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Thread: Multiple Battries

  1. #21
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    dynamo... LMAO!

    Gyro, will that also charge the second battery?

  2. #22
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    Quote Originally Posted by slushieken
    dynamo... LMAO!

    Gyro, will that also charge the second battery?
    What the hell is LMAO?
    If you use your car as anyone else is, your dynamo shouldn't have probs with charging both. This circuit is used by people owning a camper where the second battery gets (dis)charged more often as the car-battery ... I don't see any disadvantages, do you?

  3. #23
    Maximum Bitrate kiltjim's Avatar
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    Battery Isolator.
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  4. #24
    Maximum Bitrate more mods's Avatar
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    Quote Originally Posted by kiltjim
    Battery Isolator.
    I think without a Isolator you will damage one or both batteries.

    If one of the batteries is fully charged and the other one is discharged, you will be charging both. I am not an expert on batteries but I do know that over charging can cause some very bad results.
    It's the cake having/eating thing.

  5. #25
    Low Bitrate frenchnew's Avatar
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    Quote Originally Posted by more mods
    I think without a Isolator you will damage one or both batteries.

    If one of the batteries is fully charged and the other one is discharged, you will be charging both. I am not an expert on batteries but I do know that over charging can cause some very bad results.
    Actually, it is a little more like the dircharged battery will absorb energy from the charged battery and the car's alternator will be working harder to charge both batteries at the same time.

    Alternators are built to maintain a battery charge to the proper level and they are not really built to charged a battery that has been completely discharged (This would cause extra strain on the alternator which could result in premature alternator failure).

    As far as overcharging batteries, if the alternator regulator is not defective it should not be a problem as it will maintain the charge at the proper levels to prevent damage to the battery.

    Some Options to consider;

    Solenoid method (Heavy Duty Relay with a minimum of 100 Amps current carrying capacity to prevent the contacts from burning out). Direct charging of both batteries with the engine running and discharge both batteries if the ignition is in the ON position (Wired so that the Solenoid is energized with the ignition ON). The auxiliary battery would discharge separately when the ignition is OFF but as soon as you turn the ignition on, the car's main battery will drain to the auxiliary battery. A desirable option here would be to have a circuit that would energize the relay after 30 seconds to 1 minute after the ignition has been switched on (Presume engine running at this point) and it would charge both batteries. The solenoid can be wired from the car's battery post. When equipped with a sensing circuit, it becomes a Battery Regulator. Choose your Solenoid carefully as some of them are rated for intermittent usage (To Avoid).

    Battery Isolator = Most of these use diodes to isolate the batteries. A diode is a One-Way Flow Valve in simple terms. The diodes isolator generally have a voltage drop of 1 volt or more accross the diodes. This means that the batteries will never be completely charged. These Diode isolators are generally wired in the alternator output wire and if your car is still under warranty - good luck trying to get repairs on the charging circuit done under warranty with such an item in the charging circuit.

    Multiple Battery Regulators = The best choice in my opinion. Those are generally equipped with electronic circuits. The are conceived to charge the main car battery first and once this is accomplished, it will start to charge the auxiliary battery. Some of those have mosfets switches (Solid state switch with no moving hardware) and some have solenoid switches. Check Orion MBR70 (Solid State) not sure if it is still available. More costly then the 2 choices above but will maintain both batteries at their top charged levels without putting any extra load on the car's charging circuit. Usually wired to the main car battery.

    Direclty wired. No isolators, both batteries wired together. In this scenario, it is better to choose your auxiliary battery to closely match the main car battery to prevent one battery discharging the other when the ignition is OFF.
    It is best to actually by 2 batteries of the same manufacturer with the same specifications at the same time and replace the car's main battery with one of those. Failure to have 2 of the sames batteries will mean that one battery will never get fully charged which will result in the slow death of the batteries.

    Best regards from Montreal

    frenchnew

  6. #26
    Low Bitrate FishCook's Avatar
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    Quote Originally Posted by gyro
    What the hell is LMAO?
    LMAO = Laughing my *** off (or arse for the folks in the UK)

  7. #27
    Variable Bitrate danon's Avatar
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    Quote Originally Posted by gyro
    This relay is a 70amps type minimum (depending on the strength of your 2nd batt.) and can be found in shops where they have anything for your camper. Mine cost 13.00 I still can't test it because I am waiting for the pcb for my Sproggy PSU. Since I am short of free time, it may take a while before testing. If there are some people with good results on this manner of connecting, please let us know and share your experiences.
    oh boy, what you're trying to achieve, is exactly what my setup is, and there are others in this forum that has this setup. i'm about to go to work within five minutes, as soon as i got back from work, i'll give you the link of the discussions we had on the other thread. bye for now...


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  8. #28
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    Hey,

    From the theoretical electronic point of view, connecting two batteries in parallel should be fine. But if they are just plain parallel with one under the hood and one in the trunk with just a 4 gauge or bigger wire between and a fuse, they provide no protecton from running the charges dead besides holding twice the amp hours. If you run headlights, audio, computer, and all the other stuff on the battery directly charged by the alternator, and then run a diode to another battery for the starter motorand all the other stuff the car needs to start up and start charging, your car will basically never die because the electrons can only flow one way through the diode. If the starting battery is on the alternator side and the audio battery is charged through a diode, theres nothing stopping your system from draining both batteries if its run too long. Theres not much advantage of adding a battery in the trunk unless you go to drive-in movies and need to let your system bump without idling the whole movie, you leave your carputer in standby for weeks at a time, if you are competing with your sound system where system specs are very important, or any other situation that requires running lots of amphours from the battery and still being able to drive away. All in all, tossing in an extra battery without research and tests will cost you extra money and might even give a false sense of security that could leave you stranded at some point. Just my 2 cents/.0161 euros.

    -Chris

  9. #29
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    thanks for the replies.

    So it is not as simple as I thought ...well, can anyone tell how long I can use an Carputer (for example) without the car runing? Lets say I use an OPUS 150W...ofcourse I also use an audio system but lets say I only use the carputer...

    greetz

  10. #30
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    Quote Originally Posted by danon
    oh boy, what you're trying to achieve, is exactly what my setup is, and there are others in this forum that has this setup. i'm about to go to work within five minutes, as soon as i got back from work, i'll give you the link of the discussions we had on the other thread. bye for now...


    danon

    I am looking forward to your setup Danon, since this setup is used in campers hee in Belgium this setup can't be that bad, is it ?

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