Question: I have a 2001 Gulfstream Class A motorhome and I’m having trouble charging the batteries while on shore power. I replaced the batteries already, so I know that is not the problem. The batteries also charge fine while the motor is running, or when I put the charger on them while on shore power. But they will not stay charged if I remove charger. So it seems that the problem is in the charger not working when plugged in,so what do I check now?
Answer: Based on your description, it seems that the problem is in the charging system that is supposed to operate while plugged into shore power. It could be the onboard charger itself, a relay/solenoid, a wiring problem into or out of the charger or perhaps an inline fuse.
You could try to look for loose connections or a blown fuse. It is worth a call to the RV manufacturer to see if they can help you troubleshoot and resolve the problem yourself. You will probably have to take the motorhome to an RV repair shop to diagnose and resolve the issue.
In the meantime, you could continue to use an external charger to recharge your batteries. However, there will be some challenges if you travel a lot. A heavy-duty charger is heavy and bulky and should be protected from the elements. In addition, not all campgrounds provide more that one power outlet.
Regarding charging systems in general, note that for lead acid batteries, you should use a three-phase charger that can automatically switch from bulk to taper to float charge. For AGM batteries, we recommend that use of an intelligent charger that not only does a three-phase charge but also has an AGM battery voltage setting.