[Test-Equipment] "Conductance" battery checker

[Grant, Ken]

Hi guys,

Have a read of this paper:
http://www.lordconsulting.com/images/stories/TechnicalPapers/Battery-Managem
ent.pdf . It describes evaluating a battery's condition by measuring its
internal impedance and comparing it to the value of a fresh battery. There
are several inexpensive testers available that use this principal.

 Usually, you measure Zint by applying a constant alternating current
(around 1 KHz) to the battery and measuring the resultant AC voltage drop.
Zint is then E / I. Conductance (if you wish to think in a less intuitive
way), is then 1 / Zint.

 Pay special attention to graph #3. It shows that when Zint is about 150% of
its initial value, the battery is at 80% capacity and 'heading south' real
quick.

Ken, VE3FIT

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