3.7V 50mAh LiPo Battery (401020) - Ultra-Micro Lithium Polymer Cell with Protection PCB

FREQUENTLY ASKED QUESTIONS (FAQ)

1. What does "401020" mean? It signifies the standard dimensions of the bare internal cell: approximately 4.0mm thick, 10mm wide, and 20mm long.

2. What are the total outside dimensions of the battery? Including the protection circuit and outer wrapping, the total physical size is 23mm x 10mm x 5mm.

3. Why does the photo show 55mAh but the title says 50mAh? Product batches vary slightly from the manufacturer. You may receive a cell marked 55mAh, but the guaranteed minimum baseline capacity for this SKU is 50mAh.

4. What is the nominal voltage of this battery? The nominal (average operating) voltage is 3.7V.

5. What is the voltage when fully charged? A fully charged 1S LiPo battery will read exactly 4.2V.

6. Does this battery have built-in protection? Yes, there is a miniature protection PCB hidden under the yellow tape at the top of the battery.

7. What does the protection circuit actually do? It protects the battery chemistry from catching fire due to overcharging, prevents permanent damage from over-discharging, and protects against short circuits.

8. Are the wires open-ended or do they have a plug? This battery ships with 50mm open-ended (bare) wire leads. It does not come with a plastic JST connector.

9. Which wire is positive? The red wire is Positive (+), and the black wire is Negative (-).

10. What does "discharge at 0.2C" mean? "C" represents the total capacity of the battery. 0.2C means 20% of 50mAh, which is 10 milliamps (10mA). To get the maximum lifespan out of this tiny battery, your circuit should optimally draw around 10mA.

11. Will it break if I draw more than 10mA? No, it can provide bursts of higher current, but pulling heavy current continuously from such a small cell will cause the voltage to sag, draining it very quickly and potentially shortening its overall lifespan.

12. Can I charge this with a standard TP4056 module? Yes, BUT you must modify the module. Standard TP4056 modules charge at 1000mA (1A), which will instantly destroy this tiny 50mAh battery. You must desolder the programming resistor on the TP4056 and replace it with a higher value to drop the charge current down to ~25mA-50mA.

13. Can I wire this directly to a 5V USB cable to charge it? ABSOLUTELY NOT. Applying 5V directly to a LiPo battery will cause it to swell, vent toxic gas, and catch fire. You must use a dedicated Lithium-Ion charger circuit.

14. Can I power a 5V Arduino Uno with this? No. Standard Arduinos require 5V. This only outputs 3.7V, and it likely cannot provide the current an Uno requires without severe voltage sag.

15. What microcontrollers work best with this? Low-power 3.3V boards like the ATtiny85, specific Seeed Studio XIAO boards, or Nordic nRF52 series chips are ideal.

16. How long are the wires? The flexible wire leads are approximately 50mm (about 2 inches) long.

17. Can I cut the wires to make them shorter? Yes. CRITICAL WARNING: Always cut the wires one at a time. Cutting both the red and black wires simultaneously with metal snips will short-circuit the battery!

18. Can I wire two of these in series to get 7.4V? It is highly discouraged to wire individual, internally protected LiPo cells in series. The two independent protection boards can conflict and cause charging failures.

19. Why does my battery look puffy or swollen? LiPo batteries puff up when damaged, old, or severely over-discharged. If your battery swells, stop using it immediately and safely recycle it.

20. How should I store this battery if I am not using it for a while? Never store LiPo batteries fully charged (4.2V) or fully dead (3.0V). Store them at a "storage charge" of roughly 3.8V in a cool, dry, fire-safe location.