What size battery for house loads?

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lime4x4

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Currently rewring a 86 offshore24. It has twin 1987 yamaha 150 2-stroke outboards. As part of the rewiring i'm also installing a bep marine 717 which contains 3 battery switches, 2 vsr's and a emergency combine switch. I'm planning on keeping both engine batteries to start and run the engines the house battery will run all the acc. Which includes depth finder,fish finder, gps all the pumps,lights and stereo. What size house battery should i use?
 
:uhm The largest amp-hour battery that will fit. Never heard anyone complain of 'too much' battery ...
 
I agree with the above, but... you're not running any crazy-high amp loads. Plus, I would imagine that most of the time the engines will be running. It's not like you're running loads that you would see on a cruiser. Bigger the better, but in reality a group 24DC will be plenty.
 
And if he loses a generator on one of those two-strokes? Or one of the start batteries goes south? The only thing more useless than space a bigger battery could have fit into would be fuel still at the marina. At least where and how I boat, just sayin ... :?
 
Curmudgeon said:
And if he loses a generator on one of those two-strokes? Or one of the start batteries goes south? The only thing more useless than space a bigger battery could have fit into would be fuel still at the marina. At least where and how I boat, just sayin ... :?
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Ummmm... huh? :wink:

If a stator goes out, the engine will still run. For how long, I don't know - but for quite a while. Then you can swap batteries around to charge them. Still got three batteries. Is one engine wired up to be able to charge both batteries?

I do agree with you - just offering another point of view. There's no real "right" answer here - just opinions. At some point, though, it reaches a point of diminishing returns... ie, how about 4 batteries... how 'bout 5? However, for most typically-used battery trays, a group 27 will fit. It's just more than is what realistically needed. In my Sundancer, I run a group 24 starting and a 27DC for the house. I've run on the house battery only for 3 days/nights - of which there was only about 45-60 minutes of engine run time and the rest of the time the lights, GPS/Fishfinder, radio and fridge. Still had juice to start the engine the third morning. I was pulling a lot more amps than what John will be pulling and also had likely a whole lot less engine run time.
 
That is one of the reasons why i'm going with the bep 717 with daul vsr's either engine can charge the batteries
 
I would opt for the largest battery you can fit and make it a deep cycle or dual purpose. I just installed my 4th battery and tied the 3rd and 4th together to make one larger capacity battery. I kept running into low voltage after anchored for about an hour so after adding the 4th (both group 27 Interstate's) I ran a test using all electronics as if I was out fishing and 3 hours later, still have over 12.4 volts holding on the HDS units. Way better than last season. Depends upon how much draw you have with electronics, livewell, etc. At least this is my experience so far!
 
A DC group 27 is a good bet. Been using them a real long time with all the gadgets on all day.
I will be removing my on/off house switch and putting in place a 1/2/both switch and adding a 2nd house batt to flip back and forth between.
I do not like relying on 1 of anything going offshore. Always must have a fresh batt in reserve with nothing that can possibly draw off it.
And you always have to remember that there could be a time when the only thing keeping a boat afloat is your ability to keep pumping out water.
Bad things can and do happen.
For inshore, you obviously do not need so many batteries.
 
From what i can find there is now max battery for the bep 717. The i understand it is with the vsr's once the engine batteries are charged the vsr's open to allow charging of the house battery. Both engines can charge the house battery at the sametime if the engine vbatteries are fully charged. the boat was bought for some occ off shore usage. I would love to have 2 or even a 3 bank house battery setup but that's no gonna happen with limited room that i have. If i wire everything correctly the engine batteries should remain isolated from all loads except when starting the engines.
 
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