If I have a Li-Ion battery with 3 terminals and do not wish to monitor the thermal pin do I need to pull it low or high. When I measure the battery from white to red I see positive volts as do I between black and red. I assume therefore that I should either leave the white wire unconnected or connect it to the black (negative) connection. Please can someone either confirm or explain what should be done.

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    \$\begingroup\$ How many cells does it have? Whats the output voltage? Many bateries with 2 cells (~7.4V) actually have a third wire between the cells for balancing, etc (same with 3, 4, cells and so on) \$\endgroup\$ – Wesley Lee Apr 17 '16 at 14:07
  • \$\begingroup\$ If you are sure it is for thermal sensing, then just leave it unconnected. Make sure you know how to charge lithium chemistry batteries. Overcharging them can cause them to become hazardous. Does the battery say what the voltage and/or capacity is on it? If so, please edit your question and add that information. \$\endgroup\$ – mkeith Apr 17 '16 at 16:18

Unless you know the configuration of the battery pack I would suggest you recycle the entire battery pack in a responsible manner. It is dangerous to connect batteries incorrectly.

It is common to extend the life of a secondary battery pack by balancing the charge between individual cells. Here is an example of passive balancing for a 2 cell battery pack:

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It does not sound intuitive to drain the charge off an individual cell to extend the pack's life. But it works.

It may be more intuitive to think about active balancing where the charge is moved from the most charged cell to the least charged cell. However, active balancing is much more complex to implement.


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