of my Vitus/e8000/630wh external set up than a newer EP8/630wh set up simply because the bike still weighs a kg less than most of the newer bikes, and uses less power.
 
R120 said:
I suspect I would get more range out of my Vitus/e8000/630wh external set up than a newer EP8/630wh set up simply because the bike still weighs a kg less than most of the newer bikes, and uses less power.
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2kg in extra weight doesn't transpose to a higher level of resistance of the bike to move foward equal to the extra 120Wh's of energy stored in the battery. Bearings and round wheels see to that.

If your summation that a 503Wh battery has the same range as the 630Wh battery but on a bike 2Kg heavier bike is the same, then in the case of my fat arse of 95kgs compared to say a 75kgs rider, I would use ( 120 Wh's / 2 kg = 60 Wh's per kg ) 20 kg x 60Wh's =1200Wh/s extra over the same distance of the 75kg rider.

Reality shows something quite different and one of the great misnomers here on this forum, that heavier bikes use way more power. Perhaps we should start a thread to dispell the myth that seems to be building.
 
Sidepod said:
I'm convinced the current trend of big, heavy high capacity in-tube batteries is wrong. Smaller lighter external multiple batteries seems to me the more sensible configuration.
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Like the Focus Jam2 (Shimano motor) 378wh internal battery, just a shame they made a pigs ear of the TEC battery, I'm hoping @TrailwattsUK will soon be releasing a smaller range extender for the Focus ?
 
Waynemarlow said:
2kg in extra weight doesn't transpose to a higher level of resistance of the bike to move foward equal to the extra 120Wh's of energy stored in the battery. Bearings and round wheels see to that.

If your summation that a 503Wh battery has the same range as the 630Wh battery but on a bike 2Kg heavier bike is the same, then in the case of my fat arse of 95kgs compared to say a 75kgs rider, I would use ( 120 Wh's / 2 kg = 60 Wh's per kg ) 20 kg x 60Wh's =1200Wh/s extra over the same distance of the 75kg rider.

Reality shows something quite different and one of the great misnomers here on this forum, that heavier bikes use way more power. Perhaps we should start a thread to dispell the myth that seems to be building.
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I agree and disagree

A higher weight bike doesn't use more power, but it takes more effort for you and the motor to ride uphill - how much the motor uses depends on how much the rider is relying on the assistance, which is down to mode choice and riding style.

Comparison of what range i get out of my various batteries is only relevant to me, because IMO the biggest factor in how much you use is you riding and peddling style plus how you uses the gears.

One person might get much more efficiency over another of the same with and build, on identically set up bikes, purely because of how the "human element" for want of a better phrase interacts with the bike.

The weight of the bike and how it impacts the range is a constant, so obviously I am going to get less range out of a 25kg Emtb with the same motor, battery and tires than a 22kg one, but how someone of a different build would get on I dont know.

We all know the biggest effects on range is rider weight and rolling resistance of tires, but given that most of us cant magic away 20kg off our bodies, the weight of the bike is the viable area to look at (fairly incremental gains), and of course tire choice is a personal deciosn based of what you are willing to trade off in terms of grip and robustness vs weight and rolling resistance.

IMO another big variable is that I think a lot of emtb riders are lazy on gear choice, simply because you can get away with being in the wrong gear more often than not - if you try riding your EMTB more in line with a normal bike, and being in the right gear all the time, you use less assistance, and see a resulting gain in range.
 
@Bobj183 I agree with @stiv674 I have a size large, carbon-framed Focus Jam2 with its 378Whr battery contained within the downtube. The bike is a thing of beauty and it only weighs 20.4kg. The TEC pack by itself is not bad looking, but placed on the lovely Focus Jam2 it is like adding a wart! However, it only weighs 2.2kg. So even with the TEC pack added the bike still only weighs 22.6kg, and it has 756Whr! Beat that! :)
Focus (1).jpg
 
Waynemarlow said:
that heavier bikes use way more power. Perhaps we should start a thread to dispell the myth that seems to be building.
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I think what needs to be taken into account is the fact that it takes more effort ( energy, force) to raise an object over a given height than it does to move it in along the flat. So I dont think its a myth, its physics. If it was the same then it would take the same effort to lift a 1kg weight onto a table as it would a 100kg weight.
 
