My house batteries are whimpy, when unplugged, they go to 12.4 almost immediately. With nothing to lose, I equalized them for 3 hrs at 15.5.

Batteries are now at 12.8 when unplugged and still had 12.4 after 7 hours of no shore power with just the fridge and a fan running.

If your batteries are marginal, this may help, but if they're bad, the equalization will have no effect. I equalized my Marathon and it didn't help at all. After removing the 6 batteries, 5 of the 6 were bad.

So, if you have some life left in your house batteries, give it a shot...