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Old 06-21-2014, 06:06 PM   #1
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Location: Benton, LA
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Starting Batteries

We are fairly new owners of a 2005 34H Bounder, so I am showing my lack of understanding about the total electrical system.. I think I have a couple of different problems concerning my starting batteries. I must have a parasite train, because about every 30 days without using the coach, I notice that the starting batteries voltage drops below 12V.
My first question is even though the shore power is plugged in to 120V, am I correct in thinking that the Xantrex Fredom 458 inverter/converter does not act as a trickle charger to the starting batteries?
My second problem is that when I use the diesel engine and its alternator to charge the starting batteries, I have just realize that the water is being boiled out of the batteries. The inside voltage meter is showing 13.5V with the engine running and 11.9 volts without the engine running, but connected to 120 V. Running the Onan generator does not seem to affect the voltage to the starting batteries. Is the 13.5V the reason my batteries are boiling the acid out?

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Old 06-21-2014, 06:21 PM   #2
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30 days would be normal , for the electronic control modules memory to drain chassis batteries down.
13.5 volts charging should not boil the battery acid. You may have a bad battery. Time to remove batteries from the coach and load test them. Normal alternator output is 13.5>14.2v.
Not every coach will charge the chassis batteries when the RV is plugged to shore power, many owners have to install a battery tender ( low amp charger) to provide a charge to the chassis batteries, when parked.

99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
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Old 06-21-2014, 08:32 PM   #3
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When you park the RV with shore power plugged in, you should have the battery switches by the entry door turned ON. Press the tops of the switches to turn them ON.

If the generator or shore power does not cause the chassis battery to charge in this situation, you have a problem with the battery isolator solenoid in the BCC (Battery Control Center) or the sensing circuits on the BCC circuit board.

Your Bounder is definitely designed to charge the chassis battery from the house charger as long as the battery switches are ON.
'97 Bounder 34V, F53 7.5L-460
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Old 06-21-2014, 09:40 PM   #4
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Starting Batteries

I did boil the water out of the batteries about six months ago and could not get them to take a charge with my battery charger. I took them back to the store and they but them on a slow charger for 72 hours and then load tested the batteries. Both checked out good. However, your comments about possible bad batteries confirmed my thoughts also. The batteries are two years old. Normally, I would not think they were bad, but since I et them go dry, I suspect that I shortened their life.

I definitely have the battery switches in the on position and since I am not getting any charge from the shore power and the Onan, the battery control center will be my next step.

Thanks guys for both of your comments.
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Old 06-21-2014, 10:12 PM   #5
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Multiple problems

When plugged in the house batteries charge first. Once they reach a pre set voltage a relay in the BCC will trip the Trombetta switch and connect the starting batteries to the charge input.

When the engine is running it's the opposite. Starting batteries first, then house. Through the Trombetta.

Call Fleetwood and ask for a wiring schematic. They'll probably send it in less than an hour.

A bad battery does seem likely. But check the fuses in the BCC and the operation of the Trombetta switch.

I've replace the Trombetta and a section of wiring that got munched by the curbside slide to cure randomly blowing fuses. One of which controlled the stupid Trombetta.

The Trombetta is mounted in the electrical bay on the far inside wall and looks exactly like an old starter relay.

Hang in there. Lots to learn but you've come to the right place.
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Old 06-22-2014, 06:11 AM   #6
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Originally Posted by Joedean View Post
......Is the 13.5V the reason my batteries are boiling the acid out?
As mentioned by Skip426 above - No. Batteries are made up of a group of individual cells, each contributing to the whole. While you mention the store slow charged them for 72 hours then load tested them, this still does not properly test the batteries. To confirm/deny bad batteries they need to have each cell's electrolyte condition tested using a refractometer or at the very least a hydrometer. I don't use either for testing the overall charge state of the battery, but instead for testing the differences between cells in each battery. For instance, you can have a fully charged battery showing 12.7 volts (or 6.3 volts for 6V batteries) yet have a huge difference in specific gravity (.3 or more) in one or more cells of that battery.

-Yes it will show you a surface charge that seems ok.
-Yes it may load test ok as most load tests last just a few seconds and that is not enough time for a proper test of the overall battery condition.

One or more bad cells in a battery will cause boiling in adjacent cells.
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Spartan/Cummins 8.3C-300HP/Allison 3060 WTEC-II/25yr RV Tech RVIA Certified/Onan-Cummins Certified
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Old 12-12-2014, 01:21 PM   #7
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Bad batteries

One thing about lead acid batteries is they like to bounce around. I know it sounds silly but the truth is the lead plates have growths on them, something like those magic rocks they once advertised in the back of comics. If the batteries are sloshing the acid around while driving around that washes those growths off and they fall into the space at the bottom of the battery that was designed to collect them. If not they grow until two or more of them touch shorting out those plates. So the basic way to extend the life of a lead acid battery is to drive what ever it is in.

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