dead batteries

[bonfield]

2004 holiday rambler.Getting ready for a trip and the coach is plugged into shore,come to start it and the coach batteries are dead.Had a little age on them so i replaced both with new units and the problem seemed resolved.Drove 500 miles on our trip and plugged back into campsite shore power.When checking batterie statis it showed voltage of house barreries and not coach.Tried to start coach and batteries dead/very dead.what do i need it check to resolve this problem.Also what should the panel read when plugged into 120v for normal use as it always looks like it is charging batteries or on float.

[MrMark52]

When talking MoHo batteries, better to describe the two different sets as “coach” and “chassis” batteries. Makes it easier to follow.

‘04 MoHo - you probably have an old linear convertor - that needs to be replaced with one of the newer microprocessor controlled multi-stage convertor’s. Progressive Dynamics and others make a “drop-in” replacement.
The old linear convertor’s will cook your coach (aka “house”) batteries (and chassis battery if connected).

Chassis batteries don’t always get charged from the convertor. And they often see parasitic electrical loads - dash radio, ECM, or screwy coach builder interface wiring.
A lot of people put a knife switch on the chassis battery to prevent parasitic loads from burning the chassis battery.
Your every day car/truck likely has parasitic loads that are unrealized over what is seen with a MoHo.

But a knife switch would break any standby charging capability that your coach MIGHT have.

Get the wiring diagrams (coach and chassis) for your MoHo and study them to see what loads could be burning your batteries and to determine if adding switching of sorts will work for you.

[Fishar]

Originally Posted by bonfield

2004 holiday rambler.Getting ready for a trip and the coach is plugged into shore,come to start it and the coach batteries are dead.Had a little age on them so i replaced both with new units and the problem seemed resolved.Drove 500 miles on our trip and plugged back into campsite shore power.When checking batterie statis it showed voltage of house barreries and not coach.Tried to start coach and batteries dead/very dead.what do i need it check to resolve this problem.Also what should the panel read when plugged into 120v for normal use as it always looks like it is charging batteries or on float.

How long were you parked on shore power?

I don't know if your model has a bird and charges chassis batteries off shore power or not. My unit has an ird and doesn't charge chassis batteries off shore power. I had to get a battery maintainer for when I'm parked.

We've been parked and on shore power for about 6 weeks since our last trip. My magnum remote shows my house batteries float charging at 13.4 volts and 17 amps.
Batteries are 1.5 years old.

[jacwjames]

Does the coach start when you try and use the Boost button. The button will tie the two batteries together but may also have something to do with the chassis battery charging while on shore power.


In my case I had a Lambert 415 battery maintainer that was would maintain the chassis battery while on shore power. I had a BIRD and Isolation solenoid that would keep the house batteries charged while driving.

The isolation solenoid is also the ties the two battery banks together when I pressed the boost button.

So with the above if the Lambert quit working my chassis batteries would die and if the isolation solenoid quit no house battery charging while driving and/or boost function.



I refer to the above in past tenths since I installed a Bluesea MLACR and removed all of the above. The Bluesea will charge both banks when there is a charge source from any source (engine, generator, shore) and it also has the ability to boost if needed. Have had installed almost 2 years, works great and relatively cheap and a pretty easy install.

[YC1]

If you were parked for more than a few days, and if your unit does not charge the engine batteries when on shoreline or generator, you could easily have dead engine batteries unless you turn off the battery control switch. Guessing you have one for the engine and one for the house side.

I did not research to see if your engine batteries are getting charged when on shoreline but sure sounds like they are not. This may be normal for your setup, but can be cured easily with some minor modifications.

[jacwjames]

One thing I did last year was install a BMV712 battery monitoring system. I was always skeptical of what the inverter display showed as far as battery voltage. The monitor gives a lot of information on the house side as far as voltage, amperage used, amperage left etc but also has the ability to monitor the chassis battery.

This last winter I decided I didn't want to leave the coach plugged in charging all the time so I have it on a timer where it charges the batteries for 4 hours every Friday, seems to be working and when I'm in my shop I check the status via the bluetooth option.

I noticed that for some reason the chassis batteries bleed down faster then the house. I have everything off that I can turn off on both the house and chassis. After a week the house will be ~12.5-6 still +93-4% charged, but the chassis will be lower, ~90%. Still good but if I didn't charge them it wouldn't take long to go down and this is with EVERYTHING off.



Install a monitor or volt meter and watch what is happening. Prior to installing the Victron BVM712 I had a cheap digital volt meter installed in the dash, which comes off the chassis battery. I could easily see what the voltage was doing. Even though my coach does charge both batteries I thought it was important to know.

[rv4fun08]

Check you alternator you are running shore power and once you disconnect!
you're done.

[Arch Hoagland]

So bonfield what did you find was that causing the problem?

[Scooter363y]

Sounds like you need to do a battery check-up

1. Unhook your battery from the coach, check water level if needed
2. Check voltage without a load
3. If not up to voltage (12.6) charge for 24 hours and check voltage again
4. If still not good take to auto parts store and check (Orielys)
5. If battery is good then clean terminals/cables and reinstall, test voltage
6. Start motorhome and let run for about 5 mins to let alternator stabilize
7. Rev up engine to 2-3k, voltage should raise to 13.5-14.0 volts
8. If voltage is ok then your done. If not it’s time for an alternator check

If you are still having a problem with coach battery discharging when not plugged in then you have a voltage draw in the coach so where.

If you want to have the coach battery charge while you are plugged in then you will need a B.I.R.D. Unit to keep the coach battery charged when plugged in.

Good luck and RV safe
Scooter

[Stan&Jacquie]

Bonfield: I had a similar problem but at least I was getting charging from the alternator. When stored, the chassis batteries would draw down, so to fix it I installed the “Battery Combiner” by Magnum. It responds to any charging source and will charge the chassis batts when they drop to a certain voltage which you can set. That plus a couple solar panels solved my problem.