How to properly break in a new electric bike battery and extend its life

[ROJA]

After completing a ride (and assuming it will be a day or more before the next ride), is it best to:

1. leave it and don't charge until before the next ride
2. charge to 50% and then wait to fully charge until just before the next ride
3. fully charge and let it sit in the fully charged state
4. something else?

 

[Cameron Newland]

After completing a ride (and assuming it will be a day or more before the next ride), is it best to:

1. leave it and don't charge until before the next ride
2. charge to 50% and then wait to fully charge until just before the next ride
3. fully charge and let it sit in the fully charged state
4. something else?

Charge to 50% and then wait to fully charge until just before the next ride.

For those of us who need a little more flexibility and want to be able to go on rides on short notice and without waiting to charge the bike, the second-best option is to charge your battery to ~80% instead of 50%. That way, you can go out on short trips without charging to 100% before your ride, and if you need a fully charged battery, it should take less than an hour to charge from 80% up to 100%.

Lithium ion batteries will have the longest life when left at 3.6-3.7v per cell (approximately 50% charge state). Storing your bike at an 80% charge state will give your battery some of the longevity benefits of storing it at 50% charge, but is more useful for spur-of-the-moment rides.

 

[somelad]

I have had a similar problem and am testing it now. It could either be a faulty BMS or a bad group of cells. I have taken the battery apart and found one set of cells at a low voltage. This is causing (I believe) the BMS to shut down as it detects that the voltage is too low.

 

[harryS]

Lithium ion batteries will have the longest life when left at 3.6-3.7v per cell (approximately 50% charge state). Storing your bike at an 80% charge state will give your battery some of the longevity benefits of storing it at 50% charge, but is more useful for spur-of-the-moment rides.

Cameron,

Eric, the big boss at lunacycle.com, a popular battery seller to us in the do-it-yourself market, says the same thing, that 50% on a battery is about its nominal voltage. Which means we can use 36 volts and 48 volts as the 50% point on the two most popular bike batteries. Very convenient.

For those who don't know, a 36 volt battery uses 10 groups of cells in series, while a 48 volt battery is usually 13 groups in series. A cell will be 4.2 volts at full charge, and while they are rated to discharge safely to 2.5 volts, battery makers shut them off around 3.0 volts. So multiply 4.2 and 3.0 by the number of series cells, and you find our typical bike batteries are worked between 30-42 Volts or 40-54 volts.

Since my bikes are home built, I've attached an inline wattmeter behind the battery and watch the voltage that way. If all you have is the bar display on an LCD screen, I would guess two out of four bars is awful close to 50%. I will try to compare that to actual voltage of these days.

 

[Shoestring]

I too added a watt meter to my kit bike to keep track of my battery. I only get to ride it about once or twice a week, so I don't recharge until I'm ready to ride the next time. In truth, I only charge the bike about 35 times a year so the battery will probably degrade long before I get 500+ cycles. I usually charge to full 54.6 (48v) and finish the ride at about 47-48v, then park it. So far this has worked great, I can't determine any power loss so far, (two years).

 

[SuperGoop]

Is it ok to ride immediately after charging, or should I wait for the battery to "settle" before riding?

If so, how long should I wait after unplugging the charger?

 

[Cameron Newland]

Is it ok to ride immediately after charging, or should I wait for the battery to "settle" before riding?

If so, how long should I wait after unplugging the charger?

It's okay to ride it immediately after charging. You might consider putting your hand on the battery case. As long as it's not hot-to-the-touch, it's ready to ride. Besides, the only batteries that would be hot-to-the-touch after charging would be batteries using some kind of proprietary fast-charger (5A and up), and 99% of ebikes don't have those. Most ebike chargers are 2A, and most fast chargers are 3A, and at that level of current, there won't be enough heat during charging to cause any issues.

 

[SuperGoop]

Cameron,

Eric, the big boss at lunacycle.com, a popular battery seller to us in the do-it-yourself market, says the same thing, that 50% on a battery is about its nominal voltage. Which means we can use 36 volts and 48 volts as the 50% point on the two most popular bike batteries. Very convenient.

For those who don't know, a 36 volt battery uses 10 groups of cells in series, while a 48 volt battery is usually 13 groups in series. A cell will be 4.2 volts at full charge, and while they are rated to discharge safely to 2.5 volts, battery makers shut them off around 3.0 volts. So multiply 4.2 and 3.0 by the number of series cells, and you find our typical bike batteries are worked between 30-42 Volts or 40-54 volts.

Since my bikes are home built, I've attached an inline wattmeter behind the battery and watch the voltage that way. If all you have is the bar display on an LCD screen, I would guess two out of four bars is awful close to 50%. I will try to compare that to actual voltage of these days.

I have a 48v battery, which means around 54 volts when fully charged... which we know is unhealthy for the battery.

