Word of warning when trying to use all the battery

[StuckintheSpokes]

My Giant goes down to 1% and then it stops assisting, instead of 0% like on my Haibike.

I thought I could just get up the required elevation for a commute, and ended up spinning in Granny gear at 6 mph.

 

[Yielar]

Pretty common actually and could be a safeguard

 

[StuckintheSpokes]

Pretty common actually and could be a safeguard

Well you should drain the battery completely every 5 or 6 cycles.

How exactly is it a safeguard? I mean it keeps the display working, but that’s pointless without assistance.

 

[Yielar]

Well you should drain the battery completely every 5 or 6 cycles.

How exactly is it a safeguard? I mean it keeps the display working, but that’s pointless without assistance.

Our E-bikes have mini computers built-in and similar to laptops they typically shut down before 100% of the battery is depleted whether this shows on the display or not.

 

[SteveVentoux]

Yep, I'd be getting worried at 10% juice left to be honest, always err on the side of caution.

 

[StuckintheSpokes]

Our E-bikes have mini computers built-in and similar to laptops they typically shut down before 100% of the battery is depleted whether this shows on the display or not.

Are you telling me the memory of the system would disappear once the battery would be depleted?

But as stated about my Haibike, it varies from system to system. I think the 0% turning the motor off is a better way to do it.

 

[Dax]

No, it's to protect the batteries from damage due to over discharge. However fuel gauges on batteries aren't exact, so a percent of error is totally believable.

 

[Dee Scee]

Well you should drain the battery completely every 5 or 6 cycles.

is that true?

 

[Macone]

is that true?

no

 

[dirt huffer]

is that true?

No... This was only true of Nicad batteries, where you had to cycle them

LiFe batteries, which we now use, have a BMS (battery management system) to keep cell voltages balanced to maintain a healthy battery pack.

The idea of cycling Nicad batteries and fully draining them every once in awhile was to prevent cell memory from building up I believe. You could get dead spots in the battery output if you didn't erase this memory. I'm probably butchering this description as I haven't delt with NiCad in 20 years.

 

[StuckintheSpokes]

No... This was only true of Nicad batteries, where you had to cycle them

LiFe batteries, which we now use, have a BMS (battery management system) to keep cell voltages balanced to maintain a healthy battery pack.

The idea of cycling Nicad batteries and fully draining them every once in awhile was to prevent cell memory from building up I believe. You could get dead spots in the battery output if you didn't erase this memory. I'm probably butchering this description as I haven't delt with NiCad in 20 years.

Somebody was bullshitting me on the Pedelecs forum, then.
It’s good to use a full charge anyway I think, because every recharge counts as one cycle of the battery.

 

[dirt huffer]

Somebody was bullshitting me on the Pedelecs forum, then.
It’s good to use a full charge anyway I think, because every recharge counts as one cycle of the battery.

LiFe *ideally* likes a charge up to 80% and a discharge down to about 20% for maximum lifespan (total number of charges and discharges in the batteries lifespan) I personally charge to 100% right before I head out or the night before though but try not to go lower than 20%

I'm guessing there is some margin built into ebike batteries from the major brands to not allow you do actually drain the battery to 0... as this is super hard on the batteries chemistry and the battery wouldn't last very long if you drain it to 0 every time you went out.... i mean the battery might only last you 100 charges if you always went to 0.

The same goes for leaving a LiFe battery at 100% for long periods of time. At 100%, this is where the electrons are most active and will deteriorate the cathode more rapidly then when left at a lesser charge. That's why a lot of manufactures say to store your battery at around 40% and don't let the charge fall below 30%.

Again, i might be butchering this explanation... but if you're bored there is a bunch of information on the web and YouTube from actual experts in LiFe battery maintenance for longevity and it's pretty easy to digest. Check it out if you're bored, lol

 

[Carrot Cruncher]

Strangely since having the upgraded RideControl switch fitted my bike has started to switch off when battery level gets down to around 30% but runs fine again once switched back on for another 5 miniutes or so. Before I could take it down to 1 light (just below 20%) with no issues.... If this continues I think a trip back the the lbs is in order.

 

[StuckintheSpokes]

There should be a better battery management system to optimise the battery life, making life simpler. Having to keep resting battery % at 60% or whatever, then remembering to only go down to 20% is faff I shouldn’t have to deal with when buying a premium product that costs several hundred pounds to replace. I guess built-in obsolescence is a factor.

