Boat charging problem

Discussion in 'The Projects Forum' started by bignasty, Jun 28, 2013.

  1. bignasty

    Thread Starter New Member

    Jun 28, 2013
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    This my problem.

    I have a boat that has 4 batteries on it. I have 3 yellow top optimas and a marine battery. The batteries are connected to a 4 position switch. The positions are off, batt 1 batt 2 , and all. I have the marine battery on position batt1. The have the optimas paralleled for batt2. All the voltages are 12v on all positions. Here is the problem. i bought a 4 bank charger to have the ability to charge each battery separately and condition each battery separately.What is the best way to separate the optima batteries so i can charge them separately? as mentioned they are paralleled. I thought I can use three solenoids to break the circuit(bus)when i put them on a charger and have a relay to active then when the charger is hooked up. i was going to use a 120v to 12v power supply hooked to a relay to switch them. I really want to keep this cheap and easy to maintain. Is there anybody that can give me an idea on how to break the optimas from the bus so i can charge them effectively?
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,999
    745
    Easiest is four separate switches.
     
  3. cork_ie

    Member

    Oct 8, 2011
    348
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    Why do you need to charge them individually?
    There is no real need to seperate them, for normal bulk/float charging as they will all sit at the same voltage.
    Occasionally for deep cycle batteries you may need to carry out an equalising charge (special charger setting, only found on chargers speciallly for deep cycle cells) In that instance just disconnect one pole of the battery you are charging.
     
  4. bignasty

    Thread Starter New Member

    Jun 28, 2013
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    I need them separated because I already have a 4 bank charger. I purchased the 4 bank charger to know exactly the condition of each battery.
     
  5. cork_ie

    Member

    Oct 8, 2011
    348
    58
    Just connect the wires from your charger to each battery without seperating them. Bank2 are all going to be at the same voltage anyway if they are in parallel. I am an auto/marine electrician with 30 years experience and I assure you you will have nothing but problems if you start introducing multiple extra connections to seperate the 3 batteries
     
    ErnieM likes this.
  6. crutschow

    Expert

    Mar 14, 2008
    13,052
    3,244
    Is the charger connected all the time?

    You could put a solenoid relay in series with three of the batteries to insure they are isolated when you are charging. The solenoid contact current rating would need to be greater than your maximum load and be rated for continuous use (unlike starter solenoids). You would like to have normally-closed type contacts but I don't know if high current solenoids are available that way.
     
  7. bignasty

    Thread Starter New Member

    Jun 28, 2013
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    Yes, it will be connected all the time. It is an onboard type charger. The solenoids i was looking at was for car audio but i wasn't sure if it was normally closed like you mentioned.
     
  8. cork_ie

    Member

    Oct 8, 2011
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    Car audio solenoids will not do.You need a lot heavier than that.
    Please take my advice. The charger is not going to tell you anything about the state of the three paralled batteries as they will be all at the same voltage (and charge level) until just before you seperate them.

    You inadvertantly bought a four outlet charger , which is really for four seperate battery banks (ie twin engines with 2 domestic battery banks) The charger has four outlets so that all four banks could be charged automatically without switches and kept isolated so that there is no danger of draining the engine batteries.
    In your case you have one engine and one domestic bank. A 2 outlet charger would have been the ideal purchase, but unfortunately you now have four. There is absolutely nothing whatsoever to be gained by charging the three domestic batteries seperately and a lot to go wrong if you go introducing all kinds of spurious circuitry. Just connect three of your charger outlets together to the domestic battery bank and one the engine marine battery and it is the optimal solution.
     
  9. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    1,606
    If you doubt cork_ie's advice just look at the size wire (or cable) going to the starter motor and imagine the size switch you'd need to open all the current it could handle.
     
  10. bignasty

    Thread Starter New Member

    Jun 28, 2013
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    Sorry for the delay. i got an email back from the charger company, They said just connect each bank to each battery. He stated that this doesn't need to be disconnected from the paralleled bank. I am impressed with smart chargers these days. I would suspect that the internal resistance is less than the wiring resistance in order for this technology to work. Thanks for the quick replies and thank you all for being able to bounce my ideas around. It makes engineering much easier.
     
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