0
\$\begingroup\$

I bought a 100 mAh LiPo from the b&H website because it specifically said that it had overdischarge protection. I really need a reasonable lifetime for this battery so I hooked up the battery to a 15 kOhm resistor overnight to see what voltage it would be in the morning.

to my surprise, the voltage read 0.17V! Is that correct?

but when I Plug in the charger it rises to 3.0 V super fast almost as if t were there the whole time.

Does this make sense for a circuit with discharge protection? How can I be certain that this is true discharge protection?

\$\endgroup\$
2
  • \$\begingroup\$ "How can I be certain" - buy from a reputable source and make sure that you read the fine print. \$\endgroup\$ – Andy aka Feb 14 '18 at 14:15
  • \$\begingroup\$ A simple google finds, "The voltage of a discharged LiPo cell is 3.00V, and discharging below this will definitely damage the cell." So that's a worry. Also, \$\frac{3.7\:\text{V}}{15\:\text{k}\Omega}\approx 250\:\mu\text{A}\$. You should get several hundred hours from that battery, or more, at that low draw rate. Assuming it was fully charged to begin with. Had you charged it? \$\endgroup\$ – jonk Feb 14 '18 at 14:17
2
\$\begingroup\$

The over discharge protection circuitry consists of two back to back power mosfets that open when the state of charge of the cell goes below a certain threshold.

When they are open, it is normal to measure a very low voltage at the cell terminals. Also, it is normal that the voltage rises suddenly when you charge it since the protection circuitry is "untriggered" when you try to force a smallish current into the cell.

What I see as alarming is that 15 kOhm were enough to deplete the battery overnight. Either you were not using 15 kOhm, or the battery was nearly empty, or it actually is damaged.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.