Extra contacts on lithium-ion batteries

[steved]

Can anyone tell me what the extra contacts are used for on flat pack
lithium-ion batteries? I'm trying to jury rig a charger for a spare battery
for my iPAQ. The charger works fine on a similar 3.6 volt lithium battery
from an old cellphone, but does nothing when connected to the iPAQ battery
in the same way - directly to the plus and minus tabs.

I'm guessing that the additional two tabs on the battery are involved in
the charging process in some way.

 

[Guest]

Not sure what battery you are using but lithiums generally require very
specific charging.....the tabs could be for communications with BMS-some of
which can identify which manufacturer the battery came from and hence proper
charging profile, or it could simply be for monitoring temperature...SOC....

Jerry rigging a charger for lithium batts is dangerous if you don't know
what you are up to.....do a search on "thermal run-away" fire,
explosion....nasty stuff...and lithium fires are damn near imposible to put
out. Type D extinguishers and cover with clay dust....