Don't confuse power (Watts) and energy (Watt-hours). The power available on a bike can stay the same, but more energy will be used to propel a heavy guy than a light guy over the same distance/height. Therefore the reserve of energy in the battery will run out sooner.
 
Waynemarlow said:
If your summation that a 503Wh battery has the same range as the 630Wh battery but on a bike 2Kg heavier bike is the same, then in the case of my fat arse of 95kgs compared to say a 75kgs rider, I would use ( 120 Wh's / 2 kg = 60 Wh's per kg ) 20 kg x 60Wh's =1200Wh/s extra over the same distance of the 75kg rider.
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I'll repeat this as I think you guys have missed the bit about needing 1200Whs extra to ride the same distance if you have only 20 kgs difference on your terms of 2kg extra in weight for 120W/h's. That doesn't stack up in anybodys terms.
 
I didn't start this thread to imply that heavier bikes waste power. It was more to do with the fact that I'm probably toting round two kilos of battery that I don't need. From reading other threads I obviously use my legs a lot more than some so two kilos is really significant. For me weight is also about how the bike responds when you're pushing it round a bit of technical single track.
 
Waynemarlow said:
I'll repeat this as I think you guys have missed the bit about needing 1200Whs extra to ride the same distance if you have only 20 kgs difference on your terms of 2kg extra in weight for 120W/h's. That doesn't stack up in anybodys terms.
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TBH I dont really understand what you are trying to get at - the point that I was making is that a newer heavier Shimano systems bike with a 630wh battery doesn't actually have that much more range over an older 504wh Battery bike.
 
Bobj183 said:
I didn't start this thread to imply that heavier bikes waste power. It was more to do with the fact that I'm probably toting round two kilos of battery that I don't need. From reading other threads I obviously use my legs a lot more than some so two kilos is really significant. For me weight is also about how the bike responds when you're pushing it round a bit of technical single track.
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Agreed. I do a lot of 1 hour rides so I’m carrying far more weight and capacity than I need. A lighter bike with smaller battery would suit me better.......if only I could get hold of one!
 
R120 said:
TBH I dont really understand what you are trying to get at - the point that I was making is that a newer heavier Shimano systems bike with a 630wh battery doesn't actually have that much more range over an older 504wh Battery bike.
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I think you are blaming the 2 kg extra in weight for using 120Wh's of battery, which in my view is nonsense, but then sometimes my maths is pretty crap. Its far more likely other variables such as you yourself are not putting in as much energy over the same route, the latest iteration of the motor firmware is not as efficient, you have been faster over the route. Lots of things to be more likely than to blame the 2 kgs.

Bobj183 said:
I didn't start this thread to imply that heavier bikes waste power. It was more to do with the fact that I'm probably toting round two kilos of battery that I don't need.
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Correct and why there's whole bunch of homebuild batteries at around 360 Wh's per battery. Lifting a 24kg bike over a gate is difficult, now 22kgs I can do. Best ever bike we had was under 17kgs with 360W'hs on board, it was a very light early 2000's mtb with a conversion kit onboard. Cool bit of kit, but rode really badly compared to the latest monster trucks we are on.
 
Slightly off topic I know but I’ve always wondered when we eventually see lithium ion powered aircraft with massive batteries made of similar cells as in our bikes........
will we still be banned from taking our bike batteries on such a plane?
 
You know it's almost as if we could do with some sort of, ooh I don't know, engine? Then we could add fuel/weight according to how far we want to travel. Imagine that as a concept?
 
I've been reading a bit about the potential for a very high energy density aluminium battery. I understand that finding the right electrolyte and anode material is the problem to be solved but potentially an Al battery could have three times the energy density of an Li battery. Al is also one of the most common elements on Earth and much cheaper than Lithium.
 
