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Thread: Multiple Battries

  1. #1
    Rob
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    Multiple Battries

    This ones for the car stereo nuts out there.

    When adding a second battery for the ICE, do you

    a) Have it totally seperate from the rest of the cars electrics?

    b) Have it in parallel with the cars main battery

    c) Have it in parallel with the cars main battery, but with a diode inbetween the two, so it can charge of the alternator, but won't be loaded buy the rest of the car electrics.

    Answers on a post card

    Rob

    PS I can provide setchs of what I'm on about if required.
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    jol
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    Re: Multiple Battries

    i would choose b, will extend the ampere-hours. (50 ampere-hours = will give 1 amp 50 hours before empty)

    a would be almost impossible concidering grounds and when will it be recharged?

    c would fall beacuse of the same reasons as a.


    i've seen many cars using b, and it works for them

  3. #3
    Constant Bitrate jboy's Avatar
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    I have B with a large solenoid in line with the pos cable of the battery and the main battery and they only connect is in the run (not ACC) position or with a manual override. Good for 2 reasons.
    1)I can leave the comp/stereo in standby or on without any worries about starting my car.
    2)I can jumpstart my own car if needed. (interior lights and alcohol don't mix)

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    Rob
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    Re: Re: Multiple Battries

    Originally posted by jol
    i would choose b, will extend the ampere-hours. (50 ampere-hours = will give 1 amp 50 hours before empty)

    a would be almost impossible concidering grounds and when will it be recharged?

    c would fall beacuse of the same reasons as a.


    i've seen many cars using b, and it works for them
    With c every thing would have a common ground so the ground should be OK, and the diode will allow it to recharge, so I not sure that "c" would fail for the same reasons as "a"

    I had a feel that it would be "b" but I wanted to see what others had to say. I like the solenoid idea, it makes a lot of sense.
    And you say people actually pay money for M$ Windows?
    www.mp3mini.co.uk (Does what it says on the URL) www.openclassic.co.uk (The new car, with zero rust!) www.rob-web.co.uk (My other site)
    Total re-design underway: on the whole progress is very slow as the car is taking up too much time :)

  5. #5
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    It depends on if you want the stereo to keep running no matter if you can start your car or not...or if you want to be able to start the car even though the stereo can no longer run.

    The batteries are in parallel.

    that means not in series...in series would yield 24 volts at the end...not normal for automotive installations.

    If you want both batterys to maintain a level of charge, then you have to supply electricity to them. So they both have to be connected to the alternator.

    Now...

    You want a diode bridge set up so the alternator feeds the center, to charge the extra battery and the main battery, but neither battery can feed off the other. That way you can run your stereo until it is dead, but still start your car.

    The alternatives (so to speak) are to set up the diode so alternator and main battery juice flows to the second battery...that way your stereo keeps running, but the car dies.

    Or set it up so the alternator and second battery flow to the Main battery, that way you always have max power available to crank the engine.

    Consider a capacitor like a little battery...mostly...


    My diesel truck uses two batteries in parallel with no diode because they share the workload.

    BTW you need both batteries the same type or else one will get overcharged.

  6. #6
    Rob
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    Originally posted by DodgeCummins

    You want a diode bridge set up so the alternator feeds the center, to charge the extra battery and the main battery, but neither battery can feed off the other. That way you can run your stereo until it is dead, but still start your car.

    BTW you need both batteries the same type or else one will get overcharged.
    You hit the nail on the head is this actually done, I've heard loads about 2 batterys in parallel, obviously series would be suicide.

    Thanks

    Rob
    And you say people actually pay money for M$ Windows?
    www.mp3mini.co.uk (Does what it says on the URL) www.openclassic.co.uk (The new car, with zero rust!) www.rob-web.co.uk (My other site)
    Total re-design underway: on the whole progress is very slow as the car is taking up too much time :)

  7. #7
    Constant Bitrate jboy's Avatar
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    I still prefer the solenoid because of stereo power demands and 2 batteries that can be switched in and out of parallel can supply much more current than 2 isolated from each other and has no voltage drop.

    If you don't have high current draw then a diode setup is fine, try looking up marine supplies for a automatic battery isolator it will give a cleaner install than a DIY and some have the added circuits needed for certain alternators to charge properly.

  8. #8
    Retired Admin Aaron Cake's Avatar
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    Two words: battery isolator.
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    I had a friend tell me to look into getting a deep cycle battery.
    Anybody tried this, or have any thoughts on it?

  10. #10
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    deep cycle batteries are only to be used in situations where the battery is to be run for a long period of tim without recharging... so if you are planning on consistantly running it without the car running, then a deep cycle would be beneficial. BUT if you are only thinking of doing that once in a while you WILL severely shorting the life and effectiveness of a deep cycle battery. equipment like boats, motorized wheelchairs, electric forklifts, etc run on deep cycle batteries. the batteries are made to constatly discharge until they are nearly dead and then they are recharged. they are NOT designed for use in car electrical systems and WILL be ruined if you subject them to constant charging cycles from the car alternator. go to www.optimabatteries.com and read up on the uses, benefits, and shortcomings of the various types of batteries.

    if your friend has any clue what he/she is talking about they would know that a deep cycle is not to be used in a car.
    but on the flip side, i suppose a deep cycle COULD be used if it was properly installed so that it would only recharge when almost dead, and would only recharge on a regulated current, and would fully recharge before its next use.

    ~mike
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