I have two, fully charged, 3.7V standard Nokia phone batteries, that I want to connect together to use as a 7.4V battery, I connected the (+) of one to the (-) of the other, and then tested it but it does not seem to be working, what am I missing?

  • \$\begingroup\$ What do you mean by you "tested it"? How exactly did you connect them together? \$\endgroup\$ – Elliot Alderson Apr 10 at 21:45
  • \$\begingroup\$ @ElliotAlderson Well I did try soldering them together but I didn't have any experience with that so I resorted to tape, before connecting them I tested each battery individually by connecting them to a small toy DC motor and they both worked, but I didn't get the same result when I tried again after connecting them together. \$\endgroup\$ – The Riser Apr 10 at 21:49
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    \$\begingroup\$ No electronics? That's peculiar. I have believed big companies who have somehow already succeeded to collect some money use everything possible to force people to pay more. If the intention is not to collect more money it's still possible to prevent something dangerous. Check this youtube.com/watch?v=bwslG8S1kYs \$\endgroup\$ – user287001 Apr 10 at 22:25
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    \$\begingroup\$ Usually a battery pack contains more than just the bare cells, there is also usually a temperature sensor, a thermal cutoff or fuse, and in some cases back-to-back MOSFET for terminate-charge and terminate-discharge pack protection. For a name-brand company like Nokia, there is a lot of legal liability in letting consumers access a battery pack without charge management and protection. Even the lipo battery packs from Adafruit have this much pack protection. And even bare cells usually have the temperature sensor in close physical contact. It seems very unlikely you have bare Li-ion cells. \$\endgroup\$ – MarkU Apr 10 at 22:26
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    \$\begingroup\$ How many terminals on your battery pack? A simple pack with only thermal protection would have three terminals, + - T; while a "smart battery" pack would hare more connections like + - T C D for SMBus smart battery. Proprietary brands may have other communications schemes. The battery might not give any analog voltage unless it is given a command to enable discharge. \$\endgroup\$ – MarkU Apr 10 at 22:31

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