This winter I maintained the same batteries with a Guest 3-step 10amp charger
I found the resting voltage is 12.65 amps for both. This is after the batteries had been charged and then sit for a couple of weeks.
There does not seem to be much discharge at all because after 2 months, I put the charger
back on and it immediately showed a green light only. So it appears this is a little low for AGM
voltage, but they are Aug 2008 batteries.
Trojan lists this for their AGM's
AGM Rating Charge
100% 13.2 - 12.8 v
75% - 12.4 v
50% - 12.2 v
25% - 12.0 v
So ours are somewhere around 87% of the listed AH.
The CCA for both is right on what they are listed for.
If I do need to get new batteries later.
I have found our battery case will hold (2) Trojan 6V T105 GC2 in series (10.3"L x 7.06"W x 10.73" H)
This type comes in Flooded Lead (224ah) $170 each and AGM (217ah) or Gel for about $260.
We motor twice a day usually and can charge then for 1/2 hour to 1 hour. We have a small danfoss refrige (7ah x 5 hr/ 24hr) and are hoping to get a chartplotter, we have an old radar. Our house battery bank is currently only 160 ah, and we have gotten by so far, but need more ah.
We have a derated 75amp Balmar (now 65amp) for fast charge at low rpm, with a Balmar Regulator.
This question is loaded, but which type of battery will charge faster, and how much faster (is it significant amount of time that would be idling our engine?) and which battery would provide the best service life and is most appropriate for our use.
We try to keep the battery charge so it never drops below 60%-70%, but occassionally it gets down to 50%.
I am putting a 7amp Solar PV controller on the 14watt Solar PV because I saw voltages of 20 volts after returning to the boat after two weeks. The batteries were fully charged and being overcharged with a 1amp trickle from the Solar PV array. I don't think that is too good.