End of season battery partial drain

[Gordon71]

I think I waited too long to do my final ride of the season to bring my battery down to 70-80 percent for storage. Thinking of raising it on my pulley lift and then engaging the throttle
until it shows 4 out of five bars. Can anyone think of a reason that is a bad idea? Thanks.

 

[Gionnirocket]

Storage charge is typically 40% to 60%
No issue with throttling your way there other than it's time consuming. If you ride it in the cold it'll drop SoC more quickly than a normal summer ride

 

[6zfshdb]

The main reason not to do this is just the unnecessary wear on the motor, internal gears (if any) and bearings.

What type battery is it? what does the discharge connector look like? If you can safely access the contacts, a simple discharge rig can be made using a lamp with an incandescent bulb.

Many batteries use spade connectors that can be accessed by cutting the plug in half on an old extension cord:

Insert the plug halves into the battery and plug the lamp into the extension cord. The higher the bulb wattage, the more current it will draw.

If you're careful, you may be able to use this idea with other battery connectors as well.

 

[Gordon71]

The main reason not to do this is just the unnecessary wear on the motor, internal gears (if any) and bearings.

What type battery is it? what does the discharge connector look like? If you can safely access the contacts, a simple discharge rig can be made using a lamp with an incandescent bulb.

Many batteries use spade connectors that can be accessed by cutting the plug in half on an old extension cord:

View attachment 203092 View attachment 203093

Insert the plug halves into the battery and plug the lamp into the extension cord. The higher the bulb wattage, the more current it will draw.

If you're careful, you may be able to use this idea with other battery connectors as well.

Thanks. The bike is a 2020 Rad Rover ST. I wouldn't think it would be any more wear on the motor than riding it although it would take longer. I could do it in shifts.

 

[Gionnirocket]

I think the motor wear under such minimal load would be negligible.... That said under such minimal load it'll take a while.
Unless you're snowed in... I'd dress warmly and just go for a ride.

A little more difficult for me to use the light bulb method as my battery disconnects output when not installed on the bike. The safety feature can be defeated but that's another set of jumpers to make up.

 

[Gordon71]

I think the motor wear under such minimal load would be negligible.... That said under such minimal load it'll take a while.
Unless you're snowed in... I'd dress warmly and just go for a ride.

A little more difficult for me to use the light bulb method as my battery disconnects output when not installed on the bike. The safety feature can be defeated but that's another set of jumpers to make up.

It's pretty sloppy right now. These rural roads in my small town on the coast of Maine are narrow with shoulder drops as deep as 6 inches in places. I might hold off and hope for a dry day after predicted rain washes away the few inches of snow we have now. Right now I'd get sprayed with sand and a bit of slush every time a car passed me.

 

[Gionnirocket]

It's pretty sloppy right now. These rural roads in my small town on the coast of Maine are narrow with shoulder drops as deep as 6 inches in places. I might hold off and hope for a dry day after predicted rain washes away the few inches of snow we have now. Right now I'd get sprayed with sand and a bit of slush every time a car passed me.

Yeah that doesn't sound like fun.
I guess a third alternative would be to set the bike up inside as an exercise trainer

 

[JL0256]

Not a bad idea at all. Dropping it to around 70–80% is pretty much the sweet spot for long-term storage.


If you missed the chance to ride it down naturally, “running it on the stand” for a minute or two won’t hurt anything as long as the motor isn’t under real load. The controller and battery don’t know the difference — they just see light current draw.


Just keep an eye on heat. If the motor or controller stays cool, you’re fine.


One thing I’d avoid is draining it too fast or too low. You only need to knock off that top 20–30%. Once you’re at 4 bars (or roughly around that 75% zone), you’re good for winter.


I’ve stored batteries like this for years and never had any issues. The fact that you’re even thinking about storage percentage already puts you ahead of most riders.

 

[Gordon71]

Not a bad idea at all. Dropping it to around 70–80% is pretty much the sweet spot for long-term storage.


If you missed the chance to ride it down naturally, “running it on the stand” for a minute or two won’t hurt anything as long as the motor isn’t under real load. The controller and battery don’t know the difference — they just see light current draw.


Just keep an eye on heat. If the motor or controller stays cool, you’re fine.


One thing I’d avoid is draining it too fast or too low. You only need to knock off that top 20–30%. Once you’re at 4 bars (or roughly around that 75% zone), you’re good for winter.


I’ve stored batteries like this for years and never had any issues. The fact that you’re even thinking about storage percentage already puts you ahead of most riders.

Thanks, I don't plan to just let it run but do it in bursts and not at full.

 

[Gionnirocket]

Not a bad idea at all. Dropping it to around 70–80% is pretty much the sweet spot for long-term storage.


If you missed the chance to ride it down naturally, “running it on the stand” for a minute or two won’t hurt anything as long as the motor isn’t under real load. The controller and battery don’t know the difference — they just see light current draw.


Just keep an eye on heat. If the motor or controller stays cool, you’re fine.


One thing I’d avoid is draining it too fast or too low. You only need to knock off that top 20–30%. Once you’re at 4 bars (or roughly around that 75% zone), you’re good for winter.


I’ve stored batteries like this for years and never had any issues. The fact that you’re even thinking about storage percentage already puts you ahead of most riders.

Like I mentioned earlier... Storage charge according to cell manufacturer white paper is 40 - 60%.
You can further see this when you buy any new device with a Lithium battery.. It's alway at about 50%

BU has a lot of information on all batteries

From the above article:
Simple Guidelines for Storing Batteries

Lithium-ion must be stored in a charged state, ideally at 40 percent. This prevents the battery from dropping below 2.50V/cell, triggering sleep mode.

Discard Li-ion if kept below 2.00/V/cell for more than a week. Also discard if the voltage does not recover normally after storage. (See BU-802b: What does Elevated Self-discharge do?)

ySoCmv

 

[Gordon71]

But what is long term storage? Sitting on a cargo ship and then in a warehouse for months or years until sold. How about just sitting in my house from now until April?

 

[Gionnirocket]

Well that can be a bit arbitrary but personally I would consider anything over 1 month long term storage.
That said, best practice is just that. Near 50% is the batteries happy place and when kept there it's most stable. Obviously the longer the time, the more beneficial it is to do so. In the end don't stress about it but if you're bothering to put it in storage... then I would use the SoC that's most beneficial.
The only caveat is with a lower SoC you should monitor self discharge as you have a lower ceiling.... but that said, a higher SoC is more likely to self discharge.
I stored my 48v/10ah battery with Sanyo GA cells at 45.5V for near two years and when I put it back in the game it was at 45.3V.
As far as I can tell, it's working as well as new. And that's feeding a 1000w mid_drive.

 

[Gordon71]

For fun I asked AI.

For winter storage, the best charge for an e-bike battery is around
40-60% (or 2-3 bars), stored indoors at room temperature (50-77°F / 10-25°C), never fully charged or drained, and checked every couple of months to top up if it drops too low, as this minimizes stress and preserves battery health.