Pd20 no low mode on lifepo4

matlt · Feb 20, 2012

Been using the rechargeable tenergy 3v lifepo4 batteries in my pd20 for about a week now. There is no low mode. Only seems to be high and turbo. Low medium and high are all the same. I thought this was only an issue with the 3.6 and 3.7 volt batteries.

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AnAppleSnail · Feb 20, 2012

matlt said:
Been using the rechargeable tenergy 3v lifepo4 batteries in my pd20 for about a week now. There is no low mode. Only seems to be high and turbo. Low medium and high are all the same. I thought this was only an issue with the 3.6 and 3.7 volt batteries.

Sent from my SGH-T989 using Tapatalk

LifePO4 have a fresh-charge voltage of 3.6v, a working voltage of about 3.2v, and very little voltage drop while running. I don't know the details of the PD20 circuit, but it's quite possible that without adding a diode to drop the LiFePO4 voltage down a bit more (burning 0.2v times amps as heat) you won't get low/medium back. If Vbatt > Vf, then the flashlight would have to use PWM or a separate control circuit to get low modes. Quarks and a few other buck/boost lights do this at the expense of cost and efficiency.

Pd20 no low mode on lifepo4

matlt

Newly Enlightened

AnAppleSnail

Flashlight Enthusiast

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