How do I charge an electric car to protect the battery?

The charge window that suits daily use, why rapid charging is for journeys rather than habit, and what cold weather actually does to range.

Difficulty: beginner
Time: 15 min
Read: 4 min

Short answer

For daily use, charge to around 80 per cent and avoid regularly sitting at very low or very high states of charge. Use slow AC charging at home as the default and save rapid charging for long journeys. Charge to 100 per cent only when you need the range.

Electric car batteries degrade slowly and predictably, and the habits that slow it down are simple. Most of them are about avoiding extremes rather than doing anything special.

Step by step

Set a daily charge limit of around 80 per cent.Most cars let you set this once in the app or the touchscreen. Sitting at a very high state of charge for long periods is the condition batteries dislike most, and 80 per cent covers ordinary use comfortably.
Charge to 100 per cent when you actually need it.Before a long journey is exactly what it is for. Try to time it so the car is used soon after reaching full rather than standing at 100 per cent for days.
Avoid regularly running very low.Deep discharge is as unhelpful as a permanently full battery. Treating around 20 per cent as the normal bottom of the range is a good habit.
Use slow AC charging as the default.Home or workplace AC charging is gentler on the battery than repeated rapid DC charging, and it is far cheaper. It is also the easiest habit to build because the car charges while you sleep.
Save rapid charging for journeys.Occasional rapid charging is entirely fine and it is what the network exists for. Using it as the everyday method, when a home charger is available, adds heat and cycles for no benefit.
Precondition the battery in cold weather.Most cars will warm the battery on the way to a rapid charger if you navigate to it in the car's own system. A cold battery accepts charge far more slowly, which is why winter rapid charging can be frustrating.
Precondition the cabin while plugged in.Heating the car on mains power rather than on the battery preserves range and means you set off warm. It is one of the genuine advantages of an electric car in winter.
Expect less range in winter and plan for it.Cold reduces both battery performance and range because heating the cabin costs energy. It is normal, it is temporary, and it is not battery degradation.
Use the heated seats and wheel in preference to the cabin heater.Heating a person uses far less energy than heating the air in the car. It makes a measurable difference to winter range.
Leave it plugged in if you are away for a while.Set the limit to a middling figure and leave it connected, so the car can maintain itself rather than slowly discharging in a car park.
Drive smoothly and use regeneration.Anticipating and lifting off early recovers energy that braking simply wastes as heat. It is the single biggest driving influence on range.

Tips

Rapid charging is fastest in the middle of the range. Charging from 10 to 60 per cent is much quicker than the last stretch to full, so on a long trip two short stops often beat one long one.
Check whether your car's stated battery capacity is usable or gross — manufacturers already reserve a buffer at both ends.
Battery health warranties are typically long and cover capacity below a stated threshold. Check what yours actually says.

Common mistakes

Charging to 100 per cent every night out of habit — There is no benefit if the range is not needed, and sitting at a very high state of charge for long periods is one of the conditions that accelerates degradation.
Rapid charging daily when a home charger is available — Repeated high-power DC charging generates heat and adds cycles. It is fine when travelling and unnecessary as a routine.

If it doesn't work

Range much lower than expected in winter

Cause: Cold battery and cabin heating — Fix: Precondition while plugged in, use heated seats rather than the cabin heater, and expect it to recover in spring. This is normal, not a fault.

Rapid charger delivering far below its rated speed

Cause: Cold battery, a high state of charge, or the charger being shared — Fix: Precondition on the way, and arrive with a lower state of charge. Rapid charging slows sharply above about 80 per cent by design.

Car will not charge on a particular unit

Cause: Handshake failure or an account problem — Fix: Unplug, restart the session and try a different bay. Carry more than one network account or use a contactless-capable charger.

Battery percentage drops while parked

Cause: Normal standby drain, or preconditioning running — Fix: Small losses are expected. Large losses usually mean a setting such as remote climate or sentry-style monitoring is active.

Questions people ask

Should I charge to 100 per cent?

Only when you need the range. Setting a daily limit around 80 per cent and charging fully before longer journeys is the pattern most manufacturers themselves recommend.

Does rapid charging damage the battery?

Occasional rapid charging is expected and fine. Using it as the sole method every day adds heat and cycles that slow AC charging avoids, so it is a question of proportion rather than a prohibition.

Why does my range drop so much in winter?

Cold reduces the battery's performance and heating the cabin uses energy that would otherwise move the car. Preconditioning while plugged in and using heated seats recovers a good part of it.