Battery care in the cold

AF7JA

100 W
Joined
Jun 9, 2015
Messages
167
Location
South-West Kansas
I am a teacher. As such my bike sits outside all day. The first time I really noticed the impact of sitting outside all day was a day it never got above 20f (-6.67c). On the ride home the battery read much lower than usual.

Since then, if it is not projected to get above freezing all day (which is a lot of days) I have been removing my battery in the morning and bringing it into my classroom. Are there any meaningful guidelines for cold weather battery care?

I did look at this thread,https://endless-sphere.com/forums/viewtopic.php?f=14&t=74606&p=1127507&hilit=cold+battery#p1127507 they seem to be saying t take it inside at about 15f (-9.5c).
 
20-15F is where I bring Lipoly, Li-ion indoors so they can start commuting at room temperature. Begin with room temperature and working under load they can usually maintain a reasonable internal temperature.

Main safety thing is to not charge a cold lithium battery. Reason being that once it’s topped off while cold and then brought indoors where temperatures increase the voltages may also increase proportionally.

This means cells may creep up above max high voltage ratings under those circumstances.

Yes, there's a lot more voltage sag using cold cells but the heat normally generated by that amount of sag doesn't appear to be as damaging to the cells as it would be in warm temperatures. In other words, cold cells tolerate lower operating voltages better than room temperature cells. For that reason, I sometimes lower my controller LVC in order to pull a little more capacity from a "cold" pack when I'm on the fringe of capacity (Ah/Wh) range.
 
Voltage - capacity "sag" becomes noticeable near 50ºF.

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Optimal charge\discharge voltages are typically rated as ~70ºF.
See - Batteries vs Cold
 
I've also heard of people using low power (~2-5w) heating pads just before setting off.

https://www.sparkfun.com/products/11289
 
You'd best listen to my advice-I drive my bike in up to knee deep snow in -25 to -30C weather (Winnipeg) :lol:
You've got a few reasonable options. First one: Get some insulation sheet (Black stuff, foamy) Wrap two layers around your battery and then using E-tape make a complete pass over all the foam compressing it lightly. Cap off front and rear. Your batteries will keep above 0c for over 2 hours with this setup. You can then put the battery in a cardboard enclosure and E-tape over the enclosure. More insulation. Adds about 45 minutes to an hour before you hit 0. Then you can look into pack heating;
http://www.ebay.ca/itm/48V-Heated-Grip-Kit-Pads-Handlebars-for-Electric-Scooter-Bike-E-BIKE-2X10W-/171483508409?hash=item27ed36aeb9:g:DyMAAOSwxH1ULU7h&vxp=mtr

Just open up your pack and stick both of these back to back (TAPE OVER THE EXPOSED BRASS!) And splice the switch and ground to your controller. Leave the heater on while you ride-Heater+insulation will keep the pack above 10C indefinitely.
 
does it damage the battery if i start riding when the battery temp is, lets say -15c? i like to go fishing and my bike is left outside for a long time
 
Joppo said:
does it damage the battery if i start riding when the battery temp is, lets say -15c? i like to go fishing and my bike is left outside for a long time
Most batteries are more performance handicapped, rather than damaged, by operation when cold.
See - Batteries vs Cold
But, cold batteries suffer much deeper voltage sag ... possibly(?) causing excessive deterioration.
and
Most all manufacturers warn against charging when Lithium batteries are cold.
 
Joppo said:
does it damage the battery if i start riding when the battery temp is, lets say -15c? i like to go fishing and my bike is left outside for a long time

Open the pack and slap in one of these http://goo.gl/sA811w then add some foam to the outside and tape.
20W is almost no drain compared to a 500Wh pack. Go fishing for 3 hours, that's 60Wh drained (on 48v that's 1.2Ah gone) and they'll keep your battery warm. More than worth the price.
 
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