Well, I don't think I'm able to answer that question with any technical accuracy. But I can relate some recent experiences. Twice in the last few months I've forgotten to turn the charger back on after leaving it off. We leave the dock to pump out twice a month, and every other time once we hook back up to shore power I leave the charger off. Usually for 24 hours. At the end of 24 hours, we're typically down to 12.3 (after using approximately 150 amp hours). Then I turn the battery charger back on.
The first time I forgot was back in March. We came back to the slip on a Thursday evening about 6:00pm. On Sunday morning at 11:30 I finally realized I had forgotten (water pump was dragging a bit...) and turned the charger on. The batts had dropped to 11.5 over 65 hours!
A couple weeks ago, I did it again. Though this time it was only for 48 hours. Batts were down to 11.9. Both times they charged back to 13.3 within 8 hours. (I'm now developing the habit of placing a sticky on the aft door that says "Batteries!" so I never forget again...)
Then, just last week we had a battery selector switch fail. It had developed a short and was not allowing the charger to send any amps back to the bank. After 40 hours the batteries were down 12.0-12.1. Installed new switch, and they charged back up like normal.
We haven't anchored out for an extended period yet this year, so all I can say is they SEEM to be performing as expected. That, and I'm really thankful we have these Firefly Oasis batteries. I think we've tested the claims they can be discharged 80% or more of rated capacity with harming them. Otherwise, I would have killed a couple of banks worth by now!
Hope that helps...
, but have you considered employing a solar trickle charger to keep batteries fully charged?
