Hi Gregg,



You asked:

"1.) why doesn't my battery power up my laptop even though the test 

lights say it's good?

 2.) can putting the bad / dead battery on my friends laptop cause any 

damage?  "



Answer:

1.So far as I can see it's a flaw in the testing circuit.

  A proper battery test has to be done with a load applied.

  An "open circuit" test only shows that the battery has some voltage,

  but may collapse under load because of high internal resistance.

This will happen if the battery is in a very low state of charge or the chemical

composition of the active compound has deteriorated.



Only fairly sophisticated measuring equipment can tell you the capacity or state of charge.

It's done by a series of quick tests with varying loads and the interpolated results

would give you an estimated remaining capacity.



2. Usually for a Li Ion battery there will be no ill effect because, unlike other batteries,

    Li Ion batteries don't go into reverse polarity.

    Apart from that, internal circuitry usually protects against this by not accepting the

    battery as a source of power.



Some info about batteries: (2 among hundereds)

http://batterydata.com/

http://batteryuniversity.com/



Peter E.





 



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