Engine charging of coach batteries

Get a voltmeter. Takes out all the guesswork.

A good way to tell is have somebody get into the coach put and start it, put it in gear, and then put a meter on the batteries. they should be over 13V (or more). Then have the person park the coach, put and turn it off and if the batteries then immediately sink some in voltage (like 12V) then they are charging.

Your Embassy will probably charge from the alternator when driving. Our '97 Commander did. There should be a large solenoid behind the front access panel. They do fail--ours had to be replaced once in 100,000 kilometers.

From 50% discharge--that depends on what you have for batteries. A single small 24 or 27 probably would get close but I doubt the alternator would get the battery to a high enough voltage (14.4) to really fully charge it.

Interactive electrical site

This site is amazing. You can toggle things on and off and select many variations. It will give you a sense of how yours may work.

Paul,

While it is correct that there is no "typical". This is simply because most every class A ever built was built by a chassis builder and a coach builder. They each get to do what they want with what they have.

Most coaches do charge the house bank from the main engine and there are three very different ways. The most common is the isolator contactor. A big relay that closes once the main engine starts and connects the two batteries together. After that, your available charge rate is a complete **** shoot. It is largely dependent on two things. Those are the maximum capacity of the OE alternator and the vehicle wiring.

Sorry, but nobody other than the coach builder can give you a better answer.

Matt

I have always just thought of the Truck Alternator charging of the trailer battery as a trickle charge... The trailer battery is very far away from the Truck alternator and most often a small size cable is being used...

In my 2010 truck I found right away the battery was not being charged by the truck alternator setup by using a voltmeter across the battery terminals. Normally a charged up battery will read around 12.6-7VDC and when you start your truck this DC voltage should jump up to around 13.2 VDC or more depending what status the alternator is in while the truck motor is running.

On my setup the Truck battery 12V is presented to the trailer via the 7-way Cable using the #4 blade connection... I have no idea how this is accomplished with the motorhomes...


Since I didn't see any change in the DC Voltage I knew I was not getting a charge on the trailer battery. Digging around I found a small unmarked package in the Truck glove box that had a Fuse and a Relay in it with no instruction as to what they were for. Then looking in the Truck owners manual I saw where there was a fuse and relay identified as for 'TRAILER TOW'. After plugging the fuse and relay into the identified positions in the main fuse panel of truck I now have truck charging voltage now at the battery terminals.. In my case however when I turn off the truck ignition key this all goes away...

Roy Ken

There will be either a solid state drive based isolator
Or
A relay type

Open the engine cover, and follow the big wire from the alternator
It is not going to be directly connected to the converter,
They never are
It's alternator to isolator to both sets of batteries

Converter to house batteries

Solar to house batteries

kimbo1 wrote:
there is no typical answer to this question. it depends on coach and chassis manufacture.

For sure. It can even depend on year. Our first MH was a 2012 ACE and the engine did NOT charge the house batts. In my 2013 they do. I am sure putting a meter on it while the engine is running should tell you pretty quickly.

there is no typical answer to this question. it depends on coach and chassis manufacture.