Have I been running a 24-volt house setup and frying electrical?

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Joined
Feb 21, 2009
Posts
24
Location
Capitola, Ca.
For the last couple of months, I?ve experienced a number of minor electric issues and now am wondering if all or most can be traced to the way the PO had wired the house batteries.
First issue was a backup camera that look several minutes to have the image clear (was bright white when first turned on). This has mysteriously reduced to about a 5 second lag in the image being clear.
Second issue was the step working intermittently, and then stopping entirely.
Third issue was the generator failing to start. I temporarily resolved this by using the backup battery switch, which let me use the engine battery to start and the generator came right up ? this was my first indication that I had an issue with the deep-cycle house batteries.
Fourth issue was the water pump ceased to work on house batteries.
So, at the end of the trip, I remove and test the two 12 volt deep cycle batteries and sure enough they are shot, in fact one won?t even take a load. So I get two new 12-volt batteries, but as I?m hooking them up, I realize that the old ones were connected in a series (negative from one connected to the positive of the other). This seemed strange, but I went for it since that?s how the old ones were set up (and no, the old ones were not 6 volt and no, I didn't change the wiring config).
I make the connections and the water pump fires up and immediately clicks off, the generator starts fine, but when I turn on a couple of small house lights, the bulbs blow. And then I start the RV, the amp meter goes through the roof, the battery symbol lights on the dash and I can smell battery ?charging? fumes. So I shut it down and connect just one of the two 12 volt house batteries, and no more trouble with the engine lights and no more bulbs blowing.
Now I?m left wondering if it?s possible that the PO had the wiring wrong all this time and that the house batteries were pumping 24 volt to the house lines (it may have been much lower as one of the batteries was basically DOA).
I have to go back through and recheck the fuses for the water pump and step, as these may have blown when I hooked the two new batteries up, but I just want to be sure I?m on the right track.
Also, should I hook up that second deep cycle in parallel to the first one (neg to neg, pos to pos)? I'm now guessing that's how it should have been all along, but I'll need to buy a second cable to allow that config.
Thanks,
Dan
 
Batteries don't create power, they just store what's pumped into them.

Since the converter and engine alternator only put out 12 volts (or more like 13.5 - 14.5) they'll only charge batteries to that level.

With two batteries in series, each will get charged to only about 6 - 7.25 volts.  In other words, those batteries have been sitting at essentially zero charge for a long period of time, explaining why they're NG.

There's no way batteries can charge higher than the supplied charging voltage.
 
Yes -- positive. 12 volt Interstates. I'm also positive that they were wired in series -- just like you would do if you had two 6 volts.

I was puzzled when I first saw how they were wired, but I figured it was just one more of the RV tech mysteries that I didn't understand and figured that it must have been right.

Lou: That's not surprising. I guess I was lucky that they managed to power my systems and start the gen over the last 8 months I've had the RV.
 
And yes, parallel connections are the way to go with two 12 volt batteries.  Positive to positive, negative to negative.

It helps the current distribution if you stagger connect the trailer wires - i.e. put the positive trailer wire on one battery and the negative on the other.  This equalizes the wire paths to and from each battery versus connecting the trailer wires directly to one battery and making the current go through both jumpers to the second.
 
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