Clay -

All AGM batteries are not created equal. In general, they have higher charge acceptance rates as a class compared to SLI flooded cells - but as an example - an Optima doesn't have anywhere near the charge acceptance rate of a Concorde or Lifeline AGM.... and AFAIK, the Concorde/Lifeline AGMs have the highest rate by far of any AGMs.

Optima claims a charge acceptance rate of 2x flooded cell batteries for the marine blue top - that would be roughly 50% of AH capacity and for the Marine starting battery (1000M) would be .5 x 56AH (C/20 rate) = 28.0A max. charge acceptance rate. The blue top deep cycle (D900M) would be .5 x 65AH (C/20 rate) = 32.5A max charge acceptance rate. The yellow tops would appear to be about the same charge acceptance rate as the blue top deep cycle and the red tops appear to be about the same as the lower-rated blue top starting battery rate.

If all of the manufacturer's data and claims are correct, then the Optima batteries accept a charge at 2x the rate of SLI flooded cells, but Concorde/Lifeline batteries accept a charge 8x greater than Optimas and 16x greater than SLI flooded cells. The primary difference is in the amount of lead in the plates. Optimas are spiral wound and only slightly thicker than standard SLIs, while Concorde/Lifeline plates are solid lead. An Optima weighs 38-42 lbs.... my Concorde weighs about 65 lbs. <img src="/forums/images/graemlins/scared.gif" alt="" />

Frank