Engine charging of coach batteries
I have a general question about how the (Class A) coach batteries are charged from the engine alternator while the engine is running. I am not at all sure that they even are so charged, as I cannot...
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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
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
