Westinghouse LiFePO4 cell and Fenix LD10

[Mr Happy]

Following on from this thread, and also this thread where someone asked what these cells could be used for, I tested the Westinghouse LiFePO4 cell in a Fenix LD10 compared with a freshly charged Eneloop.

I used each cell in each of the modes and measured the relative brightness with a light meter.

Here are the results, with the Eneloop on high normalized to the claimed 94 lumens in this mode:

[U]Comparison of Eneloop and Westinghouse 3.2 V LiFePO4 in Fenix LD10[/U]

          [U]Relative brightness[/U]
          Eneloop    Westinghouse
Low          13         30
Medium       47         53
High         94        103
Turbo       113        185

Clearly the turbo mode gets a giant turbo boost with this higher voltage cell. Interestingly the regulated modes get bumped up a bit too. I'm not sure how these would compare with the LD20 or PD20, which I have read use the same driver in the head. If this is so then I would have thought the low mode would have been better regulated at the same 9 lumens described in the specifications? Or maybe the 3.2 V is still higher than the nominal 3 V of a CR123A cell.

I am not very familiar with Fenix lights, so maybe someone else has an idea?

I think that this might be an answer to the question of what this cell can be used for. It certainly seems to give the LD10 a big boost in light output, making it equivalent in brightness to an LD20 in a smaller package. The run time is clearly going to be less of course.

 

[McAllan]

@ 3.2 v is should be identical in brightness to an LD20.

LD10 and LD20 are _exact_ the same except the barrel and the engraving on the head.
You could try wiring two NiMH cells together and do your measurements. Or just a piece of wire and holding a second NiMH in place.

Perhaps the LiFePO4 is a little bit more directly off the charger and this is why it's little bit brighter in the lower modes too. You're using the same head. Othervise I'd say the head will also mean a little difference. There's small variations between my 1. gen LD20es, LD10 and PD20.

 

[45/70]

One thing about LiFePO4 cells in general, is that they have the least amount of voltage drop under load of any chemistry I'm aware of. In addition, the voltage remains pretty much constant throughout the discharge. This, I'm finding out, makes them very difficult to determine their state of charge when tested either under load, or OC. For example, I've been working with some 18650 LiFePO4 cells (not Westinghouse) and their OC voltage is 3.27 Volts @ 80% capacity, 3.26 Volts @ 60% and, 3.25 Volts @ 40%.

Dave

 

[Mr Happy]

LD10 and LD20 are _exact_ the same except the barrel and the engraving on the head.

Thanks for the info. I did wonder if the LD20 head might be internally recalibrated for the higher voltage, even though it looks identical on the outside?

Is it true the PD20 head is the same size too? I expected that since a CR123A is fatter the barrel and head would be thicker.

 

[McAllan]

Thanks for the info. I did wonder if the LD20 head might be internally recalibrated for the higher voltage, even though it looks identical on the outside?

Is it true the PD20 head is the same size too? I expected that since a CR123A is fatter the barrel and head would be thicker.

Yes. The PD20 is also the exact same head. You can without problem put it on and LD10 body. Output levels though will be comparable of those of the LD10 - because exact same head. The barrel on the PD20 is a bit thinner to take the larger diameter battery.

PD30 however is different since that head has a buck converter while the LD10, LD20 and PD20 are boost.

 

[McAllan]

Have you managed to measure the output with 2 NiMH cells yet?
Could be very interesting for comparison with the LiFePO4 cell. Of course this compares should be done on the same head as no two heads are exactly alike.

 

[Mr Happy]

Have you managed to measure the output with 2 NiMH cells yet?
Could be very interesting for comparison with the LiFePO4 cell. Of course this compares should be done on the same head as no two heads are exactly alike.

No, not yet. I'll post the results here when I find a moment to try it.

 

[csa]

Interesting comparison. Always good to see different battery chemistry comparisons.

 

[mitro]

My first thought when these cells appeared was that they might be a good fit for the Quark MiNi AA. It probably applies to any number of similar lights, but the mini is one that I have owned and I was uncomfortable with how quickly it got hot with a 3.7v battery (I know, its not recommended anyway). The LiFePO4 cells just might be enough of a drop in voltage to keep the temp of the mini down to a level I would feel comfortable with.

I don't even have AA mini anymore, so what do I care? I just couldn't resist picking up some to try. I'll probably just keep them as backups for my larger AA lights. (regular Quark, D10, etc.)

 

[McAllan]

Just got some 17340 LiFePO4 today for my PD20.

Can be I'll try to make some comparisons with the same head on 2 NiMH and on one LiFePO4 when I get some time and it gets dark not to obscure the readings too much.

One thing I can tell fore sure. Right out of the package (that is unkown charge state but probably >= 50%) the PD20 "lost" it's low and medium setting by eye. From medium to high there was a difference although maybe a little less difference than normally but not 100% sure.
So that means the ~3.2 v or what ever it is under load is more than LED gets at the lower modes since it's current regulated in the PD20. However voltage is less than on high and turbo so assume it's perfectly safe in contrast to ordinary LiIon cells.

Also wonder if the lower modes can be used as sort of battery check :thinking: When you start notice a difference between low and mid - time to recharge etc? :thinking:
LiFePO4 may be safe but that doesn't mean it's healthy for the cell to be deeply discharged below 2.2 v from my memory - loosing capacity fast. The PD20 using the same head as LD10 should be able to discharge it a good deal below 1 v.

Also wonder if those DX cells can take the beating the PD20. After all it sucks some juice.
A shame I haven't my hands on some known high current 14500 LiFePO4. Those I could have used in many more lights.

 

[liveforphysics]

One thing about LiFePO4 cells in general, is that they have the least amount of voltage drop under load of any chemistry I'm aware of. In addition, the voltage remains pretty much constant throughout the discharge. This, I'm finding out, makes them very difficult to determine their state of charge when tested either under load, or OC. For example, I've been working with some 18650 LiFePO4 cells (not Westinghouse) and their OC voltage is 3.27 Volts @ 80% capacity, 3.26 Volts @ 60% and, 3.25 Volts @ 40%.

Dave

Temp compensated SOC readings are the only way to get a useful measurement on LiFePO4. It can be confusing as hell to start some 10C discharge on a cell at 3.30v, and after 3minutes see the cell voltage at 3.35v. lol Request a temp/vs deltaV chart from your manufacturer, or you can get the curve data yourself taking some readings with the cell in ice, in boiling water, and a few points between, plot, find slope, and now you've got the info needed to get voltage based SOC readings that should be -+5% or so depending on the quality of the equipment used.