Dereelight DBS v2 3SD with LifePo?

[andi555]

Hello!

I am thinking about to use Lifepo cells in my Dereelight DBS v2 3SD.
Does the Lifepo cells (3,3V) have any effects of the brightness of the Dereelight as normale Li-Ion cells (3,7V)?

The 3SD has an Input Range from 2,8V to 4,2V but is the flashlight with a 3V cell as same as bright as one with a 4V cell?

 

[FlashCrazy]

Hello!

I am thinking about to use Lifepo cells in my Dereelight DBS v2 3SD.
Does the Lifepo cells (3,3V) have any effects of the brightness of the Dereelight as normale Li-Ion cells (3,7V)?

The 3SD has an Input Range from 2,8V to 4,2V but is the flashlight with a 3V cell as same as bright as one with a 4V cell?

The 3SD driver in the DBS is a boost/buck driver, so in theory it should have the same brightness, but in reality it may not. The Dereelight C2H also has a boost/buck driver, but it's much brighter using a 3.7V rechargeable RCR123 vs. a 3.0V CR123.
I think I might have a LiFePO4 18650 cell around here somewhere, I'll have to try it and let you know. The trouble is that being a boost/buck driver, it will deplete the cell well under the 2.2V limit for LiFePO4 cells, causing irreverseable damage to the cell. (This type of cell doesn't use a protection circuit, being inherently safe in and of itself). You won't notice that the cell is under recommended voltage due to the regulation of the 3SD driver keeping the LED current constant.

 

[andi555]

Thank you for your efforts.

About the overdischarge thing:
The DBS v2 shout have an overdischarge protection witch shuts down the flashlight when the cell reaches 2,8V

 

[FlashCrazy]

Thank you for your efforts.

About the overdischarge thing:
The DBS v2 shout have an overdischarge protection witch shuts down the flashlight when the cell reaches 2,8V

Yep, I was just coming here to mention that.... forgot about it earlier. :ohgeez: The trouble is that the LiFePO4 will get to that shut-off voltage fairly quickly. I found a cell and have it on charge now, I'll do a runtime test on it tonight and post the results here.

 

[FlashCrazy]

Ok, tested a couple LiFePO4 18650's, rated at 1350 mAH. They lasted about 3 seconds on high before the DBS's low voltage cut-off kicked in and shut down the light. So, no go. These were cheap LiFePO4's, perhaps A123 cells would work better.

 

[andi555]

Thank you very much!

I have one A123 Lifepo cell here, so i just have to wait until my DBS arrives from allan! :-)

I will post my experiences when the flashlight is here!

 

[FlashCrazy]

Great! I'm curious to see how it does.

 

[mdocod]

it won't be much different with the A123. In either case, you won't be able to use the full capacity of the cell due to the low-volt cutoff in the flashlight.

If it's safety you are after, use 3.7V LiMn cells. They run aroudn 1.5AH capacity (better than LiFeP04, not as good as LiCo). If you wait a few weeks, AW will be selling them with button tops, ready to roll. There is also the option of harvesting them from tool battery packs......

Eric

 

[andi555]

Yes I was also thinking about using LiMn cells, because Li-Ion Cobalt are not so good in coold weather conditions.

Is it right that LiMn cells have a similar discharging line like primary cells? (Falling down like a step)
What I know is that Li-ion and LiFepo have a flat discharging line so they have almost the same voltage rate until they are discharged.


Has somebody an output line with the DBS v2 using LiMn cells?
Here is one with Li-ion:

 

[mdocod]

LiMn and LiCo cells are similar in many ways. The LiMn will maintain slightly flatter discharge behavior than a LiCo. LiCo averages about 3.7V into most average loads, While LiMn will probably average closer to 3.8V into a similar load through the discharge.

The graph you have there is the result of a regulation circuit in the DBS, not simply the batteries discharge behavior alone.

Eric

 

[andi555]

The graph you have there is the result of a regulation circuit in the DBS, not simply the batteries discharge behavior alone.

Eric

Yes I know this is an other thing!;)
I was just thinking if LiMn cells makes the same result at the output graph of the dbs.

But back to the batteries itself:

Li-ion (Cobalt) has such an discharging line: (sorry i don't know an other word for it in englisch)

the Li-Mn has one which looks like this (the dark one, sorry havent got a better pic):

So the question is, if this differend discharging line has some effects of brightness output timeline of the dbs?


I am also wondering about this pic:

Why does the brighness falling down between 0:50 hour and 1:10 hour?
Or was there no discharging protection in the first DBS version. (I think this is a graph of the first DBS)

 

[andi555]

I now got my DBS v2 and tried it with an original A123 LiFePo 1100mah battery.
Runtime is about 25-30 minutes, but i have no idea if the A123 is same bright as a Li-Ion.

Maybe I will make some beamshot pics and will compare them!

 

[andi555]

I finally made some beamshots:

with Fepo fully charged:

with Fepo almost discharged:

with fully charged Konion 1100mAh:

All pics are made with 1/1000sec, F3,5 and Iso 400