Keeping Battery Pack Warm in the Field


10 mW
Oct 10, 2016
So, I just bought this battery:

and a IBERA large frame bag.

I want to keep the battery warm while I'm riding this winter and plan on mounting the bag into the frame, letting the two water bottle bolts go through the inside of the bag and then mount battery on the inside. I want to put a wool scarf inside the bag and one or two hand warmer packs (the ones you squeeze to activate).


Do you think that is a good idea? Will the hot packs help at all or will they damage the battery?
If you look around at the various "winterizing your bike" or "batteries in the cold" threads, there are various ideas, including handwarmers, discussed; I don't see a reason they would hurt anything since they never get too warm to hold in your hands, though you'll have to test if they actually do the job you need for the time it needs to be done.

You might get away with just the insulation, as long as the battery is kept in a warm place when not being ridden.

Regarding the bag mount, you will need to ensure the bolts are covered in a way that prevents them from poking at the battery or it's wiring, or there are various possible failures they could cause. I would recommend not using the actual water bottle bolts, and instead getting some rounded-head ones with as wide a head as possible to use instead (from a hardware store, for instance), and then using some harder dense foam padding (like mousepad type of foam) to cover the area, and then a hard covering on top of that that the screws can't bash thru as the battery is beaten onto them with every bump you hit.

If you can tie the battery down inside the bag, that will help, so it is actually tied to the frame tube and can't move with vibrations. Using straps that are themselves held down by the screws would be an easy way.
I am thinking of doing the same thing by putting a "Shark pack" inside of a custom full frame bag and using the normal water cage mounting bolts through the bag. I figure I can also store other things inside the frame bag also and the battery will also be invisible...
Does the Iberia bag have any insulation? By starting with a room temp pack, and using a padded EM3ev bag, all my winter battery performance problems vanished completely.

But to be fair, that battery that fit inside it did get pretty warm on it's own.

a bit of foam sheet or whatever in the bag may be all you need, if your battery warms itself, and starts out not frozen. But if you do need more, the hot hands is one option, though a bit pricy if you used them daily.

Starting out warm is the main thing, then have just some minimal insulation on the battery bag or box. If it's going to sit outside charging while you work,, then you'd be able to plug in a battery warmer. one of the smaller reptile tank heaters. They warm, not fry the snake.
Very few live in areas where the severe cold actually effects the ability to ride under power. You just realize that the battery will sag a little, but at anything 36v and over you won't notice a significant lack in power. If anything, calculate your trip distance you want to ride, and find a battery with enough capacity to do it, add a few amp hours to make up for the winter losses. If you can live with the added weight, I usually go the "fill as much of the center frame with batteries" approach. Then you'll never worry.

Grins Ebike calculator is a good starting point.