Jody...thanks for that link. It was interesting reading even though factually in error in too many ways to count. As you know, I favor wet cells for casual use and AGM's for full time on the hook cruising...on a purely economic comparison. This is the section I particularly object to:
So in my simple mind the AGM is about 3 times more expensive than the standard one. So the question is; if these batteries are 3 times more expensive than the standard one, what do they do that is 3 times better? Do they last 3 times longer? (I think not, more like the reverse). Do they charge 3 times faster to reduce your engine running hours? (Only in their dreams.)
I agree they do not last longer than a GOOD wet cell...but that reduces the 3x premium to about 2x...they do last longer than standard wet cells (with proper charging regimen on both).
They DO charge 3-5 times faster than wet cells...indeed, the newest AGM configurations with pure lead and foamed separators (Odyssey) have basically unlimited current acceptance and even standard AGM's can take their full rated amps...a 5 times greater charge rate than any flooded cell.
So...with the right charging system you can easily cut your on the hook charging time WAY down...cutting
fuel costs dramatically, saving on engine maintenance and saving on engine wear (or generator). So that is how you get an economic benefit even if the cycle life is only double that of standard flooded. (Please note that standard flooded as used here means mass market flooded deep cycle batteries...not premium constructed and priced flooded.)
In addition to the
economic benefits the cruiser gets:
ZERO maintenance...important when you have to bury batteries in deep dark places. Fewer ruined clothes too. No worries about acid spills.
More rugged construction. Less likely to fail due to mechanical shock or grid failure.
Placement flexibility...anywhere, any angle.
Less noise...due to less engine run time...believe me...this is important on the hook.
More time for other things...again...you don't want to have to sit around while the batteries charge and you could be out diving on the reefs!
Of course lots of cruisers choose and believe in PREMIUM flooded batteries which range in price from 1/2 of an equivilent AGM (Trojan)...to significantly more expensive (Rolls/Surrette) and there is nothing wrong with these choices but I think you have to evaluate the economics of these based on the individual boat, systems, and cruising plans...and compare specific batteries.
For example...in a 1000ah bank...comparing Trojans to Lifelines it would be hard to imagine a scenario that would economically justify the AGM's. The Trojan bank could be charged at up to 200amps (anyone have THAT size charger?) and while the Lifelines could be charged at 1000amps theoretically...it ain't gonna happen! So, the economics of faster charge times disappears and the cycle life should be about the same so the Trojans are the most economical buy. One may prefer AGM's for all the other reasons I listed...but not on the basis of economics.
OK...that's my theory and I'm sticking to it until the Fireflys come out and I can only install a 100 amp bank to replace my 1000 amp bank and charge in less than 30 minutes and go to ZERO FLAT battery levels with no damage for 1000 cycles! THEN there will be no more arguments about which battery is best...if they actually do all that!!
Tayana 52 Ketch
Linear Mode
