Builders,
The majority of experimental aircraft use Absorbed Glass Mat, (AGM) batteries, the most common brand for the last 20 years has been the Odyssey, recognizable by it’s orange top. For as common as these are, the majority of people using them miss the important detail that they should never be trickle charged, and the have vastly better performance and lifespan if you use an AGM specific charger.
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A Battery MINDer *is* a trickle charger, just a specific kind, and you’re right, is the correct tool for AGM and gel batteries. If you are only interested in maintaining a battery, the 1.5 amp Battery MINDer is about 1/4 the cost of the 8 amp version you mention. There is also the Battery Tender brand, which is almost as good but lacks the desulfating function of the Battery MINDer.
It’s not just because some authority thinks so, the reason for the different charger requirement for AGM and gel batteries versus flooded is fairly simple. Because of small variations in the electrolyte and plate separators, the current density can change over the surface of the plate, leading to spots of lower and higher resistance. With an uncontrolled trickle charger, this can lead to hot spots where the electrolyte is starved more than usual (in the case of AGM) or actually heated enough to dry out (in the case of gel cell) leading to loss of that portion of the cell. With a flooded battery this doesn’t happen as easily because the electrolyte is mobile and can flow around if there is a hot spot.
Thanks for sharing this William. This was on my list of future questions for you.
All the best,
Rob Lutz
Which setting do you use? I would think the middle one for AGM, if the top one didn’t say Odyssey.