On Thu, 14 Sep 2017 22:20:20 +0100, pamela wrote:

snip

That Peukert's Law gives the total capacity (varying with load) but
to do what you want don't you need the specific curve for that type
of battery showing voltage against time (which is what your
Flexicurve would be approximating)?

Yes / no / pass / confused. ;-(

What I *need* for my purposes is the formula I can insert into an
Arduino micro controller 'sketch' that will read the current current
g, read the current volts and apply the formula to determine if
those volts for that current equals a discharge level that
approximates 50%.

We have Peukert's Law, we have some voltages that equal a 50% DOD for
three currents and some other bits of info that might allow someone
good at such things to get somewhere near. ;-)

eg, As my outboard draws a maximum of 30A we (only / already) have two
points (currents, from the battery manufacturer) that I could have
kick in as / when I crossed those points that represent 50% DOD,

12.05V @ C5 (18.2A)
12.10V @ C20 (4.65A)

My 2 x 16 LCD display will show the battery voltage, the current drawn
and the current Low Voltage Disconnect threshold from the magic
formula. The idea being I can get a sense of how long I can continue
to run at that speed (and I may be able to actually display that time
as early on in the battery discharge voltage curve it's a reasonably
straight line and that line *could* easily be plotted by me ITRW) ;-)

Cheers, T i m