Killed my power supply and not sure why

[wopachop]

I pulled a bone head maneuver and think i have a lot to learn about grounding a trailer. Ive got a toyhauler. Added a 120v 20a dedicated circuit that gets hot when on shore power or when running the generator. My WFCO converter has been acting up, and it never charges at 14.4v anyway, so i decided to use my RC plane charger. Its an Icharger 308 Duo and uses two 750w 12v power supplies in series.

I plugged the charger into the new 120v outlet with my genny running. The trailer has a main battery disconnect. I hooked the positive lead to the disconnect post that is the positive wire back to the batteries. I had the disconnect turned off, but left the WFCO running so the trailer would have 12v power. I then hooked the negative lead from the charger to the negative terminal off my service panel. Everything looked ok. Went to start a charge and one of the power supplies shut down. I then did a 2nd bone head maneuver and rigged up the charger to pull from a single 12v power supply. Hooked it up, clicked the button to start charge, that power supply shut down as well.

I dont know if the power supplies have an internal resettable fuse. Havnt tried plugging them back in. I must be lacking a fundamental understanding of how the 120v AC and 12v DC play together. Its still confusing how the 12v ground and the 120v negative is tied together. I normally use this charger with battery clamps directly to the battery terminals. To keep the charger out of the outside dust i wanted to charge from inside the trailer. Using the main positive lead that goes back to the battery. The 12v ground is tied to the chassis. Just like the 120v. Im thinking this is where i screwed myself?

 

[Solarcabin Channel]

Well disconnect that charger and I wouldn't use it for that again.

Common ground is the frame on an RV. Usually a frame lug somewhere.

They carry RV converters designed for LFP on Amazon.

 

[400bird]

Its still confusing how the 12v ground and the 120v negative is tied together.

I don't think they should be connected at all. I wonder if this is the cause?

 

[Bkord]

It’s still confusing how the 12v ground and the 120v negative is tied together. I normally use this charger with battery clamps directly to the battery terminals. To keep the charger out of the outside dust i wanted to charge from inside the trailer. Using the main positive lead that goes back to the battery. The 12v ground is tied to the chassis. Just like the 120v.

What are you calling a “120v negative”?

 

[MisterSandals]

What are you calling a “120v negative”?

The white wire, then the black wire, then the white wire... 60x per second.

 

[wopachop]

Whoops sorry meant 120v Neutral. The 120v ground busbar is tied to the 120v neutral which is also tied to the 12v negative busbar.

I hooked the charger negative lead to the 12v negative busbar. But I'm guessing that is a mistake and caused my issue. I might be upstream of where I need to be?

 

[wopachop]

Could it be my power supplies dont like the AC wavelength formed by my Onan 5500w genny?

 

[Groscout]

It’s best to connect your model airplane dc battery charger directly to the battery being charged (the charger may have trouble charging with wire resistance loss). Connecting the dc charger to 110v ac and negative dc 12v probably did it. I might be missing something here fyi.

The first thing I would do is try to charge a hobby battery under normal conditions with the chargers in question like you normally do with batteries that worked in the past, to see if they turn on and perform normally. Then I would, if the hobby charger(s) still work and I still don't have and can’t get the proper equipment. I would connect the chargers directly to the battery and charge while monitoring with a known working volt meter.

The generator hz. could also be the issue. But if it is your likely to have bricked them.

Re test under normal conditions and post back.

 

[wopachop]

Ive used this exact charger setup to charge these batteries for years. Its how i perform an equalization on them. But i pull the batteries out and do this outside the garage. Never tried charging from the trailer service panel before. (like the WFCO converter does)
I hooked to the 12v negative, it just so happens its tied in with the 120v Neutral and 120v Ground.
Should have checked generator Hertz while running. Good call i did check a couple years back and it was 60. But there is an adjustment screw or adj spring for that setting. Forget where but its easily accessible so it means its likely part of a normal service to check it.