1979 31'- Battery has charge but won't power the trailer

[Foxbrook]

My battery registers 12+ volts but will not power the trailer when I disconnect shore power (or lose power). It still has the original 1979 univolt on the floor against the front wall with a separate fuse panel above it and testing various spots in the fuse panel reads 12+ volts. All fuses are good, I don't see that there is any sort of switch anywhere that would be able to toggle battery power off (storage switch). Does anyone have a thoughts about what I am missing?

[cwf]

Has the 12vdc worked before?

[Phoenix]

The easiest place to start is to remove the battery, charge it overnight with a regular battery charger, and then take it to an auto parts store (e.g., Autozone, Pep Boys, etc.) to have them perform a load test.

While these symptoms may be caused by several problems, having a load test done will eliminate the most likely cause, a defective battery. Plus, a load test is simple and free.

(Many defective batteries will measure 12.5-13.5 volts with no load applied, but the voltage will immediately drop to 10.5 or less under load.)

[NavyCorpsman]

My 78 had the same symptoms. It should be an easy fix. With a fully charged battery, installed, check for voltage (I like to use a heavy duty test light with a long sharp probe, and a good alligator clip ground) at the panel where the 12v attaches to the bus bar. Attach the alligator clip to the BATT NEG at the bus bar
Then work your way down checking both ends of each fuse, and the bulb in the handle should light up. Even if there is a fuse element in the glass tube, does not mean it is good. Pull each fuse out and clean any gook or dirt from the fuse holder as you go. I use a product that ATT uses called NOOXIDE. It's a brown grease that prevents oxidation between dissimilar metals. There is a prouduct at Lowes called Alumalox, I believe that I have used as well . It only takes a dab on a qtip, and a very thin coat at that. Here are two things that can aggravate you if you don't check them. 1. Just because the fuse is intact (passes visual) doesn't mean its good. I have had several old fuses and new ones that were OPEN, even though I could see the fuse metal.
2. Every once and a while pull one end of the fuse out and push it back in, top and bottom all the way down the line.
3. The most overlooked part to service. Check all of your ground connections at the panel and at the battery. Make sure that they are clean and free of corrosion and verdigris. A dab of your favorite anti oxidant or petroleum jelly to finish it off and you should be back in business
It takes about an hour and a half to do it.
Let me know how it goes for you, and if you have any other troubles.
Clayton

[Foxbrook]

Guys, Thanks for the advice, I believe it was a relatively simply problem. I have a second deep cycle battery, I charged that one over night and unplugged the other one after checking voltage in a bunch of places such as across fuses. The second battery worked to power the 12 volt functions immediately... so I began straightening/neatening the leads to the battery and the lights blinked off.

It seems that due to corrosion on the connectors in the middle of the factory battery leads, I was getting occaisional connectivity. I think perhaps vibration or movement was occasionally causing enough connection to keep the battery charged, but the times when the power went off or I disconnected the trailer I got no juice flowing back in to the 12 system.

Anyway, I cleaned up the connection and made sure it was tight and tested a few more things. I ran some lights and the furnace, that only caused the voltage of the battery to drop very slightly so I assume it is good.

It seems as though I need to spend a little more time checking for loose grounds, greasing fuses and cleaning corrosion off of some of the connections that haven't been touched in a while so that I don't have any other issues, but for now I think the main problem is fixed.

[NavyCorpsman]

Thanks for sharing the good news. A small voltage drop while running your lights and fans are normal. 60% of my electrical troubles with DC have been intermittent ground due to poor connections. I'm glad you found the problem(s).