Battery charging/Electrical guidance, please!

[GeoffnJules]

Hello and good wishes to all here!
I have a perplexing and continuing issue with our 2004 Kountry Star's charging system, and I'm looking for some clues or advice on how to proceed.
We just replaced both chassis batteries with new GC2 duracells - the old ones were 7 & 8 years old and only pushing 300-400 CCA per a Batteries+ test. I'm hoping their old age didn't cause damage to another component. One of the cables to the old batteries (the positive) was almost completely deteriorated, and I'm shaking my head for letting this happen (we've only had the camper for 1-1/2 years and I'm still learning).
The symptoms are as follows:
1)When hooked up to 20-Amp shore power with a 12ga cord, the batteries do not seem to charge. We've spent a couple nights in the camper in our back yard while plugged in, and the battery strength indicator drops to 1/5 over (a long) time.
2)I've put a battery charger on the chassis batteries on a 6-volt charge setting, but that doesn't seem to charge the batteries per the onboard indicator.
3)If I run the camper's motor for 45 mins, this seems to charge the batteries nicely. I know not nearly completely, but its the only thing that seems to go in the right direction.
Q)Could this indicate a bad inverter? Something with the transfer switch? Should the 6-volt batteries be charged at a 12-volt setting? That sounds counter-intuitive to me, but I don't know.
The rig is in good condition and I don't suspect any damage from rodents, if that helps. A visual inspection of all the wiring i can find reveals no damage.
If anyone could offer an answer, or even how to diagnose this issue further, I would greatly appreciate it!!
Thanks in advance!
Geoff (and Jules)

[dgapilot]

Not knowing the set up for the Kountry Star, I can only comment relating to my Mountain Aire (2002 vintage). In my coach there are 2 sets of batteries, one set of two 12 V batteries for the chassis connected in parallel (total 12 volts. The other set is four 6 volt deep cycle batteries set up with two in series, and the two sets in series then connected in parallel (again 12 volts total). If you are connecting a battery charger set to 6 volts to a 12 volt battery bank, it won't do anything!

All that said, how the batteries are connected is important. Like you, I have something connected incorrectly and my chassis batteries are connected to the house some how. Still trying to figure that out. They will discharge even if plugged in. The prior owner replaced them before I got the coach, and I'm still trying to find out what he connected wrong. Sure would be nice if the wires were labeled!

[Lt Dan]

Originally Posted by GeoffnJules

Q)Could this indicate a bad inverter? Something with the transfer switch? Should the 6-volt batteries be charged at a 12-volt setting? That sounds counter-intuitive to me, but I don't know.

Your coach may not have a source for charging the chassis batteries. A lot of coaches of that vintage did not. I had to add a Trik-L-Start to my '06 Itasca as it did not charge the chassis batteries when on shore power.

Are your sure your chassis batteries are 6volt? Most chassis (starting) batteries are 12v in parallel. If they are 6volt and hooked in series, yes you need to charge at 12v. If you are charging at 6v then they need to be disconnected and charged separately. If they are hooked parallel, then they are wrong as the chassis needs 12v. Six volt batteries connected in series will yield twelve volts. If they are connected parallel then they will only provide six volts but double the amperage.

Your engine alternator is charging the batteries correctly.

The illustration shows 12 volt batteries connected in series and parallel but the concept holds true for 6 volt batteries.

[twinboat]

6 volt batteries are not starting batteries and not rated for CCAs.
If there in the chassis position and used for starting the engine, they don't belong there.

If you mean house batteries, they should be wired in series and charged as a 12 volt battery. That's what the engine running does.

A few pictures of your batteries and the cable connections will help us get to the bottom of this.

[GeoffnJules]

Originally Posted by twinboat

6 volt batteries are not starting batteries and not rated for CCAs.
If there in the chassis position and used for starting the engine, they don't belong there.

If you mean house batteries, they should be wired in series and charged as a 12 volt battery. That's what the engine running does.

A few pictures of your batteries and the cable connections will help us get to the bottom of this.

Boy, did I mis-word that. I meant the HOUSE batteries - sorry! (still learning here - <blush>). I attached a pic showing them wired in series. So I can put a charger on the outside ends (one battery's positive and the other battery's negative) and charge it at 12v? That makes sense to me.
The only change I made when replacing the batteries is that the two cables going to the inner-most positive were wired together with a jumper of similar gauge connecting them to the battery (where the deteriorated cable was). My logic told me that two cables going into one similar-sized cable could create a hotspot, and I was easily able to connect them both directly to the battery. I don't see how that could create an issue, but more info for you guys the better, right?
That being said, I don't expect the shore power to charge the chassis (engine starting) battery, but it should top off the house batteries, right? Or does that only happen when I'm plugged into a 30A or 50A service?
And why would it be that the house batteries would drain when I'm hooked up to shore power? We had one A/C unit on "fan only" and using a few lights and the TV. No actual A/C or heavy usage items. The fridge was on, but had been on for days, so was only maintaining its cool.

DgaPilot - sorry to hear - If I learn anything pertinent I'll let you know, but I agree it sounds like you have a mis-wiring problem to deal with - ugh!

[twinboat]

The connectors you used are going to be problematic.
You should have used a mixture of baking soda and water to clean them up. Any green is corrosion.

If that corrosion is up inside the cables, it should be cut back and a new end crimped on.

Yes, charge as a 12 volt battery, end to end.

If everything is working except the charging on shore or generator power, look, first for a converter circuit breaker tripped on the 120 volt side and then bad fuses on the 12 volt side.

Did you leave any wires off the the battery terminals ? That happens a lot.

[GeoffnJules]

Gotcha on the connectors - I'll have to have those re-crimped by a pro. No tools for that here, unless I can find a good-quality crimper to borrow.
I'll check again for a blown fuse tomorrow in the light. All the breakers check out, and the fuses I have found so far are ok, but I know there are hidden ones all over.
Definitely no wires left off - just the three primary ones that are visible. No 12ga or 10ga tag-ons like I've seen on many cars.
Thank you, Twinboat (and the others)! I'll post any updates I have.
Geoff