That is such an old cell with poor chemistry and high internal resistance. You get a lot of voltage sag with it and boost drivers need as much voltage as possible.
The protection circuitry also adds resistance and reduces voltage.
What I’m refering to is mainly in reference to turbo run times. If you are only concerned about steady output on the lower levels, then it’s an okay battery for that.
I must have missed your question.
Here is DB Custom’s thread on the first version that uses the xp-l.
I need to get with the times as I thought it had modern chemistry. I've replaced most of my 18650's with 30Q's but haven't replaced any 26650's as of yet.
I think the KP 5200 mah came out in 2014. They have since been replaced by the 6000 mah version which is superior. The blue Liitokala came out, I think, in 2016 and is also superior. There have been a lot of better cells that have came out since the KP 5200 mah.
They could have used screws with a bit larger head to press down the MCPCB against the shelf and use thermal paste in between instead of using thermal glue. :person_facepalming:
They abandonned the driver retaining ring, it is now glued.
The older chemistry has to do with performance, not safety.
I’ll try to explain why I think the protected KP 5200 mah is not a good choice for this light.
A boost driver tries to put out a set amount of voltage and amperage to the emitter on Turbo.
On the other side of the driver, it is pulling in roughly half the voltage and roughly double the amperage. I say “roughly” because driver efficiency and some other things come in to play.
As battery voltage drops, the driver has to pull more amperage out of it to compensate. This is Ohms law.
Now the driver has its limitation on how much amperage it can draw to keep from burning itself up. The driver engineers will decide on a safe limit. Once this amperage limit is reached, the light will either step down the the next lowest level or maybe do a half step down. This reduces the amperage being drawn by the driver, keeping it safe.
I don’t have the batteries to test it, but I’m sure that a fully charged protected KP 5200 mah will show a larger amp draw compared to an unprotected blue Liitokala 5000 mah, for instance, due to its voltage sagging a lot under load.
What this means is that you can test these two batteries by running the light on Turbo for 2 minutes, let it cool, run Turbo again for 2 minutes, repeat over and over.
The Liitokala may be able to run full Turbo for a combined 30 minutes (just an example as I haven’t ran this test). While the protected KP 5200 mah may only get 15 minutes.
So the KP 5200 is a perfectly safe battery to use, but you won’t get as much run time on turbo.
I would love to see Maukka or other more professional reviewers graph the output of this light with some different batteries to see how they compare. Other boost driven lights have shown to give more Turbo run time when used with unprotected high drain cells.
EDIT: For more on this boost driver design, see post #49 below.
That was a great read, thanks Jason. It's probably the same scenario with the 18650's then as I tested my protected KP 18650 vs the 30Q and the 30Q was substantially better.
Here is a comparison at 10A. You can see the big voltage sag. This is the unprotected KP 5200. If you add the protection circuitry, the voltage sag will probably be even more.
Oh yeah, I edited that explanation post above to make it a bit clearer.
That's quite the drop and not even protected cells Looks like I've been missing out on the all the fun with my 26650 lights. Luckily I don't have many 26650's so I'm going to look around to start getting better ones this week. In the beginning I was so paranoid about unprotected batteries, but now nearly all my 18650's are unprotected.
KeepPower uses a lot of different 18650 models to rewrap with their protection circuitry, so you have to know what cell is under the wrapper.
Concerning older and newer chemistries, the same thing does apply to 18650’s as well. The Panasonic NCR18650B 3400 mah (aka Panny B) came out in 2012. It can not compare to a newer cell like the Samsung 35E. The test below is a protected Panny B (not a KeepPower version). This is only at 3A! Huge voltage sag.
The voltage sag is almost depressing in those graphs. I use my protected NCR18650B's only in my C8, SP32 v2.0 and my sofirn diving light and they seem ok in those ones. I'm pretty sure all the protected KP18650's I have are all using the NCR18650GA cells.
For linear drivers they seem fine. A Panny B in a Buck, Boost or FET driver tends to reduce performance, though.
Panny B in a Buck driver can make it fall out of regulation really quick. In a boost driver light, you lose Turbo quicker. In a FET driver light your max output is reduced. Overall, they are not so bad. Newer cells are definitely better, though.
Whenever you turn on the light there is a battery indicator feature in the switch which will light up green for about 5 Seconds when the battery is above 3.4 volts. Below 3.4 volts, it will light up red.
At 3.7 volts High mode (920 lumen) is only accessible with a double click. Another way to put it is to say that Turbo mode becomes the High mode. You have Eco, Low, Med and a 920 lumen Turbo mode.
At 3.4 volt, Med is only accessible with a double click.
I testing this with a low capacity junk 18650 which has a lot of voltage sag.
Candela is 18.6 kcd or 272 meters of throw.
Parasitic drain is 121 microamps/0.12 milliamps. Very nice!