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Discussion Starter · #1 ·
I am trying to choose a battery(s) needed to finish my install in my boat.

Currently I have two group 27 Interstate Marine batteries on a selector switch that allows me to choose both batteries individually or combine them both.

I do 85% of my listening with the engine off and need a good cell that will keep the tunes going during the party. 4-8hrs easy.

My thought was eliminating the selector switch and dedicating one of the existing interstates as a starting battery only, then going with a second bank that will run the stereo, amps, cabin LEDs, and anchor lights. I'm in Thor process of building an automated relay system that while the engine is off all house power is routed to the power cells, when the engine is on at idle the house is still on the same battery but the alt is charging the starter battery, then when the engine is on at high revs the alt is charging all batts. Then there will be a main power cut off switch that turns off all batteries when the boat is in storage mode, but power will be kept to the memory wire using a simple 12v home alarm system backup battery, that will be charged by a small solar panel on the helm.

So now that I have at figured out what cell(s) should I go with to reach my goal?

Headunit is Alpine iDA-X305S with PXA-H100 imprint module
Amps are JL 300/4v2 and 500/1v2
Anchor lights are standard automotive 12v bulbs
Then I have about 80 LEDs strung around the boat.

Kineteks website suggests a HC800 cell but I think that is assuming there is alternator support. I've heard bad things about the slash v2s cutting out when there is not enough power to them, and changing amps at this point is not a real option.
 

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it's not exactly the same thing as you described but you could simply put a battery isolator before the second battery and run your system off of it. that would allow only the second battery to be draining/powering with the engine off and then both batteries would be charging with it running.

i have an hc800 as the only battery in one of my cars but it is very small. i don't know if i would trust that battery alone to power everything you have for any great length of time. on top of that none of the HC series are deep cell.
 

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Discussion Starter · #3 ·
I know about the easy route of an isolator, but this is whqt happens when you build an embedded system to monitor engine systems and find you have extra memory space in flash for more procedures. I got voted the lucky one to prototype it on my boat and we are trying to knock something out fairly quick so we can have a working unit for the summer boat shows.
 

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Do you have space for some large batteries?

If so, Sears Diehard Marine Platinum PM-1. It's a Enersys made battery, same as the Odyssey series, best combination of value/performance/warranty available as far as I know. They should take some serious abuse.
 

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Discussion Starter · #5 ·
I like the cost, $239 each. 205 reserve mins, 1150 cca. So for 4-8 hrs of engine off listening, how many in parallel, 1, 2, 5...

I've got a separated storage area on the port side of the engine compartment that I could put the batteries in, then make a shelf out of starboard to go about 5" above the top of them to regain the storage. (I keep extra life jackets, line, and a first aid kit in there)
 

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Hmm, a bit of a crapshoot but I would think 4 would be very safe for out to 8 hours, hopefully someone will chime in that has some experience in a similar situation.

If I had to do some educated guessing, 205 reserve minutes means the number of minutes the battery will carry a 25 amp load before dropping to 10.5 volts... which you probably want to avoid. Those amps could probably draw 100 amps or more if you had them pinned out all the time... which probably isn't going to happen. But I bet they could pull a good 50 amps with it turned up at a party. All the other **** is probably minimal relative to the amplifiers. I'm not sure how linear this would be, but that puts you at about 100 minutes reserve per battery... and they could be pretty dead by then.

So the rough math kinda bears out my guess of four batteries, but YMMV.
 

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I would think you can get over 2hrs from each battery, I can get over an hour in my car easy with similar amps fairly loud. It really depends on how loud, amps don't take much power until after ~3/4 output. What helps on boats is to use class D or hybrids, then maximize your output with ported subs or IB, and larger more efficient speakers...and more of them.
 
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