Balmar smart gauge and 10 hour AH testing
So this guy was selling an open box Balmar smart gauge on fleabay. They are expensive and I go by voltage to gauge my batterys by that. Well he had a make offer price so I lowballed @ $140. He didnt ...
Forum Discussion
My opinion on 10 hour tests using the 20 hour rate is that one can use such a test at cycle 100 and compare it to results at cycle number 400, and from that comparison gauge capacity loss/ remaining.
I do not feel that the 20 hour load placed for 10 hours and judging voltage rebound or SG, can say whether the battery is still at full capacity, or some percentage thereof by trying to gauge 50% SOC.
Mex has stated before that the voltage below the 50% mark is not linear with teh voltage dropping from 100% to 50%, and while some batteries say 10.5v is 100% discharged, some others will have this 100% discharged number in the 11's.
Granted this is for an AGM, but Crown in the following PDF says 100% discharged is 11.64v:
https://www.wholesalesolar.com/cms/four-star-solar-crown-48-vdc-10-560-wh-with-mnbe-d-enclosure-8-battery-bank-agm-battery-maintenance-2936570746.pdf
After a recent rezeroing/reset of my AH counting battery monitor when known full, I can take my 52 month old ~750 Deep cycle 90AH Northstar AGM to 45Ah from full at 2x the 20 hour rate, and voltage rebounds to over 12.2 within 5 minutes on a battery well below 77f.
Northstar's 50% SOC OCV is spec'd at about 12.11v.
So if I were to infer 50% from rebound voltage, I Would conclude this well used and aged battery even now, has significanlty more than its rated capacity.
But it cannot, it does not, and I do not feel one can actually figure out remaining capacity without doing an actual 20 hour load test with a precice load applied and kept as voltage drops, with the battery kept at 77F for the whole time.
Who has the equipment or time to actually achieve this, and is it even worth the effort on a pair of Marine flooded group 24's? Can we dismiss battery temperature, no. CAn we dismiss hydrometer inaccuracy? no, can we dismiss ammeter inaccuracy and the 20 hour rrate being 5% higher or lower? No.
Perhaps if one were setting sail somewhere where there is no place to acquire a new battery and their premature death might also cause hardship to human, would it be worth it to actually perform the 20 hour capacity test, but such a person who puts their faith in group 24s in such a situation might just succumb to Darwinian principles en route, well before the batteries failed to 'hold a charge'.
So my opinion is 10 hours tests at the 20 hour rate are useful only for comparison to later tests when all variables are kept the same, and not useful for determining actual remaining battery capacity.
With SG readings, well same thing, One does not know if their hydrometer is actually accurate, nor what the true 100% SG reading should be, and the SG reading will be different with the electrolyte level 2Mm above the plates compared to 12 mm above the plates.
Too many variables that cannot be accounted for outside a laboratory environment.
But it will be obvious if a 20 hour rate applied for 10 hours on a questionable battery, that is destined for the recyclers soon. I doubt it would take 10 hours to determine this, especially if this is the second time one has tried and can compare data from the same battery using the same equipment and accounting for variables like temperature and electrolyte levels.
I do not feel that the 20 hour load placed for 10 hours and judging voltage rebound or SG, can say whether the battery is still at full capacity, or some percentage thereof by trying to gauge 50% SOC.
Mex has stated before that the voltage below the 50% mark is not linear with teh voltage dropping from 100% to 50%, and while some batteries say 10.5v is 100% discharged, some others will have this 100% discharged number in the 11's.
Granted this is for an AGM, but Crown in the following PDF says 100% discharged is 11.64v:
https://www.wholesalesolar.com/cms/four-star-solar-crown-48-vdc-10-560-wh-with-mnbe-d-enclosure-8-battery-bank-agm-battery-maintenance-2936570746.pdf
After a recent rezeroing/reset of my AH counting battery monitor when known full, I can take my 52 month old ~750 Deep cycle 90AH Northstar AGM to 45Ah from full at 2x the 20 hour rate, and voltage rebounds to over 12.2 within 5 minutes on a battery well below 77f.
Northstar's 50% SOC OCV is spec'd at about 12.11v.
So if I were to infer 50% from rebound voltage, I Would conclude this well used and aged battery even now, has significanlty more than its rated capacity.
But it cannot, it does not, and I do not feel one can actually figure out remaining capacity without doing an actual 20 hour load test with a precice load applied and kept as voltage drops, with the battery kept at 77F for the whole time.
Who has the equipment or time to actually achieve this, and is it even worth the effort on a pair of Marine flooded group 24's? Can we dismiss battery temperature, no. CAn we dismiss hydrometer inaccuracy? no, can we dismiss ammeter inaccuracy and the 20 hour rrate being 5% higher or lower? No.
Perhaps if one were setting sail somewhere where there is no place to acquire a new battery and their premature death might also cause hardship to human, would it be worth it to actually perform the 20 hour capacity test, but such a person who puts their faith in group 24s in such a situation might just succumb to Darwinian principles en route, well before the batteries failed to 'hold a charge'.
So my opinion is 10 hours tests at the 20 hour rate are useful only for comparison to later tests when all variables are kept the same, and not useful for determining actual remaining battery capacity.
With SG readings, well same thing, One does not know if their hydrometer is actually accurate, nor what the true 100% SG reading should be, and the SG reading will be different with the electrolyte level 2Mm above the plates compared to 12 mm above the plates.
Too many variables that cannot be accounted for outside a laboratory environment.
But it will be obvious if a 20 hour rate applied for 10 hours on a questionable battery, that is destined for the recyclers soon. I doubt it would take 10 hours to determine this, especially if this is the second time one has tried and can compare data from the same battery using the same equipment and accounting for variables like temperature and electrolyte levels.
