Alternator not charging deep cycle battery

Hi wiscobadger, have you found out what the problem was? How about sharing with us? It might help the next guy with a similar problem.

I had a 1 volt drop between the engine battery and the house battery with the engine running. This prevented the hous battery from fully charging on the road. It turned out there was half a volt lost in a connector under the vehicle where power was taken from the wiring cable heading to the hitch jack. Another half volt was lost in the battery disconnect switch at the door plus wires to and from it. I fixed the first with a soldered joint bypassing the connector (carefully sealed with heat shrink) and the other by connecting straight to the battery instead of going through the switch.

I'm thinking battery isolator may have an issue. While coach is running, house batteries should be 13v+

Measure the voltage of your alternator at your chassis battery while the engine is running. It should register 13.5-14.7. Now measure the voltage at your house battery. The voltage should be identical or very close. If not, it is probably the isolator solenoid, or B.I.R.D that is faulty. If the house battery does not take or hold a charge after driving a long distance, it is probably bad. You should have the battery tested.

Some alternators only output around 13.8 volts. Any 12 volt lead-acid battery needs at least 13.8 volts to start to charge. This voltage will be enough to fully charge or maintain a battery on a trickle charge, but charging time will be very long at 13.8 volts. To charge most batteries in a reasonable time, alternator output must be around 14.2 to 14.5 volts measured at the battery posts. The most likely culprits could be the battery is on its way out, loose connections, or the alternator is no longer outputting sufficiently.

Just asking, are you sure that the battery is good? Get it load tested, just in case. Good luck.

Bob

Hi,

My OEM fuse was 60 amps. It is in the engine compartment in a box near to and in front of the coolant reservoir.

I could not find a 60 so put in a 50.

I've since caused the fuse to be replaced with an automatic circuit breaker.

Because I use a LOT of power the OEM solenoid lasted less than one year before the contacts burned. I upgraded to something better.

Mine has a solenoid near the chassis battery that is turned on by the ignition switch. The solenoid connects the house battery to the chassis battery when energized thus charging the house battery. There was also a 50A fuse in this circuit. The solenoid failed in my MH several years ago and I replaced it. All has been well since.