Originally Posted by MrJoe
Mine charges from the alternator and the converter. I know that because I used a meter to check.
I've also confirmed the alternator charges the coach batteries and the convertor charges the chassis battery by using a digital multimeter (voltmeter).
PLEASE NOTE: Read the BIRD manual that I posted. The coach or chassis system must be above 13.1 volts for the relay to kick in. It will charge either way. A heavy load in the coach, including charging flat coach batteries, may hold the coach voltage below 13.1 volts so the relay may not connect to the chassis battery. Of course, it's possible that there's a problem with the poster's system.
I used this feature once when the battery in our toad ran down after powering the brake controller for 2 1/2 days. When we got to the campground I jumped it off with a portable jumper battery, then connected jumper cables from the chassis battery to the toad battery. I confirmed voltage at the toad battery and left it overnight.
So why do I do belts-and-suspenders by carrying a jumper battery AND jumper cables? See above!