Your battery is the most expensive single part of your bike, and it's the one you can quietly ruin without noticing for two years.
The good news: looking after it is mostly about avoiding a few specific things, not about doing anything clever.
The short version
- Don't leave it sitting at 100% for weeks. Lithium-ion ages fastest when it's held full.
- Don't leave it flat, either. Deep discharge sitting for months is the other way to kill one.
- For storage longer than a few weeks, park it around half charge and top it back up every couple of months.
- Heat is the real enemy. A hot car in summer does more damage than a hundred charge cycles.
- Don't charge it below freezing. Charging a cold lithium battery causes permanent damage in a way discharging it doesn't.
- Use the charger it came with. Cheap replacement chargers are a genuine fire risk, not just a warranty problem.
That's most of it. Everything below is the why, plus the range question.
Charging, done sensibly
You don't need to be precious about this. Charge it, ride it, repeat.
Two habits are worth having, though. If you know you're only doing a short ride tomorrow, there's no need to charge to full — partial charges are completely fine for lithium-ion and slightly kinder than always topping to 100%. And if your bike or charger has an 80% or 90% limit setting, using it for everyday riding and saving the full charge for long rides is a free win.
The thing that actually matters more than any of that: charge it where a fire wouldn't be a catastrophe. Hard surface, not on carpet or a sofa, not blocking the only exit from a room, and ideally not overnight while everyone's asleep. E-bike battery fires are rare but they're fast and extremely hard to put out.
Look for UL 2849 (whole-bike) or UL 2271 (battery) certification when you're buying. Some cities now require it. It's the single clearest signal that the pack has been through real safety testing.
Why you never get the range on the box
Because that number was measured by a light rider, on flat ground, in mild weather, in the lowest assist setting, with no wind and no stopping.
Here's what actually eats range:
- Assist level. The biggest factor by a wide margin. Riding in max assist can roughly halve what you'd get in a middle setting. Nothing else on this list comes close.
- Cold. Expect meaningful losses below about 5°C / 40°F — often 20-30%. The capacity mostly comes back when the pack warms up; it isn't gone forever.
- Total weight. You, the bike, the groceries, the kid on the back.
- Hills. Obviously. But also: what goes up doesn't give it back.
- Wind. A headwind is a hill that never ends.
- Stop-start riding. Every acceleration from zero is expensive. City riding costs more than the same distance on an open road.
- Tire pressure. Soft tires cost you range on every single rotation. It's the cheapest fix on this list — see the pre-ride checklist.
Estimating range you can trust
Take the manufacturer's number, assume it was the best case, and plan on 60-70% of it for normal riding. In winter, plan on half.
If you're going somewhere unfamiliar, ride the outbound leg in a lower assist than feels necessary. Battery you didn't use is easy to spend on the way home. Battery you already spent is a long walk.
Cold weather specifically
Two separate rules that people mix up:
Riding in the cold is fine. The battery just gives you less until it warms up.
Charging in the cold is not. Below freezing, charging a lithium-ion pack can cause lithium plating inside the cells, which is permanent capacity loss and a safety issue. If the bike's been out in the cold, bring the battery inside and let it come up to room temperature before plugging it in. An hour is usually plenty.
Store the battery indoors over winter, at about half charge, and top it up every couple of months. There's more winter-specific advice in riding in rain and cold.
Water, washing, and connectors
Most e-bike batteries handle rain fine — they're designed for it. What they don't handle is pressure.
Never pressure-wash an e-bike. Never aim a hose at the battery mount, the motor, or the display connectors. Water forced past a seal sits there and corrodes contacts, and corroded contacts produce intermittent faults that are miserable to diagnose.
Wipe the contacts dry if they've been soaked, and keep the mount free of grit.
Signs your battery is on the way out
Batteries lose capacity gradually. Most stay useful for several hundred full cycles, which for most riders is years.
Worth paying attention to:
- Range dropping noticeably compared to the same ride a year ago
- The gauge falling off a cliff at the end rather than declining steadily
- The pack getting hot in normal use
- Physical swelling, or any smell — stop using it immediately, don't charge it, and get advice on safe disposal
Batteries are not household waste. Bike shops and municipal hazardous-waste programmes take them; the manufacturer often does too.
The genuinely useful habit
If you take one thing from this: stop leaving it plugged in after it's full, and stop storing it empty.
Everything else is optimisation. Those two are the ones that decide whether you're buying a replacement pack in three years or in eight.