House Batteries Not Charging When Underway

[GeoDoc]

The chassis battery is fine but house two batteries under the entry step are not getting a charge. Dead. Shut down refer, gen start and everything else.

What could be happening?

I am assuming that the total batteries on board are three??

[JLeising]

There are multiple charging circuits for the house batteries. When a circuit is charging the house batteries, the voltage measured at the batteries should be over 13 volts (assuming batteries aren’t internally shorted).

Common house battery charging issues include:

Plugged in to shore power? Verify 120 volts in vehicle (plug something into an outlet). Check for tripped breaker on converter circuit.

Running generator? In addition to breaker on converter circuit, check breaker on generator. Also verify 120volts in vehicle, as above.

Running vehicle engine - charging house batteries by chassis alternator? A special bi-directional relay (BIRD) is supposed to start charging the house batteries after the chassis battery is fully charged, as I understand. May have to drive a while (hour plus?) before the BIRD starts charging the house batteries from the chassis alternator.

[valleyduo]

Assuming you have a house battery disconnect, make sure that didn't get switched off.

[GeoDoc]

Originally Posted by JLeising

There are multiple charging circuits for the house batteries. When a circuit is charging the house batteries, the voltage measured at the batteries should be over 13 volts (assuming batteries aren’t internally shorted).

Running vehicle engine - charging house batteries by chassis alternator? A special bi-directional relay (BIRD) is supposed to start charging the house batteries after the chassis battery is fully charged, as I understand. May have to drive a while (hour plus?) before the BIRD starts charging the house batteries from the chassis alternator.

I installed two new batteries yesterday and they are not charging when running vehicle engine. They do charge on shore power and generator.

Is this BIRD a Mercedes part or a Forest River part?

[JLeising]

The BIRD would be a Forest River part.

Note that the BIRD will only allow house battery charging after the chassis battery is fully charged (as I understand).

[SeaDog]

Just for piece of mind look under the hood and see if there is a 150 amp breaker coming off the alternator that goes to your battery charge controller I believe located by the front steps. I found this to be a problem on a sun seeker ( i know like your) not charging the house batteries underway, but worth a look.

[CharlieS3]

A friend of mine just had this exact same problem with his brand new Sprinter Mercedes RV . The problem was that the output wire at the generator had not been stripped before the connector was crimped. Not a problem you would expect on a Mercedes factory installed part.

As always, this type of troubleshooting starts with a schematic and a good multimeter

Charlie

[mdf123]

I did not see what model you have. I have a Prism that had a similar problem. A fuse had blown. Forest River developed a workaround to prevent the fuse from blowing. After installation I have not had that problem again.

[GeoDoc]

Coachmen recommended a repair center and we spent the day there. Elizabethtown, KY.

They diagnosed the problem as a blown 100 amp bus bar located just behind the start battery (under the driver's floor) that sends power to the solenoid in the house battery compartment.

The did not have one so we are going to the Coachmen factory tomorrow to see if they will fix it.

[lacamastraveler]

Originally Posted by GeoDoc

Coachmen recommended a repair center and we spent the day there. Elizabethtown, KY.

They diagnosed the problem as a blown 100 amp bus bar located just behind the start battery (under the driver's floor) that sends power to the solenoid in the house battery compartment.

The did not have one so we are going to the Coachmen factory tomorrow to see if they will fix it.

Glad you found the problem. Hey, while at Coachman would you ask if the Chassis has to be fully charged before the House batteries charge as someone mentioned. I’ve wondered about that. Thanks.

[mickanddon2]

Originally Posted by GeoDoc

Coachmen recommended a repair center and we spent the day there. Elizabethtown, KY.

They diagnosed the problem as a blown 100 amp bus bar located just behind the start battery (under the driver's floor) that sends power to the solenoid in the house battery compartment.

The did not have one so we are going to the Coachmen factory tomorrow to see if they will fix it.

we just had the same issue. could not find a fuse that size anywhere. finally Mickey Shores said an ams fuse try BEST BUY car audio and indeed! like $6 for a bag!

[GeoDoc]

We pulled into the Coachmen factory at 1:00 PM today and they had a tech waiting for us to fix the problem.

Just aft of the start battery is a 100 amp fuse which is on a line that feeds the house batteries. The size is mandated by MB although it could have been larger since the generator hits 150 amps when it starts. Mine was blown.

On newer Coachmen of this type the 100 amp fuse has been replaced a automatic re set breaker that will come back online after a minutes when tripped. It would only trip if the house batteries were so low that they had a hard time starting the gen set. A problem for boon dockers but not for us who did not anchor our boat or boon-docker our RV.


But, Kudus to Coachmen for the great service. Their facility is huge.

[mickanddon2]

so glad to hear. So did they replace your buss fuse with the re set breaker? I also have a 2016 prism

[GeoDoc]

Originally Posted by mickanddon2

so glad to hear. So did they replace your buss fuse with the re set breaker? I also have a 2016 prism

Yes fuse is gone and re settable breaker has replaced it.