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.