Using WFCO 75 amp to charge batteries

I just used jumper cables to charge one off a trailer

Yes it will charge the battery. Just do not expect it to do it super fast. The 75 amp charger can put out 75 amps to a set of batteries, say a 600 amp hour battery bank, for around 2 hours. But after the 600 AH battery bank is over 50% full, then it will only charge at say 50 or 40 amps.

Your typical 85 AH car battery might accept 50 amps for a few minutes, then drop down to accepting 25 amps or less once the battery voltage rises to 13.8 or 14.2 volts (depending on the charger output voltage.)

If you have a older style converter, then I can boil away a lot of water, and heat up a small battery.

I have a very smart Trace 20 amp Truecharger and I made it portable, by installing #8 jumper cables to the charger output. It works fine for charging anything from my car battery to my 20 AH wheelchair battery, to the 400 amp hour battery bank in my RV.

Good luck,

Fred.

Yes either way (car or RV) 75 amp WFCO will just slow charge at 13.6 volts.

Yes it can be done
Depending on the model of the converter it may or may not have the RCMS remote control interface, a simple RJ11 connector. If so a simple push button switch plus an indicator LED will enable full manual control. Manual control when desired is set at 13.2/13.6/14.6 but can easily be changed.

The WFCO 75 is really designed as a power post power supply unit for your travel trailer while being hooked up to a pedestal in an RV park. That means what it does best is runs the lights, fans and water pump in your rig, since it has a constant power supply. As such, it really doesn't do much recharging of batteries, or does so at a very slow pace.

A better solution is to.... wait for it... buy an actual battery recharging device for car batteries, like a battery recharger. That should come as no surprise. Buy a battery charger, not a Power supply for an RV parked at a pedestal. There is a huge difference, a manual battery charger will put out up to 16.0V at low amps, a WFCO will never put out that kind of voltage. Yes, you do really need that kind of voltage on a flooded lead acid battery to fully recharge it, otherwise a battery recharger wouldn't provide that kind of voltage.