 

[dirt huffer]

There should be a better battery management system to optimise the battery life, making life simpler. Having to keep resting battery % at 60% or whatever, then remembering to only go down to 20% is faff I shouldn’t have to deal with when buying a premium product that costs several hundred pounds to replace. I guess built-in obsolescence is a factor.

Cell phones are the same way. It's up to the end user to *know* to only charge to 80% and let it fall to no less than 20% to maximize the health of the battery cells. They make money selling $1000 phones that are slippery so they fall out of your hand, need a replacement screen, and the battery is shot after 2 years because the end user lets they're phone sit on a charge at 100% for half the day and then lets it go dead several times a week.

I'm not too worried about ebike batteries though. It's not so bad to charge to 100% if you ride within a day or two. It's just worse if you go to 0. They might have a built in feature that tells you 0 when you're really at 10% or 15% to prevent much cell damage. Considering how much reputation matters in the bike industry, i see manufactures being more responsible then cell phone makers. I see ebike technology and battery management systems of ebikes more closely aligned with car makers like Tesla rather than stupid Apple... lol

 

[jerry]

I shouldn’t have to deal with when buying a premium product that costs several hundred pounds to replace. I guess built-in obsolescence is a factor.

I should not have to fill up my 80.000 premium car every 600 miles either. Or be bothered with a "low fuel" warning lights. Or Oil changes. For that money, it should just work all the time, every time

Jeeeezzz...

 

[jerry]

My Giant goes down to 1% and then it stops assisting, instead of 0% like on my Haibike.

I thought I could just get up the required elevation for a commute, and ended up spinning in Granny gear at 6 mph.

If your giant does 35 miles in full charge, the 1% that your Haibike could theoretically provide "more" would put you half a mile further down the road. And you complain that you had to spin for that last half mile?
This is a joke, right?

 

[Borist]

Zero indicated is just that. Indicated. Unless BMT is poorly designed, it will turn power off at the safe cell voltage level that poses no danger to the packs predicted longevity. BMT may turn power off unexpectedly when remaining voltage is close to safe low and power drain is high as a safety precaution. This might be the scenario mentioned by OP. Gauge accuracy is another possibility.
As dirt huffer mentioned, don't leave the battery at zero for too long. There is a tiny loss of voltage in the pack even when removed for the bike. This over time may get below safe level and battery will not recharge again or the charger will refuse to charge it.

 

[MattyB]

Agreed. Also there is nothing to say that the “100%” charged mark may be limited by the BMS to reduce damage caused by storage at elevated SOC. This is common practice in many consumer electronic devices (laptops, phones etc).

 

[flash]

It's simply, near impossible to drain a LiFe or LiOn type battery to zero if it has a properly functioning BMS (battery management system) as part of the battery build. All eMTB specific batteries have this. If you did get to 100% discharge you'll have a dead battery. The BMS cuts the power supply from the battery at approximately 80% discharge.

Our batteries are made up of a group of CELLS. Each cell provides a maximum voltage of 4.2V fully charged, 3.7 volts storage charge and 3.4 volts (approx) at 80% discharge. Discharging a lithium battery cell below 3V per cell, under load is over discharging and damages the cell, often irreversibly. To get more power/capacity you hook cells together in series/parrallel.

The BMS is responsible for cutting off the charge and discharge at 3.4 (some do this at a higher point) and 4.2 volts per cell (again not all BMS will charge to full charge. It also ensures the cells charge and discharge at the same rate (balancing). Unbalanced cells are the biggest reason for battery failure.

100% on your gauge is the cells all at 4.2V (if the BMS allows it). Zero is all the cells at 3.4V. (again if the BMS allows it) The gauge is calibrated to this (in millivolts). Depending on the BMS and gauge accuracy 1% would be withing the normal margin of error. Power output is not linear as the power drops but the battery meter is, usually. So it's common to see the battery level drop faster as the percentage lowers.

From my research, which may not be ALL eMTB bike batteries, they appear the be LiFePO4 batteries rather than the LiPO batteries found in phones and drones. LiFePO4 cells are safer, more stable and much more robust but much much more expensive. They are also use in caravan and camper trailer lithium cells. So while they do like to be stored at 70% (3.7-.8V per cell) they tend to be more stable at higher voltages than LiPO. So charging them to full and leaving them for a few days isn't a big deal. Storage for more than a month should be at approx. 70% though. Many chargers quick charge to 70-80% and trickle charge the remainder. You can use this as a basic idea of how long it'll take to get your battery to a storage charge.

