Charging guide
How to Charge a Car Battery
Step-by-step guide to safely charging a car battery: preparation, connections, charger settings, and when to stop.
Steps to charge a car battery safely
Park in a well-ventilated area (garage with door open or outdoors). Turn off the engine and all loads. If the battery is in the vehicle, identify positive and negative terminals (usually red and black; positive may have a + or red cover). Connect the charger’s red clip to positive and black to negative (or to a bare metal earth point). Do not reverse polarity—it can damage the charger and battery.
Set the charger to the correct mode (standard, AGM, or EFB) and voltage (12V or 6V). Switch on and allow the charger to run until it indicates full or maintain. Disconnect in the reverse order (charger off first, then negative, then positive). For batteries that are still in the vehicle, some manufacturers recommend disconnecting the negative terminal from the car before connecting the charger; check your vehicle handbook.
- Ventilation is important; charging can produce hydrogen.
- Match polarity and voltage; use the correct mode for your battery type.
- Disconnect charger before removing clips.
Related charging guides
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.