| It
becomes very easy to recover junk batteries coming from dead laptop
computer or considered as dead by their owner .Very often these
batteries
are not completely junked component and some elements can be
recovered to power the various electric devices you own like VHF
transceiver , audio preamplifier ..... The first thing is to check whether the battery is ok
, dead or in between .You will have to locate the + and minus
terminal using a voltmeter .. | |
| Sometimes this is not an easy task as the battery as a more or less sophisticated protection system to prevent overcharging the battery .If you are not able to locate the output pins the only way is to open the battery using a cutter And remove the regulator system which is tied to the parent computer .with various gold contacts |  |
| When this is done is becomes easy to located the various lead and to check each battery to determine the ones which can be recovered..Very often only one element is out of order , the others being good .It is sure that their capacity can be a little bit lower than the nominal capacity but this is not genrally a problem .After removing the dead element you will have to proceed to a charge at an amperage anywhere between C/10 and C/3 (assuming the nominal capactiy written outside the battery is 4 amp.h the charging current can be between .4 amp during 10 hours or 1.3amp during 3 hours ) |  |
| As
you will see by opening of a battery the elements are both in serie and
in parallel to reach the design voltage and capacity .As an
example , to get a nominal voltage of 10.8 volt you will see that
the battery has 3 packs in serie each pack made of 2 or 3 elements in
parallel ..Very often a visual inspection of the external aspect is
enough to find out which elements are bad . The discharge voltage of a Li-Ion battery is far to be constant during its useful service , this is not a problem for the switching power supply of the computer which was using the battery but this can be a different story when using it to power you transceiver.As an example a battery with a rated voltage of 10.8 volt see its output varying from 12.0 volt at the begining going down to 9 volt at the end as shown on the curve on the left showing a CHARGE/DISCHARGE/CHARGE cycle . As you probably know some care has to be taken when charging Li-Ion battery .especially in trying not to overcharge the elements .A lot of information is available on the subject over the internet . |  See a full size diagram |
