Two issues herein...
After having my dealer do a fluids & filters service (around $1,100) I asked them to check the chassis batteries because of occasional (apparent) insufficient cranking performance.
They replaced the two, 12-volt chassis batteries with RV deep cycle, sealed batteries.
I'm a long-time radio comms tech (commercial & amateur) so engines aren't my forte. I thought I understood the difference between construction & service demands for RV batteries. The dealer assured me that, "They're what we use for everybody."
Really? Uhh, OK. In case they're right, on to my problem:
So after a cross-country (NC -- WA) in 2018, "Bertha" sat at the dealer a year for body repairs (hit & run by a DOT forklift) about 13 months. Six months after I got it back, when it was time to renew the registration, I charged the house batteries after properly filling them all properly. That was via the shore power line & equipped inverter/charger, and all went well.
Next day I walked confidently to the battery bay, ensured the master was off, & attached my ~15-amp charger to the two paralleled 12-volt Deep Cycle RV batteries that had recently been installed by the local dealer as chassis batteries. My confidence was jarred somewhat at the exciting ten-second light show I caused by having hooked up the terminals *backwards." After waiting an hour, I hooked the charger up *correctly" this time. The outboard charger showed max charging current (somewhere around 18 amps) for the ensuing 12 hours.
Next morning the charger was still cranking out around 9.5 amps. When I read the open-cell voltage on the two batteries, it read 11.1 vdc. It didn't occur to me to uncouple the paralleling jumper, so I don't know if I killed both new batteries, or just one.
So, two questions, I guess:
Did my "big chain dealer" dump the wrong style batteries on me, figuring I wouldn't know the difference? And,
Assuming these *are* acceptable chassis batteries, what'cha think my next troubleshooting step(s) should be?
Many thanks & 73 de Barney KL7HNY/4