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Thread: Replacing battery's, deep cycle or standard group 27's

  1. #1

    Replacing battery's, deep cycle or standard group 27's

    I am getting ready to replace both battery's on my 24 Glasply which is new to me this season. It is an I/O 305 GM and looks like it's rigged through a standard two bank Perko switch. I just bought a cabelas two bank pro series charger to mount on the boat to keep the battery's fresh during non-use. The main use of this boat will be short run time on the main engine of less than an hour, followed by several hours of trolling on a kicker.

    The electrical demands while on the kicker will be two Cannon Mag 10 downriggers, 2 big Jon planer reels, TR-1 autopilot, Two screens of chart plotter/sounder units, VHF, intermittent wiper use, Nav lights, and maybe a car stereo type audio system.

    I know the kicker will give a little charge back into the system but I don't think it will be much at low RPM use. I know just about enough about battery's to make the wrong decision so I figured I would throw it out here for advice. I am steering towards a couple of Interstate battery's which Costco carries for a decent price and it seems like, it's hard to beat their return and replacement policy. They have both the deep cycle marine/Rv in group 27 and 24, and the standard automotive group 27 (which actually has a much longer warranty than the deep cycle). From what I think I know about battery's, the deep cycle is much more tolerant to discharge and recovery which is the direction I'm leaning for both. Is there any disadvantage to going with two deep cycle battery's for this set up? Seems like maybe I should leave one battery on the main engine starting side turned off while trolling on the kicker and just run off one so I don't end up dead in the water on the main engine.

    Any advice is appreciated.

  2. #2
    Whatever you do, make both batteries the same. Your alternator and your new Pro series charger will do a better job at keeping both batteries at equal charge. From my experience, and I have much the same demands as you do, I use all Interstate Deep Cycle Marine/RV Group 24 batteries. Each engine has it's own and the house has 3 batteries in a bank. The main reason mine are all the same is I rotate the batteries every year putting both engine batteries into the house bank. In your case I would use two Deep Cycle Group 27's as they will give you plenty of capacity for starting and as you suggest isolate one of them to assure the ability to start the main engine.
    "Joint Venture" 1978 28' twin 2017 Vortec roller cam 383/6.3L 350hp engines - You name it, I've either replaced it, restored it, rebuilt it or repaired it. That's my job now that I'm retired.

  3. #3
    Senior Member gordo's Avatar
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    The Costco ones are a good choice. That's what I run. If you had the old battery switch like me it wont matter though. The switch would lead you to believe its only draining one but its actually draining both. Here's a quick video on the newer switch witch requires an addition ACR to isolate the main so it never drains while trolling.

    https://www.youtube.com/watch?v=B4830QsybbM

  4. #4
    Quote Originally Posted by gordo View Post
    The Costco ones are a good choice. That's what I run. If you had the old battery switch like me it wont matter though. The switch would lead you to believe its only draining one but its actually draining both. Here's a quick video on the newer switch witch requires an addition ACR to isolate the main so it never drains while trolling.

    https://www.youtube.com/watch?v=B4830QsybbM
    i run the ACR on my last couple of boats and are great. one thing worth noting is costco has changed battery suppliers and are not the same quality as the old ones. i have been running agm northstar batteries and really happy with them, but really expensive
    1980 2400 Cuddy I/O, 2017 Cummins 4BT coupled to a Volvo DP-SM with F9 Props, and a 2014 Mercury 15HP Pro-Kicker "LOOSE CHANGE"

  5. #5
    Great info guys, I knew I would find it here. I didn't know there was an upgrade to the old style Perko switch but it makes sense to upgrade the rest of the system now. I can't remember how many times I have left the switch in the wrong position. The new switch and ACR would make it idiot proof which is what I need on a boat.
    Thanks for the info!

  6. #6
    Senior Member gordo's Avatar
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    Quote Originally Posted by Killer B's View Post
    The new switch and ACR would make it idiot proof which is what I need on a boat.
    I as well!
    Last edited by nova7163; 04-09-2018 at 09:23 PM.

  7. #7
    Thanks for spending my money Gordo.
    1981 Hardtop Cuddy Alaskan Bulkhead Rebuild Thread
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  8. #8
    Senior Member gordo's Avatar
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    Quote Originally Posted by nova7163 View Post
    Thanks for spending my money Gordo.
    Not so loud. My wife has no clue.

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