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Subject: TWL: AGM Batteries
Does anyone have experience or comments, good or bad, about AGM batteries?
Michael Rowe
I take this verbatim from Powerboat Reports, September, 1999. This came up
while searching for information on portable jump start power packs.
Sealed lead acid valve-regulated batteries in general, and the Absorbed
Glass Mat (AGM) battery and its hybrid variants in particular, are different
animals (from wet cell batteries). Instead of lead compound plates with acid
and water mixtures (electrolyte) sloshing around, a thick electrolyte paste
is applied to the plates. (This is why you can use these batteries upside
down.) Some chemical substitutions in these sealed cells dramatically
improve resistance to self-discharge, and just enough liquid acid is
integrated into the paste to provide for peak efficiency. If you broke open
a valve-regulated sealed cell, liquid would not pour out (but the mix would
still be caustic). Instead of losing electrolyte during charging, the cells
are under slight pressure (controlled by valves that can release under
extremes) and charging gases are forced to recombine back to usable
chemicals. The close proximity of lead to electrolyte and tight plate
spacing make for extremely low internal resistance and greater efficiency in
energy discharge.
Rather than go into more detail than necessary, suffice to say that the
AGM is charactorized by extremely low self-discharge and extremely high
controlled discharge rates.
AGM manufacturers list cycle life on the order of 500 to 1,000 cycles,
which starts to border on "too good to be true". *******
Also mentioned in this article is a brand new (1999) technology called "thin
film" which is supposed to be even better than AGM chemistry. Bolder
Technologies in Golden, CO is a maker of thin film batteries.
A call to Bolder Tech revealed they don't have one yet that will start a
diesel, but the portable marine model they have will start an eight cylinder
gasoline engine. It weighs all of 5 pounds. www.boldertmf.com
Zeke Anderson
Texas Cookin'
Rockport TX
