How to store an e-bike battery in winter

It’s November, the evenings are dark and the bike is going in the garage until March. What you do with the battery in the next 15 minutes decides how it starts in spring. This guide covers the charge level, where to keep the battery, and how to charge it safely when you bring it back out.

What charge should an e-bike battery be at for winter storage?

Store an e-bike battery at the charge level its maker gives: 30 to 60% for Bosch, about 70% for Shimano STEPS. Both keep the battery away from full and empty, which Bosch says shortens battery life when a pack sits for a long time.

Bosch and Shimano describe temperature differently. Bosch gives an ideal range. Shimano gives the limits the battery is rated for, and the “-A” models (the versions built to the European battery standard EN 50604-1, such as the BT-E8036-A) have a much narrower range than the rest. So check the full model code on your label, letters included.

So “store it at 50%” is right for a Bosch pack and a little low for a Shimano one. For any other brand (Yamaha, Brose, Bafang, Specialized and so on), use the number in your own manual. If the manual doesn’t give one, email the bike maker. Don’t average two brands’ advice.

Most displays show bars, not percentages. On a Bosch battery, 30 to 60% is 2 to 3 lit bars on the charge indicator, according to Tern’s Bosch battery guide. You don’t need an exact number. Anywhere inside the range is fine. That reading is the battery’s state of charge, an estimate of how full it is right now. It tells you nothing about its state of health, which is how much capacity the pack has kept since it was new.

If the battery is too full, ride it down on your last few trips of the season. If it’s too low, charge it with the original charger until it reaches the range, then unplug it. Never leave the battery on the charger for the winter. Tern says so directly for Bosch packs, and every safety agency cited here tells you to unplug once charging is done.

Can I leave an e-bike battery in a cold garage?

You can leave an e-bike battery in a garage only if the garage stays dry and inside the battery’s storage range. For Bosch that’s 0 to 20 °C (32 to 68 °F). A garage that freezes on January nights is outside it, so bring the battery indoors. Shimano STEPS batteries are rated for colder storage, down to −20 °C (−4 °F), or −10 °C (14 °F) for “-A” models. But they still need 0 to 40 °C (32 to 104 °F) to charge.

Two kinds of advice pull in different directions here. Battery makers want the pack cool but not freezing. Fire-safety agencies want it away from where people sleep. The UK Department for Transport suggests a shed or garage separate from your home where possible, but also says to avoid very hot, cold or damp places. Your garage passes both tests only if it stays dry and above freezing.

Not sure how cold your garage gets? Put a min/max thermometer where the battery would sit and leave it for a week. The overnight low is the number that matters, not the reading on a mild afternoon. Then use this table:

Indoors, pick a room with a working smoke alarm, away from heaters and radiators. Keep the battery out of hallways and off the stairs you’d use to get out in a fire, and out of shared corridors in a block of flats or apartments. That’s the UK government’s advice, and Bosch says the same: a well-ventilated room with a smoke detector, away from heat sources and flammable materials.

In Switzerland, the Swiss Fire Prevention Advisory Service (BFB) gives the same direction: keep batteries away from heat and direct sun, and disconnect them from the device during long breaks. Elsewhere in Europe, from Germany and Austria to the Netherlands, the rule is the same as in the US and UK: follow the manual for your exact battery.

How to store an e-bike battery for winter, step by step

Storing the battery takes about 15 minutes if it’s already near the right charge, plus charging time if it isn’t. You need the battery’s manual and its original charger. No tools, and you never open the battery case.

The 4 to 6 week check is our suggestion, not a manufacturer rule. Every lithium-ion battery loses a little charge on the shelf through self-discharge, and some bikes draw a small current while the battery stays fitted. The check takes a minute, and it catches a battery that’s draining faster than it should long before it gets close to empty.

Is it safe to charge the battery after winter storage?

Yes, if you let the battery warm up first and stay with it while it charges. The Swiss BFB singles out the first charge after months of storage as especially risky, because a battery that has drained very deep has a higher fire risk when it’s recharged. That’s the main reason to store the battery part-charged and check it through the winter.

Before that first charge:

1. Let it warm up on its own. Bring the battery into a room at normal temperature and give it time. A battery straight from a cold garage stays colder inside than the air around it for a while. Never use a radiator, oven, hair dryer or heater to speed it up: BFB lists external heating as one of the ways lithium-ion batteries catch fire.
2. Charge somewhere safe. Use a hard, non-flammable surface with nothing that burns nearby, in a room with a smoke alarm. BFB’s general advice is to charge at 10 to 30 °C (50 to 86 °F), which sits inside the Bosch and Shimano charging range.
3. Stay home and awake. The UK Department for Transport, the US Consumer Product Safety Commission (CPSC) and BFB all say not to charge while you’re asleep or out. Unplug the charger when it’s done.
4. Use the original charger, or a replacement the bike maker approves. The CPSC warns against “universal” e-bike chargers. A plug that fits doesn’t prove the charger is right for your battery.

If the battery won’t charge, shows an error or reads zero after the winter, stop trying and don’t look for ways around the battery management system. It may be blocking the charge on purpose. Take the battery to your dealer for a test. Bosch dealers, for example, can measure a pack’s remaining capacity with Bosch’s CapacityTester.

To plan that first charge, put your charger’s amp rating, the battery voltage and its capacity into our battery charging time calculator. If it says 4 hours, start in the morning, not at bedtime.

Riding in winter instead of storing the bike

If you keep riding through the winter, keep the battery indoors between rides and fit it just before you set off. Bosch recommends this below 0 °C (32 °F): bring the battery into a heated room and let it reach room temperature before the ride. A cold battery also gives less range until it warms up.

Our guide to how far an e-bike can go explains how much range you lose near freezing. The e-bike range calculator has a temperature setting, so you can check your usual route at winter temperatures before you rely on it.

Mistakes that shorten battery life over winter

• Storing the battery full or empty. Bosch and Shimano both set a middle level for a reason.
• Leaving it on the charger “to keep it topped up.” That’s a fire risk, and the battery’s electronics don’t turn it into a storage plan.
• Charging it straight from a freezing garage, or warming it on a radiator to save time.
• Forgetting it until April. A battery that drains to empty over 5 months is the riskiest one to recharge.
• Keeping it in the hallway because it’s warm. That’s your way out in a fire.
• Buying a cheap universal charger because the original went missing. Order the right one from the bike maker or your dealer.

Where this advice comes from

Every number on this page comes from the battery makers (Bosch and Shimano), Tern’s Bosch support guide and three public safety bodies: the UK Department for Transport, the US CPSC and Switzerland’s BFB. We checked them all on October 31, 2026. We did not test batteries for this guide. The garage table, the reminder schedule and the temperature chart are our own summary of those sources. No brand paid for this page, and it has no affiliate links. We’ll recheck the sources by January 29, 2027, or sooner if a manual changes.