Chassis batteries 2.2VDC

[Jerry Emert]

Getting ready to leave Central Florida for the summer.  Already in the 80s here. 
Tried to start the coach and nothing.  Its been plugged in here at home for 5 months  I started it once a couple of months ago and everything was fine. 
Checked the batteries, 2.2v. Top of the Bigboy, 2.2 on chassis side and 13.4 on house side.
BIRD, no voltage on the ignition or solenoid terminals except spurious.
There is another relay in the compartment with the bigboy, not sure what it is but maybe boost relay to connect both banks.  No voltage there.  Ive got an appt to get LOF change and Transmission filters and fluid change Friday so I just ordered all three from amazon.
Then I remembered the battery boost switch that i didnt even know where it was because in 9 years I havent needed it.  Found it and pushed it, tried to start and engine turned over maybe once and that was the end of that.
I went out to hook up a really outclassed battery charger hoping to start the coach in a day or two.  Put a meter on the connections and it read 13.4 volts?  Took it off and measured again and still 13.4.
I guess somehow the battery boost gave it enough juice to get the bigboy to cycle and apply the inverter charger to the chassis batteries but whats my bad component?  I havent got a clue and was hoping one of you might know.  I'd really like to cancel some of those parts from amazon but? Plan on replacing the BIRD first because there was no indication at all that it was working before.
Thank you for your patience and your expertise.
Jerry

[Steve Huber Co-Admin]

Jerry,
The Bird will disconnect (open the Big Boy solenoid) when the chassis batteries drop below 12.5v for over 1 minute. From your description, I think you've got one or more bad chassis batteries. Consider removing them and having them tested. I wouldn't throw any $ at anything else until you know the chassis batteries are good and the coach still won't start.
Steve

[Steve Huber Co-Admin]

Jerry,
Once you get the batteries checked out, you can verify the Big Boy solenoid is working. It will energize when either the house or chassis batteries are at 13.2v or higher. Once energized, you should measure the same voltage on both of the large teminals on the Big Boy. If not hit the battery boost switch a couple of times and recheck the voltage on the large terminals. If OK, the brass washer or contacts in the Big Boy are probably corroded. You can disassemble and clean it.
Steve

[Jerry Emert]

New wrinkle. I had turned the chassis battery disconnect switch off. Decided to try to start after charging all night. Coach started right up, with the switch still off. I did some measurements and had charge voltage 14.4, obviously alternator voltage, that’s when I noticed the switch off.
I walked away to do some other things. Going to still take batteries in to be checked because they were reading 8 VDC after I turned the engine off.
I’ve seen posts mentioning that those do go bad. Just wouldn’t expect it to bad that way.
Thoughts?
Thanks

[Steve Huber Co-Admin]

The chassis disconnect switch does not disconnect the battery to starter connection.
Steve

[Jerry Emert]

Ok, makes sense although it ran for 15 minutes or so with the switch off.
Anyway, 2 new batteries. Seems to have fixed it. The old batteries would not hold the charge. Read 0 volts on one battery. The other was 8 v.
I’ll start again tomorrow and see what’s up.
I guess 9 years on the old chassis batteries is not bad.
Thanks for y’all’s help.
Jerry