Troubleshooting

Use a path

Reproduce the fault safely. Check source, protection, conductor, connection and load in order. Measure voltage on both sides of each device under load; a large difference identifies drop.

Not charging

Confirm battery/BMS permits charge, charger sees its source, fuses are intact, settings match chemistry, temperatures are allowed and output reaches the bus. For alternator charging, verify trigger and input voltage while running.

Inverter trips

Check event code, battery SOC, voltage at inverter under load, surge demand, BMS current, cable/lug heat, ventilation and DC fuse/switch ratings. Measure at both battery and inverter to separate battery sag from cable drop.

Low solar

Compare with season, sun angle, temperature and shade. Inspect string voltage/current, dirt, connectors, fuses and controller limits. A full battery will intentionally reduce solar output.

Parasitic draw

Record stable key-off current at the shunt, pull branch fuses one at a time, then inspect the circuit that causes the drop. Common loads include inverter idle, routers, monitors and standby controls.

Rule of thumb

If you cannot state the expected current, full conductor length, protection rating and manufacturer limit for a circuit, the circuit is not ready to build.

CHAPTER CHECK

• I can explain the purpose of every component covered here. • I can identify the exact manufacturer limit that controls my design. • I have added the decision, rating or measurement to my schematic/worksheet.