new batteries

Rick486 · Dec 23, 2018

dakno said:
Is getting close to the time for new house batteries. I am currently on the second set of 3 4D AGM 192ah each batteries. This is what came with the boat as new from Hunter. I can replace the 3 4d's with 6 T105's for 1/2 the price and probably get 25% longer service. With the T105's I would have to do the regular watering. I like the no watering and venting aspect of the AGM's. Most people that make this conversion don't seem to be concerned by the venting aspect of conventional LA flooded Batteries. My question is why did Hunter spend double the $ for AGM batteries when they could have just as well stuck golf cart batteries in there? No one would have not bought a Hunter because it did not have AGM's. There must have been some logic for spending the extra dough on AGM's, what's the reason?
Thanks

2 points:
1. Are you sure it wasn't the dealer who installed the AGMs?
2. Consider gel rather than AGM.

Don S/V ILLusion · Dec 23, 2018

Less batteries - less labor installing/wiring them. That saving offsets at least some of the $$$.

jeepbluetj · Dec 23, 2018

Go for the Golf Car batteries. Way more bang for the buck. Off gassing is minimal unless you're really hammering them during charging. I'd guess the dealer that did the initial fit-out selected the AGMs..

SG · Dec 23, 2018

The AGM's have the least (if almost no) outgassing. The gel cels do release some hydrogen -- not a lot, but you need a compartment which has some ventilation. The conventional lead-acid batteries emit a lot more than you'd think. Maybe not hydrogen dioxide, but still a bunch.

I don't the configuration of your Hunter. If you're used to the almost 600 ah battery main bank, then do you get an equivalent bank in the same space with 6 volt batteries?

DayDreamer41 · Dec 23, 2018

I replaced our house and bat's last spring with T105's, (4) under the nav station seat and (2) below the sole kinda next to the nav seat, as for watering I checked them regularly last year and only had to add water twice, once about mid point in the season and then again once the boat was on the hard, about (1) ounce per cell each time. I have left the seat top off while charging a couple of times just to see how much odor was evident, couldn't be much as there was no detectable odor.
The 4D's I replaced were also LA bat's contained in battery boxes and based on the date stamps on (2) of the 4D's they were original equipment, perhaps the original on yours were a buyer upgrade.
I purchased a battery watering system for next year, but I realize that this will have to be decommissioned come fall to prevent freezing of the watering lines.

Ted · Dec 23, 2018

AGM batteries will be charged in much less time than LA batteries. If your boat uses a generator often to keep batteries topped up, AGM's would be a better choice.

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jeepbluetj · Dec 24, 2018

AGMs do indeed have a significantly higher bulk charge acceptance rate, but once you get to absorption, its around the same. So an AGM won't charge in a lot less time, just less time. (Mainesail has an article somewhere on this..)

AGMs are killed much more quickly if you don't get them fully charged. (all the way to and held in float). FLA is much more tolerant of abuse than AGM.

AGMs don't outgass. FLAs do.

LiFePO4 wins on all counts except for cost and the need for different charging circuitry.

Valerio · Jan 9, 2019

i have the same boat and i manage to fit inside the seat 4 trojan 6 volts l16, now i can navigate 24 hours before i need to charge again. very easy the see if you need to refill.