12 V Electrical
A travel trailer runs almost everything that matters on 12 volts: the furnace blower, the fridge control board, the water pump, the lights, the detectors, and the slide. When the battery sags, those systems fail in confusing ways that look like appliance problems. The furnace runs but never lights. The fridge throws a fault. The propane detector chirps at 3 a.m.
So the first test on this site is almost always the same: measure voltage at the load, with the load running. These guides cover the converter and charger, the battery and its real usable capacity, the fuses people forget exist, and every alarm the rig can make.
Guides
- How Long Will an RV Battery Last Boondocking? Load Math for 14 Common Draws
Add up amp-hours per day for each device, divide into your bank's usable capacity, and you have your answer. Typical draws for 14 common loads inside.
- How to Test a Deep-Cycle RV Battery With a $15 Multimeter (and When You Need a Load Test)
A rested voltage reading tells you state of charge; only a load or capacity test tells you if the battery is worn out. Here is the order, with the tables.
- Lead-Acid vs Lithium in a Travel Trailer: What Actually Changes in Your Converter, Fuses, and Solar Controller
Swapping to lithium usually means a new converter profile, a better fuse at the battery, and a DC-DC charger if you tow-charge. Here is what changes and why.
- RV Battery Not Charging on Shore Power: The 15-Minute Converter Test
When an RV battery won't charge on shore power, the usual cause is a blown reverse-polarity fuse on the converter, a disconnect switch, or a bad connection.
- RV Furnace Runs but the Battery Dies by Morning: Blower Draw Math and the Fixes That Work
An RV furnace blower pulls 7-11 A, so a cold night can use 30-50 Ah, more than a single Group 24 can safely give. Here is the math and the fixes, by cost.
- 7-Pin Plug Not Charging the Trailer Battery: The Pin-by-Pin Test
A 7-pin plug that won't charge the trailer battery usually has an unpowered 12 V pin: a missing fuse or relay in the truck. Here is the pin-by-pin test.
- Why Is My RV Beeping? Every Alarm, What It Means, and How to Silence It Correctly
An RV that beeps at night is usually the propane detector chirping on low battery voltage, a CO or smoke alarm at end of life, or an inverter low-battery alarm.