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...
Forum Discussion
Naio wrote:
I thought the key in this type of test was to read the voltage while the load was on. That way you don't have to worry about whether your surface charge has really dissipated (I know mine can take hours). Is that wrong?
I have killed an AGM battery or two by taking them down to 10.5 with a 20 amp load. Whether they were already on their way out, I do not know. Do you guys routinely go that low, for testing or cycling?
At rest, a good surface charge can last for days, but under load, only seconds. This is not a test to see the peukert effect of a particular load; although that's not a bad thing to get familiar with. This is to see how the bank handles the load that would be relevant to an overall capacity test.
My 6's are rated at 215Ah, over a 20hr time span. 215Ah / 20h = 10.75A. But my bank (four 6's) is 430Ah, so 430Ah / 20h = 21.5A, which means they should handle a 21.5a load for 20 hours, before being completely discharged. Of course, in practicality, one should never go below 50%, so this is a somewhat half-azz way of doing it. But it should still be a fairly good indicator of how well the bank can handle a fairly significant load. And the resulting SG and Vbatt readings should help determine if there is an issue with any particular battery or cell(s)... at least that's what I'm hoping to accomplish.
