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Old 02-01-2023, 02:50 PM   #1
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Thumbs down Batteries not charging on shore power, is my converter bad

I've got a 2016 rockwood ultra 23 foot tt. it has a wfco wf-8955 converter in it. i first noticed the power center fan was coming on a lot more often. my batteries are old, so i just got 2 new 6 volt golf cart batteries. getting ready to install them but i'm suspicious that the converter is bad. here's what i've done

with batteries out, shore power on do not have 12 volts at battery terminals. fuses and disconnect switch at battery test good for conductivity. no obvious signs of damage to the wiring around the battery. checked the reverse polarity fuses and they are good.

inside , with shore power and no batteries, i have lights, water pump runs but not slide outs. so it looks like i've got 12 volts inside but only for low power. if i flip off the 120 volt breaker labeled conv, the lights go out. flip the breaker on, lights come on, the power center fan briefly comes on.

can my converter be bad but still provide low load power for things like lights but not charge the battery?

don't want to spend $200+ to throw a new converter at the problem. but not sure what else i can try. thanks for any help
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Old 02-01-2023, 03:07 PM   #2
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You have already purchased new batteries.

So, install the new batteries and then with shore power on, take readings at the batteries.

With 6 VDC batteries, be sure they are wired IN SERIES to provide 12 VDC.
Brett Wolfe
Ex: 2003 Alpine 38FDDS. Ex: 1997 Safari Sahara. Ex: 1993 Foretravel U240
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Old 02-01-2023, 03:58 PM   #3
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The converter is working, the lights and fans work.

The slides are probably wired to the batteries because the converter doesn't have the power to run them.

How many wires go to the positive post of the battery.
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Old 02-01-2023, 07:14 PM   #4
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All the above, and you can take a basic digital voltmeter and watch the voltage across the batteries. Charged batteries will be around 12.75V, turn on the converter and the voltage will jump to ~14V.

Mark B.
Albuquerque, NM
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Old 02-01-2023, 09:27 PM   #5
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Thanks all. There are 2 factory wires that go to the positive side of the battery disconnect. So maybe one for the converter charging, the other for slides, jacks. In any case, I'll hook up the batteries and monitor.
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Old 02-02-2023, 07:52 AM   #6
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Possible loose or corroded positive cable to battery.
Possible loose or corroded negative cable to battery.

WFCO supplies regulated 13.6 volts even when battery is disconnected.

You can measure the output of the WFCO on the WFCO board near the fuse bank. There should be two screw connectors holding large gauge wires. 13.6 is nominal. 14.4 is bulk charging. 13.2 is long term storage. See manual for exact testing procedure.

Check torque on the two connectors. (Hand tighten. If the screws do not turn, they are tight.)

see page 9

Check voltage at each connection point along the wire to the battery. Battery on tongue will often have a connection box underside near the battery.

Self resetting circuit breaker often on the "A" frame near battery.
Paul Bristol
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Old 02-02-2023, 10:28 AM   #7
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Originally Posted by brucewol View Post
In any case, I'll hook up the batteries and monitor.
I would wait. Installing the batteries wont change how you find the problem. All that can happen is potential to drain or damage the batteries.
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Old 02-02-2023, 10:58 PM   #8
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Persistent - thanks for the manual link. i only had a quick reference. and thanks for the tip on how check output voltage at the converter rather than the unconnected battery leads. i might have an open breaker between the converter and battery. ugh - need to crawl around under the trailer to find it.

wopachop - agree with your comments. i would have connected the batteries and see if the voltage increased indicating charging was happening. if not, disconnect them. someone earlier posted that if you have a smart converter, the voltage might be 0 when batteries are disconnected. not what the wf-8955 has for troubleshooting tips but my better trickle chargers do have 0 volts with no battery connected. but with the tip persistent provided, i know how to check output voltage at the converter which will help me to diagnose if it's a bad converter or wiring/breaker issue to the battery.

hope to have more time tomorrow to look into this. will post my results after that.
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Old 02-03-2023, 10:46 PM   #9
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Success!! I put the new batteries in. with the converter powered and battery disconnect engaged, I only had 12.7 volts at the battery, so not charging, I checked heavy wires at converter and had 13+ volts. after looking at the wiring of the converter, expected that as I had lights working inside and the heavy wires supplied the fuse panel. The jack now worked, again expected as it is wired to the battery disconnect and I have a good battery,

so it looked like the there was a break in the wiring between the converter and the battery. crawled around under the trailer and found a circuit breaker. Pushed in the reset plug and then checked the battery. now it as at 13.5, so was charging.

My prior batteries had failed and were putting a larger load on the converter. That's why the fan in the converter was running a lot more. The fact that I had lights meant that the converter was working. But the power wasn't getting to the battery. Eventually the bad batteries caused the converter to continually work so hard, that it tripped the circuit breaker. So I just needed to find, then reset the circuit breaker between the converter and battery.

Makes sense now. Thanks all for the tips that helped me understand the situation.
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batteries, charging, converter, power, shore power

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