Originally Posted by Jesse Toler
You're probably right. I'm not familiar to be honest. I'm used to boats. My boat definitely uses an inverter to charge the batteries. These may be different but either way I think mine is good. I see a increase in voltage when I plug in so I'm sure that's a good sign.
Inverter/Charger units are used in larger motorhomes. You probably have one of the units pictured below with AC circuit breakers and DC fuses. It also contains the Converter that charges the house batteries from either shore or the generator.
BIRD stands for Bidirectional Isolator Relay Delay and it will allow the alternator to charge the house batteries and the converter to charge the chassis batteries if everything is working correctly. The Delay part means that which ever power source is charging it will not close the contactor that connects the two battery systems together until the host battery system is charged. This can be a short period or a long time depending on how discharged the host battery system is. If you have the BIRD then your chassis batteries should be charged from shore power or the generator. I suspect that your house batteries (they would be the host battery system when on generator or shore) were discharged to far so the BIRD never connected the chassis batteries to be charged.
While we are on the subject there is also an IRD device. That takes the Bidirectional part out of the acronym and if you have the IRD your chassis batteries are NOT charged by shore power or the generator but your alternator will charge your house batteries after the chassis battery is charged. Sometimes folks think they have a BIRD when in fact they have an IRD. We owned a Class A diesel pusher for over 13 years and it had the IRD. I had to add a device so the chassis batteries would be charged from shore power.