Some of the advice being passed around on some of the RV forums is pretty bad, some of the "advisors" claim to have electrical or engineering backgrounds. A guy just started a topic, he has a barn fed with a neutral bonded 3 wire service, he had electricians hook up a 4 wire 50 amp RV service and now his coach batteries overcharged and got ruined, he is asking if the electrician is to blame. Everything he describes points to a proper installation and a coincidental converter/charger failure in the RV, yet the speculation continues about the electrician/electrical being to blame. (The electricians came back and checked everything and found nothing wrong)
Here's the latest response this morning regarding the neutral bonded service in the barn.

It sounds like they just have a loose neutral somewhere between the circuit the charger is on and the transformer if the readings are really 140/100. All the rods in the world won't help that. If it is bad in the wire coming out of the meter pan to the service disconnect enclosure bus bar, call the utility. The problem is on their side. Otherwise it is on the customer side somewhere.

There are no readings of 140/100, that guy was just offering a possible scenario. The only problem is the batteries overcharged and the owner is looking to blame the electric hookup, and others are now chiming in blaming the neutral/ground bond on the 3 wire service to the barn.

OK. I see the point tho. Most problems like this end up being a bad neutral. A meter will find that right away as soon as you start moving loads around. If the voltage is right, the guy just might have a bad charger.