Battery Choice

[witeagle]

Any advise on Batteries? They were in the boat when I bought it and I am not sure how old they are however one seems a bit weak. My guess is that they are 8D however I didn't really get a chance to get a good look at them.
There is also a group 27 on then GEN but this is a generic marine starting battery that is in very good shape.

I would believe the best replacement would be a deep cycle 8D.

Is there really an advantage to an AGM? I know they claim to last a bit longer however I can replace a wet cell multiple times for the cost of an AGM.

On my last boat I tried OPTIMA batteries and they were no better than the standard deep cycles.

What about cranking amps? Deep Cycle vs Starting?

Any specific brands that you've had luck with? I was looking at West Marine and have heard good and bad things about their dual purpose batteries.

Has anyone upgraded to 3 batteries (2 starting and one house) If so what size did you change to? I would think that diesels would require no less than about 1000 MCA to turn them over.

I also heard gel cell need a different charger than wet cell or agm? I really don't want to replace my charger if I don't have to.

thanks for any help

[irishrogue]

we have stuck with flooded lead acid batteries for all 3 batts. Yes, the two main batts for starting batteries are 8D. the gen should be group 27.

we replace the 8Ds every 2 years or so. at a cost of only $150 or a piece, the cost isnt bad. we leave them in the boat over the winter and cannot trickle charge them so they tend to die prematurely. we have used the standard Interstate 8D. cheapest place to buy is an automotive interstate dealer.

we do not use deep cycle as these function primarily as starting batteries and are typically not deeply discharged...if you are running the batteries down frequently rather than using the genset, then you may want to look into having one deep cycle and one starting. i m not sure how well deep cycle8Ds work as starting batteries....

i have only read good things about gels and AGMs but the cost is high and we "abuse" our batteries....whenever i remember to check the water levels 1 time per year at most they are always down quite a bit....

[witeagle]

The GENSET provides 120vac to the system (and the charger) So are you saying that running all the DC accessories on the boat will not drain down starting batteries as long as the charger is running on the gen?

[irishrogue]

depending on your DC draw, the battery charger should be able to keep up and avoid drawing down the batteries. do you have a 15 or 20 amp battery charger? check your DC amp draw on the meter mounted above your circuit panel overhead....also when running the genset, the fridge runs on AC. So the only DC draws are lights....

[Douglas Fairchild]

For starting wet cells are the way to go. They deliver high cranking amps and can be charged without smart chargers. They will be damaged if you run them down too much too often so they are not good as a house battery. Gels and AGM's can be run down often without damage and thus they make great house batteries. The drawbacks are they cost a lot and they require smart charging i.e. advanced regulators. Gels and AGMs can be destroyed by over charging thus they need smart regulators to prevent overcharging. The West Marine catalog explains these batteries in great detail. Ideal setup would be to have both engine starters wired to one engine alternator/battery for charging. The second engine equipped with a smart regulator wired to a GEL or AGM for the house bank. You eliminate the battery switch thus your starting batteries are always fresh. No matter how much you drain the house bank your starting batteries will be fine. Each engine charging system will be dedicated to it's own battery bank.

[flbluerunner]

:patriot:I have had great luck with the Deka maintenance free batteries. When I bought batteries from marine stores I was lucky to get 18 months of service.
My last set of Deka's went 3 1/2 years.
Even though they call them maintenance free they still have fill holes. I found that odd but hardly ever found them down on fluid.

[witeagle]

So I finally got down into the engine room to find out what was there and see if I could find any markings on them. Turns out they are Deka and in service since July 2007. I was expecting to have to replace them but it appears I should be ok for now. :)