This is a scratch-build meter for measuring the internal
resistance of Lithium Polymer cells. [Bleuer Csaba] uses the
LiPo cells for RC vehicles and thet take quite a beating from
the motors they’re supplying. This means that he only gets about
100-200 cycles out of each cell. To figure out where one is in
its life cycle you can measure the internal resistance where a
rising resistance indicates greater age. [Bleuer] mentions that
you can buy a meter to do this for you, but what fun is that?
Since he’s rolling his own tool he defined his own parameters
for the readings. After experimenting with different loads
driven for different test periods he was able to extrapolate an
equation that estimates the resistance measurement. As you can
see in the clip after the break, this happens very fast. All he
has to do is connect the cell and press one button. The
measurements are made and various data points are displayed on
the quartet of 7-segment displays.