How do freezing conditions affect voltage output of battery?

[elemenohpee]

I'm assuming that freezing temperatures will affect the performance characteristics of a Lithium-Ion battery.

What I'm trying to accomplish is making these:

http://samjacoby.com/projects/ir-led-throwies/

And then freezing them inside spheres of ice.

How will operating in freezing conditions change the voltage output of the battery?

 

[dnmun]

when the lithium ions migrate to the carbon electrode, they will precipitate out of the electrolyte away from the electrode and form lithium dendrites on the surface but disconnected electrically from the electrode itself. so if you have to do this to the battery for some reason then keep the discharge rate as low as possible to keep it alive as long as possible.

 

[neptronix]

Internal resistance will be cut dramatically.
You could still do this, it's just that you need to overrate the battery performance by a factor of ~5x.

I did some testing long ago here:

http://endless-sphere.com/forums/viewtopic.php?f=14&t=35668

 

[dmwahl]

Are you planning on using the 2032 batteries? If you're using a larger li-ion battery, the led current will be pretty minimal load and I suspect you'll get pretty good performance. Although definitely worse than room temp you may not notice the difference.

 

[bowlofsalad]

https://www.endless-sphere.com/forums/download/file.php?id=170627

This graph illustrates what happens to the discharge curve of a single NCR18650PF cell. This isn't a parallel for how all chemical batteries will react to various temperatures, some will react much more poorly or better than others. The point is you will certainly see a negative impact on your cells performance.

I can't tell you if what you are trying to achieve will work out, but you'll learn all you need to learn simply through doing what you plan to do, seems like a pretty easy test to perform. You could probably set your cells up in a 1s2p configuration if you encounter any capacity issues.

 

[spinningmagnets]

Freezing temps are bad for all types of batteries. I recall reading about a car that had been converted to electric in Canada, and clearly the battery could not be removed from the vehicle. Although the EV was kept in a garage that was kept above freezing, taking this car to work or the store meant parking outside. In the area where this person lived, his work and also the local stores provided electrical outlet right next to each parking spot. This was to allow employees/customers to plug in an "engine warmer", since engines could get so cold that they had a very difficult time starting. Half the problem was trying to turn over a cold engine, the other half was trying to do it with a cold battery.

This person had the EV battery heavily insulated, and the build included a very thin heating element underneath the battery, which kept the pack at room temperature (70F/21C?). The battery pack would easily make the round trip to work/store (so he only needed an expensive EV pack charger at home), but when he arrived anywhere he plugged in the battery heater.

When I was a memeber of a web based car forum, one member lived in Alaska. He had an electric external engine block heater, and oil-pan heater, a radiator heater, and also the battery was inside an insulative cover with a similar battery warmer underneath it.

 

[neptronix]

You can mitigate battery performance issues in the cold by three ways:

1) Massively overspec the C rate of the battery. I do this with my bikes. My only below-freezing ride i willingly did ( 18F outside in Colorado Springs, CO ) was no problem. I was running a 20C rated battery at like 2C peak from the controller. Voltage sag was minimal and capacity delivery was excellent. Normally at full tilt, this 36v battery would sag 0.5 volts.. at 18F, it'd sag about 2.5 volts... so i was seeing 5 times the voltage drop.
If you had a battery that sagged 2 volts under 70f discharge, you'd see it sagging 10 volts in the same condition.. in that case, you'd be hitting your LVC very quickly.

2) Battery heater.

3) Battery insulation - this works if your battery manages to create some heat on it's own during discharge. Wouldn't work well on the setup mentioned above though because a 20C battery on a 2C load really doesn't make any heat.