Battery current draw.

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JD Sharp

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Joined
Jun 20, 2009
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248
Location
Ferndale, WA
Just replaced starting battery for 2000 Ford F53 chassis V-10, it was time. During installation noticed stpark when connecting positive lead, so I checked the current draw with ignition off. It was .3 amp, is that normal?
 
0.3 amp draw is maybe a little on the high side. Radio memory, computer, etc. all draw from the battery when the ignition is off.  Yours equals about 8AH per day if your meter is accurate. If that is true it equals about 8 AH per day. Sitting any longer than 10 days to two weeks would drop the battery considerably. I would check again using a known accurate meter with a milli-amp scale (1000 ma = 1 amp).
 
The last time I had my Bounder in for service, and installation of a 160amp alternator, the mechanic spent over an hour trying to track down a current draw on the coach battery.  (He also was alarmed by a spark when he hooked the chassis battery back up).  He could not find the problem, so he called me and asked if I wanted him to continue looking or to just leave it alone.  I told him to stop and allow me to come check it out.

When I arrived, I closed the entry door and asked him to recheck his meter readings.  The current draw was gone, and after a little persuasion, so was the labor charge for his search.  My coach has an under-step light that comes on when the step is extended, and stays on while the door is open.
 
Lou,
Shouldn't the step light be on the house battery circuit? OP says the Starting Battery has a draw.
 
Rich D. said:
Lou,
Shouldn't the step light be on the house battery circuit? OP says the Starting Battery has a draw.

Maybe it should, but mine is not.

EDIT - Just checked my BCC electrical diagrams, and mine is correctly wired to the Chassis Battery, after the
Disconnect, but before the Ignition.
 
I closed door but still have a .24 amp draw. On mine steps and light are on house, except override to close when engine starts.
 
The step is considered safety equipment and thus is powered from the coach battery. You want the step to function even if the house battery is dead, so you can get out of the coach.  Or so the RVIA construction standards say, at any rate.
 
Gary RV Roamer said:
The step is considered safety equipment and thus is powered from the coach battery. You want the step to function even if the house battery is dead, so you can get out of the coach.  Or so the RVIA construction standards say, at any rate.

Gary, OK, I'm confused with the terminology. Two battery banks: Chassis and House. Which one are you referring to when you say "coach" battery.  I'm assuming you mean coach = house. Chassis  = starting.
 
Sounds like we need an addition to our Glossary of RV terms.
 
Coach = chassis = starting battery in this context.
 
Ned said:
Coach = chassis = starting battery in this context.

Thanks, That now makes sense to me. My setup is a bit confusing as I have 10 Lifeline Group 4D batteries. Two in series are the starting batteries (24V) and 8 are for the house. That part is easy BUT when all batteries are charged, the two banks are connected together through a huge relay and voltage monitoring system. They only separate (automatically) when the voltage drops to a point where the starting batteries are in danger of discharge to a level where starting could be compromised. They will re connect a few minutes after the engine is started and warmed so the load from two 140 amp/24 volt alternators wont be applied top a cold engine. 12 VDC items in the house are powered from 24V banks through  24 to 12 converters. Inverters are powered directly by 24V. Add to that, a fully multiplex wiring system for the house and another for the chassis makes a big learning curve for someone who understood "normal" wiring of my old coaches pretty well.

When I shut off the "Coach Master" on my bus it kills power to the house AND chassis but not the charger side of the inverters, starter motor or any 120VAC items. And, to further confuse the issue, the step light control circuit is disabled but not power to the light which stays in the condition it was in when you shut off the "Coach Master". (If "On" it stays "On", if "Off" it stays "Off".) In order to see where the power for the step light originates I either have to wait for a condition that separates the banks and test to determine the source of power or sort through drawings to see which of the multiplex systems powers it. See why I'm confused? Please excuse my ignorance on how a "proper" step light should be connected!  ???  In the meantime I will read, ask and learn. Thanks.
 
What year, make and model coach do you have?  I'm not familiar with any US RVs that use a 24V DC system, either for chassis or house.
 
Ned said:
What year, make and model coach do you have?  I'm not familiar with any US RVs that use a 24V DC system, either for chassis or house.

2006 M450 LXi Blue Bird Wanderlodge. Total of 57 built (in 2005,6,7) for private use many others for OTR bus service. They were designated 4500 Express.
All stainless from the ground up, chassis and body,m except for an aluminum roof.

 

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Ah, a rare bird indeed ;)  Beautiful coach, as are most Bluebirds.
 
Thanks Lou,

I don't want to hyjack the thread but suffice it to say that simple things like a step light circuit need much more study than in my last, conventionally wired Bird, thus my confusion, beg pardon for dumb questions. I've had this coach for nearly 4 years and am finally getting a handle on the electrical system. Much more to learn yet. Intellitec Corp, who made the Multiplex system is reportedly working on an iPad interface for all lighting, shades, etc., just when I memorized what all the switch panels do, I won't need them!
 
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