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Old 10-26-2020, 07:49 PM   #1
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Chassis battery connected to coach batteries?

I have a 2004 Forest River Lexington 235s with a Ford E-450 chassis. I had the rv in for work for a propane leak and had them check the refrigerator to make sure propane operations were good (only had rv 3 months and never tried it). RV was ready for a week before I called (long story). When I picked it up they said they had to jump it and the coach batteries were dead. I suspect they left the refrigerator on for the 8 days before I picked it up. But when home:

1. Would not start next day. Chassis battery low.
2. I put a battery charger / conditioner on one of the two coach batteries figuring it would charge both. It did.
3. Went to check chassis battery for possible drain. When I checked the meter by measuring battery voltage it was back to 13. I have to conclude it was charged overnight along with the coach batteries.
4. I found .03 volt drain on chassis battery. But remembered shore power was connected to coach. I disconnected that and got 0 drain.

So, I’m confused. Expected that other than alternator charging and engaging coach batteries via switch on dash to start if needed they were separate systems.

I can only assume that whatever drained the coach batteries also impacted the chassis battery.

Does this make any sense?
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Old 10-27-2020, 09:24 AM   #2
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Quote:
Originally Posted by S101 View Post
I have a 2004 Forest River Lexington 235s with a Ford E-450 chassis. I had the rv in for work for a propane leak and had them check the refrigerator to make sure propane operations were good (only had rv 3 months and never tried it). RV was ready for a week before I called (long story). When I picked it up they said they had to jump it and the coach batteries were dead. I suspect they left the refrigerator on for the 8 days before I picked it up. But when home:

1. Would not start next day. Chassis battery low.
2. I put a battery charger / conditioner on one of the two coach batteries figuring it would charge both. It did.
3. Went to check chassis battery for possible drain. When I checked the meter by measuring battery voltage it was back to 13. I have to conclude it was charged overnight along with the coach batteries.
4. I found .03 volt drain on chassis battery. But remembered shore power was connected to coach. I disconnected that and got 0 drain.

So, I’m confused. Expected that other than alternator charging and engaging coach batteries via switch on dash to start if needed they were separate systems.

I can only assume that whatever drained the coach batteries also impacted the chassis battery.

Does this make any sense?
S101,

Welcome to the forum.

If these are original batteries, they are old enough they may be doing excessive "self-draining". In a case like that, they could easily go dead in a short time all by themselves. Even brand new lead acid batteries slowly self-discharge, but it generally gets worse as they age. It would probably pay to get them checked. It takes a simple portable load machine about the size of a portable charger. Automotive stores may do it for free since they hope to sell us the new ones.

This battery trouble isn't unusual in RVs since they are more likely to not be driven daily and owners aren't very diligent in keeping them plugged in right away, including me. I usually think I'm going to drive them sooner than I actually do. Lead acid batteries permanently deteriorate faster when in a slightly discharged state and provide the longest service if kept fully charged, or at least up to 13.5 volts or so. Going completely dead, even one time, takes a big chunk of overall life out of them, so it is to be avoided if at all possible.

I've used simple, but reliable, Harbor Freight float chargers for years on several vehicles, boats and bikes. A float charger is made to maintain the charge at about 13.5v rather than charge a dead battery, but they slowly will at about one amp. These only cost about $5 if on sale and are much smaller than the size of my laptop supply. I leave the batteries installed over winter and just peek once in a while to make sure they have power yet. Full size batteries won't run out of water, except very small motorcycle batteries which may get low over six months.

As an example, I had a 1994 pick-up that I knew I wouldn't drive much and was pretty good about hooking the HF charger up right away when I parked it. The original battery lasted for 15 years and was still working when I put a new one in. I did note that the cranking began to slow quickly in our frigid ND winter and didn't want to take any chances. It never quit me though. The truck always started.


So what you suspected is probably true. All the batteries suffered the same fate... they were old.

Good luck.

Wes
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Old 10-27-2020, 10:45 AM   #3
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Thanks

Thanks for the reply.

The batteries are only 3 month old - replaced when I bought the rv.

I do think something was left on to cause the coach batteries to drain. My real puzzle is the chassis battery also draining and behaving like itís connected to the coach batteries.
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Old 10-28-2020, 07:33 AM   #4
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S101,


A compartment light perhaps? Did a previous owner jumper the batteries together so that they all charged at once?


I leave our RV plugged into home shore power and run a 110v cord from the exterior outlet over to the chassis battery with one of those small under-hood float chargers I spoke of, but I've considered either the same type charger inside the camper through the dash power ports or, alternatively, jumpering all together with a switch.


Like I said before, I am lax about charging the chassis battery right away when I park at home. It's easy to forget later. On our last camper, a TT, I tended to forget the SUV tow truck battery and once found it down to only 12v.


Wes
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Old 10-28-2020, 01:37 PM   #5
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Here is an easier idea....

When stored, I leave the house batteries on charge by plugging my coach in.

Additionally, I uncouple the negative wire on the truck battery and leave it next to the battery. Maybe the Harbor Freight trickle charger would work better, but I've never had a problem with this plan.
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Old 10-28-2020, 01:49 PM   #6
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Follow the battery cables and you will probably find a battery isolator inline. The isolator will isolate the chassis and house batteries when in use so using the house batteries the chassis batteries are isolated. House systems don't drain your chassis battery. It also protects the house and chassis batteries if one goes bad. When a charging current is detected (on shore power or an external charge such as solar) the isolator will charge the house batteries and once detected at full will charge the chassis battery. The same happens when the alternator is charging, charge split or alternated between the house and chassis battery keeping both charged.

If you are correct and found the chassis battery charged when you charged the house battery, there has to be an isolator involved.

"A battery isolator is an electrical device that divides direct current into multiple branches and only allows current in one direction in each branch. The primary benefit of such an arrangement is the ability to simultaneously charge more than one battery from a single power source without connecting the battery terminals together in parallel."
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Old 10-28-2020, 05:27 PM   #7
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There is a good chance the battery isolater installed between your chassis battery and coach batteries is stuck in the open position . probably needs replaced
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Old 10-28-2020, 05:32 PM   #8
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New info

Took rv in for repair for something else and asked them to look at batteries/wiring. Seems the coach and chassis batteries are connected with a solenoid between them that allows current to flow both ways if one side is charged to 13v and the other is low the solenoid opens so the alternator or converter (if coach is plugged in) can charge all the batteries.

Issue I had is the converter isnít charging coach batteries and is causing some drain so they are replacing part of it.
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