Some of the batteries used in bolt on kits are LiPO batteries used in large drones and RC applications. These are LiPO cells with a balancing plate but no BMS. Prone to fire on impact. Probably not a great idea on a mountain bike. I use these on my larger commercial drones.

A charge cycle is one full cycle from 3.4V to 4.2V. Charging form 50% to 100% is a half cycle. Most batteries are rated for full cycles. So if you charge your battery 50% each day you can do so 1000 times. 1/3rd each day then 1500 times.

Lithium batteries do not get memory. However some BMS systems like a full cycle occasionally to re-calibrate the way they send information to the battery gauge.

Gordon

p.s. How do I know this boring shit? I had to do a class on battery management and chemistry as part of my licencing requirements to fly drones commercially in Oz. Never did I think I'd use that class when buying a bike....

 

[njn]

Unfortunately, manufacturers keep the BMS data a secret.

Shimano will run the display and di2 with the battery showing 0%.

 

[MattyB]

Unfortunately, manufacturers keep the BMS data a secret.

Shimano will run the display and di2 with the battery showing 0%.

Nothing surprising about that really - the display and Di2 requires absolutely tiny currents and is a 7.4V (2S) circuit. Even a pack exhausted to 3V/cell (which is essentially 100% discharged) could deliver that current.

 

[StuckintheSpokes]

I got the every charge = one cycle from EMBN If you disagree with me, take it up with Chris or Steve.

 

[Dax]

As above, a cycle is a charge from flat to full.

 

[Rob Rides EMTB]

There’s also legal factors to take into account as well. In Germany they require enough battery power to run lights even when the battery doesn’t have enough power left to provide motor support. So at 0% (showing on display) there’s actually around 5%, or thereabouts, battery power left for the lights to remain on (IIRC needed to be 30 minutes after motor power has been lost).

 

[MattyB]

There should be a better battery management system to optimise the battery life, making life simpler. Having to keep resting battery % at 60% or whatever, then remembering to only go down to 20% is faff I shouldn’t have to deal with when buying a premium product that costs several hundred pounds to replace. I guess built-in obsolescence is a factor.

Re: the optimum storage voltage the BMS cannot change the fundamental chemical processes going on in a Lithium based cell.If you store it above 4V/cell you will increase the rate of dendrite formation which reduces cell capacity, cycle life and the ability to deliver high currents. It’s chemistry, pure and simple. Your assumption about not discharging below 20% is also incorrect as the BMS is the bit protecting the pack to ensure it is not over discharged. Going down to an indicated 0% (which is well above the 3V/cell that is considered the lowest sensitive discharge voltage of a Li Chen battery) will do no harm at all providing you then put some charge back in within 24hrs or so.

 

[MattyB]

I got the every charge = one cycle from EMBN If you disagree with me, take it up with Chris or Steve.

Yeah, they have talked rather a lot of waffle about batteries since EMBN started - they have good info about the fundamentals of mountain biking, but I’m afraid battery knowledge is not one of their strengths.

In summary 1 charge from 0-100% = 1 full charge; a charge from 0-50% = a half charge, etc etc. Lithium batteries are not nicads nor should they be treated as such.

 

[flash]

I got the every charge = one cycle from EMBN If you disagree with me, take it up with Chris or Steve.

And if you read the comments you'll see they get called out on the errors they make when it comes to eMTB technology. What was the one they tried to pass off as an April fools joke a couple of weeks ago?

I like the channel and I get a lot from it regarding riding, as they really can ride. But sometimes the answers on ASKEMBN are plain bizarre, like they did no research beforehand. Batteries aren't their strong suit.

Of course, you can do some research on the web and verify for yourself how our batteries work and how to take care of them. I'm just one person with a little bit of training in this field. There are many others with vastly more knowledge than me.

Gordon

 

[flash]

There’s also legal factors to take into account as well. In Germany they require enough battery power to run lights even when the battery doesn’t have enough power left to provide motor support. So at 0% (showing on display) there’s actually around 5%, or thereabouts, battery power left for the lights to remain on (IIRC needed to be 30 minutes after motor power has been lost).

I did not know that. Interesting. Probably the same charge that allows the Di2 shifters about 300 changes after the motor shuts off.

Gordon