Thor Forums

[16ACE27]

You said:

Originally Posted by The_Breeze

They sit for an hour and lose .1v or more doing almost nothing but running the onboard stuff.
They'll drop into the 12.4's and stay pretty much in that range for the rest of the day.

Then you asked:

Originally Posted by The_Breeze

Why, when doing nothing, do they lose that much voltage, yet at night when doing almost the same thing, they gain .02 or .03 volts?

So is there a load on the batteries or not?

When determining the state of charge of the battery bank the batteries have to be at rest - no load at all on them. Your batteries have internal resistance so if there is a load on them their supplied voltage will be less than their state of charge would indicate. As current increases the supplied voltage decreases.

So you're trying to do science experiments with your batteries but you aren't adhering to established data taking techniques; therefore your data is flawed.

If you want to compare daytime voltage vs nighttime voltage all other variables, like temperature, SOC, and current draw have to be the same.

If your current draw was almost nothing when you measured 12.4 VDC then you could almost say that voltage indicated your batteries' SOC.

I mentioned before that any voltage measurement above 12.7 VDC would reflect a capacitive charge not a chemical charge but I didn't add FOR A FULLY CHARGED BATTERY.

If the true SOC of your battery is reflected by 12.4 VDC then any voltage measured above 12.4 VDC would also be due to a capacitive charge and would quickly dissipate down to the voltage for the batteries' true chemical SOC.