12v system issues

[Paul T]

Hi, I have a bighorn 3870 fb. I realized that my 12v system will shut down when shore power goes out, so no 12v at all. When I tried to turn on the inverter two error codes came up. Both indicated no battery or low battery. My batteries are both at 13.5 and 13.7. Between the batteries and the inverter is the circuit breaker followed by a buss fuse then to the transfer switch which is plugged into the inverter. I’ve found that where we are located it’s a $200 plus time just to have a repair company come out. I’m hoping someone can give me an idea of how to isolate which unit has failed. Please keep in mind that my multimeter skills are limited to checking dc and ac voltage unfortunately. Thanks for any advice.

 

[B52Bombardier1]

How old are the batteries? Many people take comfort in measured voltages such as your 13.5 and 13.7 VDC but please understand, if those two batteries cannot deliver much amperage, they are dead.

Volts x amps = watts or power. The ability to do useful work.

Rick

 

[TheLooks]

I am one of those insanely priced repair guys. When you shut off shore power, it does not shut off 12 VDC. What does shut it off is the disconnect switch for storing the camper or just turning off the 12 vdc power. There is a momentary contact switch, probably near the door that says something like disconnect or store. It will turn on all the 12 vdc things until the batteries run down. If you don't have it on, the converter is supplying the power while hooked to shore power. The batteries need to be turned on most times in order for the converter to charge them also.

 

[Paul T]

I am one of those insanely priced repair guys. When you shut off shore power, it does not shut off 12 VDC. What does shut it off is the disconnect switch for storing the camper or just turning off the 12 vdc power. There is a momentary contact switch, probably near the door that says something like disconnect or store. It will turn on all the 12 vdc things until the batteries run down. If you don't have it on, the converter is supplying the power while hooked to shore power. The batteries need to be turned on most times in order for the converter to charge them also.

Hi, thanks. If I understand you correctly you are talking about the 12v shut off switches. They are turned on to allow the batteries to be operational in case of a power outage. So that would poin to another issue. Is it possible that the batteries read 13.5v but they don’t have any amperage available to operate the syste? They are 6 years old and always plugged into shore power.

 

[TheLooks]

6 years is getting on in age. I would have to do an amp test to verify battery condition. You do not turn on the 12 vdc in case of power outage. 12 VDC runs your whole rig, all the time. What kind of rig do you have?

 

[TheLooks]

Ok, a Bighorn so a 5th wheel. When you pull the shore cord, unless you have turned something off, you will still have lights, slide controls, leveling systems, water pump, and the furnace will work, and the fridge unless you have a residential. My guess is a fuse is blown in the front compartment from your batteries to the main panel. Possibly even a resettable fuse, not the self resetting type.

 

[Kevin D Pem]

Hi, thanks. If I understand you correctly you are talking about the 12v shut off switches. They are turned on to allow the batteries to be operational in case of a power outage. So that would poin to another issue. Is it possible that the batteries read 13.5v but they don’t have any amperage available to operate the syste? They are 6 years old and always plugged into shore power.

The test is called a load test! Harbor freight has a fairly cheap load tester.

 

[Rich W.]

Hi, I have a bighorn 3870 fb. I realized that my 12v system will shut down when shore power goes out, so no 12v at all. When I tried to turn on the inverter two error codes came up. Both indicated no battery or low battery. My batteries are both at 13.5 and 13.7. Between the batteries and the inverter is the circuit breaker followed by a buss fuse then to the transfer switch which is plugged into the inverter. I’ve found that where we are located it’s a $200 plus time just to have a repair company come out. I’m hoping someone can give me an idea of how to isolate which unit has failed. Please keep in mind that my multimeter skills are limited to checking dc and ac voltage unfortunately. Thanks for any advice.

One thing that jumps out at me is that your batteries are not at 13.5 or 13.7v. This is charging voltage and to find out the actual voltage of your batteries, you have to disconnet them and let them sit (rest) for a few hours. Doing this you should find something close to 12.7v for healthy batteries. If the resting voltage is down around 12.1 they are basically dead.

Resting voltage is a test you can do with your multi-meter and it will give you an idea of the condition of your batteries although voltage alone is not a great indicator of battery health. Also as stated above six year old lead acid batteries and bound to be about used up and getting that much life out of RV batteries is actually fairly unusual.

This is a good article on battery charging and health: https://deepcyclebatterystore.com/how-to-maintain-batteries/

 

[TheLooks]

But if he thinks unplugging shore power shuts down the entire camper he is not using his 12 volts system. There is a disconnect somewhere in the camper and his thinking.

 

[Rich W.]

But if he thinks unplugging shore power shuts down the entire camper he is not using his 12 volts system. There is a disconnect somewhere in the camper and his thinking.

Or his house batteries are to weak to provide sufficient power when unplugged. That’s why I suggested he test them at their resting voltage (since he just has a multi-meter) to determine the relative health of the house batteries. It may not be a disconnect at all but simply bad batteries although if this were the case he should at least have 12v lights.