logging amp hours only - calculating watts

StevenB

My Pentamatrix logs three channels, ...battery, wind, solar. The way the Pentamatrix works, the third channel ( connected to solar) only displays amps and only logs/records amp hours to a report.
If over a specific time period I know the total amp hours.....and I can calculate the average battery volts over the same time period.....I don't multiply that together for watt hours do I? ......do I multiply it times the Pmax or the Open Circuit volts for my panels (just two panels in parallel )?

Thanks,
Steven

BB.

Re: logging amp hours only - calculating watts

Yes--that will work pretty well... However, you really want to know if the amperage is charging or discharging...

For example, say a battery has 12.5 volts average during your loads. And 14.5 volts average for your charging profile:

20 Amp*Hours * 12.5 volts = 250 Watt*Hours supplied to load
20 Amp*Hours * 14.5 volts = 290 Watt*Hours absorbed by battery during charge

Roughly, for Lead Acid Batteries, Amp*Hours out equals Amp*Hours in (excluding equalization).

However, you have "losses" because power in (charging) is greater than power out (discharging) because of the difference in voltages.

-Bill