Waynemarlow said:
I think you are blaming the 2 kg extra in weight for using 120Wh's of battery, which in my view is nonsense, but then sometimes my maths is pretty crap. Its far more likely other variables such as you yourself are not putting in as much energy over the same route, the latest iteration of the motor firmware is not as efficient, you have been faster over the route. Lots of things to be more likely than to blame the 2 kgs.


Correct and why there's whole bunch of homebuild batteries at around 360 Wh's per battery. Lifting a 24kg bike over a gate is difficult, now 22kgs I can do. Best ever bike we had was under 17kgs with 360W'hs on board, it was a very light early 2000's mtb with a conversion kit onboard. Cool bit of kit, but rode really badly compared to the latest monster trucks we are on.
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i think the odd kg here or the odd kg there ain’t gonna make much difference to us e-bike riders

1F6E0B2E-EB33-400D-BB4D-E7AB3768D19E.jpeg
 
Waynemarlow said:
I think you are blaming the 2 kg extra in weight for using 120Wh's of battery, which in my view is nonsense, but then sometimes my maths is pretty crap. Its far more likely other variables such as you yourself are not putting in as much energy over the same route, the latest iteration of the motor firmware is not as efficient, you have been faster over the route. Lots of things to be more likely than to blame the 2 kgs.


Correct and why there's whole bunch of homebuild batteries at around 360 Wh's per battery. Lifting a 24kg bike over a gate is difficult, now 22kgs I can do. Best ever bike we had was under 17kgs with 360W'hs on board, it was a very light early 2000's mtb with a conversion kit onboard. Cool bit of kit, but rode really badly compared to the latest monster trucks we are on.
Click to expand...
No I still dont get what you are saying - I am saying a heavier bike use more battery than a lighter bike with the same system, which is obvious.

I was also saying dont assume an EP8 bike with a 630wh Battery has that big a jump in range form an e80000 with a 504wh battery, simply because the weight of the bike maybe up to 2kg more and you need to factor that in.

How this impacts in the real world much by is dependent on who is riding, how they ride, and how the bikes is set up.

I have no idea how you would try to apply any time of mathematical formula to that.
 
Wayne is extrapolating your experience/theory. But, he's applying the weight difference of bikes and then applying it proportionally to a rider - in energy terms and then effectively inverting that back to say that what you're saying is wrong because the numbers don't add up - ie, if 2kg's make that much difference then 20 kg's of rider would make 10 times the difference - basically :)

Alas, it's not that simple. What he's saying is correct, but at the same time in the real world it's wrong because of our basic lack of understanding of how physics really interacts not only with the rider weight, but the bike weight. For instance , the rider mass might be on a stable trajectory up and over a series of bumps, but the bike isn't.

This is another one of these things though which will be hugely dependent on how a person rides and on what terrain. So ultimately there is no fixed formula, there are just different opinions because it's different for everyone.

Wayne might get the same range on a 50kg or 20kg bike with the same battery/motor. You will get massively less range on a 50kg bike compared to a 20kg bike. This is only meant as an example and implies nothing, only that how we ride and how that affects range which then corresponds to bike weight, is a variable - not a fixed.
 
I have two Merida E160's. A 2019 900 with E8000 and external 504WH battery and a 2021 with EP8 and internal 630WH. The new bike weighs about 1.5kg more than the old one. I have a choice. Same power and more range or More power and same range. 2kg isn't going to eat up all the 25% in increased capacity with a 90kg rider on board. Riding it at a higher power is.

Gordon
 
It's amazing how these threads morph from one subject to another isn't it? :D
 
I’ve never been a stats geek but recently I’ve started to log my rides from a power/torque/mode use point of view.
It’s surprising how little torque the motor puts in relative to its full potential.

I always have a guilt trip and try to use as little e-power as possible for obvious reasons.
In fact I’m actually starting to question why I have 2 eebs at all.

One thing is fo sho, I could deffo downgrade, which is good news because I’ve always liked the Fazua system (Nox Helium).
 
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