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Old 01-26-2012, 09:46 PM
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Yorgi Yorgi is offline
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Location: Toronto
 
Join Date: Mar 2005
Posts: 3,650
Mein Auto: '04 M3 / '06 650i Cab
I would go for the AGM over the old lead cell.

AGM (Absorbed Glass Mat) are far superior to lead cell and it looks like BMW is switching over to AGM across the board. Optima "spiral" batteries are AGM. The TIS lists the old lead cell as 110AH 850A and the new AGM as 90AH 900A. The AGM is a little smaller but has several advantages over a lead cell:
  • Very efficient - charges faster and loses about 1% charge per month vs 1% PER DAY for lead cell.
  • No acid fumes or need for venting
  • Highly shock resistant
  • Less affected by being fully discharged
  • Works better in low temps

So even though the AGM battery is a little smaller it will recharge faster on short trips and discharge less in storage.
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'04 M3 - track
'06 650i Cab - daily driver
'02 Highlander - kid hauler
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