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

[4x4van]

The battery boost solenoid on your '88 serves double duty. It is triggered by a wire that is hot when the engine is running, which engages the solenoid to allow the alternator to charge both banks. The momentary pushbutton does the same thing (likely through the same trigger wire on the solenoid); connects the two battery banks to serve as an emergency start if the chassis battery is dead/low. As "enblethen" says above, it needs to be a continuous duty solenoid.

Adding a switch in the line WILL eventually lead to both battery banks being drained and you being stranded when (not if) you forget to turn it off once you get to your campsite. It's an extremely simple and foolproof setup. Don't try to reinvent the wheel.

[pnichols]

heyobie wrote:
Which solenoid did you buy? I'd like to replace mine

Here's the Trombetta "Bear DC contactor" solenoid that I now use in our Class C that connects the coach batteries to the engine alternator system - note that the one I use is the 2nd one down in the chart, rated for 225 amps continuous duty, and is the version with silver contact material. It is not inexpensive, but IMHO on-the-road-reliability should be very high on one's list:

https://www.trombetta.com/wp-content/uploads/2019/07/bear-family.pdf

[enblethen]

Tekonsha 7000 is agood quality battery disconnect relay. Comes as shown in link a three terminal and also comes with four pole. Tekonsha 7001
NAPA carries same type of relay. Relay must be continuous duty and not a starting relay.

[pianotuna]

heyobie wrote:
Which solenoid did you buy? I'd like to replace mine

I got 2 rated for 200 amps. I don't remember the brand name.

[heyobie]

Which solenoid did you buy? I'd like to replace mine

[pnichols]

theoldwizard1 wrote:

pnichols wrote:

The two voltmeters on the dash read just about the same whenever the engine is running (if the solenoid has been activated and if it's contacts aren't too corroded).

Curious. What kind of numbers do you see when driving ?

Both voltmeters read very close whenever the engine is running ... except for two times in the past of our 17 year old Class C when the two meters did not agree when the engine was running.

These were the two times when I had to replace the solenoid that connects the chassis battery system to the coach battery bank. Both times the solenoid had 12 volts on it whenever the engine was running and I had heard the "clunk" as the solenoid engaged as I started the engine.

I assume that the reason that the two voltmeters read differently in those instances was because the solenoid contacts had corroded/pitted surfaces badly enough such that there was resistance in the charging current path to the coach batteries.

This caused the reading of the dash voltmeter to be lower than that of the engine system's voltmeter. This meant that the coach batteries were not getting charged because they weren't seeing high enough voltage on their terminals from the coach's 12 volt system as we were traveling.

I replaced the solenoid those two times with much more rugged non-stock heavy duty 12V solenoids that had silver plated contacts - which were not carried in parts stores. I had to order them special.

So ... what these dash meters tell me as we go down the road is:

1) Is the coach refrigerator getting 12 volts as we travel so food doesn't spoil?
and
2) Are the coach batteries getting charged via enough voltage being applied to their terminals from the engine alternator?

[heyobie]

Just compared my cheap digital gauges to my Klein multimeter. Identical.

Going down the road, the alternator reads 14.5 and the house reads 14.5 When I turn on the lights and the heat, both drop to 14.2

[theoldwizard1]

pnichols wrote:

The two voltmeters on the dash read just about the same whenever the engine is running (if the solenoid has been activated and if it's contacts aren't too corroded).

Curious. What kind of numbers do you see when driving ?

[theoldwizard1]

heyobie wrote:
Just added 2 digital volt meters to my dash. I can now see the house battery and car battery voltage levels with the engine off. When driving I can determine if I need to charge the house and monitor the alternator. Life is good

Some of those cheap volt meters are very poor quality. They can be off by a couple of tenths of a volt.

[heyobie]

Love it

[pnichols]

heyobie wrote:
Just added 2 digital volt meters to my dash. I can now see the house battery and car battery voltage levels with the engine off. When driving I can determine if I need to charge the house and monitor the alternator. Life is good

I have installed the same two digital voltage meters showing the same two voltages on the dash of our 2005 Itasca Class C E450 motorhome - all the time whether we're stopped with the engine running or not ... or traveling.

I also have a 3rd digital current flow meter on the dash that shows current into (positive numerical reading) and current out-of (negative numerical reading) the coach battery bank - all the time whether we're stopped with the engine running or not ... or traveling.

Our motorhome came stock from Winnebago wired to automatically (via a solenoid activated whenever the engine start key is turned on) connect the engine starting battery to the coach battery bank.

The two voltmeters on the dash read just about the same whenever the engine is running (if the solenoid has been activated and if it's contacts aren't too corroded). The preceding of course is assuming that the built-in generator isn't running or we're not parked on hookups.

Whenever the engine is running, the current flow meter on the dash shows how much current (positive numerical readings) the coach batteries are receiving from the engine's 130 amp alternator. When the engine is not running, the current flow meter on the dash shows how much current (negative nummerical readings) is being pulled from the coach battery bank to power the coach's 12 volt circuits. The preceding situations of course assume that the built-in generator isn't running or we're not parked on hookups.

By the way whenever we stop to gas up the E450's fuel tank, for safety I turn off the coach's 12V system switch so that the refrigerator's gas flame can't come on ... as the refrigerator's outside ventilation port is close to where I refuel the motorhome. Also after gassing up if I forget to turn back on the coach's 12V system switch (thus the refrigerator can't operate), the two voltmeter's on the dash don't read close to the same ... which immediately tells me to stop somwhere soon and go back into the coach and turn on the coach's 12V system switch so that the refrigerator can operate while we travel!

[bobndot]

heyobie wrote:
Just added 2 digital volt meters to my dash. I can now see the house battery and car battery voltage levels with the engine off. When driving I can determine if I need to charge the house and monitor the alternator. Life is good

X2 🙂

[heyobie]

Just added 2 digital volt meters to my dash. I can now see the house battery and car battery voltage levels with the engine off. When driving I can determine if I need to charge the house and monitor the alternator. Life is good

[Bordercollie]

heyobie wrote:
My 88 is in much better shape than you have deduced. My Onan generator works great. The inverter/charger has been updated. This unit only came designed with one 12v house. I now have 2 in parallel.
My issue was that the charging system with the car alternator had been kinda stripped out and modified.
With everyone's help here, I got it straightened out and now it works perfectly.
So I am good to go.

Sorry, I had your post confused with Scadaman's