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Old 12-20-2015, 09:36 PM   #1
Junior Member
Join Date: Dec 2015
Posts: 2
Overcharging chassis battery with shore power

Lurked here for while and feel like I have read every electrical related thread but I can not find anything related to my issue. I have several questions that I hope all of you can help answer.

I have a 2008 Sunseeker on a E450 chassis. I just replaced the house batteries with a couple of 6V golf cart batteries and recently installed a new chassis battery. Checked the voltages of both (12.8 chassis and 6.2 for each house battery)and then plugged in the shore power to charge the house batteries up. Converter switched to bulk charge like it should (~14.4V). I checked the voltage again of the chassis battery and it read 14.4V as well.

Q1: Is this "normal" operation? I was hoping the battery control center was smarter than that to unnecessarily charge the chassis battery. I am afraid of the chassis battery getting overcharged over time.

If this is "normal" I am thinking of putting a disconnect on the big red wire connected between the chassis battery and the house battery system so that I can have a say in when the chassis battery is charged.
Q2: Any problems with this other than I have to remember to use it?

While digging through the system trying to find what was connected to what and which magic wire would disconnect the chassis battery, I got a brilliant idea to try. I disconnected the negative connection from the chassis battery and tried to start the engine. It fired right up! I have the emergency/auxiliary battery switch but did not use that.
Q3: Is this a sign that that emergency battery start solenoid is bad?
Q4: if the solenoid is bad, could that be the reason for the chassis battery being charged unnecessarily?

I disconnected the big red wire for the house battery system from the chassis battery, tried to start again but there was no juice to the engine as expected. All of this was while attached to shore power.

Other things to add that may or may not be helpful. When the engine is running, the house batteries charge as expected. The WFCO 9855 converter seems to switch between the 3 charge stages correctly. The old interstate marine house batteries sucked but I am not positive that I don't have some parasitic load in the motorhome that wants to kill batteries. The motorhome only has 16000 miles on it but I am concerned that connections and grounds may not be that great after 7 years so I will be going through those as well. I have only owned the motorhome for the last 1.5 years and 7000 miles. The battery control center is a fr-500l.

Thanks for the help

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Old 12-22-2015, 11:22 PM   #2
Junior Member
Join Date: Dec 2015
Posts: 2
Doing some more research leads me to believe that this behavior is normal and that these systems will charge all the batteries when it can, regardless of the condition of the other batteries.

I also determined that my solenoid was sticking. I have since cycled it a bunch and it appears to now be working correctly, although I am not a fan of the 0.75 amps it draws all the time.

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Old 12-23-2015, 04:37 PM   #3
Senior Member
Join Date: Apr 2012
Location: South Carolina
Posts: 1,269
This is normal. The chassis battery is connected to the coach batteries and convertor by the battery control center. On our 2011 Sunseeker the BCC is located on the left side of the steps. If you want to prevent the convertor from charging the chassis battery you can pull off the connector on the controller. Ours is an Intellitec brand. You can find a descriptive document about it in this forum's library in the electrical section. Sorry but I'm using my phone and can't look up the link for you.

The controller is called a Bidirectional Relay Delay, or BIRD. It controls a relay in the same compartment that connects the coach and chassis 12 volt systems. The document explains it.

There have been several threads on it. Search for "BIRD".
2011 Sunseeker 3100
1997 Pathfinder Toad
RamblerGuy is offline   Reply With Quote

battery, charging, power

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