New Coach Batteries
It is about time to change batteries in the coach. I have the standard two 12-volt system, which I think I will stay with. But I am considering going to AGM batteries. When we camp, we usually ha...
Forum Discussion
Hi BFL13,
It is my understanding that 'normal' AGM cells are a "starved acid" design. So once all the electrolyte has been moved to the plates, charging more won't cause the battery to gas.
Telcom jars are a surplus acid format--so best to not push the charging rate, or they may gas.
Of course, all lead acid formulas are subject to positive plate shedding. Once those plates erode there is permanent loss of capacity. In the case of flooded jars, the space beneath the plates may fill up and eventually may short them out. That is what happened to my Marine jars after nine years. One of the seven became a vampire. I was able to save the larger bank because of having a disconnect switch.
The other failure mode is dendrite growth. When they penetrate the plate separators, it is game over, and a catastrophic failure, with lots of heat and gassing.
Dendrites are a problem for LI batteries, too.
It is my understanding that 'normal' AGM cells are a "starved acid" design. So once all the electrolyte has been moved to the plates, charging more won't cause the battery to gas.
Telcom jars are a surplus acid format--so best to not push the charging rate, or they may gas.
Of course, all lead acid formulas are subject to positive plate shedding. Once those plates erode there is permanent loss of capacity. In the case of flooded jars, the space beneath the plates may fill up and eventually may short them out. That is what happened to my Marine jars after nine years. One of the seven became a vampire. I was able to save the larger bank because of having a disconnect switch.
The other failure mode is dendrite growth. When they penetrate the plate separators, it is game over, and a catastrophic failure, with lots of heat and gassing.
Dendrites are a problem for LI batteries, too.
BFL13 wrote:
"The battery with the LEAST sensitivity is an AGM. They recharge until the electrics run into a stone wall then refuse to charge more."
The thing there is that if you keep the charger on, the AGM will not charge more, but instead the amps go back up and so does battery temperature.
With Wets, if you do that, all that happens is it gives off more fumes and you can replace the lost "water".
To me, that makes the AGMs more sensitive to recharging when you aren't right there when they get to "full".
