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PaxInstruments / t400-electronics

Electronics for the Pax Instruments T400 temperature datalogger
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Battery draw #218

Open charlespax opened 8 years ago

charlespax commented 8 years ago

It has been reported that the battery can be drained to zero. http://community.paxinstruments.com/t/t400-battery-life/149. Investigate this and determine what changes may need to be made to the circuit in future revisions.

Questions:

Here are the relevant schematic sections: screen shot 2016-02-29 at 17 17 36 screen shot 2016-02-29 at 17 17 43 screen shot 2016-02-29 at 17 17 25 screen shot 2016-02-29 at 17 17 32 screen shot 2016-02-29 at 17 17 51

Originally posted in https://github.com/PaxInstruments/t400-firmware/issues/203

slowcoder commented 8 years ago

As per the datasheet for the DW01z in the BL-5C battery, it has "Overdischarge protection".

This means that if the cell voltage drops below a safe value, the cell is disconnected from the external connectors on the pack for safety. Meaning, the battery pack will measure 0V, but the actual cell-voltage is higher (should be 2.4V when the protection kicks in)

Once charging commences, the protection will disconnect, and the cell is connected to the external connectors again.