Capacity Testing and 20 HR Rating
I'm thinking about doing a capacity test on my four GC2's. They have a 20hr rating of 215Ah. One thing I'm curious about is how the 20hr rating would have been determined. Being 6v, would they h...
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You first charge them up to baseline SG near as you can.
Then run them down at their 20 hr rate ( 430/20 = 21.5) for 10 hours or till they get to 50% SOC by SG (around 1.190 depending on brand) whichever comes first.
The trick is to find the constant amps load. Your DC lights draw fewer amps as time goes on and battery voltage drops. (lights get dim, so draw fewer amps) You keep turning on another light to stay even. With an inverter load, the amps creep up as battery voltage goes down, so you have to juggle that.
It isn't a science lab, so somewhere close is good enough to get you the info you are seeking.
So let's say it took 9 hrs to get to 50% instead of the 10 hrs. Your capacity is less than rated AH. How much less?
9 x 21.5 = 193.5AH your capacity is twice that = 387AH and 387/430 = 90%. (I keep thinking 9 out of 10 for half is 20% missing, so I have to do it this way to get it right)
EDIT if you have a Trimetric, you can confirm the AH count to 50% (by SG) and compare with the time based calculation above to see if it all "matches"
Then run them down at their 20 hr rate ( 430/20 = 21.5) for 10 hours or till they get to 50% SOC by SG (around 1.190 depending on brand) whichever comes first.
The trick is to find the constant amps load. Your DC lights draw fewer amps as time goes on and battery voltage drops. (lights get dim, so draw fewer amps) You keep turning on another light to stay even. With an inverter load, the amps creep up as battery voltage goes down, so you have to juggle that.
It isn't a science lab, so somewhere close is good enough to get you the info you are seeking.
So let's say it took 9 hrs to get to 50% instead of the 10 hrs. Your capacity is less than rated AH. How much less?
9 x 21.5 = 193.5AH your capacity is twice that = 387AH and 387/430 = 90%. (I keep thinking 9 out of 10 for half is 20% missing, so I have to do it this way to get it right)
EDIT if you have a Trimetric, you can confirm the AH count to 50% (by SG) and compare with the time based calculation above to see if it all "matches"
