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      10-10-2009, 08:27 AM   #139
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Drives: Lemans Blue M3
Join Date: Aug 2007
Location: Texas

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Originally Posted by doba_s View Post
are there any specs on MC battery vs M3 one ?

did anybody swapped them yet?
E9x M3 OEM battery specs: 90Ah 1050CA/900CCA

Mini Cooper OEM battery specs: 55Ah 640CA/480CCA

In my experience, battery weight and battery power are tied together very closely. After extensive trial and error, I can tell you without hesitation that I have never found a battery with a huge disparity between these two key details that actually worked long term.

I am always amused by some of the claims made in regards to these small batteries, as each individual application has it's own unique current profile. BMW electrical systems are a very erratic in regards to a predictable/consistent current draw.The various modules in the car seem to have a mind of there own.

The reason I suggested the Mini Cooper battery to swamp2, is because it seems to be the perfectl balance between power and weight reduction. (for his application)

It suits his needs for a lighter weight replacement for the stock battery. (that has fewer downsides than the aftermarket options)

The aftermarket alternatives are a crap shoot IMO.

Having dealt with the headaches associated with this particular mod, I have acquired quite a bit of anecdotal experience in regards to these battery swaps.

The Mini Cooper battery has the nessesary size and power to work for what swamp2 is looking for, and it's also a more realistic size for the E9xM3. (long term)
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Last edited by Lemans_Blue_M; 10-10-2009 at 10:06 AM.