RV Electrical Troubleshooting

So I decided to immediately upgrade our recently acquired travel trailer to (2x 100ah) lithium batteries. That went fine, and everything seemed to work, including the lead-acid based converter that simply charged slowly and not all the way to full capacity. That is all normal, expected, and shouldn't harm anything. However, I also didn't want to effectively be limited to trickle charging, so I bought an upgraded power center with lithium compatible converter. I did get it installed, and the DC side was all working fine. Subsequently, I also let the batteries drain down to the low-voltage cutoff, which is supposed to 'calibrate' the BMS for state of charge.

When I plugged the trailer in to charge the batteries up, using household shore power in the GFCI next to the garage doors, it tripped the GFCI which is a first for me but I've heard it's not uncommon with lithium batteries and the associated chargers. So I plugged it into the non-GFCI outlet adjacent to the panel, that I'm pretty sure is on the same garage circuit, which has also been used for welding recently. Well my plugging in not only tripped the breaker, but immediately sparked, popped, and smoked like a short. Even when I turn off the main breaker in the trailer, it still trips the shore breaker. As far as I'm aware, it's just a simple 3-wire (hot, neutral, ground) romex run from the receptacle direct to the main breaker.  I'm more of a mechanical than electrical guy, so I'm struggling with trying to figure out where to look for what else could be causing this. Any ideas?

Find a non GFCI outlet to plug it in.  I had the exact same problem on our camper until I switched to the 20A welding outlet that isn't GFCI.  Not entirely sure why it does that, but it fixed it for us.

Can you post some specs of the components you are using and how they are wired?

Tripping a 15A breaker immediately with a charger seems like a major issue.  

Did you or some one else do the power center install?

In reply to alfadriver :

He tried that and got a pre-4th of july show.

In reply to 93gsxturbo :

I'm guessing that it's not the charger at this point, as it's still tripping even with all (including the shore power main input) of the breakers switched off. I've even tried switching out the main breaker, with no change.

Old power center: WFCO 8735

New power center: PD 4135

It's looking like I'll be spending some quality time in the trailer with a multimeter tonight.

In reply to iansane :

Self-install. The new unit is a 'direct' replacement, so it's literally just disconnect the wires on the old unit, and reconnect the same way on the new unit. It's something I *should* have been more than capable of.

While others installing this power center have used metal cable clamps to hold the wires as they come in through he knockouts on the back of the box, as opposed to the one time use plastic ones from the factory, but now I'm also wondering if this could be where the short is occurring on the shore power line. Perhaps damaged wire insulation from overtightening there?

If it is blowing breakers immediately upon plug insertion with the main breaker "off" They must have a jumper some how running from the hot to ground or neutral.  I would determ the shore power whip, carefully ensure the leads are separated and plug it back in and see if the whip alone blows the breaker.  

It's possible when jostling it to make the connections you grounded our the wires in the whip.  Is there a clamp anywhere that you tightened or installed?

Per the wire diagram it looks like you connected to the neutral and ground bus bar, and then direct to the main breaker so it doesn't look like there is anywhere else other then that main breaker that shore power goes when the breaker is open.  

If you are not tripping with that breaker open and then tripping with that breaker closed then there is some wiring defect that they did between the main breaker and the BMS/Charger. 

If you hooked up the neutral and ground backwards it would likely trip a GFCI because the voltage would return only through the ground and the GFCI is looking for current in the ground that isn't also in the neutral, but it  shouldn't trip a non GFCI circuit.

In reply to Driven5 :

Something seems off as the power center spec shows 725W input load, which should not be tripping a 15A breaker. 

Are there any other loads when connected to shore power?  Does the refrigerator automatically switch to 120V mode?  That might add enough additional load to trip a 15A breaker. 

In reply to nocones :

Whip alone doesn't trip the shore breaker.

I edited my previous post adding that I did install reusable metal clamps to hold the wires coming into the box, same as many others show having done... I'm leaning towards that right now though. Like you've noted, everything is pointing to the short being between the shore receptacle and the main breaker. That clamp is about the only thing there, especially that I've done anything to change.

In reply to Ian F (Forum Supporter) :

With the main (input) breaker off, none of the circuits should be receiving shore power. Additionally, all of the other (output) breakers are off for redundancy.

I found the problem. It was me.

Damaged wire insulation at the metal cable connector. Thanks for helping talk me through it!