Why isn't my RV battery charging?

Short answer: start with the simple things: battery disconnect switch, breakers and fuses, then check each charging source with a multimeter. Lithium batteries often show 0 A when full or below freezing; that is protection, not failure.

Pick by use

If you need…Look for
SolarController display, PV voltage, PV breaker, MC4 connections, controller-to-battery fuse
Shore powerConverter breaker and fuses, battery disconnect ON, lithium charging profile
Driving7-pin charge line or DC-DC charger fuses and ignition signal
Battery itselfBMS state, temperature, resting voltage, capacity

Diagnose it

Step-by-step checklist

  1. Turn on the battery disconnect switch and check its fuse/breaker.
  2. Measure battery voltage at the terminals (rested, if possible) and compare with the LiFePO4 voltage chart.
  3. Check every fuse between each charger and the battery (sized per the fuse calculator).
  4. Solar: read PV voltage at the controller; zero means a wiring, MC4 or disconnect problem upstream.
  5. Check the controller and converter are set to your battery chemistry.
  6. Look for loose or corroded lugs; a hot lug means a bad crimp.
  7. Check battery temperature (LiFePO4 below freezing won't charge).
  8. Confirm the charge current with a clamp meter or shunt battery monitor.

Still stuck? A qualified RV technician can test the converter and BMS. Upgrading? See choosing a charge controller and DC-DC chargers.

Safety: These are general estimates, not a design. Follow your equipment manufacturer's instructions and local electrical code, and consult a qualified electrician for anything connected to shore power, a house, or high-current batteries.

FAQ

Why does my RV battery show 0 amps from solar?

A full lithium battery accepts little or no current, so 0 A can be normal. Otherwise check PV voltage at the controller, the PV disconnect, fuses and MC4 connections.

Why won't my RV converter charge my lithium battery?

Many older converters use a lead-acid profile that stops around 13.6 V. Lithium needs a converter or charger with a LiFePO4 profile, and the battery disconnect must be on.

Can LiFePO4 charge below freezing?

Most LiFePO4 batteries block charging below about 32°F (0°C) to protect the cells. Warm them up or use a self-heating battery.

Does the RV battery charge while driving?

Only if the 7-pin charge line or a DC-DC charger is wired and fused correctly; check voltage at the house battery with the engine running.

Gear for this project

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