single MCE + single LiFePo (3.3v nominal) @ 2+ amps = what driver?

[archer6817j]

So I want to drive a single MCE with a single lifepo battery at near full power. Say 2.2-2.8 amps or so. I'm not opposed to direct drive but I'd like to have the ability for at least a high and low mode if at all possible.

I have a little twisty with a single li-ion (3.7v) that direct drives at about 2 amps. But...In terms of voltage, when is a lifepo battery considered "dead?" They are (I'm sure everyone already knows) 3.3v nominal and 3.6v fresh. I realize if the LED is high vf it may fail to light even at the nominal charge voltage. Too bad they don't make (or I can't find) M size li-ion batteries.

I'm also open to other creative solutions for driving an MCE with a single lifepo.

 

[45/70]

...In terms of voltage, when is a lifepo battery considered "dead?"

There are better folks here to answer your other questions, but as for your above question, when the rested OC voltage of a LiFe cell gets down to about 3.15 Volts, it starts to go down pretty fast from there. I have never really run down (eg. to 2.2 Volts) any LiFe cell, as of yet, and my experience has been limited to the DX variety of 15270, 17340, and 18650 sizes. There may be significant differences with cells from different manufacturers, but ~3.15 Volt seems to be approaching the "hump" in my experience.

As for the voltage under load, I can't really help you there. Of course, it would be dependent on the load applied during discharge. I will say however, that LiFe chemistry Li-Ion cells hold their voltage under load better than any of the other Li-Ion cell chemistries, in my experience.

Dave

 

[archer6817j]

anyone have a driver recommendation?