Is it only unhealthy if kept at that 100% state over time? For example, if I ride immediately after a full charge (ie. immediately draining the battery), would that be okay? Or should I never charge to 100% even if I ride immediately, thus the battery is never at that 54v range for long. Thanks.

 

[Cameron Newland]

I have a 48v battery, which means around 54 volts when fully charged... which we know is unhealthy for the battery.

Is it only unhealthy if kept at that 100% state over time? For example, if I ride immediately after a full charge (ie. immediately draining the battery), would that be okay? Or should I never charge to 100% even if I ride immediately, thus the battery is never at that 54v range for long. Thanks.

Yes, it's only if kept at 100% charge state for a long time. If you charge your bike to 100% right before going on a ride, that will extend your battery's cycle life versus keeping it fully charged at all times.

 

[Solom01]

There's so much information going around about the best way to care for Lithium ebike batteries that it's really confusing for a newbie. I don't know much about ebikes, but I've been dealing with lithium batteries in other systems for a while and I'm wondering if there are that many differences? It's especially hard to know what to do since the manufacturer's advice seems to be flat wrong a lot of the time. Do you guys know:

(1) My manual says to fully recharge the battery after each use, even if it's nowhere near discharged. My understanding was that if possible leaving it at 50-80% percent is best (I'm thinking the manufacturers are more concerned about making the range seem longer, since that's what the customer cares about initially).

(2) More bikes seem to be coming with 4amp chargers and Court always points this out as a huge plus in reviews. In every other instance of lithium battery use I've seen fast charging is fairly harmful to a battery. In fact, the Tesla manual in the fine print talks about shorter battery life if you use a fast charger more than 10% of the time - so what's the optimum charge rate for an ebike battery if your goal is to maximize it's life and the time to recharge isn't a concern?

(3) I know that allowing a battery to fully discharge or to charge it much above 80% will shorten the battery life. In an electric car the battery management system automatically prevents this from happening, and on better laptops there normally is a function to prevent over/undercharging also. Is this true with the bms of most ebikes, or is this something I need to keep track of manually? Any input would be much appreciated.

 

[Cameron Newland]

There's so much information going around about the best way to care for Lithium ebike batteries that it's really confusing for a newbie. I don't know much about ebikes, but I've been dealing with lithium batteries in other systems for a while and I'm wondering if there are that many differences? It's especially hard to know what to do since the manufacturer's advice seems to be flat wrong a lot of the time. Do you guys know:

(1) My manual says to fully recharge the battery after each use, even if it's nowhere near discharged. My understanding was that if possible leaving it at 50-80% percent is best (I'm thinking the manufacturers are more concerned about making the range seem longer, since that's what the customer cares about initially).

(2) More bikes seem to be coming with 4amp chargers and Court always points this out as a huge plus in reviews. In every other instance of lithium battery use I've seen fast charging is fairly harmful to a battery. In fact, the Tesla manual in the fine print talks about shorter battery life if you use a fast charger more than 10% of the time - so what's the optimum charge rate for an ebike battery if your goal is to maximize it's life and the time to recharge isn't a concern?

(3) I know that allowing a battery to fully discharge or to charge it much above 80% will shorten the battery life. In an electric car the battery management system automatically prevents this from happening, and on better laptops there normally is a function to prevent over/undercharging also. Is this true with the bms of most ebikes, or is this something I need to keep track of manually? Any input would be much appreciated.

Optimum charge current for longevity is 1A. Most ebike chargers are 2A, which is nearly as good. For fast charging, I wouldn't personally go over 4A, however, there are some bikes with huge batteries that need a ton of current in order to make the charging time reasonable (i.e. <4 hours), so I guess there is a good reason that some ebike batteries offer 5A-8A fast chargers. Anything above 8A should be for experts only.

Regarding ebike BMSes and whether you need to keep track of your charge state manually, it's quite unfortunate, but manually managing charge state is a must if battery health/longevity is your goal. The only solution I've seen out in the wild that takes care of it for you is the $300 Grin Tech Cycle Satiator, which can be programmed to charge your bike to 80% charge state and no further. Lunacycle also sells an Advanced Charger that makes similar claims, however, I've never come across anyone who has had any luck with their Advanced Charger, and one guy who bought one said that it didn't actually stop charging at 80%, but rather just charged much more slowly from 80% to 100%. I don't have one so I cannot speak with authority about the Luna Advanced Charger.

The way I manage my battery charge state is by taking a look at the charge when I get the bike home, attaching the charger, and then I make a rough estimate of how many hours I think it will take to get to 70% or 80% charge, then I set an alarm for that time and then check the battery charge state again, and unplug if it's around 80% charged. I've found it to be pretty easy.

 

[ROJA]

@Court Going back to your first post, I have a new battery that I'm trying to break in properly. Do you have any idea how many times I should run it down to 50% as you suggest? Would 3-4 be sufficient or should I do it a bunch of times?

(My commute requires more than 50% of the battery capacity, so I'm stuck doing only local rides until I'm comfortable that the battery is properly broken in!)