Safe 123A rechargeable chemistry for dummy

Hello, I've read a lot of threads, but despite (or maybe because of) that, I'm still not sure what the tradeoffs are of the safer-chemistry lithium-based rechargeables. For the sake of this discussion, please assume that I understand lithium ion rechargeables, and for simplicity we're talking about rechargeable 123A form factor, for use in an LED light.

I'm uncertain I understand the tradeoffs of lifepo4's vs Li-Mn (like the IMRs). Here's what I think I know:

- They charge to different voltages. The LiMn can be used in lights that can handle standard Li-ion batteries, the Lifepo4 can probably be used in all lights meant for a single 3V primaries, unclear if Lifepo4s can always be used in lights meant for multi-cell primaries (they're safe stacked, but lifepo4 voltage is a touch higher than primaries, so stacking them widens the gap from primaries). I'm running my KL4 head on two Lifepo4s and it been working great.

- LiMN can be used in most Li-ion chargers ... though double-check your particular charger/battery w/ a multimeter to make sure the reduced resistance doesn't result in over-charging. Lifepo4s have their own charger.

- LiMn has marginally higher energy density (10%)?

- Both have very low self-discharge, both can sustain the current requirements from most high powered LED lights

- Other than lower energy density, it's unclear to me what other disadvantages these battery types might have vs Li-ion.

So it feels to me as if my fave 123A lights can handle RCR123A, and I already have a UF-139 or Pila IBC charger, I should be looking at IMRs. With them, I should be expecting similar performance to Li-Ion with lower runtimes (perhaps drastically lower, 550maH vs 750maH protected). Since they're unprotected, extra care must be taken around overdischarge, vs protected Li-ion.

If my fave 123A lights only like primary levels of voltage (circuit or LED might poof?), Lifepo4s are interesting. I note that my Novatac 120-P is finicky on Lifepo4s ... it just plain doesn't like running on the highest setting on Lifepo4s, not sure why. Tried all kinds of tricks with the battery reset, or not doing battery resets at all after primaries, but it's still finnicky. Not sure why this is.

I'm not sure about LED's but I've run Lifepo4's on Incans.

Generally, stacked is more tolerated then single.

The more voltage a device is designed to take, the high voltage an overdrive it can tolerate.

Imagine any given device can take a 10% overdrive, the highers its working voltage, the larger the value of that 10%.

So, I've poofed 2cells bulbs running off one lifepo4, but any 4cell bulb has no problem running off 2xlifepo4's.

Once again, I've only ever worked with Incans.


The specs on your 120P rate it from 1.8v to 4.5v, I see no reason why it should be having any problems with a lifepo4 cell.

I love the IDEA of LiFePO4 batteries for safety sake - in fact it's why I won't use RCR123 batteries BUT it's a terrible shame that they cannot be designed to run EITHER at the same voltage as the RCR123 OR the CR123 primary. This means that NO flashlight is really designed to work at the voltage of the R123. Some may be driven too hard losing low modes while othere may have no real high because they are designed for the 3.7 volts.

I don't mind recharging more often or paying more money BUT I DO want batteries that will WORK in my flashlight.

I hope that manufacturers will begin to design flashlights with these cells in mind.

Is there any sign that 18650 sized LiFePO4 will be coming out soo and if so what voltage they will produce?

recDNA said:

.... Is there any sign that 18650 sized LiFePO4 will be coming out soo and if so what voltage they will produce?

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18650 and more (up to 200000mAH) http://www.batteryspace.com/lifepo4rechargeablesinglecells1c-15crate.aspx

The nominal voltage of LiFePO4 cells is 3.2V.

I don't really get the point of safe chemistry rechargeables. Lithium Ion rechargeables are used in millions of electronic devices every day, and there are very few explosions or fires.

u238 said:

I don't really get the point of safe chemistry rechargeables. Lithium Ion rechargeables are used in millions of electronic devices every day, and there are very few explosions or fires.

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Most, if not all, of that useage is in medium to low drain devices. The lights many of us lumen-crazed nut-jobs like to run are high drain devices, which can drain the cells past their recommended low voltage quickly.