An e-bike battery can cost several hundred dollars or euros to replace, so winter is a good time to give it a little extra attention.
Cold weather itself isn't necessarily the problem. Your battery may simply give you less range on a chilly ride. The bigger mistake happens when you bring a cold battery inside and put it straight on the charger.
Charging a lithium-ion battery when it's extremely cold isn't a good idea either. UL Solutions lists charging in extreme conditions, both hot and cold, among the factors that can contribute to lithium-ion battery failures and fires.
The good news is that avoiding the problem is simple.
Let a cold battery warm up first
If you've just come home from a cold ride, don't plug the battery in immediately.
Bring the battery indoors and let it warm up to room temperature first. The exact temperature range varies between batteries, so it's worth checking your manufacturer's instructions. Bosch, for example, recommends charging its e-bike batteries at room temperature.
This is especially important if the battery has been sitting outside or in an unheated shed for hours.
And when you do charge it, use the charger made for your e-bike. The US Consumer Product Safety Commission warns against using incompatible or universal chargers with micromobility batteries.
Don't leave the battery in a cold shed
If you're putting your e-bike away for the winter, the battery doesn't necessarily need to stay with it.
A cold, unheated shed can expose the battery to temperatures outside its recommended storage range. Instead, if your bike has a removable battery, take it indoors and keep it somewhere dry and away from direct sunlight.
You also don't need to leave it fully charged for months. It’s recommended to charge batteries at around 30% to 60% charge.
If you're not riding for several weeks, that's a much better state for the battery than leaving it sitting at 100%.
A shorter range in winter is normal
If you keep cycling through the colder months, you may notice that your battery doesn't take you quite as far.
That's normal. Cold temperatures reduce battery performance, so the same battery can deliver less range than it does on a warmer day. Bosch eBike Systems notes that as temperatures fall, a battery's performance is temporarily reduced, which can mean less range in winter.
That doesn't automatically mean your battery is damaged. Its performance should improve again as it warms up.
What you shouldn't ignore are physical warning signs. If a battery is swollen, cracked, leaking, badly damaged or unusually hot, don't charge it or continue using it. The National Fire Protection Association recommends stopping use when a battery shows signs of damage or other unusual changes.
So when the temperature drops, you don't need to put your e-bike away.
Just remember the three simple rules: keep the battery out of the cold when you're storing it, let it warm up (around room temperature) before charging, and don't leave it sitting at full charge for months. A little care now can help your battery last longer, and keeps an avoidable charging problem from becoming a much bigger one.