So I’m pretty new to flashlights. I bought a 2.8a Convoy M1 XML2 t6 last month and just a couple days ago a 3.0a XinTD c8 XP-g2 S4 from mtnelectronics.com. I also bought a single LG 18650MH1 and a pair of his cheapest 18650 cells the enova 2600mah. They looked pretty good for the price. I was looking at the Maximum Continuous Discharge Current and they both seemed to have more than enough headroom for a 2.8a and 3.0a light, at 7a and 10a for the LG.
Anyways, I noticed with the XinTD c8, when I’d test the current at the tailcap with my dmm (12ga copper speaker wire for leads) that the current falls very quickly from a charged cell. I can read 3.0a on a freshly charged cell, with either the LG or Enova, but say currently, the LG is at 3.84 volts and reads 2.24a, and the enova is at 4.02v and read 2.69a at the tailcap. I pop those same batteries in the Convoy M1 and I get 2.78 and 2.76 respectably, which is perfect for the 2.8a rating. I don’t get the same behavior there.
I try to figure this stuff out myself before hopping on the forums, so I took the pill out of the C8 and tested the current straight on that, process of elimination, same thing. Then I started searching here for the answers. I keep coming a crossed the statement the the XP-G2 has a high vf, forward voltage, not quite sure what it is, but apparently that might be the issue. Is such an aggressive drop in regulated current to be expected with the XP-G2? Is there anything I can do to improve it, I’m assuming from my reading soldering some of this 12ga copper speaker wire I have laying around on both the driver and tailpiece springs might help this?
I took both the M1 and the C8 out last night to compare them in some open fields and while at first I was happy with increased throw/much brighter hotspot of the XP-G2 it seemed that the aggressive current drop quickly makes the difference less impressive. I’m wondering if I shouldn’t have gone with another XML2.
3.84v is pretty dead to get 3A out of an XP-G2 S4 on copper. What do you get with a fully charged MH1?
An XM-L2 does have a lower vF (forward voltage), and the aluminum mounted boards also always pull more amps because they run hotter (which doesn't mean they're actually putting out more light).
Copper braiding the tailcap spring will help give you some more maximum runtime, but the biggest upgrade will be charging your batteries.
Basically, you need voltage to pass a certain amount of current through LEDs. It doesn't matter if your cell is rated for 100A continuous, if you don't have enough voltage you can't pass that much current. It just so happens that generally the higher-discharge batteries sag less under load so they are still beneficial to us even though we usually don't use the full discharge rating.
Thanks for the comment. I’ve tested both the LG and the Enova at full charge, and they both read 3.04 amps.
It might just be a 18650 reality check for me. It just takes like ~15 minutes on these cells to drop to 3.8v, on the high modes, and I’ve been running them down to ~3.6-3.5v regularly. I’ve read that higher discharge cells experience less voltage sag, but I’m assuming the difference between one of those and a MH1 would be minor, at least to the eye, if not to the DMM.
That’s good to know. So there’s heat efficiency to account for as well.
If it continues to bother me, I might just buy a different emitter from you! But I’ll probably soon forget about it and just enjoy what I have.
Oh and I thought i’d mention while I have you, you might already know, the flat top enova don’t work well in the xtar mc1 charger as they are, at least how mine are. The positive end contact nub on the charger is oblong and doesn’t make contact with the flat top very well. I’m using some jacketed speaker wire cut to an inch to make contact, but I’m assuming I can take a razor and cut alittle of the positive end wrapper back to try and make better contact. They were really inexpensive compared to your other cells, so I’m assuming that’s part of it, or maybe constant modification is just a part of the high power flashlight scene.
