I think I need to re-do the batteries and charger
in my boat, but I'm having a hard time deciding which way to go.
Currently the boat has 3 g31 and 1 g27 gel batteries of unknown age. Guy I bought the boat from says he thinks the batteries were replaced in '06 (he bought the boat in 08), but the "date sold" on the batteries are all different. Year marks are "3", "9" and 2 "7"s. Since I know the guy I bought the boat from didn't replace the batteries, then I'm guessing the "9" must be 99, and I suspect the 7s to be "97".
I don't know the age of the charger
either, but it makes a lot of noise
when it's flipped on and during the survey
it was noted that it was getting rather warm and only feeding about 12.7v to the batteries. I tend to leave the charger off unless I'm actually on the boat in case it decides to get really hot.
So now to my questions and confusion. I've only seen over 13 volts once on the batteries, most of the time the battery
monitory says about 12.65-12.75v. Now, according to the "electrical study hall" thread, 12.75v equates to 100% charge, but in all the charger threads I've read everyone talks about reading 14.Xv on the batteries when they're fully charged. So which is it?
I know Gel batteries take a little care to set the boat up for, and I believe my boat was done properly. All Gel batteries, with a 3 stage alternator regulator
, and (I'm guessing) a charger set for gel batteries. I don't want to deal with the maintenance
of standard lead acid batteries so I'd like to stick with Gel or AGM
. What advantage do the Gel batteries have over AGM
? If I go with the same brand that is currently on the boat, The G31 AGMs have 8Ah more than the Gels and are $100 cheaper. Is it worth sticking with the Gels?
I'm also a little confused about what size charger I need. Supposedly Gels and AGMs can be charged with higher amps than normal lead acids, but even for lead acids, with the ~300Ah bank and charging
at 25% of total capacity, I could have a charger rated at 75 amps. Nearly all the chargers I see though are only rated to 20-30 amps, with the occasional one rated at 50 amps. The 30 amp chargers seem like the appropriate size for my boat based on the manufacturer specs, but that would only be ~10% of total bank capacity then.