Anyone charging there battery in cold room?

[Samuel]

I am planning on charging my limn battery in the garage which can get a bit below freezing. I get that it is bad to leave a battery cold, but if it is charging, wont this keep it warm? Anyone else doing this? How cold before it becomes a problem?

Thanks,
Sam

 

[Ziggurat]

It's not bad to keep li batteries cold, but it is bad to charge them cold. See http://endless-sphere.com/forums/viewtopic.php?f=14&t=36720. That thread was for rc lipo but limn is the same family.

As to warming from charging, the internal resistance of these batteries is not so high, so at reasonable charge rates there isn't a lot of heat generated.

I charge in the garage too, but heat it up a bit with a portable heater for a while before charging, if garage temp is below about 5 C. I also charge slowly, well under 1C charge rate. I'm thinking that coldness slows chemical reactions, so charging slower gives more time for the right reactions to occur, as opposed to the damaging ones. I think that is correct ...slower charging is in general less damaging at any temperature so I think it should help.

 

[deVries]

I am planning on charging my limn battery in the garage which can get a bit below freezing.

I definitely would not recommend charging anywhere near freezing or below. Either create a warm area with a space heater or bring the battery inside house or warm area to charge or warm-up before charging. 50 degrees Fahrenheit battery temp would be near the low end for me. Maybe a few degrees lower if you slow charge & the temp will not drop towards the 30's.

 

[el_walto]

If it's not below -5c, i would not worry about it at all.

Battery will have a much longer shelf life stored at 3c compared to 20c.

 

[Ziggurat]

From http://batteryuniversity.com/learn/article/charging_at_high_and_low_temperatures

Li‑ion batteries offer reasonably good charging performance at cooler temperatures and allow fast-charging in a temperature bandwidth of 5 to 45°C (41 to 113°F). Below 5°C, the charge current should be reduced, and no charging is permitted at freezing temperatures. During charge, the internal cell resistance causes a slight temperature rise that compensates for some of the cold. With all batteries, cold temperature raises the internal resistance.
Many battery users are unaware that consumer-grade lithium-ion batteries cannot be charged below 0°C (32°F). Although the pack appears to be charging normally, plating of metallic lithium can occur on the anode during a subfreezing charge. The plating is permanent and cannot be removed with cycling. Batteries with lithium plating are known to be more vulnerable to failure if exposed to vibration or other stressful conditions

 

[dogman dan]

Id say the thing to do in this case would be to make a warmer place to charge.

Go to the drugstore, and get a small heating pad. Put it under the battery, and a small blanket on top. Then set the thermostat on the pad, so you get above 40F but not much above 80F. Aim for room temp, more or less.


A battery that just warmed itself considerably on the discharge, could be charged in a moderately cold place. Particularly if the warmth is kept in with a blanket over the box. So if it's just slightly below freezing, it will take a loooong time for a battery that is hot to freeze.

A simple remote reading thermometer on the battery could help you know how hot the battery actually is, if you must charge outside in the cold. If the battery is not removed from the bike, a reptile heating pad built into the battery box might be a good option.

 

[Samuel]

Thanks all for your helpful responses!

It really is a doozy trying to satisfy these three things:
- charge where a battery fire would not be a problem
- where it is warm enough
- on the bike to keep things quick and easy...

One really needs a heated space separate from the house...
For now, when the weather gets colder, I will charge in a metal box inside the house

Thanks everyone for your input. I'm still listening here if anyone else has more suggestions, love hearing them.

Sam

 

[dogman dan]

Limn shouldn't be that risky to charge inside. It's lico that bursts into flames overcharged.

Commonsense though, says don't put a charger or battery in contact with the drapes of course. Just a fire resistant sheet under it on a wood table might be plenty. Something like a scrap of sheetrock rather than wood.

As long as it's 1 degree above freezing, the pack will be fine. If warm from discharging when you start charging, that internal warmth will last plenty long enough in a room that is right at freezing. Batteries hold heat a long time due to their density. Just throwing a blanket over it could be all you need. So as long as it's not 10 below freezing, you can charge outside for quite some time longer into the winter.

 

[dnmun]

if you are using a BMS or a balancing charger the risk of fire is less than the risk of fire from having a short in the wiring which is much more common and may be the source of the fires we have seen here.

if you charge with a bulk charger, with no BMS to protect from overcharging then there is the risk of fire at some point when one of the cells shorts out internally while charging or as the cells age and go out of balance enuff to drive one up to 4.3V+. with a BMS the charging is turned off when a cell shorts out and the voltage on one cell drops under the 2.5V LVC.

 

[Samuel]

OK, thanks all for your help!
Sam