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I have 2 - 225ah 6v golf cart batt in series. My SOC is 85% and voltage is 12.09 as seen in this screenshot. Looking at the typical charge chart for voltage my battery should only be slightly Over 50%! Is there something wrong here? What am i missing.Screenshot_20210615-060831.png
If they are lithium then voltage does not mean much. If lead acid then a bit better. But if the system is under load then the voltage means nothing as voltage drops with load.
working with a shunt or bmv is more accurate when the settings are good. In your case it is possible that they have not been getting to 100% or absorption each day for their type (moving through bulk absorption and float cycle)? Will need more info to work it out.
Thank you. I am trying to understand how dc systems work as it does not come easy to me. I will put this on ac to charge up batteries for next couple days and take s look again at my numbers. These Readings have been like this after camping 2 weeks in almost full shade with only generator to charge up to 100% soc and voltage to 13.4. By next am I'd be at 79 %soc. And 11.93 volts and would recharge. My dc fridge takes a heavy toll. Your explanation therefore makes sense.
Is this guide any help?
I've got 460ah available and am showing 67.5ah consumed. That's 86%. SOC currently shows 90%, so that's at least pretty close. Voltage (under light load) is, of course, 12.5v which is not particularly helpful.
But is SOC really correct? If I use half my amp-hours would SOC show 50%?
If you set your Peukert Exponent to 1.00 then you'll get a closer match. But then the SOC won't be correct, unless you have 'perfect' batteries. And you don't..
What's an Amp-Hour contain in energy anyway? Varies with Voltage, and not many batts charge and discharge at the same V.
So you have to trust a little, understand, and get your settings tuned in. The Victron shunt based devices can be very accurate for SOC if set up correctly. They don't use direct V or Ah readings to do that though.
I guess my big question (If I were to correctly phrase it) is - can I trust my SOC readout?
When I had only two batteries I would routinely hit 75%, sometimes lower. I was also attempting to power some things I shouldn't have, forgetting to switch things to gas, etc. Also clouds. Now that I have four batteries I rarely drop below 90% before the next day's sun hits the panels. So I guess the SOC is pretty accurate?
