MrWizard wrote:
There is only one way to know SOC with sealed AGM batteries
And that is
Use an Amp Hour counter
The voltage vs SOC graphs for my particular AGMs do have a "bandwidth" or "range" so it is not very useful as a marker for SOC, as such. It seems to come out close enough cross-checking with AH count if I use the middle of the band.
Scroll down to the graph bottom right OCV vs Residual Capacity:
http://www.wegosolar.com/products.php?product=SKR%252d125AGM-Stark-AGM-12V-Solar-Battery-Sealed-125AFull resting is easy to establish with the voltmeter. Mine is 13.0v, which happens to be in the middle of the band. The middle for 50% is 12.4v, and that seems to correspond with the AH count using my estimated AH capacity as adjusted for temperature.
But it is true the volts vs SOC is something of a guess with that range of values. Of course the true capacity of the bank that is used for zeroing the AH counter is also an estimate.
