Test SAFT batterys under load as a well as by voltage
Posted: Mon Aug 02, 2010 6:05 pm
This maybe obvious to some of you, but I have included here as it gives real data to back up the practice.
Before examining my Berlingo batts, I ran the vehicle until low charge light came on (at about 45%) to help identify the weakest cells. All cells (within the middle pack) were within 0.02v apart from one which we replaced. Anyway, we ran around the other cells with a battery tester set to 125A and tested for about 5 seconds not expecting any issues. However, one of the cells dropped by just under a volt over the 5 sec period, even though it was in a low state of charge and its voltage was within 0.02 of the others at the start of the test.
So the moral of the story is that it is worth doing a load test of 125A for 5 secs even if the voltage looks ok.
Summary :-
Dudd cell
...o/c voltage = within 0.02 v of other good cells.
...125A 5 sec load volt drop = approx 1 v
...recovery time to 0.02v of other good cells = TBC
Good cells
...o/c voltage = 6.02v (50% charge)
...125A 5 sec load volt drop = approx 0.25 v TBC
...recovery time to 0.02v of other good cells = TBC
Before examining my Berlingo batts, I ran the vehicle until low charge light came on (at about 45%) to help identify the weakest cells. All cells (within the middle pack) were within 0.02v apart from one which we replaced. Anyway, we ran around the other cells with a battery tester set to 125A and tested for about 5 seconds not expecting any issues. However, one of the cells dropped by just under a volt over the 5 sec period, even though it was in a low state of charge and its voltage was within 0.02 of the others at the start of the test.
So the moral of the story is that it is worth doing a load test of 125A for 5 secs even if the voltage looks ok.
Summary :-
Dudd cell
...o/c voltage = within 0.02 v of other good cells.
...125A 5 sec load volt drop = approx 1 v
...recovery time to 0.02v of other good cells = TBC
Good cells
...o/c voltage = 6.02v (50% charge)
...125A 5 sec load volt drop = approx 0.25 v TBC
...recovery time to 0.02v of other good cells = TBC