Battery voltage monitor

Question

Have a 2006 Roadtrek 210 Versatile. Lately, the battery voltage monitor lights are not working correctly. After a long drive or being on onshore power, the battery monitor shows the batteries in good condition. But about 30 minutes later, the lights n the monitor go down to the last one. I checked the specific gravity on the batteries (2 batteries that are 6 v with 230 amps each) and all cells look good. Voltage out of the batteries is a steady 12.2

What could be causing the lights to behave that way ? i could not find any parasitic loads. Could that be a problem with a poor ground ? I know I could get a Trimetric battery monitor installed to do away with looking at the "idiot lights", but like to see if there is another thing that could be the problem before I go that route. Any ideas are welcome.

psw · Answer

I think most would concur that at 12.2 volts your batteries are only charged about 60% or a little less. Last year I replaced my twin sixes with new batteries that had been manufactured the previous month (so they were very fresh) and they showed 12.67 volts. At the end of the season fully charging returned them to about that number.

When driving your RT is probably putting almost 14 volts into the batteries and it may be quickly dissipating to 12.2 which might indicate a defective battery.

Different charge charts show different numbers but all will approximate what I written above. Here is a pretty good source for information on all things battery:

http://www.marxrv.com/12volt/12volt.htm

Paul

sam_spade · Answer

Yes, 12.2 really is kind of low.It might mean that your batteries are nearing the end of their lifeOR there is a loose connectionOR your alternator isn't keeping them charged up.And yes a battery can be almost fully charged as gauged by the specific gravity and not be able to give back the energy when it should (low voltge).Next you need to take some voltage measurements when they are SUPPOSED to be charging......like when the truck is running and when shore power is connected without the truck running.

pianotuna · Answer

Fully charge the battery bank (which can take 168 hours). Then do an equalization charge. The batteries may be quite sulphated and it may take some work to recover them. Most often, it may not be possible to get them back to the original "new" capacity.

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Battery voltage monitor

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