Guide
Battery drains while parked: normal or a fault?
Every battery loses a little charge standing still. Losing a lot overnight is not normal. Here is how to tell the difference.
Quick answer
A healthy battery loses only a few percent a month when switched off, a little more in heat. If yours drops noticeably overnight, something is drawing power: an alarm, GPS tracker, accessory, wiring fault, faulty BMS or a weak cell. Switch fully off, remove add-ons, then get it tested.
What is normal
Battery University puts the self-discharge of a lithium-ion cell at about 1 to 2 % a month after the first day, plus about 3 % a month for the protection circuit. Lead-acid loses about 5 % a month. Heat speeds this up: the rate roughly doubles with every 10 degrees. So a few percent over a week or two is normal; 10 % or more overnight is not.
Common causes of fast drain
- An anti-theft alarm or immobiliser that stays awake.
- A GPS tracker or connected (IoT) unit that keeps talking to the server while parked.
- Extra accessories such as a USB charger or lights wired straight to the battery.
- Faulty wiring, a sticking key switch or water in the harness after the monsoon.
- A faulty BMS, or a weak cell that empties itself faster than the others.
Lead-acid and lithium behave differently
A lead-acid battery left partly empty for days starts to lose capacity for good, so keep it charged. A lithium pack that drains to the bottom triggers the BMS cut-off, and if it then sits empty for weeks it may not wake up again. Either way, a drain problem shortens battery life.
What to do
- Note the charge when you park and again the next morning, with the key off.
- Switch the scooter fully off and use the battery isolator switch if it has one.
- If you added an alarm, tracker or USB charger, ask the fitter to disconnect it and test again.
- If it still drains, bring it in. We measure the current drawn with the scooter off and test each cell group.
Questions
Frequently asked questions
How much charge does an electric scooter lose when not in use?
A healthy lithium pack switched off typically loses only a few percent a month, a little more in heat. Big overnight drops point to a fault.
Why does my scooter battery go down overnight?
Usually something stays switched on: an alarm, a tracker, an accessory or a wiring fault. A weak cell or faulty BMS can also cause it.
Is it bad to leave a lead-acid scooter battery half empty?
Yes. Lead-acid should be kept charged; days at a low charge cause lasting capacity loss.
How should I park my scooter during Diwali holidays?
Switch it off in a cool, dry place. Leave lithium at about half charge and lead-acid fully charged; see our battery care guide for longer breaks.
Losing charge for no reason?
Bring the scooter to Simada Naka. We find the drain for free, any brand, and tell you the cost before any repair.