Need Help with a Battery Issue

[f6maniac]

I have a 2010 3150RL that came new with a single Interstate 12v deep cell battery. When the battery went bad I decided to switch to 2 Interstate GC2 6v batteries connected in series. The problem is the batteries loose charge even when I connected to shore power.

I enjoy doing a lot of DIY projects, e.g plumping, carpentry, mechanical repairs, but I've never been confident in electrical repairs and troubleshooting. So let me run through the issue as I see it and hopefully you guys can enlighten me on this issue.

So I removed the single 12v battery and installed a 2 battery tray and 2 6v 220AH golf cart batteries. Connected the two batteries in series and tested the connection and had 12.77v. Connected the house positive cable and then the negative cable and had a strong spark on connection to the post. Checked voltage again and had 12.75v. Connected shore power to the trailer and then checked the battery voltage and the reading had dropped to 0v. I couldn't get any reading. Disconnected the shore power and battery voltage tested at 12.75v again. Is this normal, or do you think this may be a bad converter?

I didn't change any other wiring so I didn't introduce any other wiring issues, but like I said electrical isn't my strong suit, so any assistance or troubleshooting suggestions are appreciated.

[Starmaster]

To connect two 6volt batteries to gether to get 12volts, you connect the positive of "Battery A" to the negative of "Battery B". Then, when you connect a volt meter between the Negative of "Battery A" and the Positive of "Battery B", you will read ~12.6volts. Sounds like you have that part correct.

The next thing I would check is to make sure the polarity is correct when connecting the trailer to the battery bank. With most all trailers, the WHITE wire should connect from the frame of the trailer to the NEGATIVE side of the two 6volts battery string. There should be a BLACK wire from a connector/buss bar looking thing mounted on the frame (actually its a circuit breaker, probably has a red rubber cover on it) to the POSITIVE side of the battery string.

FRAME, WHITE WIRE, TO BATTERY NEGATIVE (-)
BREAKER, BLACK WIRE, TO BATTERY POSITIVE (+)

If the battery bank is connect with reversed polarity, it will read 12volts until the converter is turned on at which time the converter voltage will cancel out the battery voltage and your net voltage would be 0volts, like what you're seeing. Reverse polarity connection would also explain the "strong spark" you saw when you hooked up.

If you did in fact connect the battery string backwards, be sure to check all of your 12volt devices (radio, tank level gauges, frig, etc.) for proper operation once you get things connected correctly. Reversed polarity can damage devices. If any of your 12volt items are not working, check for a blown fuse first, then enlist the assistance of someone with electronic troubleshooting experience.

Dave

[f6maniac]

Hi Dave and thanks for your input.

I've checked the polarity and it's correct. The white ground wire is connected to the negative post on one battery and the chassis. The black wire is connected to the positive post on the other battery and then to a power block.

[Irlpguy]

If you are reading the voltage always at the battery terminals (poss on one and neg on the other) even with a bad converter you should read 12V or better on your new batteries. A bad converter would not change that reading or make it go to 0V. The initial spark could have happened for a couple of reasons, either there were lights on or other draw from the 12V or you momentarily hooked the battery cables to the RV in reverse and blew the reverse polarity fuse/s in the converter. The white wire is ground and the black is poss.

If you turn off your battery disconnect switch usually located in the convenience center while plugged into shore power then try a light in the RV, if the light operates then the converter is supplying 12V to the unit and is ok. If not then either those reverse polarity fuses are burnt out or the converter is not operating properly.
With the battery disconnect switch turned on and not connected to shore power your 12V lights should work but will be running strictly off the batteries with nothing coming from the converter, again this will not happen if the reverse polarity fuses are blown.

Make sure your connections are good and tight at the batteries, the ground strap to the frame and the poss strap to the circuit breaker.