Shore power doesn't charge my battery!

[maalox]

I have an older RV (1986 Chevy Dolphin) with yet another weird problem.

When I'm plugged in to shore power, all of my 12v stuff works fine (lights, water pump, etc), but my battery level doesn't go up.  In fact, if I plug my inverter in to one of the cabin cigarette lighters, I can slowly discharge the battery.  I have a fairly poor understanding of how this stuff works, but my intuition tells me that the problem lies between the converter and the battery.  I've checked all the relevant fuses, disconnected the battery, etc. 

What gives?  It seems like if the converter is working, so should the battery charger.

 

[Ned]

Look for a battery disconnect switch, either on or near the house batteries.  Also look for an inline fuse in the battery positive cable to the converter.  It's appears that the converter isn't connected to the batteries but the 12V outlets are directly wired to the batteries.

What make and model is the converter, that may help us in tracking down the problem.

 

[tennsmith]

Following up on what Ned said, if your 12v stuff is working when plugged to shore power, then your battery should be being charged.  My 5th wheel had a fuse in the battery compartment that was in series with the line that charged the battery.  What I don't understand about your situation is why your battery is not being charged, but that you can operate an inverter when plugged into a cigar lighter.  On my camper, the same wire functions to both charge the battery and power the 12v accessories on battery power only.  When  you plug inverter into cabin cigarette lighter, do you have shore power plugged in?  If so, you are using that, not the battery.  Try it again making sure shore power is disconnected.  If you still see battery being discharged, then you must have multiple wires going to the positive terminal of your batteries, one for charging and one for driving the 12 v loads.

 

[Ned]

It's also possible that the 12V outlet(s) are being powered from the chassis battery, especially if the outlet is in the dash.

 

[maalox]

Thanks for the help, guys!

There was indeed an inline fuse in the battery compartment.  Even though it looked fine, I went ahead and replaced it.  No effect so far-- It's been an hour and the battery still reads "empty".

The converter is a B-W Manufacturers model 6235.  I reckon the last one was produced about 20 years ago, so the model number may not be much of a help here.  All the fuses appear to be in tact, including the one that leads to the battery charging circuit (according to the diagram anyway).  I've attached a picture of it below.

And yes, there are multiple connections to the battery.  Perhaps one of the previous owners used the cigarette lighter to charge the battery via solar?  Just a thought.

 

[carson]

Some of the old type chargers (Magnatek etc) have 2 output leads. One for the overall 12 volt feed to the RV.  The other lead is for charging purposes only, usually at a low rate , 9 amp only.

  Speaking from experience, my old charger supplied 12v power to the RV but 0 on the charge line.. Guess you may have the same problem. New charger needed, probably.

  Hope this makes sense.
carson

 

[Lou Schneider]

Looking at your picture, it does indeed look like your converter has a separate battery charging output.  While it might be repaired, replacement with a newer, better regulated converter is a better idea.

 

[Just Lou]

Lou, I think you're right.  From what I can determine, the B-W Manufacturers and the older Magnetek's were pretty much identical.