E-bike battery care: charging, storage and when to replace it

The battery is the most expensive part of most e-bikes. A few habits keep it healthy for years, and a few warning signs mean you should stop using it. Makers give slightly different numbers, so where we quote one we say whose it is. Your own manual wins.

Charging

• Use the charger that came with the bike, or a replacement the maker says is approved for it. CPSC warns against "universal" chargers, because a charger can fit the plug and still be wrong for the battery (CPSC charger warning).
• Stay nearby while it charges, unplug it when it's done, and don't charge overnight or while you're out (CPSC micromobility center).
• Plug the charger straight into a wall outlet, not a power strip or extension cord (Battery Network rider guide).
• Don't charge near your exit, where a fire could block your way out, and keep the battery away from heat, direct sun and anything that burns (UL Standards and Engagement, Bosch battery safety).
• Let the battery cool after a ride and look it over for damage before you charge. Bosch gives a charging range of 0 to 40 C (32 to 104 F), ideally room temperature (Bosch battery FAQ).
• If it's very cold, let it warm up slowly on its own first, with no direct heat. Shimano says charging at 5 C or below shortens range for that charge (Shimano winter battery tips).

Storing it for more than a few weeks

Store it partly charged, indoors and dry. The makers' numbers differ a little:

• Bosch: 30 to 60% charge, at 0 to 20 C (32 to 68 F) in a dry room, in a ventilated space with a smoke detector (Bosch battery FAQ).
• Shimano: about 70%, at 10 to 20 C, topped back up to about 70% every six months, then fully charged before the first ride (Shimano winter battery tips, Shimano STEPS FAQ).
• Rad Power Bikes: about 75% for storage longer than two weeks, kept at 10 to 25 C (50 to 77 F) and checked monthly (Rad cold weather tips).

Bosch adds that storing at very low or very high charge, and high temperatures, shorten battery life (Bosch battery FAQ).

Stop using it and get it checked if

• UL Standards and Engagement lists punctures, dents, leaking, swelling, extreme heat, unusual smells, smoke and hissing or popping as warning signs, and says a damaged battery can fail hours or even days later (UL Standards and Engagement).
• The Battery Network adds a discolored case, corrosion and loose or damaged wires, and says not to ride or charge a damaged or recalled battery (Battery Network rider guide).
• Take extra care after a crash or fall, and with a bike that has been left outdoors (UL Standards and Engagement).

Never open the case. Bosch says only trained personnel may open a battery housing, and that defective batteries can't be repaired and should go back to a dealer (Bosch battery safety). CPSC says never to use a pack that was reworked by unqualified people or built from used cells (CPSC micromobility center).

Check for recalls

CPSC keeps a searchable list of recalls and safety warnings, and its micromobility page links the e-bike and scooter recalls (CPSC recalls, CPSC micromobility center). If yours is listed, follow the maker's instructions in the notice.

When it's done

Batteries are wear parts. Heavy use, heat and storing at very low or very high charge all shorten their life (Bosch battery FAQ). When it no longer gets you where you need to go, use a replacement pack the maker has approved for your bike (CPSC micromobility center). If the maker no longer sells one, see battery rebuilders and replacement pack builders for what to ask before you buy.

Never put a lithium-ion battery in the trash or curbside recycling (FDNY). Take it to a battery recycler, your bike dealer or a drop-off point. The Battery Network runs an e-bike battery program with a drop-off locator (Battery Network e-bike program). Charging trouble? See battery won't charge.

Videos

Sources

• Micromobility information center, CPSC
• Warning on universal chargers, CPSC
• Recalls and product safety warnings, CPSC
• E-bike and scooter safety tips, UL Standards and Engagement
• E-bike battery safety, a guide for riders, The Battery Network
• E-bike battery recycling program, The Battery Network
• Battery handling and safety, Bosch eBike Systems
• 12 questions about your eBike battery, Bosch eBike Systems
• Looking after your e-bike battery in winter, Shimano
• Shimano STEPS FAQ, Shimano
• Cold weather tips for your electric bike battery, Rad Power Bikes
• Lithium-ion battery safety, FDNY
• Battery Safety, Bosch eBike Systems (YouTube)

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