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PNW RVer · 08-03-2020, 02:09 PM

I am new to the RV community. I recently purchased a 94 Fleetwood Southwind from a friend. I have been learning quite a bit (mostly from trial and error, as well as reading posts from this site). When I purchased the rv, it had new batteries that the seller had just purchased. However, the aux batteries were not hooked up because he couldn't remember how the old ones were connected. I'm not an electrical expert, but I know enough about cars and basic electricity, that I went ahead and hooked it up myself. Everything was working for awhile. I took the rig out a few times, and then some weird things started happening which have me stumped. I have tried researching my issue online to no avail, so I'm hoping you fine folks might be able to help.
A few weeks ago, my genset would not start. Tested voltage, and it was low. Jump started the generator from another battery, and it worked, which led me to focus on the batteries. Upon testing the batteries, I noticed that one was showing just over 12v, but the second was reading negative voltage. Took the battery back and found out the battery had reversed polarity. I had it replaced since it was still under warranty. Success, everything was working again. Took her out again last week, and things got weird again. First, shortly after starting my trip, a few of my interior lights were suddenly pretty dim. This was while hooked up to shore power. Not a big deal. I figured I would just deal with it when I got back. Well, once back at my friend's house where I store the rv, I tried to fire up the genset so I could have some power while I did some renovating to the interior. Again, no power to the generator. Tested the batteries again, and now the other aux battery is showing negative voltage. From what I can tell through my research, this is rare, but has now happened to me twice. It typically happens when batteries are charged backwards. It is also my understanding that there are fuses that will blow if the batteries are hooked up in reverse. No blown fuses, though. I'm assuming that this issue has something to do with human error, but I can not find ANYTHING online showing how the batteries are to be hooked up on my particular rig. According to the owners manual, they are series batteries. Plus, there was only one jumper, so that made sense. There was a red wire on the right side, and a wrapped wire on the left with one black and one white wire. I hooked up the red to the positive terminal on the right battery, then the jumper from the negative terminal on the right battery to the positive terminal on the left battery, and finally the black and white wires to the negative terminal on the left battery. Seemed pretty straight forward. I don't know what I'm missing here. Also, not sure if the dimmed lights while on shore power is related, or if that's a different issue altogether. I could really use some help here, because I don't even know what else to check or test. I DO know that I can't keep replacing batteries constantly.

Martind4 · 08-03-2020, 02:24 PM

Others are more qualified than me on 12v systems, but something I saw in your post doesn't sound right.

You said the owners manual indicated they should be wired in series, that's true if you have two 6V batteries. Could the previous owner purchased 12V batteries instead of 6V?

If you have two 12V batteries, they should be wired in parallel (positive to positive, negative to negative). 12V batteries have 6 caps, 6V batteries have 3.

Do you accidentally have a battery turned around?

Hope this helps.

Talloaks · 08-03-2020, 02:55 PM

Can you post a picture of your batteries as they are currently set up? I think it may be obvious right away what the problem is. Suspect you wired two 12 volt batteries in series.

Old-Biscuit · 08-03-2020, 03:05 PM

Two 12V batteries in PARALLEL vs Two 6V Batteries in SERIES

What do you have---12V or 6V---and how do you have them wired ?????

twinboat · 08-03-2020, 03:27 PM

Send pictures.

PNW RVer · 08-03-2020, 03:37 PM

So, it turns out the previous owner DID purchase 12v batteries. So..... first off, would this cause the issues I described? Second, should I replace with 6v, or just hook these in parallel? Third, are they even connected correctly if they were 6v?

twinboat · 08-03-2020, 03:45 PM

If you can get the reversed one exchanged, hook the two in parallel and you should be fine.

If you can return them both and get 6 volt batteries that works too.

If your stuck with the reversed battery, discharge it completely with a tail light bulb or something and then charge it up the correct way.

Outbound · 08-03-2020, 03:53 PM

Before going to (4) 6v batteries do you have room for them, cannot tell from photo.

PNW RVer · 08-03-2020, 03:55 PM

The brackets for the batteries are for that size battery. Not sure if 2 6v batteries would fit in the same bracket as a 12v. So, if i go with 6v, then I need 4 batteries?

Talloaks · 08-03-2020, 04:11 PM

No, you don't need 4 batteries. Two 6 volt in series or two 12 volt in parallel will give you roughly equivalent capacity depending on the ratings of the batteries.

Outbound · 08-03-2020, 04:13 PM

Better to have (2) 12v batts than (2) 6volt., Looks like rv came with 12v batts.

PNW RVer · 08-03-2020, 04:27 PM

Great. I will try and get the battery switched out and hook it up parallel. I'll post after to let you know if the problems are resolved or not. O e more quick question while I have you here. There was a red wire that looks obviously like it was put in by the original owner, not the factory. Not sure what its for, or where to connect it. I currently do not have it attached to anything. It is connected to the ignition relay. Any thoughts on that?