You are generally best to get charge efficiency and Peukert numbers direct from the manufacturer. With some this is like pulling teeth... For example some the available Peukert calcs out there, including the Victron calculation, suggest a Peukert of 1.39 for a T105 yet Trojan Battery says it is a 1.24...???? That is a huge difference in counting errors to the battery monitor.

I ran another battery I use and that is a US Battery L16 HC. It comes up with a Peukert of 1.16 yet the VP of Engineering at US Battery says it has a Peukert of 1.26562.

Why is it important to be pretty accurate with your Peukert value?

Lets take a 450Ah bank of Trojan T105's at 1.39 and apply an average load of 6A. With a Peukert of 1.39 we would get approx 750Ah's out of that bank with a 6A load.

Now take the same battery and apply a 1.24 Peukert, and the same 6A load. The bank now becomes 618Ah's at the 6A load....

This is how battery monitors can add up the counting errors......