Hello,
I have two 80Ah AGM batteries in series utilizing an APC battery backup as it's charging source.
I have had this setup running for 7 years now but one of the batteries is finally giving up the ghost.
The other battery still seems to be working and charging but I'm not sure of the capacity of the working battery and therein lies my dilemma.
There are actually two dilemmas.....
I need 24v for the battery backup device so I need two batteries (because I don't have a 24v battery). And since they will be in series, the capacity needs to be similar if not exactly matched. If, for example, the still good battery can now only supply 30Ah of capacity, then what I'd like to do is get another 30Ah battery so that I can use the existing battery as long as it will work. Is that ok to do that?
But how do I find the remaining capacity? I basically know that I need to fully charge it then discharge it with a known load and measure the time it takes to drop below a certain voltage. That will give me the capacity. The average load on it in practical use is about 120watts. So can I assume that connecting a 120watt load to it is what I need to do?
Also, does it matter if one battery is AGM and one is Lead Acid as long as they both have equal capacities?
What cut-off voltage should I use? 12.4v ?
Thanks for any help.
I have two 80Ah AGM batteries in series utilizing an APC battery backup as it's charging source.
I have had this setup running for 7 years now but one of the batteries is finally giving up the ghost.
The other battery still seems to be working and charging but I'm not sure of the capacity of the working battery and therein lies my dilemma.
There are actually two dilemmas.....
I need 24v for the battery backup device so I need two batteries (because I don't have a 24v battery). And since they will be in series, the capacity needs to be similar if not exactly matched. If, for example, the still good battery can now only supply 30Ah of capacity, then what I'd like to do is get another 30Ah battery so that I can use the existing battery as long as it will work. Is that ok to do that?
But how do I find the remaining capacity? I basically know that I need to fully charge it then discharge it with a known load and measure the time it takes to drop below a certain voltage. That will give me the capacity. The average load on it in practical use is about 120watts. So can I assume that connecting a 120watt load to it is what I need to do?
Also, does it matter if one battery is AGM and one is Lead Acid as long as they both have equal capacities?
What cut-off voltage should I use? 12.4v ?
Thanks for any help.