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I've tinkered with electronics and components for quite some time now, but I'm kind of a noob when it comes to taking things to "production".

I've this project using an ESP12-E, powered by 2 (or 3) Li-ion cells (3.3 V 18650s) through a TP4506 charging module.

I'm now building a custom PCB for the whole think and my question is, for production purposes, what's the best way to add the batteries?

  • Leave the +/- pins in the PCB and solder the cells there directly (and between them)?
  • Leave the +/- pins in the PCB and solder a cell holder to them?
  • Solder the cell holder directly into the PCB and then just insert the cells?
  • Another option :)

I'm asking also about "best practices" for mass assembly (Ideally these will be assembled in China)

Thanks!

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  • \$\begingroup\$ "powered ... through a TP4506 charging module" - I trust you have implemented a proper power path to prevent the cells being overcharged and potentially causing fire or explosion? \$\endgroup\$
    – Finbarr
    Jul 24 at 10:11
  • \$\begingroup\$ Hello, can you please explain what's a "proper power path"? Thanks \$\endgroup\$
    – webnator
    Jul 25 at 5:48
  • \$\begingroup\$ One that doesn't have the TP4056 powering your load as well as charging the battery. That makes it impossible for it to detect a fully charged battery and shut off the charging cycle so it doesn't overcharge it. \$\endgroup\$
    – Finbarr
    Jul 25 at 23:13

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a TP4506 charging module.

From that, I assume the cells are in parallel (2P or 3P).

Therefore:

Absolutely not cell holders. Cell holders allow people to pull cells out and put new cells in at different State of Charge levels, which is really bad. Cell holders are fine for when you have a single cell.

So, the correct approach is to:

  1. Use cells that come with tabs spot-welded to their ends
  2. Check voltages of all the cells, to make sure they're within ~ 50 mV of each other
  3. Solder the tabs permanently to the PCB

Another option :)

A single, larger, higher capacity cell. Then you can use a cell holder. They do make 26650 Li-ion cell holders. That's safer at the factory and allows the user to change the cell and do so safely. Make sure to have reverse polarity protection in your circuit.

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