Will an RV’s built-in converter charge a lithium house battery properly?

Direct answer: Only if the converter can deliver a lithium-suitable charge voltage. Many older RV converters were designed for lead-acid and hold around 13.2 to 13.6V most of the time, which charges LiFePO4 slowly and may never reach full. Check the converter manual for a lithium mode or adjustable voltage; if there is none, replace it with a lithium-capable converter or add a separate lithium charger.

What LiFePO4 needs. The 12V 100Ah page lists 14.6V maximum charge, 10V cut-off, a 14.6V 20A charger and 50A or 100A maximum continuous charge depending on version. The 12V 200Ah lists 14.6V maximum and 100A to 200A charge versions. The 12V 100Ah Ultra lists 14.6V and 100A. Chargers usually stop a little below the maximum, often around 14.2 to 14.4V; ask Redway for its recommended setting.

How converters differ. Some converters have a fixed output; some have boost, normal and storage modes based on lead-acid; newer models have a lithium setting. Desulphation or equalisation modes for lead-acid should not be used on lithium.

How to check yours. Read the model and manual, then measure voltage at the battery terminals while charging from a part-charged state. If it never rises above about 13.6V, the battery will charge slowly and the BMS may rarely balance cells. Also check that the converter’s current suits the battery and wiring.

Temperature. These batteries list charging from 0°C. Below freezing, charging must stop unless the battery has self-heating; the 12V 100Ah lists self-heating, the 200Ah lists it as an option. See cold-weather charging.

Other charging sources. The vehicle alternator usually needs a DC-DC charger with a lithium profile; see alternator charging. Solar controllers need their own lithium setting; see solar controller settings.

When to replace. If the converter has no lithium setting and the battery rarely reaches full, a lithium-capable converter is the clean fix. Size it to the battery’s recommended charge current, not its maximum.

Other checks. Remove any battery-isolator logic that relied on lead-acid voltages, and confirm the battery monitor’s full-charge setting matches the new charger.

Wiring and fuses. A converter that charges lithium at higher current than the old one may need heavier cable between converter and battery, and the fuse at the battery must suit the new current. Voltage drop on long thin cables also lowers the voltage the battery sees, which can stop it reaching full even with a lithium setting; measure at both ends while charging.