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I selected two non rechargable CR123A lithium-manganese battery to power my project due to their ability to operate under extreme temperature. A single battery is 3V with a rated capacity of 1550mAh. Since I need more capacity I decided to wire them in parallel so that the total capacity is 3100 but the voltage is the same.

Bonus question: Is it bad to wire them in parallel for a consumer product? :)

I read somewhere in this site that non-rechargable batteries might explode if someone inserts a fully charged one with a semi charged. I have not a safety circuit in there.

Now I need this to regulate them into 3.3V for my project.

Since I want efficiency two options exists:

  1. Boost converter
  2. Buck/Boost converter

Theoretically we want to go from the battery pack's 1.2-3V into 3.3Volts so we go up. A boost converter is the best choice since it can accept cut-off voltages down to 1.2Volts squeezing every little drop of energy from the batteries.

Practically I measured a battery bought from a local supplier and its voltage is 3.25Volts. What if a weird CR123A manufacturer makes a battery more than 3.3 Volts? Should I use a buck/boost converter and sucrifice the efficiency? Buck/Boost converter start from a Vin min=1.8 Volts and I would rather not use them if I could avoid them...

How should I solve this?

I could use a boost converter to regulate 3.3 from 3Volts but what if a user inserts a 3.5Volt CR123A bought from a weird chinese manufacturer from eBay?

Do I need a buck-boost converter to regulate 3.3V from rated 3V battery? I am afraid that the actual voltage in the batteries might be more than 3V in the beginning.

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    \$\begingroup\$ Never connect batteries in parallel. Small differences in discharge curve in individual batteries will lead to self-discharge. \$\endgroup\$ – Ale..chenski Dec 28 '16 at 18:07
  • \$\begingroup\$ you can easily join matched CR123A's with SMD fuses. Just verify Voc before assembly. <<1% is achieveable \$\endgroup\$ – Sunnyskyguy EE75 Jan 3 '17 at 21:18
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I wouldn't worry about a battery exceeding 3.3 V. The voltage comes from the chemistry. Someone would have to use significantly different chemicals to make a higher voltage.

You might consider putting the batteries in series, then using a buck converter. By the time the cells get down to 1.65 V each, there is so little energy left that you're not really getting any advantage draining them to 1.2 V.

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