To me it seems that if I was to setup a nanjg 105c for an e-switch and do a zener mod to it, I’d have a large parasitic drain active all the time, draining the batteries in a couple of days. Is this correct?
I have an OL light with this setup and it does seem to drain the batteries quickly. I have not done a measurement on the current drain. If I remember I will if you like. A switch in the tailcap would fix the problem.
No need to measure, I can guestimate the current. I just wanted to make sure I understood the arrangement properly. Thanks for confirming.
Parasitic drain depends on how the firmware handles the MCU's sleep function. STAR momentary works fine (7135 or FET, don't matter), but something like trying to use a 7135 slave board on a SRK driver still running the stock MCU (PIC? whatevs...) will not shut everything down completely.
comfychair, it seems to me that the resistor/zener bit is the issue. For example, with this BOM we’ve got a 4.3v Zener and a 200 Ohm resistor. When I whip out my Ohms Law calculator here’s what I do:
This is the voltage that goes through the Zener in order to maintain 4.3v if the battery is at 8.4v
8.4v - 4.3v = 4.1v
Ohms Law says
4.1v / 200ohms = ~0.0205amps
and that looks like a really high parasitic drain to me. Way too high for an eswitch light.
That is why they use low drain voltage regulator instead of zener diode. They consume current in uA class.
LM2936 low quiescent current regulator chip… less than 10 microamps standby current. But if your firmware does not sleep properly, you are wasting your time.