A smart charger doesn't just push current in. It follows stages for your battery type.
A modern smart charger changes how it charges as the battery fills. Using the right profile for your battery makes a big difference to how long it lasts.
1. The stages
- Bulk: the charger gives its full current until the battery reaches a set voltage.
- Absorption: it holds that voltage and the current slowly drops as the battery fills.
- Float: it drops to a lower voltage to keep a lead-acid battery topped up. Many lithium profiles skip float or use a low one.
2. Battery types need different settings
| Type | Typical absorption (12V) |
|---|---|
| Flooded lead-acid | about 14.4 to 14.8V |
| AGM | about 14.4 to 14.7V |
| LiFePO4 | about 14.2 to 14.6V |
These are only typical figures. Always use the battery maker's numbers.
3. Charge current
A higher current charges faster but adds heat. Many batteries list a maximum charge current. Work out the C-rate with the Battery C-Rate Calculator.
4. Temperature
- Lead-acid needs a higher voltage when cold and lower when hot. Many chargers have a temperature sensor.
- Lithium batteries must not be charged below their low temperature limit, often around 0°C. Their BMS may block charging.
5. Safety
- Charge lead-acid batteries with ventilation. They can give off hydrogen.
- Use a charger designed for your battery type.
- A charger plugged into 240V AC must be in good condition. Damaged leads or cases need repair by a qualified person.
6. Quick summary
- Bulk, absorption, float.
- Match the profile to the battery type.
- Watch current limits and temperature.
240V AC mains can kill. In Australia, work on household mains wiring must be carried out by a licensed electrician. Low-voltage DC can still deliver very high current, so treat batteries with respect.
