Shorai lithium battery cold charging how is it done?

[Sugarkryptonite]

Hi guys

I've been reading more and more about DIY LiFePo4 batteries, and how charging them under cold temperatures (say under -5c) can actually damage the cells severely.

I have a LiFePo4 powersports battery from a well known brand called Shorai that I've used for many years and in many different temperatures. They speak often on their website about needing to "warm up" the batteries before starting your ATV, motorcycle or snowmobile (loading a big draw on the battery), by first turning the ignition on and turning lots of accessories on such as lights, heated grips, etc. But, they never speak about cold charging. So how do they get past this dangerous cold charging problem?

I've opened my own Shorai battery and there isn't much inside. The main battery power leads do not even go through the BMS directly like you see in other high current BMS systems as I'm guessing because the high power a start motor requires, a regular BMS can't handle the current. It seems like it's just a regular balancing BMS with a few small wires coming out of it, so there's no way it can cut the power internally if it's too cold out.

I've used the battery for years in cold temperatures, and haven't had any problems with charging so how do they do it safely without damaging their batteries at say -20c? Is it because after using it to start the vehicle it is warm enough to be charged?

I'm looking into building my own LiFePo4 pack for my camper trying to learn as much as I can, but that has me stumped.

 

[upnorthandpersonal]

To charge a LiFePO4 battery in cold temperatures requires a higher voltage than usual, because the internal resistance will prevent any meaningful current from flowing. I demonstrated that here:

It could be they just ignore it altogether... We've seen plenty of batteries like that without low temp charging protection.

For your own battery, I recommend some small heating pads and don't charge below even +5 C.

 

[Sugarkryptonite]

To charge a LiFePO4 battery in cold temperatures requires a higher voltage than usual, because the internal resistance will prevent any meaningful current from flowing. I demonstrated that here:

It could be they just ignore it altogether... We've seen plenty of batteries like that without low temp charging protection.

For your own battery, I recommend some small heating pads and don't charge below even +5 C.

Thanks for your reply. Interesting test you did.

In my own 400Ah pack in my van yes I installed a DIY heating pad under the batteries in an insulated box with temperature control.