Batteries seem dead after load checking

[Domi]

I wanted to check the state of the batteries (2 X 12V in parallel) since when we were dry camping recently they did not last very long. I bought a 100A battery load tester to see what they would read. I disconnected AC power from the trailer then disconnected the batteries from the trailer. I ran the load test on each battery with nothing connected, and both batteries showed "weak" with about 10V under load. Need new batteries but I suspected that.

I hooked the batteries back up and looked at the voltage and it was 12V with no AC on the trailer still. The problem is that nothing will run on the batteries, no lights inside, and the electric tongue jack will not work on the outside. I have disconnected everything except the tongue jack and it will not work hooked just to the batteries. If I hook everything up and plug in AC the tongue jack and everything inside works fine. This tells me the converter is working and because the tongue jack works I am getting 12V from the converter to the batteries.

I left it to charge for about 2 hours and still the tongue jack will not work off the batteries.

There is no little breaker on the blocks, I replaced that a while ago with an auto reset breaker. The batteries are hooked up correctly, double checked twice.

Did the load test ruin the batteries?

Have I missed something I need to reset to get the batteries to work. I would have thought the tongue jack would have at least tried to work.

Thanks for the help. New batteries tomorrow evening at least.

John

 

[cookie]

If the voltage number you gave, 12 volts, your batteries are dead.
You should get 13+ volts from the converter, not 12.

Peace
Dave

 

[Domi]

If the voltage number you gave, 12 volts, your batteries are dead.
You should get 13+ volts from the converter, not 12.

Peace
Dave

I rechecked this morning and the voltage with converter is 12.88. Without the converter the batteries read 12.81.

If the auto reset breaker is messed up would I get power from the converter to the tongue jack? It is just hooked to the batteries not inot the bus bar so I would suspect that the converter is getting to the batteries.

Confused about why stuff does not work off the batteries at this point.

John

 

[cookie]

I don't know about the North Trail but there could be a main breaker or fuse that protects your 12 volt system.
It would not be an auto reset breaker.
Look around for a breaker that will have a tiny reset button or an in-line fuse.

Peace
Dave

 

[danemayer]

I ran the load test on each battery with nothing connected, and both batteries showed "weak" with about 10V under load. Need new batteries but I suspected that.

10V under load probably explains it. Take your batteries to an auto parts store and get the testing done with a different tester. If the same results, get new batteries.

 

[Apropdoc]

if you are using deep cycle batteries and under a 100 amp load getting a 10volt drop reading, your batteries have either dropped a cell, or are sulphated. Either way, just as mentioned before, take them to the parts shop, let them load test with their growler, and get another set of batteries as you are operating off of two batteries at a time. One more thought, if you use two batteries together, then they should be load tested together as one battery may be compensating for the weaker one.
Just sayin...

 

[jnbhobe]

I would check the fuses on the converter also you should be getting 13.4V from the converter.

 

[Domi]

Re: Batteries seem dead after load checking - SOLVED

I would like to thank everyone for their help on this. You would never know that I work on electronics for a living as many issues as I have with the electrical on the trailer.

This afternoon I got a chance to look again at this issue. I found that measuring the voltage from the buss bar to the frame was 2.3V. I knew that was messed up so I went from the battery post to frame and got the same thing. Yet across the batteries was 12.6V. I measured the resistance from the negative battery post to the ground and found it to be open. Turns out that there was either junk on the terminal/lugs or junk from a piece of duck tape that was making it open. I cleaned up the terminal and it was working.

I have replaced the batteries as I am sure they were weak if not bad.

The new batteries work better. I turned on all the trailer lights and even uncharged they stayed up and bright.

Thanks again for the help,

John

 

[Jim.Allison]

I have heard it said that "bad grounds" are responsible for many electrical problems. I read on a battery website, that DC appliances, such as a 6 point level up system and other DC connections, prefer a copper wire ground wire back to the bus. Chassis grounds are OK but a chassis ground and a copper wire ground together are much more reliable and effective.