Dead Chassis Batteries - House Batteries OK

[2B1Ask1]

We have a 2003 Newmar 3803 diesel motorhome. We keep the unit at our home plugged into 50 Amp shore power.

While plugged in to shore power, the house batteries constantly charge and the battery display panel shows a bulk or float charge keeping them around 13.5 V.

However, each time we go back to crank the unit (we try to crank it about once per week), the chassis batteries are dead…usually reading around 12V which is not large enough to crank either the engine or generator. The most recent time, the voltage was so low the generator wouldn’t even make any cranking noise.

When plugged into shore power, the house batteries read around 13.5V but the chassis batteries read around 12.5V after running the coach for about 30 minutes. I was told that both house and chassis batteries should charge when plugged into shore power, but that is not the case.

I understand the small solar panel on the roof is independent of the BIRD and wired only to chassis batteries but isn’t enough to keep them charged, only to slow the parasitic discharge.

The batteries are 12V DEKA brand with around 1000 CCA each replaced within the past year.

What could be the cause of my chassis batteries going dead (below 12V when we need around 14V for cranking).

 

[Kevin D Pem]

12.0 is dead 12.67 is fully charged. Put a battery maintainer on the chassis battery pack. Many have your problem here.

 

[Joe Hogan]

Verify inverter charging circuit is on and producing voltage, verify solenoid, BIM or BIRD , depending on design is functioning.
And the battery switch located most likely in the battery area is switched on.
Do you have User Manuals? This might help verify system and capabilities.
From a quick search looks like 2003 DutchStar on a Freightliner chassis has a solenoid that regulates power between chassis and house battery banks.

 

[2B1Ask1]

Thanks for the note. I forgot to mention we have a Spartan chassis.

After calling Newmar, the tech we spoke with led us down a path. Apparently our BIRD has gone bad and we have ordered another unit (only $107 so I'll take that all day long). Still don't know what could be the parasitic drain on the chassis batteries. They said all the lines to/from the batteries match their factory schematics so nothing extra added by previous owner. Also, there is apparently not a "master" cut off which would cut off literally everything in the unit...wish there was, but can possibly understand not since it's good to have the smoke/CO2 sensors running in any case.