Are Engine and House Batteries Connected?

[Olddud]

On a long trip home, after stopping to get gas, I turned the key to start, and the dashboard went dark. After a bit of panic in the 95 degree weather, I tried the "battery boost" switch, and feeling relieved, it started. I immediately assumed the engine battery was shot. Also, noticed the gas gauge now was pegged all the way to the right and way past "full".

I called ahead to a RV Park and stopped about 2 hours later. Got my voltmeter to check the engine battery, but the door automatic step didn't go down, so I assumed the house battery was now dead. Checked the engine battery with the engine off and hooked to shore power and it showed 6.5 volts, but didn't think about checking the house battery because it was late and I needed to get a new battery before the only auto store in town closed down. BUT, before removing the engine battery, I again tried the "battery boost" feature, and it did NOT start (but dash lit up), so the house battery must have been way down. Got the new engine battery and put it in, and all was well, except the gas gauge was still pegged to the right. Turned the key off and on several times in all directions, checked window operation, locks, etc., and somehow the gas gauge started working right again. Strange.

After thinking about it for a few hours, and worrying I fried the alternator somehow, went outside to check the voltage on the new battery without the engine running, and it was showing 14.5 volts! Checked it with the engine running and it showed 15+ volts.

Questions:
1. Why does, after 2 hours, the new engine battery show 14.5 volts without the engine running -- is it being charged by the house charger?
2. And, are they always connected in some way, or only when the "battery boost" switch is operated?
3. Why did I run down a brand new house battery? Western Kansas is a bad place to almost have a complete shutdown.
4. Have I ruined the new house battery?

By the way, I traveled 400 miles today and everything is working fine, charging right (checked it), etc.

I will check battery voltage on both batteries in the morning to see how they look.

[CharlesinGA]

Replace the boost relay, it sounds like the contacts are going bad. They eventually burn up and don't work at all.

There is no isolalator, other than the boost/charge relay. Mine had got to the point it was not passing any current at all.

If its a round silver contactor, the generally accepted replacement is the Cole-Hersee 24213, which will require a 14 or 16 gauge ground wire with a large ring terminal to fit the mounting screw, and a small ring terminal to fit the small terminal stud on the contactor.

Charles.

[tatest]

Olddud wrote:
I was able to do some checks this morning on the battery boost relay. Before doing anything, the house battery read 12.7, and the engine read 13.2. This was after sitting in my driveway overnight without shore power.

Turned the key to accessory (just before start), pushed the boost switch several times just for grins, and heard the boost relay operating. Started the engine and measured voltage (no boost). The engine battery read 14.4, and the house read 13.7. So I assume the alternator is charging the house battery. Wonder why the voltages aren't the same?

There is enough resistance in the battery isolator and wiring to cause that much of a voltage drop. Both voltages may go down as the voltage regulator responds to the charge state of the engine battery.

[Olddud]

I was able to do some checks this morning on the battery boost relay. Before doing anything, the house battery read 12.7, and the engine read 13.2. This was after sitting in my driveway overnight without shore power.

Turned the key to accessory (just before start), pushed the boost switch several times just for grins, and heard the boost relay operating. Started the engine and measured voltage (no boost). The engine battery read 14.4, and the house read 13.7. So I assume the alternator is charging the house battery. Wonder why the voltages aren't the same?

[CharlesinGA]

Olddud wrote:
Thanks Charles. Looking at the wiring diagram, it appears these two solenoids are inside a two handled "Battery Mode Solenoid and Relays" box. I will check into it.

Very good info.

In my View, you lift a lid in the floor between the seats, then remove a panel screwed over the power box. Later model Views put it under the RH seat. No idea where they hid it on yours.

Be sure and disconnect BOTH the CHASSIS and COACH/HOUSE batteries before working in this box to disconnect/connect or remove/replace anything.

The fact that your boost switch worked tells me the relay is probably OK. There have been a few Views (only a couple I have read about) found with the Boost switch wired wrong, and the boost portion worked OK but the battery charge portion did not work, as two wires were cross pinned at the switch. One owner went for several years before he discovered the problem. He always used shore power and never noticed. He then started boondocking and then had house batteries going dead on him.

Charles

[CharlesinGA]

DrewE wrote:

CharlesinGA wrote:
Forgot to add. The House/Coach batteries will not charge from the 120v to 12v converter UNLESS the house battery switch (aka salesmans switch) is ON. Turn the house batts off, and the converter, if powered by shore power or generator will provide 12v, but is not connected to the house batts and will not charge them. Gotta have the house batts on.

Charles

While that is the most common setup, it's by no means universal. On my RV, the converter is connected on the battery side of the house battery disconnect switch. That means that, with the switch off, the converter will charge the battery but will not power the house circuits.

(You may wonder why they connected it up that way. I suspect it's because it made the wire runs simpler and shorter. The converter is a standalone deck-mount converter that's closer to the battery than the DC distribution panel.)

I agree, every manufacturer is different, but I think virutally all of the Winnebago and Itasca models have the same basic concepts as far as circuity, as, most likely, the same engineers designed all of their C models.

The OP has an Itasca by Winnebago.

