Can I charge the house battery with the engine alternator?

[heyobie]

I have a Class C, 1988 Ford 350 Travel Master with one good house battery. When I boondock in cold weather, my propane furnace can get me thru 1 night. If I want to drive to another non electric spot,I'm out of electric and therefore heat.

I am considering adding another house battery as a solution. But I want to know if it is a simply solution to charge my house battery using the engine alternator.

Also, a battery cable has been run from the house battery into the engine. It is terminated in the engine bay but not connected to anything. It looks like factory work. Maybe a factory option.

Thanks for looking

[JaxDad]

Hmmmm…. 2 pages of almost entirely wrong answers.

It’s a 1988 rig, it ran an old school continuous duty relay, AKA a Ford starter relay, on the drivers fender. One heavy lug to the alternator, one heavy lug to the house battery and the light lug goes to an ‘engine on’ circuit.

When you start the chassis the alternator is connected to the chassis AND house battery(s), when you shut off the engine house and chassis batteries are separate.

Any auto parts place $20…….

[bobndot]

Ed_Gee wrote:

bobndot wrote:
12v vs two 6v batteries

Just keep in mind that joining two 6v batts will keep the amps the same, where by joining two 12v batts, the amps will double.

The above is misleading, and possibly erroneous. The capacity of a quality GC2 Six volt battery is generally around 220AH, where the capacity of a good 12V battery is around 100AH ... so you will end up with slightly more capacity with the heavier duty two 6V batteries anyway.

Some people think the 220 6v will give them 440 amps at 12v . All i am saying is a GC-2 at 220 amps is still 220 amps when adding the 2nd GC-2.
However, if you add two 100amp 12 v batts together the amps double to 200 amps but keep the 12v supply to the rv.

[enblethen]

The relay that you found often is powered by a three-position center off rocker switch behind the driver. one position is momentary for aux start function other position is for holding relay in for charging.

[Ed_Gee]

bobndot wrote:
12v vs two 6v batteries

Just keep in mind that joining two 6v batts will keep the amps the same, where by joining two 12v batts, the amps will double.

The above is misleading, and possibly erroneous. The capacity of a quality GC2 Six volt battery is generally around 220AH, where the capacity of a good 12V battery is around 100AH ... so you will end up with slightly more capacity with the heavier duty two 6V batteries anyway.

[bobndot]

12v vs two 6v batteries

Just keep in mind that joining two 6v batts will keep the amps the same, where by joining two 12v batts, the amps will double.

The 6v batts are true deep cycle batteries that allow them to be discharged lower without damaging them. They have heavier thicker plates than the 12v batteries.

Most 12v deep cycle batteries are really ‘hybrid’ batteries. Maybe you can find a true deep cycle 12v , but you would have to have a knowledgable source to locate such.

IMO, it comes down to the size of your battery compartment. The 6v models might be too tall by a 1/2” or so.
As an example, If your battery compartment was under your entrance step, some people have removed the lid and installed some wood trim around the edge. Then reinstalled the lid allowing the clearance needed. 1/2” is not that drastic a change to become used to while going in/out of the rv.

[Ed_Gee]

SJ-Chris wrote:
Most RVs are designed to have the alternator charge the house batteries through a solenoid while the engine is on (...presumably while driving from one campsite to the next). A built in feature of that solenoid is an "emergency start" switch usually mounted on the dash or near the driver side steering column. When working properly, if you push and hold that button you should hear a "click" and the solenoid temporarily connects the house batteries to your chassis battery so that you can use the house batteries to help jump start a dead/weak chassis battery. This is all by design.

It is not rare at all for that solenoid to wear out and break. They are cheap and usually fairly easy to replace. Let us know how it goes.

-Chris

What Chris said, above. Sounds, from your previous posts, that your old RV may have already have that feature. ... boost at least. you could simply change that momentary contact boost switch on the dash to a toggle switch that will stay on when you want it ... thus maintaining your starter battery connected through that solenoid you found to your house batterys. You should check that that solenoid still works ... they can and do fail at times ... but easy to replace.

[SJ-Chris]

heyobie wrote:
Gritdog,

To get the charge from the alternator to the house, can I just run a wire from the positive car battery terminal to the battery switch that goes to the house battery! I don't want to play with the alternator if I don't have to.

If so, does it need to be a large diameter cable or a 12 wire sufficient?

The positive car (chassis) battery terminal IS connected to the alternator output. So connecting to one connects you to the other.

This wire could be pumping 30-100amps of current back to your house battery(s) (depending on the alternator and # of batteries in your house bank), so it needs to be thick battery cable.

I assume when you say "battery switch" you mean the solenoid. The switch on your dash is an override switch to the solenoid to force it to be "on" (connecting the house batteries to the chassis battery). So you won't be hooking up your battery cables to the "switch"...you will be hooking them up to the solenoid. Make sense?

Good luck!
Chris

[IAMICHABOD]

This You Tube Video might be of help to you.

[SJ-Chris]

Most RVs are designed to have the alternator charge the house batteries through a solenoid while the engine is on (...presumably while driving from one campsite to the next). A built in feature of that solenoid is an "emergency start" switch usually mounted on the dash or near the driver side steering column. When working properly, if you push and hold that button you should hear a "click" and the solenoid temporarily connects the house batteries to your chassis battery so that you can use the house batteries to help jump start a dead/weak chassis battery. This is all by design.

It is not rare at all for that solenoid to wear out and break. They are cheap and usually fairly easy to replace. Let us know how it goes.

-Chris

[time2roll]

For the effort I would go #6 wire minimum.

[heyobie]

Gritdog,

To get the charge from the alternator to the house, can I just run a wire from the positive car battery terminal to the battery switch that goes to the house battery! I don't want to play with the alternator if I don't have to.

If so, does it need to be a large diameter cable or a 12 wire sufficient?

[heyobie]

Thanks guys. I'll order the isolator.

Klutchdust,
What's the advantage of two 6volt batteries in series vs two 12volt in parallel?

[klutchdust]

On my C, I installed two of these. Battery life greatly improved.

[Grit_dog]

Yes you can and it’s common, as said, to have a charge wire from alt to house batt.
May or may not provide enough amps to effectively charge as fast as you want or need it to.

[MDKMDK]

heyobie wrote:
Thank you guys for all the info.

There is more to the story. I didn't want to glog up my post but since I have found interest and intelligence, someone may be able to explain this.

The large positive wire comes from the house battery to a post on a selenoid which is mounted on the driver side wheel well. Then on the opposite side of the selenoid, another large red positive wire goes up and across a plastic channel over to a block attached to the passenger fender. My guess is that this is all factory but not sure. But what is not factory is a push button has been installed inside the cab on the dash. It connects to the selenoid and a power source. The push button doesn't work, but the purpose was to activate the selenoid so that the house battery power would run over to the car battery/passenger side of the vehicle.i thought it may have been a system to use the house battery to start the car. Maybe someone can explain what it is. I'm gonna pull it since it has no purpose it seems. This is probable the battery switch, but why it has a push button makes no sense to me

Sounds like a "battery boost" system, which allows you to borrow some cranking amps from the coach battery, if the chassis battery is too low to start the engine. The push button would connect the 2 systems for the duration of the starting attempt, allowing current flow from the coach battery to "help" the chassis battery turn the engine over. They're still fairly common on modern motorhomes.