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I want to parallelize few non-rechargeable batteries like this one (Tadiran TL-5104/S, lithium 3.6V and 2.1Ah) for bigger capacity.

https://www.digikey.com/product-detail/en/tadiran-batteries/TL-5104-S/439-1012-ND/512514

What option do I have for longest self life aka, not discharging one to another, of course, in context of maximum efficiency.

I am thinking of back-to-back mosfets on each battery but not sure this is the best option.

Thanks.

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    \$\begingroup\$ Just connect them in parallel. Or use fewer, larger cells. Less is more. \$\endgroup\$
    – Dampmaskin
    Commented Jun 12, 2017 at 14:30
  • \$\begingroup\$ Instead of parallel connection, you could connect them in series and add a switching voltage regulator. \$\endgroup\$ Commented Jun 12, 2017 at 14:52
  • \$\begingroup\$ @shortCircuit the quiescent current will ruin long term (years) goal \$\endgroup\$ Commented Jun 14, 2017 at 14:27

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It is not safe to run primary lithium batteries in parallel! One will drive current into the other and overheating may occur. The batteries may vent and the electrolytes in these batteries are highly caustic.

Two options:

If you need the combined current, use a pair of schottky diodes, one from each battery to the load. This will cost you a fraction of a volt, but is simplest.

If you use mosfets to turn them on one at a time, be sure that there is no scenario in which current is able to flow out of one battery and into another.

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