I was looking at HKJs great work and trying to read the understand the curves when comparing my Eagletac 3100 mah batt to my Xtar 2600 mah batt. They are being used in single cell lights with XPG emitters (Nitecore EC2 and Eagletac D25LC2 mini).
Looking at the curves at 2 amps I see the Eagletac 3100 will get more total amp hours but that the xtar 2600 curves are higher from the 3.6v to 3.3v mark. At 1 amp, the Xtar has higher curves from 3.7v to 3.3v but again with less total amp hours than the Eagletac. (Longer run time for the Eagletac but…for the Xtar?)
How should this be interpreted and which battery would you say is best for a single cell XPG flashight? Thanks guys.
I guess it depends on the light and it's draw but I don't think you are going to see a lot of difference beyond slightly longer run time for the ETs. Have you ever tried doing a timed runout test? Just make sure you have a fan blowing on the light for cooling. I've done it once comparing XTAR 2600 vs Callie's Kustom 3100 - got an extra 15 minutes out of the CK if I remember correctly.
Thank you guys for this info…very helpful (I really appreciate it). And I Love that Chart. It’s so clear that even I can understand.
I may do some runtime tests but I’m thinking the greater run time is more valuable to me than slightly more brightness at certain intervals…so I’ll consider the Eagletac 3100 my best battery for my single cell lights.
In theory yes, but there are many lights, where the stabilization is less than perfect with a single LiIon battery, especially if the driver is 1x18650 or 2xCR123 batteries.
Here is a example:
Lights with boost converter (i.e. 1xAlkaline or 1xLiIon) that goes into direct drive with LiIon will have same regulation problem.
Someone correct me if I am wrong, but with a typical linear regulator driver, any voltage above the LEDs Vf at the current provided is wasted. According to CREE, a typical Vf for an XM-L @ 3A is around 3.34, so for as long as the battery voltage remains higher than that, the brightness should be relatively constant. We have to take driver losses into account as well of course. So it seems to me, referencing the graph above, that the EagleTac and the AW cell will provide roughly the same level of brightness for a certain period of time, but with the EagleTac the driver will drop out of regulation sooner, and provide a somewhat reduced level of brightness for longer.
I’d love to know the exact point at which this occurs, but I imagine it would vary depending on the light.
Yes, it will vary with the driver and also with the led current. I usual measure it in my reviews (But I have not done much on lights this year, I have used all the time on batteries and charges).
When I first learned about all this, I started to regret my decision to invest in Panasonic NCR cells exclusively. But I subsequently realized two things. First of all, I don’t often run my cells down far enough for it to matter before recharging them. Second, in the rare cases that I have, it was typically because I needed all the runtime I could get. For me, reduced output toward the end of the discharge is an acceptable trade-off for increased runtime.
So, ky70, I guess you just need to ask yourself the same question.
I prefer Panasonic cells for double 18650 lights now. I just bought 4 x Solarforce 2600 (V3) batteries for my single cell lights. As my late lights are mostly 2x Rcr123 compatible, they require a bit higher voltage for the buck circuit.
