Proper way to charging dual batteries?

jbl_91762

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Sep 23, 2017
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KAYAK
Wondering if I am charging my batteries the right way. I hook up the charger on one battery and put the selector switch to "ALL" and thought it would charge both till meter shows full and in float mode. Went out to Cat and had switch to ALL during the trip there and was showing 13.5 - 13.8v underday.., switched to Bat 2 while anchored to run bait and electronics and after 2 hours it did not have enough juice to start motor and had to switch to Bat 1 to fire up. So it could be a bad battery and will pull to get tested. So I am wondering if I am charging correctly and should I bring a volt meter next time to make sure both are being charged. Thanks gents.
 
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C_Parm

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Aug 8, 2016
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If the batteries check out as fine look into changing the Perko switch too. Those things go bad and have the exact symptoms you're describing. As far as charging, I would have the battery selector switch to "off" and plug in your charger or chargers.
 
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Mike_I

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Charge the batteries by connecting the charger positive to the positive of one battery and the charger negative to the negative of the other battery.
 
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Jul 24, 2017
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Joseph Gratteau
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I was wondering the same thing. I put my Perko to "all" and attach my charger to one battery. How is putting the positive on one and negative on the other different? Thanks!
Charge the batteries but connecting the charger positive to the positive of one battery and the charger negative to the negative of the other battery.
 
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Capt.C.Delany

The only fishing I do is trolling the Internet
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    First thing I would do, and you should have this in your tool set is a hydrometer. This will tell you the gravity of each cell and should be done as preventative maintenance a couple times a year. They are cheap and tell you a lot about a batteries health without having to pull it out and put it on a load tester.

    For instance, a battery could read fully charged but if it has a dead cell, it will not have the amp power (the umpff) to turn the motor over but it has plenty of power to make a bait pump or other low amp draw 12v device work.

    In theory, a battery switch placed on all will charge all batteries. Though the old school 1, 2, all, Perko switch is tried and true, the "next generation" so to speak are the ACR's. They are about $125 and take all guess work out of it when wired correctly.

    Myself, I have an onboard dual bank Promariner Prosport 20 amp charger so charging is very simple. This charger is considered a "smart charger" in that it will charge both batteries, and then when one is full it will divert the excess charge from the full battery to the battery still needing a charge.

    The simple test for your situation would be to follow your normal charging pattern of only hooking up the charge leads to one battery and setting the battery switch to all. Take a volt meter to each battery and see what it reads. If it is 13v or higher, especially on the non-connected battery, you should be good to go. If the non-charger connected battery does not read like it is charging, wait a while,there is a possibility that the charger connected battery is not fully charged yet allowing the excess charge to flow to the second battery.

    If the second battery (non charger connected battery) is not charging, check the circuit, really pay attention to your negative lead.
     
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    Unassailable

    Professional Amateur
    Aug 26, 2009
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    If you and anyone else have issues with remembering how to charge both batteries while underway and have a 2-1-all switch, you need to get a Yandina 100 combiner! Great investment I made on my boat since I simply set the switch to 2 and forget the rest! It will combine or isolate charging based on volt limits.

    Plus, when I had questions installing, a real human picks up the help line (the business owner) and actually helps you out. You can install in under 20 minutes.
     
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    dktool

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    Aug 11, 2010
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    Get your #2 battery tested, sounds like it's junk.
    Install an ACR, that way you don't need to switch your perko to combine while underway for charging.
    When you stop the loads are on whatever battery the switch is set to and the other one is your reserve.

    As for shore charging a dual output smart charger is best as long as the perko is not set to both, if set to both a single output is fine.
    If you do install an ACR it will act like a "both" setting unless you wire in a disable switch.

    I have a dual output charger with an ACR and a disable switch, works great.
     
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    Mike_I

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    May 19, 2006
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    look up balance charging, it's been too long since my electronics classes and since I built my PV solar power systems at my house and had to deal with wiring a charger to a battery bank. Also too much killing of brain cells to remember the details enough to explain here.

    I was wondering the same thing. I put my Perko to "all" and attach my charger to one battery. How is putting the positive on one and negative on the other different? Thanks!
     
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    reelbadlarry

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    unless you have a high end charger trying to charge two batteries at once is confusing it... buy the two bank charger and charge them individually and you will be better off.
     
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    sickcat

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    Aug 5, 2003
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    Most likely that second battery is weak as others have mentioned.

    Assuming both batteries share a common ground and your charger has enough capacity then putting the charger on one battery and setting the switch to all will charge both batteries fine. The battery that is lower will get more charge going to it both from the charger and the other battery if there is a lot of difference in the voltage between the two. The higher the state of charge is in a battery the higher the internal resistance in it. That means if you have two batteries on a single charger the first battery that has a higher charge will have a higher internal resistance and that will "force" the charge into the lessor charged battery because it has a lower internal resistance. Basically it self regulates.

    That said the best thing to do is install an ACR and forget about always switching the batteries. I am also a fan of the Yandina units. They are the most cost effective way to go plus they have a nice feature where you can have a wet battery along with an AGM and the ACR will adjust the voltage so the AGM battery is happy.
     
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    Walker Inc.

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    Jun 24, 2013
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    All of the above is true, but how big of bait pump, amp load of the electronics? Was the stereo and VHF on too? What size is the battery? You could have just ran it down.
     
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