AGM Batteries

[JonBill]

I bit the bullet and bought two Optima AGM Marine batteries. Don't plan to worry about juice until about 550 cycles from now.

AH rating could be higher on the Optima and seems low until you factor in they can draw down to 20% of their total depth of discharge rather than 50% for standard wet lead acid deep cycle.

So having 80% of the AH available in an AGM instead of 50% boost the total power/time output in AGM's favor or is part of the equation in a side by side comparison. In other words if you have a deep cycle wet acid battery rated at 80ah and an AGM rated at 55ah you have more available power (useful capacity) with the AGM (44 for AGM vs. 40 for wet acid). So in this case less is more. However the price is 2 to 2.5 times more for the AGM’s.

Also the AGMs cycle more times with some AGMs cycling more than other AGMs depending on the design and mnfg. A very good deep cycle wet acid battery will cycle 350 times while a very good AGM will cycle 750 times. A good wet acid battery will cycle 300 times while a good AGM will cycle 550 times. So AGM's have better cycling and depth of discharge over the wet batteries.

AGM’s recharge in about half the time a wet acid battery would. AGM’s need no watering. AGM's can be mounted in any position, require no room for venting and therefore can be installed in living quarter sections of your boat without any safety concerns. AGM’s are far more shock resistant than wet acid and this can be a concern in boating with the pounding the boat takes in some situations.

AGM’s don’t self discharge like wet acid batteries. They self discharge at about 1% to 3% per month vs. up to 15% per month for a wet acid battery. What this means is, you can let the boat sit all year long without charging the batteries and the AGM will still start your motor – no problem.

AGMs cost a lot more but you get what you pay for. And all battery banks have to be managed properly regardless of battery type. Or you’ll run out of juice.

Kind Regards,
JonBill

[beene]

Congtrats JonBill

I hope they prove to be all you were expecting them to be. I just have the stock batt and 1 large DS house batt. So far, so good.

G

[Frank C]

. . . AH rating ... seems low until you factor in they can draw down to 20% of their total depth of discharge rather than 50% for standard wet lead acid deep cycle.

So having 80% of the AH available in an AGM instead of 50% boost the total power/time output in AGM's favor or is part of the equation in a side by side comparison ...

jb,
Good analysis. I never pondered that advantage ... going deeper into an of AGM's reserve capacity. But combining that with the AGM's other benefits, and considering you can prolly save 20 bilge-pounds of dead weight, the cost premium almost evaporates.