How RV Solar, Shore Power, a Generator, and Alternator Charging Work Together
Part 7 of 8 in the RV Solar Planning Series.
An RV battery bank may charge from several places, but it should not receive several unrelated ideas about charging. Every source needs a defined device, compatible settings and proper protection.
Solar charging
Panels feed an MPPT controller, which supplies regulated charging to the battery. Its battery profile, current limit and temperature behavior must match the battery maker’s requirements.
Shore power and generator charging
Shore power normally supplies a converter, charger or inverter/charger. A generator usually feeds that same AC charging path. Confirm the device model, available charge profile and current. Replacing lead-acid batteries with LiFePO4 does not automatically make an older converter appropriate.
Tow-vehicle or alternator charging
A factory charge wire may provide limited or poorly controlled charging, and lithium batteries can demand substantial current. A properly designed DC-to-DC charger can regulate the current and voltage between the vehicle and house battery. Manufacturer documentation for units such as Victron’s Orion XS also notes that controlled charging can protect an alternator from the high current associated with low-impedance lithium banks. Vehicle and charger designs vary, so confirm alternator capacity, wiring and isolation for the exact installation.
Avoid the inverter-converter loop
An inverter changes battery DC to AC. A converter changes AC back to DC to charge the battery. If inverter output feeds the converter charging the same bank, energy runs in a wasteful circle until protection trips or the bank is depleted. Transfer arrangements and branch circuits must prevent that loop.
Give each source a purpose
Record the maximum charge current, battery profile, cable and fuse path, isolation method and operating conditions for each source. Then compare their combined possible current with the battery’s allowed charge current and BMS limits.
The charging-source worksheet in the Gram & Pap RV Solar Planning and Setup Guide puts solar, shore or generator charging, tow-vehicle charging and a backup charger on the same page so conflicting assumptions are easier to spot.
Make the handoffs boring
A good integrated system can move between sun, driving and campground power without improvisation. Boring handoffs are a compliment. They mean each source knows its job and the battery is not being asked to referee.
Safety note: This article is a planning aid. RV electrical systems and equipment requirements vary. Follow current manufacturer manuals and applicable codes, and use a qualified RV electrician when the work or requirements are uncertain.
