Judging/comparing Battery Performance
We've all read about person X who does nothing more than plug in their converter and claims the batteries are just as good as new 6 years later, although this is an impossibility.
More accurate would be is that the batteries still meet the needs of the owner, 6 years later.
Some of us are more anal, use the batteries more, and have a bunch of tools to measure and count amps into and out of the batteries, Specific gravity, and notice the voltage held under load for a certain amount of amp hours removed. Mex's "trends and tendencies"
While Fulltiming, I've been judging several sets of dedicated house batteries on how much voltage they were able to hold under such and such a load, but not until recently have I been seeing what the batteries would rebound to when all loads are removed as this would have required moving a bunch of wires. Back and forth in cramped quarters.
Now I can do so just by moving a switch or 3.
Right now, I have both a Northstar group 27 AGM rated at 90 amp hours and 930CCA and a Flooded USbattery Group31 Deep Cycle rated at 130 amp hours and 620CCA. I can task either for house or engine starting duties, by the turn of a switch or 2 or 3, which allows for much more flexibility and ease of testing/ comparing.
This has thrown a wrench into my expectations, because the lesser capacity AGM holds higher voltages for the same amount of amp hours removed( Upto 70 a/h so far anyway) It also has a much higher fully charged resting voltage of nearly 13.1v compared to ~12.7 for the USbattery.
Now neither battery has gotten so low as to to threaten the food in my compressor fridge, and my engine starts easily enough even with 70 amp hours removed from either battery when used as the starting battery. I rarely parallel them without a charging source available keeping them over 13.1v.
I do have small dashboard voltmeters with sense wires right to the battery's (+), and once again the AGM holds higher voltages during engine cranking and noticeably turns the engine over faster even when 70 amp hours are removed from either.
I have not been cycling the AGM as much as the flooded, because I really like the quick starting aspect of the AGM, though it does not really matter. I also have not been testing to see how much the voltage rebounds on the AGM after a nightly cycle and then loads removed before sunup. Unfortunately I have not been keeping records as to the number of cycles on each, so the longevity, when one or the other fails is not going to mean much either.
NorthStar claims 12.2 rested OCV is about 54% SOC. I cannot find a USbattery SOC chart.
I am not trying to turn this into another AGM vs flooded war that get so many riled up on these forums. This is my First AGM, and so far I find it impressive, but I paid nearly 300$ for it, and I also expect a lot from it.
What is my issue is I do not know how to judge its performance, as I only have, and have had, flooded batteries to compare it to, and my traditional judgement methods of voltage held for capacity depleted might not be fair to the flooded.
After all it is not as if either battery has come close to letting my food go bad, or been too weak to start the engine on its own. If I treated them exactly the same, who knows which would outlive the other. If we consider the ultimate longevity of the battery while it still meets the needs of the owner, how important is it how fast a battery can turn over an engine or power a microwave, or if it holds 0.1v more for the same A/h removed compared to the other?
Is holding a higher voltage under load, just bragging rights and nothing more?
More accurate would be is that the batteries still meet the needs of the owner, 6 years later.
Some of us are more anal, use the batteries more, and have a bunch of tools to measure and count amps into and out of the batteries, Specific gravity, and notice the voltage held under load for a certain amount of amp hours removed. Mex's "trends and tendencies"
While Fulltiming, I've been judging several sets of dedicated house batteries on how much voltage they were able to hold under such and such a load, but not until recently have I been seeing what the batteries would rebound to when all loads are removed as this would have required moving a bunch of wires. Back and forth in cramped quarters.
Now I can do so just by moving a switch or 3.
Right now, I have both a Northstar group 27 AGM rated at 90 amp hours and 930CCA and a Flooded USbattery Group31 Deep Cycle rated at 130 amp hours and 620CCA. I can task either for house or engine starting duties, by the turn of a switch or 2 or 3, which allows for much more flexibility and ease of testing/ comparing.
This has thrown a wrench into my expectations, because the lesser capacity AGM holds higher voltages for the same amount of amp hours removed( Upto 70 a/h so far anyway) It also has a much higher fully charged resting voltage of nearly 13.1v compared to ~12.7 for the USbattery.
Now neither battery has gotten so low as to to threaten the food in my compressor fridge, and my engine starts easily enough even with 70 amp hours removed from either battery when used as the starting battery. I rarely parallel them without a charging source available keeping them over 13.1v.
I do have small dashboard voltmeters with sense wires right to the battery's (+), and once again the AGM holds higher voltages during engine cranking and noticeably turns the engine over faster even when 70 amp hours are removed from either.
I have not been cycling the AGM as much as the flooded, because I really like the quick starting aspect of the AGM, though it does not really matter. I also have not been testing to see how much the voltage rebounds on the AGM after a nightly cycle and then loads removed before sunup. Unfortunately I have not been keeping records as to the number of cycles on each, so the longevity, when one or the other fails is not going to mean much either.
NorthStar claims 12.2 rested OCV is about 54% SOC. I cannot find a USbattery SOC chart.
I am not trying to turn this into another AGM vs flooded war that get so many riled up on these forums. This is my First AGM, and so far I find it impressive, but I paid nearly 300$ for it, and I also expect a lot from it.
What is my issue is I do not know how to judge its performance, as I only have, and have had, flooded batteries to compare it to, and my traditional judgement methods of voltage held for capacity depleted might not be fair to the flooded.
After all it is not as if either battery has come close to letting my food go bad, or been too weak to start the engine on its own. If I treated them exactly the same, who knows which would outlive the other. If we consider the ultimate longevity of the battery while it still meets the needs of the owner, how important is it how fast a battery can turn over an engine or power a microwave, or if it holds 0.1v more for the same A/h removed compared to the other?
Is holding a higher voltage under load, just bragging rights and nothing more?
