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Old 06-01-2014, 10:22 AM   #1
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When does chassis battery charge?

So, I'm dry camping this weekend, been running the generator twice a day to keep batteries mostly topped off. I had a small inverter (100 watt) plugged into dash plug and I found that my chassis battery was discharging quite a bit and doesn't seem to be charging off the converter while the generator is running.

So, I thought the chassis battery was supposed to charge along with the coach batteries. Is this not the case?

For now I have moved the inverter to a coach accessory plug.

Wes
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Old 06-01-2014, 11:02 AM   #2
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Mine charges from the alternator and the converter. I know that because I used a meter to check.
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Old 06-01-2014, 03:06 PM   #3
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Generator, like shore power, provides 120v to coach and power to the converter. The converter provides 12v to the coach and charges the coach batteries. The chassis battery is not connected to the coach unless you are holding down the emergency start switch. In other words, the chassis battery was not being charged in your situation and the inverter was running it down.

If you do not have enough power left in the chassis battery to start the engine, you can hold down the emergency start switch found on the left side of the drivers seat base while cranking the engine. That ties the chassis and coach batteries together to enable you to start the engine. It only ties together while you are holding the switch down.

You already solved your own issue--move the inverter to a coach 12v socket.
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Old 06-01-2014, 06:08 PM   #4
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RVBill,

That is what I thought. I did use the switch to start the motor.

Thanks
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Old 06-01-2014, 06:25 PM   #5
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I don't believe RVBill is completely correct. Correct me if I am reading the BCC manual wrong, but:

Running the generator will charge the chassis (starting) battery through the battery control center. HOWEVER, the power will only flow FROM the coach battery to the chassis battery when the generator is running (charging voltage available). The override button is to connect the coach battery to the starting circuits when the generator is not running.

You are using the inverter when the generator is not running when it is plugged into the console with the generator off. In this mode the inverter has no access through the BCC to the coach battery. The starting battery is NOT a deep discharge type battery and can only deliver amperage (Though a lot!) for a very short time before it is "used up." High CCA but relatively LOW AH.

A 400 watt inverter will draw over 33 amps. Since most starting batteries (if calculated using their RC or reserve capacity) only have about 30 AH of capacity. So you will kill your starting battery in about an hour of use; maybe much less if you adjust for capacity as the battery is used up at that high constant draw.

Moving that inverter off the starting battery (Bill's recommendation) is exactly the right thing to do.
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Old 06-01-2014, 06:55 PM   #6
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Great info, the drawing is just what I needed. Where did you get it?

Wes
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Old 06-01-2014, 08:31 PM   #7
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Quote:
Originally Posted by wesslvm View Post
Great info, the drawing is just what I needed. Where did you get it?

Wes
I never reveal my sources....
Mostly because I don't remember.
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Old 06-02-2014, 08:23 PM   #8
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Bi-directional Relay Delay

Our 2011 Sunseeker has a different BIRD from the one that Herk posted. The old one has four connections, the newer one has five connections. The fifth connection is for the emergency start switch, which was sort of patched into the wiring with the older BIRD.

The document shows two battery disconnect relays. Ignore them. The Forest River Class C's don't have these. They have a manual disconnect for the coach battery and no disconnect for the chassis battery. The vendor just happens to sell these disconnect relays. (The Class C coach disconnect is just above the battery compartment, so why add the cost and potential failure point of a relay?)

Could someone post this PDF to the Forum library?
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Old 06-02-2014, 08:32 PM   #9
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Quote:
Originally Posted by RamblerGuy View Post
The document shows two battery disconnect relays. Ignore them. The Forest River Class C's don't have these. They have a manual disconnect for the coach battery and no disconnect for the chassis battery. The vendor just happens to sell these disconnect relays. (The Class C coach disconnect is just above the battery compartment, so why add the cost and potential failure point of a relay?)

Could someone post this PDF to the Forum library?
I posted what I had on the motorhome charging circuits. If someone has the correct one, I would be most interested in a copy myself.

I also assumed that since the generator was running, the voltage would be sufficient to close the relay to the starting battery. If that is not the case, I stand corrected.
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Old 06-02-2014, 08:58 PM   #10
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Quote:
Originally Posted by MrJoe View Post
Mine charges from the alternator and the converter. I know that because I used a meter to check.
I've also confirmed the alternator charges the coach batteries and the convertor charges the chassis battery by using a digital multimeter (voltmeter).

PLEASE NOTE: Read the BIRD manual that I posted. The coach or chassis system must be above 13.1 volts for the relay to kick in. It will charge either way. A heavy load in the coach, including charging flat coach batteries, may hold the coach voltage below 13.1 volts so the relay may not connect to the chassis battery. Of course, it's possible that there's a problem with the poster's system.

I used this feature once when the battery in our toad ran down after powering the brake controller for 2 1/2 days. When we got to the campground I jumped it off with a portable jumper battery, then connected jumper cables from the chassis battery to the toad battery. I confirmed voltage at the toad battery and left it overnight.

So why do I do belts-and-suspenders by carrying a jumper battery AND jumper cables? See above!
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