Radio and batteries

Most RV's do not have a feature that charges the starting battery when rig is connected to shore power.Those that do, have a device called a "BIRD" that connects the converter charger to the starting battery and trickle charges it while rig is plugged into shore power. Our 2004 Tioga had no such device. I installed a "Trik-L-Start" device that connects the house battery to the starting battery, stealing some charging current from the house battery and trickle charging the starting battery when rig is connected to shore power
Installation of Trik-L-Start on our rig was not "easy" as it required running a long heavy guage wire from house battery to the starting battery along the frame and up under a wheel well to the starting battery with a 15amp circuit breaker near the battery.

So many differences among manufacturers. Our Jayco switches over somehow. Not clear to me how it does it but it's wonderful. Winnebago uses (or least to use) as switch.
With the old coach we had, I re-wired to power the radio and its memory backup to the House Battery. One reason for doing it was to not have to turn the ignition key to ACC. Key in ACC makes the power steps want to react to opening/closing the door. That coach did not have a house battery disconnect switch, so I had to add another switch to turn the radio display off when the RV wasn't being used.

Just to add to the mix, on my unit the radio appears to be wired only to the coach battery (despite being mounted in the dash).

Even if the radio is connected to the chassis battery, it might not be a concern because some battery isolators work bidirectionally, allowing the converter/charger to charge the chassis battery when plugged into AC. That's not a universal feature by any means.

This works great. Keeps starting battery charged, and when you use your dash radio it supplies the current for it, and other things dash related, and charges the battery up font. Plus when you put it up for winter just plug in. Your three stage converter will keep the house batteries charged and your starter battery. It is an AMP-L-Start. Wires up under the hood and connects back to your converter. Look it up online. I replaced my dash radio with a do-everything radio with satellite receiver. Never ran down the battery when plugged in.

On mine I have a switch to use the radio off the coach batteries. So I can have it run off either the chassis or coach battery. The switch is in the dashboard on my unit.

Just turning the key off on mine would make not tell me if it worked off from either or. It would shut off my radio also, I have to hit the switch to allow it to work off my coach batteries. Chassis battery is always the default battery unless I hit the switch to cause it to run off the coach.

X2 on my radio being powered by the chassis battery. Easy way to find out is to take the key out of the ignition and turn the radio on. No sound means powered from chassis battery only.

I would expect it would take weeks to run down the chassis battery with the ignition switch on only when you want the radio.

In mine the, radio is powered only by the chassis battery. I understand that some MHs switch the radio over to the chassis battery when the engine is off but I have no idea which ones do.