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.
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....
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