Fenix P3D 1 cell regulation observation test

[regulator]

I did a simple test (not very accurate) to see how well the P3 would run on 1 17670 lithium ion cell. I decided that I did not want to run the cell down too much since it is an unprotected cell and I did not want to ruin it. I would stop the test once Turbo mode could not be achieved without seeing the low battery warning blinking. All modes work with one cell.

The light ran regulated for 2.5 hours in high mode before Turbo mode could not be used without seeing the battery warning flicker. At this point the light was still regulating in high mode without any problem and could also switch to all the other modes without problem. I stopped the light at this point and put the battery on charge (I'm using the new Pila charger which is very nice). I do not know how much longer the light would run in high mode but I was satisfied at this point and showed me the light would still run in regulated mode using only 1 unprotected 17670 cell. I seen a graph by someone else who ran a 17670 in turbo mode for 40 minutes - and the light was fully regulated.

 

[nanotech17]

Thanks for the observation.
received my p2d after exactly 14 days.
But my p3d is somewhere around the world - it has been 20 days and it hasn't arrived :mecry:
The 17670 cells are ready to be install but the P3D is late 🙁

 

[ensile]

i'll sit next to you, i'm still waiting, hopefully the courier brings me happiness, my life will not move forward.. huhu

 

[regulator]

One thing to note - the unprotected 17670 cell I had was a very tight fit and I ended up removing the label - and it slid right in. It would flicker with the bare cell wall. I put some thin tape (the kind that is used for closing large boxes - clear and thin) and it fixed the problem.

 

[Mike abcd]

The "low battery warning" on the P3D is Fenix marketing speak IMHO. It's really the buck regulator going into oscillation when the battery voltage drops too low to maintain the regulated current for the level in use.

Since less voltage is required to maintain regulation on the lower levels due to the lower current, the "warning" will happen at lower voltages. On low, it probably won't happen until a single LiOn is severely over discharged. That might be a problem even on medium and will also vary between P3Ds depending on the Vf of the Cree.

Some other flashlights with buck regulators such as the VB-16 have much more graceful behavior and the output simply drops as the emitter goes into direct drive without the annoying oscillation.

Hopefully Fenix will improve their buck regulator design on future shipments. I'd like a real low voltage warning that happens when the battery reaches 2.75-3.0 V under load but I think the present behavior makes the P3D less useable on a single LiOn than it would be without the annoying oscillation.

Mike

 

[HiltiHome]

Good point Mike abcd,

this is exactly what i thought, when i read that the "low-batt-warning" only works on burst mode.

My Inova T2 also starts oscillating, when battery gets low, but Inova does not mention this as a low-batt-warning.

 

[regulator]

Mike - correct. The high stobe is more a function of the regulator not being able to regulate - and marketing calls it a "feature". I have a Peak Glacier Bay that does the same thing when the battery is getting low and cannot regulate well.

I think a good indication of when to charge the single cell in the P3D would be when it starts to stobe in HIGH mode and should not deplete the cell too far. I may do a test to see how long this is and take a voltage reading of the cell when this happens.

 

[TORCH_BOY]

Interesting, Thanks for the observation

 

[regulator]

I ran the P3D on high mode for 3.5 hours before stopping the test because it was getting late. I used one 17670 rechargable cell. It was in full regulation when I shut off the light. It would flicker if set in Turbo mode but would still work in this mode. I took the cell out and it measured 3.76 volts. I was impressed at how well the light ran using only one cell.

I also ran my Pila G2 for 4 hours that night to see how it would perform. I already knew it would not run regulated on only 1 cell after seeing graphs by Chevrofreak. It could have run longer according to the graphs but it was late. It was still very bright (more output than my Streamlight 4AA Luxion at full regulation). I like the Pila very much. The 18650 cell provides plenty of capacity.

The Fenix must have a more efficient regulator compared to the Pila. The Pila seems to regulate only when using 2 cells where as the Fenix can regulate using either 1 cell or two.