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Sorry, trying to get the hang of this site. I'll try this one more time. Could the circuit in the previous post (schematic and link below) be adapted to cut off a 13,200 mAh 11.7 volt battery running at 3 amps full power for an LED light similar to the one also in the link below? What would be a suitable cutoff voltage? People are leaving the power on and running the LiPo dead. An auto cutoff modification, like the one shown, would be a great addition to the original lamp design.

A Lipo battery protection circuit

https://www.aliexpress.com/item/2255799854674302.html

enter image description here

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2 Answers 2

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I recommend these modifications (not tested):

  1. Use TLVH 431 because TLV 431 is only specified up to 6 V
  2. Use a thermally more robust P-FET as Q1 (e.g. 2SJ652-RA11)
  3. Assumed this is a 3S LiPo battery, use a cut off voltage of 9.6 V.
  4. Add a resistor of around 15 Mohm between ADJ pin of IC1 and the load output (drain of Q1) to produce a hysteretic behavior.

Resistor calculation is R1 = R2 * ((Ubat / Upin1) - 1), set here R2 = 100 kohm

R1 = 100 kohm * ((9.6 V / 1.24 V) - 1) = 674 kohm, take 680 kohm

This circuit will continue to slowly drain the battery even after turn off like most BMS do. It must be recharged within some weeks.

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Yes, the circuit shown in that old question will work. You will need to change the components to work with your "11.7 V" battery (Meaning it is probably a 3S battery.)

I would recommend that you just buy something like this Voltage Protection Module and set it to 11.2V.

The 11.2V comes from the 80/20 rule for LiPo batteries and shown in this handy chart where the "3S" section shows 20% is around 11.18V.

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