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I got a 260mAh LiPo battery from Aliexpress fot which I have very little info. I noticed that there is a small PCB bundled together with the battery.

Some images:

Battery

PCB_front

PCB_back

The markings on the ICs are as far as I could see:

  • 8205S
  • DW01

Is this a small and basic BMS/protection (overcharge/discharge) circuit?

If so, can I just safely connect a +5V power source to it to charge, and then connect my load (3.3V with LDO) to it without any extra charge/load controller?

When I opened it up, I checked the pins on the back of the PCB and it seems like that the P- and B- are connected together. I thought that they shouldn't be connected so the BMS can actually disconnect the battery (B-) from the load (P-) to prevent over discharge, or is that only true for more advanced BMS?

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    \$\begingroup\$ A BMS is not a charge controller, so even if your LiPo battery has a built-in BMS (which is likely), you still need a LiPo charger to safely charge it. Connecting a 5V power source will likely destroy your battery, possibly in a spectacular way. \$\endgroup\$
    – StarCat
    Commented Feb 19, 2023 at 16:47
  • \$\begingroup\$ P- and B- are only connected when there is no overdischange, overcharge, or short circuit detected \$\endgroup\$
    – UnknownDagger
    Commented Jun 26, 2023 at 8:42

1 Answer 1

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Yes, the battery has protection, DW01 is a lithium protection chip.

No, it sure does NOT mean you can connect the battery directly to 5V without a charging circuitry.

Protection circuit is not a charger. BMS circuit is not a charger. Only a charger is a charger, and there MUST be a charger between a lithium battery and a 5V power supply, because a 5V power supply is not a charger either.

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  • \$\begingroup\$ Technically connecting to 5V would work as the DW01's overvoltage protection would prevent voltage going above 4.25V (not ideal, 4.20V better), but the risk is worsened by charging at too much current as there is no limit on how much the battery will take so it will take as much is it can, likely to be over 2A, not very safe. \$\endgroup\$
    – UnknownDagger
    Commented Jun 25, 2023 at 22:14
  • \$\begingroup\$ @UnknownDagger Please understand that technically connecting e.g. a 3.9V battery directly to a 5V supply must not be done. If it is a strong 5V power supply would just trigger overcurrent shutdown or overvoltage shutdown of the battery protection, or trigger overcurrent or undervoltage protection of the 5V supply when shorted to battery that tries to suck as much current needed to bring the voltage down 3.9V. If it is unsafe, you should not say it can be done, people will try it if they think it can be done, and it may result in explosions, fires and burnt houses and injured or dead people. \$\endgroup\$
    – Justme
    Commented Jun 26, 2023 at 7:28
  • \$\begingroup\$ It would charge the battery, but yes, it wouldn't be very safe. You are relying on your power lines to have enough resistance as not to charge at a current that's too high. A sane approach to this would be using a current limited power supply, but you still would overcharge slightly to 4.25V. What would work however is using a constant voltage- constant current power supply, but at this point it's much cheaper simply using a dedicated <30 cent charging module. \$\endgroup\$
    – UnknownDagger
    Commented Jun 26, 2023 at 8:39
  • \$\begingroup\$ @Razero the way these charging modules sense the charge is done is when the battery no longer takes much current, so you need to use a power path to safely charge and power devices at the same time \$\endgroup\$
    – UnknownDagger
    Commented Jun 26, 2023 at 8:40
  • \$\begingroup\$ @UnknownDagger It would not charge the battery if the short circuit or overcurrent protections kick in. You can do it if you want, but it is best not to do it, and best to not suggest anyone to do it. \$\endgroup\$
    – Justme
    Commented Jun 26, 2023 at 9:10

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