Tried to build one, and finally managed after destroying the first two batteries (puffed up, I assume because shorted). This was despite using kapton on both the battery and tweezers (in case it slipped off the battery a bit like it did for the first one).
The issue is that the side of the battery is still + so you have to scoot it as far as possible away from the negative contact on the board, else you can trivially solder bridge the battery (the fate of battery #2).
Third try was sorta the charm (as in it worked), but when I broke out the milliohm meter, it never did better than 33-35mOhm (it was near 50mOhm if when I clamped to the top of the 45% IACS unbridged spring from MTN). I compared a bridged plain Omten 1288 (and not one of my better ones, either) and got 19mOhm.
And then while trying to install in a light, the negative contact ripped right clean off the PCB from the most minor pressure against the battery (it was encased in two layers of kapton, btw). Iād liked to have run a test with spring bypassed for the most fair comparison, but after 3 batteries and nothing to show for it, I was done.
If youāre using a S2+ host, youāll need to trade your metal washer bottom plate for something thinner, or the retaining ring for the spring assembly wonāt sit flush with the shell (risking a short, depending on how much of the bottom of your battery is a contact).
If you could use the through-hole legs, this would be MUCH easier to assemble and try to use ā and much less likely to rip apart just trying to install it.
This is a neat idea, but the battery choice / mounting is too fragile, making it practically unusable. Pretty disappointed.
My (attempted) design change. Not yet assembled or tested, but idea was to switch out the LFPAK56 FET (so only uses the LFPAK33 FET) for a coin cell retainer that the same sized cell should fit (4.6mm). The pathway to load it has to be free(ish) of components, and I tried to keep the components out from under the switch otherwise. Comments/feedback welcome (trying not to be just a negative review, but rather a suggested direction for improvement).
It is possible, but you may need to replace cell when it is empty. Rechargable battery avoid the need for this. I also have pcb order for this to finish my s2+ flashlight, hope it work out since schizobovine had a few problem with the batteryā¦
I wouldnāt write it off, Iāve got a project Iām in the midst of right now running the entire driver at the tail of the light off a capacitor bank charged up through the bleed resistor(s).
If I can run an entire driver off caps I would think someone could run just a FET, and just full-on/off in the same manor.
50ohms of resistance at the head (needs to be rated 1w or using a bank of 1/4 or even 1/10 Watters) and ~350uF at the tail has been working on the breadboard without issue. Time will tell when I switch to a real PCB with smaller package caps but folomov did it so Iām betting I can too.
I bring this up here cause like I said, I donāt think it should be impossible or even difficult at all to run the switch FET without a battery, just need to do a lil backyard EEāing.
Oh also lumintop does it in the Ti Tool AAA (but their implementation isnāt all that great TBH)
So, Iāve finally decided to make about 10 of these FET switches.
Iāve finally understood of how this works, but one thing is still unclear to me:
Is it possible to use a super capacitor with a very high value resistor to prevent overcharging to the cap?
Itās the only component that Iām unsure if I should actually order.
According to post 24 it is being charged to 3.3 volts and the charging is limited with a 2.2k resistor in series with a diode, looks like changing
the charging rate is pretty easy.
The spec sheet for the battery says it has ācontinued stable capacity characteristics even after the battery is overdischarged down to 0.0V. ā
So maybe its possible to drain the battery to keep it from shorting out and destroying itself while its being installed.
If your going for the lighted indicator fet switch then rev.B has a lot lower quiescent current. I think loneoceans also added a second fet pad in the middle of the spring in rev.B. Are you building fet switch with the indicator or just the fet switch?
