Thrunite Catapult V3 Parasitic Battery drain?

Hey, I figured I would repost because I can't seem to find my original post and I'm still looking for answers...


I have a Thrunite Catapult V3 XML and it appears to exhibit some parasitic drain. I leave fully charged AW protected 18650s in the tubes -- a few weeks later the batteries are dead w/ no use.


I love this light, but am concerned about the drain. Has anyone else experienced this problem? If so, or if not, are there any fixes that I might be able to perform to keep this light topped off?


Thanks for all your help!

The Catapult uses a physical click switch, so there is no parasitic drain caused by an electronic circuit.

A couple of troubleshooting questions:

1. Are you sure the batteries aren't damaged, and showing a high level of self-discharge? What happens if you store them outside the light for a few weeks?

2. Have you used a lube on the threads? If so, are you sure it isn't at least partially conductive? On its own, this wouldn't explain a drain, but it could if there was something connecting the circuit (i.e., a short in the tailcap).

3. Do you have a digital multimeter (DMM), and if so, have you tested the electrical conductivity of the switch in the off position?

Assuming the batteries are ok, my best guess is you have a partial switch failure, or some sort of short within the tailcap. A DMM would allow you to investiage further. Failing that, you may want to take the tail switch assembly apart and throroughly clean everything with a contact cleaner and/or alcohol. Lubes can be an issue if they migrate onto contact surfaces and have any electrical conductivity.

thanks for the reply. I will recharge my AW's and let them set for a while to see if they self-discharge. I doubt this is a battery issue, as this has happened to two different sets of batteries of different brands (i.e. x2 AW's and x2 trustfires).

I don't have a digital multimeter so I'll have to ask around my friends to see if anyone can help.

I unthreaded the plug in the tailcap and visibly examined the clicky. I didn't see any evidence of moisture in there, although maybe there is and I'm missing something.


thanks for the reply!

Hi guys. I wanted to bring this thread back to life to clarify that I'm not crazy.


I had my good friend bring my Catapult to his lab at MIT, and we measured that the device WAS drawing some current in "off" mode. something like between 1-10mA. we had to use some special expensive multimeter or something b/c the draw was so low. but in fact, it was drawing a tiny bit of current. It does explain why the flashlight kills batteries over the course of a few months.

But Selfbuilt is right -- it's a mechanical switch, so when it's off, it should be cutting the circuit completely.



I took apart the tailcap switch and what do I find? There's a capacitor on the PCB where the switch is mounted. it's quite small. we're guessing that the capacitor was faulty or something. we just pulled the capacitor out and the light still functions just fine. i still can switch through strobe, low/med/high. problem fixed though!



just wanted to share. and many thanks to my friend at MIT, who really was the brains behind this whole operation. i should have taken pictures, i wasn't thinking about it at the time. sorry about that.



i'm not crazy!

midget said:

I took apart the tailcap switch and what do I find? There's a capacitor on the PCB where the switch is mounted. it's quite small. we're guessing that the capacitor was faulty or something. we just pulled the capacitor out and the light still functions just fine. i still can switch through strobe, low/med/high. problem fixed though!

Click to expand...

Interesting, I wonder what it is doing there. :thinking: Any circuit component on a switch pcb raises the question of a standby drain. I will check out my V3 to see if has one. On the newer TN30/31, there is a circuit element on the switch that provides some sort of assist, and it draws a miniscule uA current. It may be that something similar is happening here, but yours has "malfunctioned" into the mA range. I will check mine out when I get back home.