okay, so, I'm not got at all with coding in VB 08 and I need help!
I'm was trying to figure out the amount of "charge" my iPod touch can hold from it's original state.
I used y = Ce^(kt) to model it.

Here it is:

ln(%/100)/(ln(4/5)/400)=c

The variables are % and c

% = the percent of change you are aiming at multiplied by 100 (i.e 50% = .5*100 = 50, so the percent without the percent sign)

c = how many charges it will take to reach that capacity percent

Now with than and simple algebra you can figure out when your battery reach a desired capacity.

How I got the formula:

First, things I assumed:

1. Battery capacity exponentially decreases
2. Battery capacity goes from 100% to 80% in 400 charges



OK, here is the math stuff:

y = Ce^(kt)
or
% = Ce^(kc)

Plug In the info we know

80 = 100e^(kc)
80 = 100e^(k400)
(80/100) = e^(k400)
ln(80/100) = k400
(ln(80/100)/400) = k

again

% = Ce^(kc)

% = 100e^((ln(80/100)/400))c
%/100 = e^((ln(80/100)/400))c
ln(%/100) = ((ln(80/100)/400))c
ln(%/100)/(ln(80/100)/400) = c

80/100 simplifies to 4/5

ln(%/100)/(ln(4/5)/400)=c



SOURCES:
Charge Cycles

A properly maintained iPod battery is designed to retain up to 80% of its original capacity at 400 full charge and discharge cycles.
http://www.apple.com/batteries/ipods.html



ALL HELP APPRECIATED!!!