Charles

[DrewE]

CharlesinGA wrote:
Forgot to add. The House/Coach batteries will not charge from the 120v to 12v converter UNLESS the house battery switch (aka salesmans switch) is ON. Turn the house batts off, and the converter, if powered by shore power or generator will provide 12v, but is not connected to the house batts and will not charge them. Gotta have the house batts on.

Charles

While that is the most common setup, it's by no means universal. On my RV, the converter is connected on the battery side of the house battery disconnect switch. That means that, with the switch off, the converter will charge the battery but will not power the house circuits.

(You may wonder why they connected it up that way. I suspect it's because it made the wire runs simpler and shorter. The converter is a standalone deck-mount converter that's closer to the battery than the DC distribution panel.)

[CharlesinGA]

Forgot to add. The House/Coach batteries will not charge from the 120v to 12v converter UNLESS the house battery switch (aka salesmans switch) is ON. Turn the house batts off, and the converter, if powered by shore power or generator will provide 12v, but is not connected to the house batts and will not charge them. Gotta have the house batts on.

If the vehicle lighter/power socket is hot all the time (as opposed to being hot only when the ignition is on) then you can use a small solar panel to backfeed the lighter socket to maintain the chassis batteries. Search Ebay for "VW solar panel" without the quotes, to see what I mean. These came with every VW shipped to the US, but the dealer employees stole them and sold them on Ebay, and the new VW buyer never knew they should have got them.



Charles

[jauguston]

If your electrical system doesnt charge your chassis battery when you are on shore power get yourself a "ultra Trickle/Start". Its a little electronic box that has three wires that are simple to connect. The instructions are good and easy to follow.

Best Converters has them.

Jim

[Olddud]

Thanks Charles. Looking at the wiring diagram, it appears these two solenoids are inside a two handled "Battery Mode Solenoid and Relays" box. I will check into it.

Very good info.

[CharlesinGA]

The battery boost/charge relay is a high failure item.

Note that the steps and the slide outs are powered by the chassis battery. Logic here is that if you can start it, they want you to be able to retract everything. If they were off the house batteries, you might have run them dead, but still be able to start vehicle and drive away with stuff extended.

I suspect your 2010 Itasca Cambria 30C has many of the same components and wiring logic that my '07 View has. There are two relays, one is a black one with two fused in holders made into it. It is the house battery relay. It stays in whatever position it was driven to by the solenoid, even if you disconnect the batteries, it will stay in its last position, it does not have a normally open or close position.

The other relay is a silver cylinder with two large terminals and one small one. This is the high failure boost/charge relay. Every time you start the engine, and the alternator begins to put out voltage, this relay is automatically closed, to allow the vehicles alternator to charge the house batteries. When the alternator voltage drops off (as in shutting down the engine) it opens back up (spring loaded to open). If you use the boost switch (and the house battery switch has to be on for this to happen), you are manually operating this same solenoid to connect the house batteries to the chassis battery to boost a weak chassis battery and keep you from being stranded.

My View has about 19K miles on it, and the boost/charge relay was receiving control power to the small terminal, everything else was normal, and it was simply not passing current thru its contacts. It would neither boost nor charge, but from all outward appearances (till I took a volt meter to it) it was working. I replaced it with a nearly identical Cole-Hersee 24213 200 amp relay. The major difference is two small terminals rather than one. The old relay had the solenoid windings grounded internally, while the Cole-Hersee has to have a separate ground wire run from one of the terminals to a good ground, most likely one of the solenoid mounting bolts.

Everything is fine now, and when I start the motor, I see 14.1 volts on the HOUSE batteries AND the CHASSIS battery, and if I disconnect the chassis battery ground, turn on the house battery switch by the door, and hit the boost switch, I get house battery voltage at the positive chassis terminal (when measured to a chassis ground). This proves the solenoid is working properly.

https://www.amazon.com/gp/product/B005K2429I/ref=oh_aui_detailpage_o07_s00?ie=UTF8&psc=1

Charles

[Olddud]

I meant to say my unit is a 2010 Itasca Cambria 30C.

Also, just measured the voltage after a night of no charge, and the engine battery was 14.3, and house 13.8. I would have thought both would be lower than that.

I will do some tracing of the wiring to see what I might find.

BTW, the engine battery was 7 years old! Something told me to replace it before the trip because my hi-tech charger wouldn't go into de-sulfate mode on it's own. It's one of those maintainer chargers that switches to de-sulfate after charging is complete. I actually think the battery shorted out in a place or two due to age, heat, and the gawd awful bumpy roads in Colorado, at least where I was driving.

[YC_1]

If your engine battery was 6 volts or so and now a replacement shows 14 volts with the engine running, my vote is for a loose battery connection. It could be loose at the combiner solenoid or at the battery terminal. When you replaced the battery you tightened those connections but did you follow those heavy wires and tighten anywhere they are connected???

The boost switch, if connected to the engine battery, would not close due to low voltage. If you get into a situation like that again, you can often just use one jumper cable between the positives to get things going.

[pianotuna]

Hi,

You may have a bad ground. Finding it may not be easy. Check where the dash electrical system fastens to the ground.

[Chopperbob]

Mine did that turned out to be the house circuit breaker.

Also had to run a new trigger wire to the alt. That's
after I replaced the alt. But now I have a 150A alt.