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lithium battery performance vs tempreture?

Posted: Jan 23 2020 12:19pm
by jimmyhackers
my batteries sit/charge in my garage whcih is usually the same as outside tempreture (UK midlands)

i noticed as i charged up in my mates warm house (20degrees c ish) that the batteries were more peppy (torquey) on the way home. ... erformance
ive read this atricle which is informative but not very precise with its estimations as to losses

im just wondering how much percentage in AH and longevity and (other stuff) i am loosing out on by keeping my batteries in the cold garage?

i am contemplating using the thermal output of my pc PSU that i use to power my charger as a heater of sorts. enclosing the shelf space that my batteries sit and charge on/in with a curtain.....

just wondering if its worth the effort?

Re: lithium battery performance vs tempreture?

Posted: Jan 23 2020 1:17pm
by goatman
ive noticed im losing about 10 percent maybe more near freezing, my power tools at minus 10c suffer greatly and minus 15 to 20c they don't work period

Re: lithium battery performance vs tempreture?

Posted: Jan 23 2020 4:51pm
by amberwolf

Re: lithium battery performance vs tempreture?

Posted: Jan 24 2020 11:58am
by jimmyhackers
thanks for that link.....quite a few far more informative posts on this site than i expected. ive read through a fair few and will summarise several things that i understand to be the case.

a hotter battery is better as it will lower the internal resistance. some people even preheat theres to 45 degrees C and above. this is safe as long as under use it doesnt heat it beyond safe temps (no one seems to know what a safe max temp is).

keeping a battery at 45c will degrade its cycle life/capacity more than at 25c but less than at 5c

20ish degreesC seems to be a reasonable/acheavable sweet spot. with diminishing gains going higher than that.

a cold battery will degreade quicker than a warm battery but not as quickly as abusing it with higher charge/discharge rates.

looks like i should be keeping my batteries at room temp rather than cold garage temp :s

Re: lithium battery performance vs tempreture?

Posted: Jan 25 2020 7:53am
by dogman dan
I don't have any real good numbers, but I found on my commute, that if I rode home under 50F temp, I might not make it all the way with the 700wh pings lifepo4 I was using. Id get only about 500wh ( estimated), even though charged full, which was about what I needed to get up that long hill to home. .

Other types perform about the same, I never noticed much difference between chemistry, all would perform sluggish in winter, when my garage would get down to around 40f. If your battery freezes, thaw it before use. Then next spring, the first 80 degree ride home,,, Wow what an improvement even over 60f the month before. With enough battery, it never mattered too much above 50f. I tended to have enough range for my general use needs, unless I had a lot of wind. So I never had to worry till it got close to 50f. Riding to work, downhill all the way, I could always make it, even when it was very very cold.

Re the cold garage,,, I never let a battery in my garage anymore. My storage is an old kitchen stove, but in winter I put them in an old refrigerator, with a reptile heater in it. Keeps them un froze, and warm enough to use.

Re: lithium battery performance vs tempreture?

Posted: Jan 25 2020 2:20pm
by FlyingFinn
I have a 78 cell 18650 pack and I’ve been riding in temps as low as -15C. Key is to never let the battery cool down. Take the battery from inside warmth and use it all the time. Don’t stop or otherwise you might get stranded. By using the battery all the time I get only a loss of power around 5% in temp ranges from 0 to -15C.

Re: lithium battery performance vs tempreture?

Posted: Jan 27 2020 8:12am
by dogman dan
Yes, in general a battery that leaves the house warm performs great through the ride. Many have enough IR to warm them selves, ( especially if near froze) but then it costs you range. Start out above 50f is all you really need.

Pretty warm winter here, but keeping a snake heater in my old fridge storage really worked great. I don't ride in very much cold, but having it stored at 60F vs 35 made it a lot better to ride in 50F afternoons. I did one test ride where I took a battery out almost froze, and it sagged like mad till it warmed itself up.