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How many CCA is sufficient for the m42?

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    How many CCA is sufficient for the m42?

    1991 m42 with ac and a stereo and that's about it. I wanted to find a smaller AGM battery but most seem to have pretty low CCA. I think the manual calls for quite a bit more than that is typically available in an AGM battery.

    This is for a swap car without a rear battery so a smaller battery would be best to avoid yet another project.

    Also I'm in Texas and it doesn't get too cold here.

    #2
    Battery

    I've been reading up on batteries because I want to set up a solar charging station. I also use li-po batteries for my rc hobby toys, so no idea what you will get out of it.

    They have those portable li-po battery packs that are being used to jump start cars. I wouldn't use these in the car because the charging system just isn't set up to safely charge these.

    The feasibility of using a small agm battery is there as I've been told racers do this to cut down on weight. When I was in japan, the battery on my r32 skyline was half the size of the ones in the e30.

    From my solar project reading.... cca because you need the juice for the cold mornings but you will need to keep the battery charged for its longevity. Deep cycle batteries so you can draw down the amps and still have a battery you can charge up the next day. Agm, so you can order it online and have it shipped, lol. Draw that agm down and it will gas off and go flat.

    Agm batteries also have a different charging profile but it is similar enough to wet cells that you can get away with it.

    For a daily, I can't be bothered and would just get a full size wet cell battery, cheaper than the full size agm and compatible with '80s technology. I disconnect the battery between runs (I go months at a time on each car).

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      #3
      Im running in to the same issue.. Every battery type is a series of pros and cons. At the end of the day, I think I'm just going to do a battery relocation. I already have half the carpet up anyways.


      Does BMW run the negative terminal all the way up to the engine or just ground out to the wheelwheel or somewhere else in the trunk?

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        #4

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          #5
          AGM batteries in general have fewer CCA's than their wet cell counterparts. AGM batts resist self discharge moreso than wet cells and allow for faster charging, and are more vibration resistant. But if you don't need any of these, a standard wet cell with around 600CCA's should suffice


          it's a Kenny Powers quote on wheels

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            #6
            there is a threaded bracket welded inside the wheel well where the battery grounds, so only the power cable and fusible link go from the battery to the engine bay.

            i have been using the same odyssey 680 AGM battery since i bought my car about 4 years ago, it will start my m20 in temperatures all the way down to about 35-40*, but that's always been sufficient for me because the car gets stored in the winter. but i didn't have AC or power steering so that's obviously a fair amount of resistance that is avoided. when i store the car i remove the battery, put it on a slow charge for a few days, then bring it inside the house and store it at room temperature until spring. it seems to be holding up just fine with this process after almost 4 years of use

            1989 Coupe build thread: http://www.r3vlimited.com/board/showthread.php?t=312012
            IG: @mitchlikesbikes

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