Converter not charging - possible shorted battery?

[jayspi]

Hi everyone, sorry for the long post.

I have 2 6 volt batteries wired in series. We've been in very cold weather and I recently noticed voltage is a little low. I already planned to replace them, but haven't done it yet.

Anyway, I fired up the generator today and the voltage plummeted from 12.7 volts to less than 9. All internal lights started flashing on and off (like a strobe, not flickering). Once the generator stopped trying to start they started flickering and all other 12 volt systems stopped working. Voltage was showing about 10.5.

Problem is, after that my converter stopped charging the batteries. Fuses are good and it has power, but it doesn't seem like it's trying to charge. The fan isn't going.

At first I thought I damaged the converter. But now I'm wondering if a battery shorted. Perhaps the converter has a failsafe where it won't charge after detecting a short? Is that possible?

I also see a red light flashing on the slideout synchronization controller. The manual says 9 flashes means it detects a short. I HOPE that it is all because of a bad battery. Otherwise I'm worried I shorted something in the system.

What do you guys think?

My RV is a Grand Design Momentum 354m and the converter is a WFCO WF-9855.

Thanks!

Edit: I have a battery charger on them now and 12 volt systems are working, but any draw, even something as small as the water pump, makes them flicker.

[jayspi]

Figured it out! Ultimately I only have myself to blame.

The issue was that one or both of the batteries shorted when I started the generator. They were obviously worse off than I thought. The converter started working after I swapped the batteries.

I think my original theory was correct...the short triggered some sort of failsafe in the converter and it needed to be reset.

To answer the other questions & comments...

BFL13 wrote:
Very confusing! If you have shore power why start the gen? If no shore power and the gen won't start, why do you expect the converter to work?

Meanwhile, just use jumper cables from your truck to start the gen (assuming no shore power) and then see if the converter works.

Sorry that my original post wasn't clear.

We had shore power when I started the gen. We were getting ready to move and I was about to unplug the shore power. Our transfer switch automatically flips us to gen even if shore power is plugged in. The generator is connected directly to the batteries and uses them for juice, even if shore power is present. The converter is not in the loop at all.

The 12.7 voltage was WITH them plugged in, so I knew they were dying. I just didn't realize how bad they were. A couple of weeks ago I had run the gen under load for 2 hours (as the manual recommends when not using it regularly) and it started fine.

I don't think that there's an easy way to jump start our gen. I asked the dealer and was told in no uncertain terms to not do it. However, if you put a good charger on the batteries then you can start it. I tried that last night and it wouldn't start, which was a good indication they were shot.

Edit: Right after posting this I understood what you were saying. I could have hooked a jump starter to the batteries and then tried to start the gen. That would have worked, and if we didn't have shore power that would have been a great way to do it. Thanks for the tip!

ScottG wrote:

That does sound like one of them has shorted internally but the blinking thing is odd. Sounds like an auto-resetting breaker doing its thing.

Unfortunately. The flashing is still happening after replacing the batteries. The manual says to make sure that the slide motors are operating at the same speed. They are, so I don't know what's going on. I'm going to ask a shop.

wa8yxm wrote:

The short detector on the slide out controller should be post-controller (motor side).

Sounds more like a very bad connection or batteries past end of life.. IE.. When my Original hit 9 years old they had relatively little capacity (30%) of what they had when new.

Batteries have several failure modes. One is HIGH RESISTANCE this can be Mimiced by a dirty connection (high resistance connection) and on my chassis battery that happened 3 times... That sounds like what you got.

Loss of capacity.. that is also a failure mode. a 200 amp hour battery is down to 50 or less

And shorted cell.that is the bad one because with shorted cell it never comes UP and the non-shorted can boil dry.

OH speaking of boil dry.. Check the fluid level (IT's not water) and if needed add DISTILLED WATER to the mix.

Thanks for the explanation! Very helpful. I noticed a bulge in the batteries. When I saw that I immediately replaced them. That solved all the problems, except that darn light is still flashing.

I brought it to the shop today for something else, and I asked them to check it. Maybe the unit just needs to be reset. I hadn't noticed that light flashing until the problem yesterday.

I was going to take your advice about the distilled water until I saw them bulging. Then I said forget this, and just put in new ones 🙂

[Chris_Bryant]

I would be more inclined to think the converter is toast. I would disconnect the batteries, stick a good charger on them and see if the converter will power the lights by itself. I bet it won’t.

[wa8yxm]

The short detector on the slide out controller should be post-controller (motor side).

Sounds more like a very bad connection or batteries past end of life.. IE.. When my Original hit 9 years old they had relatively little capacity (30%) of what they had when new.

Batteries have several failure modes. One is HIGH RESISTANCE this can be Mimiced by a dirty connection (high resistance connection) and on my chassis battery that happened 3 times... That sounds like what you got.

Loss of capacity.. that is also a failure mode. a 200 amp hour battery is down to 50 or less

And shorted cell.that is the bad one because with shorted cell it never comes UP and the non-shorted can boil dry.

OH speaking of boil dry.. Check the fluid level (IT's not water) and if needed add DISTILLED WATER to the mix.

[BFL13]

Very confusing! If you have shore power why start the gen? If no shore power and the gen won't start, why do you expect the converter to work?

Meanwhile, just use jumper cables from your truck to start the gen (assuming no shore power) and then see if the converter works.

The batteries may or may not need replacing--they were at 12.7, which is ok just sitting, but then they collapsed under load (gen starting), so how long have they been sitting in the cold with no float charger because no shore power?

Or what is happening there????

[ScottG]

That does sound like one of them has shorted internally but the blinking thing is odd. Sounds like an auto-resetting breaker doing its thing.
You need to disconnect them and measure inderpendantly of each other.
I would not keep trying to charge it.

[Lwiddis]

How old are your batteries? Water checked how often? Clean cables? Recharged to 12.7 regularly? How cold is it?