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  1. #1
    Member
    Join Date
    Jun 2015
    Location
    Knoxville, TN
    Posts
    73

    Dual Cranking Batteries in Parallel - Wiring Recommendations

    Good morning BBC'ers. I've dropped in a second Optima D31M to assist with the low voltage issues created by adding two Solix units. I'll wire these in parallel so I won't have to upgrade my on-board charger and my first instinct is to keep all of the electronics on one battery and the wiring to/from the ProXS and the on-board charger on the other. Theoretically I don't believe it makes a difference due to the batteries being parallel but I thought I would check with anyone with experience before proceeding this evening. Thanks in advance!

  2. Member
    Join Date
    Jan 2005
    Location
    Red Oak Va.
    Posts
    10,597
    #2
    The alternator may not keep charge on two batteries because it's only designed to charge one according to Don.

  3. Banned
    Join Date
    Jun 2008
    Location
    roscoe
    Posts
    159
    #3
    what batteries? are your batteries in good shape? I know they are expensive but, a northstar agm31 series battery should handle your problem I believe. I have a 200 opti that requires 1000 cca , I'm running a 1197, 899, live wells on for hours, my 520 in dash, it can be showing 11.0 volts on the volt meter and it will crank the motor like its fresh off the charger. I found out the hard way about a battery not being up to snuf, really just 1 year old, cost me almost $6k when I could not get back in.......just my opinion

  4. Banned
    Join Date
    Feb 2014
    Location
    Eastern Ontario
    Posts
    478
    #4
    I had that problem with low voltage during motor starting.
    Turned out to be corrosion of the battery leads and wiring connections.
    If you are connecting batteries in parallel use the same wire gauge as is for the motor.
    Did you have your battery checked to see if it is 100%?
    Post some pictures of your upgrades

  5. Member
    Join Date
    Mar 2018
    Location
    Chicago
    Posts
    1
    #5
    You might want to check about getting another battery, but use it as a house battery to power just the electronics. I just had this setup on mine (but haven’t used it yet). There is a special device that automatically charges between the batteries, as well as another switch which lets you use both batteries if your engine won’t start with the engine battery.

  6. Member
    Join Date
    Jun 2015
    Location
    Knoxville, TN
    Posts
    73
    #6
    OK Gang. I installed a second Optima D31M and connected it parallel to original D31M. I then simply moved the on-board charging cables and the wires from the Mercury to the new battery leaving all electronics on the original Optima. To me this keeps everything very clean and organized. I crossed my fingers and took the boat out Friday afternoon and everything works flawlessly. We ran both Solix's on Mega imaging most of the day and never had the voltage drop below 12.0v. Although I added another 60+ lbs to the boat I appreciate the peace of mind that I can run my voltage-heavy electronics and likely livewells all day and not need to make unnecessary runs to recharge the cranking batteries. I'll have some pictures for the group so that I might help anyone else that decides to upgrade their electronics to the new Mega Birds and need some extra go juice.

  7. Member
    Join Date
    Mar 2018
    Location
    Queensbury,New York
    Posts
    1
    #7
    thanks this was helpful