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Thread: Split charge Relay and power drain

  1. #1
    Variable Bitrate slarty's Avatar
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    Split charge Relay and power drain

    Hi

    I had an SV24 with a DC/DC PSU from MGPower and ran a 600w AMP @ 30 AMP.

    I now have a regulated C134 EPIA-M and run it off the same system, i.e. a second battery in the boot/trunk. The problem I have is that the PC and AMP on together will drain the battery in 20 minutes flat. I can only surmise that the relay is not charging the battery. I get 14.3v at the main battery terminal and going into the relay but ony 12.3v at the second battery terminal on the relay and on the second battery terminal.

    The relay has

    Power In from main battery
    Power Out to second battery
    Fridge Power Out
    Ground
    Ignition light

    When I take a reading off the ignition wire it only reads between .1 and .15 of a volt, I thought that this may be the cause?

    Basically the voltage off Power out to the second battery seems to be just the voltage from the battery and when I power up the PC it just steadily drops about .1 volt every 40 ish seconds

    I have searched the forum on split charge relays and found some interesting links and coments made on the "Black Art" of Lead Acid battery charging

    Any help welcomed
    Lilliput 8", C134 EPIA-M 900 (Black), A1-ITX, 256 Mb RAM, 40 Gb HDD, DVD, 802.11g, mini keyboard

  2. #2
    FLAC Spaghetti's Avatar
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    Sounds a bit too technical for me, but..... I don't suppose you have any pics of your set up do ya...?? I wanna Prelude myself...

  3. #3
    Variable Bitrate slarty's Avatar
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    Quote Originally Posted by Spaghetti
    Sounds a bit too technical for me, but..... I don't suppose you have any pics of your set up do ya...?? I wanna Prelude myself...
    I do but they are of the old setup, I had an sv24 and a 10.4" screen but I got sick of the size of the screen and the space that the sv24 took up

    http://www.btinternet.com/~jonathan_porter

    The site will be updated as soon as I solve this power issue!
    Lilliput 8", C134 EPIA-M 900 (Black), A1-ITX, 256 Mb RAM, 40 Gb HDD, DVD, 802.11g, mini keyboard

  4. #4
    FLAC Spaghetti's Avatar
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    That's a lotta wires!

  5. #5
    It ain't easy being a green moderator meddler's Avatar
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    It definately sounds as tho the second battery is not being charged. If you could draw a diagram of how it is wired up I will be able to help you. Obviously your alternator is working because you have 14.3v at your main battery. If you have wired it up correctly, when the car is running you should have about 14V (varies due to resistance in wire from alternator to the back of the car.) at the second battery.

    My first suggestion is double check all your wiring.
    Never let the truth get in the way of a good story

  6. #6
    Variable Bitrate slarty's Avatar
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    Quote Originally Posted by Spaghetti
    That's a lotta wires!
    There's a lot less now
    Lilliput 8", C134 EPIA-M 900 (Black), A1-ITX, 256 Mb RAM, 40 Gb HDD, DVD, 802.11g, mini keyboard

  7. #7
    Variable Bitrate slarty's Avatar
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    Quote Originally Posted by meddler
    It definately sounds as tho the second battery is not being charged. If you could draw a diagram of how it is wired up I will be able to help you. Obviously your alternator is working because you have 14.3v at your main battery. If you have wired it up correctly, when the car is running you should have about 14V (varies due to resistance in wire from alternator to the back of the car.) at the second battery.

    My first suggestion is double check all your wiring.
    Thanks for this. Its a bad diagram but it gives the idea The wire to the rear battery is a heavy guage and about 2 metres

    I don't know what else to try at this time.
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    Lilliput 8", C134 EPIA-M 900 (Black), A1-ITX, 256 Mb RAM, 40 Gb HDD, DVD, 802.11g, mini keyboard

  8. #8
    It ain't easy being a green moderator meddler's Avatar
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    Quote Originally Posted by slarty
    Thanks for this. Its a bad diagram but it gives the idea The wire to the rear battery is a heavy guage and about 2 metres

    I don't know what else to try at this time.
    It should be wired up as shown in the pic below. I have drawn in the connections for a standard bosch type auto relay, but you should be able to figure it out if you are using something else. It sounds as tho you have the relay wired up incorrectly. Any more dramas let me know.
    Never let the truth get in the way of a good story

  9. #9
    Variable Bitrate slarty's Avatar
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    Quote Originally Posted by meddler
    It should be wired up as shown in the pic below. I have drawn in the connections for a standard bosch type auto relay, but you should be able to figure it out if you are using something else. It sounds as tho you have the relay wired up incorrectly. Any more dramas let me know.
    85 does go to ignition on but it goes to the ign on the head unit loam. is .1v enough to switch the relay. Also does the relay switch immediately to charge the second battery as it has the ignition on.

    Thanks for the help!
    Lilliput 8", C134 EPIA-M 900 (Black), A1-ITX, 256 Mb RAM, 40 Gb HDD, DVD, 802.11g, mini keyboard

  10. #10
    FLAC shakes's Avatar
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    most 'ignition' inputs need 12v to trigger. sounds to me like that's the culprit

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