What batteries to buy

[Dave K]

I know that there are formulas which are way over my head to figure out how much battery reserve power is required to run the boat stereo for a specific length of time and at how loud.

Having said that and to keep it simple I am wondering if I should get 2- 31 series batteries for my stereo or 3- 24 series. The 3- 24 series will have alittle more reserve but I dont know if I really need it. In the past I have had 2 battery in one boat and 3 in another. However I have not had as much power in my system as I do now. (kicker 450.2 kicker 350.4 Sony amp for sub around 750.

I am not planning to connect these batteries up to the alternator for charging.

On average... what do you guys go with or what would you reccommend?

Thanks

[philwsailz]

Dave-

I usually go the relatively cheap and easy route. I will go to Wal Mart and buy the big group 29 yellow marine batteries... Two at the same time, both put into service at the same time. I bought one Saturday for $75.00...

You can get probably get longer reserve time batteries... You can probably buy AGM, or any other number of technologies, and you will usiually pay more. You might get slightly longer play time, but who else will let you just bring a battery back in and often exchange it largely hassle - free?

This is jsut one man's opinion, but with the batts I buy, if even they won't exchange me, I can usually cout on being able to purchase an exact replacement in just about any small town...

Phil
Kicker

[Dave K]

Thanks Phil.

You only run 2 batteries? Roughly how long do they last before recharging?

[philwsailz]

Thanks Phil.

You only run 2 batteries? Roughly how long do they last before recharging?

I don't know.

I am using an ACR, with one battery only connected to the starting and helm circuits, and the other tied to the stereo. I am using a single in-boat amp, (ZXM700.5) and a digital tower amp for the towers, (IX500.4). I have never run the stereo battery dead in the last three years... I did the first year, but that year I was "that guy." These days, cranking it full tilt for hours on end gets old...

Know that for my system, I do use the alternator for charging both batteries, and I did not want to install a hotter alternator, so two batteries is about my limit. Trying to charge three deeply depleted batteries is a recipe for premature alternator failure.

For your needs, you say you are not connecting to the alternator, so your situation is different. You could go three batteries in parallel and get 3x my playing time, but then you also will need to know that you need 3x the re-charging capacity when you get back to land. More batteris means more expense, be it alternator or 110v battery charger. Your cost is just diverted from the alternator to the charger; you still need quality equipment to charge your batteries.

That being said, my hunch is that your playing time is going to be what it is, and between cheap batteries and super expensive ones, the playing time is not vastly different. Understand, I share this largely as my opinion....

This and convenience point to me just using what is pretty cheap and readily available....

Phil
Kicker

[Dave K]

3 batteries did well for us in our 22i, but those where 24 series. I'm trying to determine if the 2- 31 series would work. I would then only need a 2 bank charger.

Thanks

[philwsailz]

3 batteries did well for us in our 22i, but those where 24 series. I'm trying to determine if the 2- 31 series would work. I would then only need a 2 bank charger.

Thanks

With the right two-bank charger, you can charge one battery by itself from bank 1 and then on bank 2 you can charge two batteries in parallel. I'm just saying.... For that matter, three stereo batteries in parallel can be charged with a single bank charger... They are all parallel, so they look like one BIG battery... See where I am going with this?

[philwsailz]

I think your charger selection should not be based on two or three bank, but rather how well it will charge multiple batteries as a single bank. To my thinking, you use a dual bank charger where you have a cranking battery and a house battery that routinely are at different depletion levels, so the dual cbank charger will charge them up to float independently without overcharging.

For your application, with the stereo batteries always in parallel, they deplete at the same rate, charge at the same rate, and normalize with respec to each other. You only need a single bank charger for even four batteries wired this way.... Your run time is longer, and your charge time is longer, based on the fact that you are splitting the charging current between all the batteries.

On that line of thinking, the right dual bank charger can be connected to three batteries... You just split the combined two-bank current over the three batteries...

I am pretty sure I am right on this, based on the charging investigation I put into selecting batteries and a charger for my sailboat... Limiting yourself to a dual bank charger does not limit you to dual batteries...