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For temperatures between 0 F and 32 F, to what extent, if at all, should I insulate electric bicycle batteries? I have read that they do not like temperature extremes. Should I wrap a battery in 1 layer of bubble wrap during weather like this? Multiple layers? What about other types of insulation? What amount of insulation will cause the battery to heat itself to optimum temperatures without overheating? I realize that this depends on the temperature range, speed, and reliance on the battery when riding, so some sort of algorithm that takes all of these factors into account would be ideal, or at least some safe minimum amount, assuming the temperature is below freezing.

For clarification: I am talking about when the bike is being used outside during the winter. I intend to store it inside all the time when it is not in use.

  • ebike batteries already have a reasonable amount of built in insulation. There is likely 2 layers of plastic wrap (one around each cell, and one to form a pack) and finally a plastic outer casing. Assuming the battery starts warm (stored inside), then the current draw from the motor should keep it warm in use. – Andy P Jun 5 '19 at 13:09
  • That would be the case if this were a single battery, but I should clarify that my bike has a dual battery setup, and the batteries alternate every 5 minutes, so they will cool off during their 5 minute break if not insulated. I've decided to make a neoprene cover for the triangle on my bike that will hopefully contain the heat from both batteries, confining it to the inside of the triangle, so we'll see how that goes. – kloddant Dec 5 '19 at 23:29
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General advice is to store the battery at room temperature and install it in on the bike just before the ride. If the ride is under about 30 minutes the battery will stay warm enough not to be badly affected by the cold. For longer rides, a layer or two of insulation would not hurt (as long as it is not so much the battery over heats). Bubble wrap would be a great way to experiment and work out how much was needed and if it made a difference for your rides, but I would look at something a bit more durable in the form of an insulated zip up or Velcro cover for a long term solution.

When charging lithium batteries in cold climates you need to be careful. Never charge Lithium below about +5C. Ideally bring them up to room temperature before charging. Note this is the internal temperature of the battery - don't bring a battery that's been on a bike at -10C inside and start charging after a few minutes when the case feels warm, I would give it a couple of hours.

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  • Thanks for the advice! I've added the clarification above. It's good to know that bit about leaving the battery a couple hours to cool off - I would have probably given it just 1 hour otherwise, but a couple sounds much more conservative. – kloddant Jun 4 '19 at 22:31
  • Great answer - want to add anything about condensation too ? – Criggie Jun 5 '19 at 1:08
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    Discharging will warm the battery to some extent, so it's best to bring it indoors immediately after riding, rather than letting it cool down internally. This will give the warming a head start. – Chris H Jun 5 '19 at 6:18
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    @ChrisH Charging will also heat up the battery. So it's always a good idea to bring it indoors. – Carel Jun 5 '19 at 8:06
  • @Carel it certainly will, but my comment was in response to the 2nd paragraph in the answer: (don't start) to charge when cold. – Chris H Jun 5 '19 at 8:22

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