Charging problem
Battery Draining
Battery drains when parked? Parasitic drain, faulty alternator, or a failing battery. Diagnose before choosing a charger or replacement.
Battery drains when the vehicle is parked
If the battery goes flat when the car or van is not in use, the cause is usually one of: parasitic drain (something drawing current with the ignition off), a faulty battery that no longer holds charge, or (less often) a charging system fault. Common parasitic drains in the UK include interior or boot lights left on, aftermarket dashcams, trackers, or faulty control modules.
A normal parasitic drain is under about 50mA. To check: fully charge the battery, disconnect the negative terminal, and put a multimeter in series between the terminal and the lead; measure current with everything off and doors closed. If it is high, start pulling fuses to find the circuit. Until the drain is fixed, a battery maintainer can keep the battery topped up so the vehicle still starts.
Problem this addresses
Battery keeps draining when not in use
Recommended tool
Use our charger tools to confirm the right charger or check compatibility for your battery.
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Related charger types
Related use cases
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Recommended chargers
Smart chargers and maintainers that work with car, van, motorcycle and leisure batteries. Check AGM/EFB compatibility for Start/Stop vehicles.
CTEK
CTEK MXS 5.0 Smart Charger
Advanced 8-step charging with automatic reconditioning for dead batteries. The gold standard for battery maintenance.
Best for:
- •Vehicles parked for weeks at a time
- •Maintaining battery during winter
- •Recovering deeply discharged batteries
Prices and availability vary by supplier. Always check compatibility with your battery type.
CTEK
CTEK CS ONE Battery Charger
Compact APTO adaptive charging for cars, motorcycles, leisure and marine. One-button operation, AGM/EFB compatible.
Best for:
- •Start/Stop and AGM batteries
- •Motorcycles and leisure batteries
- •Simple one-button charging
Check compatibility with your battery type (AGM/EFB/lead-acid).
NOCO
NOCO Genius 5 UK Smart Charger
6V/12V 5A smart charger with Force Mode for dead batteries and desulfation. Works with AGM, lithium and leisure.
Best for:
- •Recovering very flat or dead batteries
- •AGM, EFB and lithium batteries
- •Cars, bikes and caravans
Ensure correct voltage (6V/12V) and battery type setting.
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Next steps
Match your battery type and use case with our charger sizing guide. For product options see our best car battery chargers UK. If the battery is beyond charging, use our Battery Fitment Finder. Not sure what’s wrong? Run battery diagnostics, or browse our battery guides.