Biscotti driver acting weird?

Flashlight Modding and DIY Parts
1

I received from Banggood a new driver (8 chips) with Biscotti firmware for my Convoy S2+ with T6-4C led.
I replaced the old driver (6 chips –3/5 modes) with the new one. It was my first more “serious”mod.
Everything fine, apparently.

Then I ran a test with a Samsung 30Q (non-protected, button top).
On the 4th mode (35% of the nominal power) it ran about 2,5 hours then the intensity suddenly dropped twice (in about 10 minutes) and then the the flashlight shut off without warning.
With the older driver (6 chips), on the intermediate level of power (roughly the same), the flashlight functioned more than 3 hours before the warning of LVP.
I sticked the 30Q in the Lii-500 and I was at 3,2 V. The older driver sucked up the energy from the cell until it reached 2,8 V.

Is this behavior normal for a Biscotti driver with 8 chips?

Thanks!

P.S. The Convoy C8+ with Biscotti (8 chips) I have, behaves better.

2

Battery level detection on these (and most) drivers is done through a pair of “voltage divider” resistors connected to an MCU pin. Unless the manufacturer splurged for the pricier 1% tolerance resistors (which they wouldn’t for these drivers), they’ll each have a 5% tolerance. It’s possible that you got unlucky and the variance is such that the driver thinks the voltage is lower than it really is. It’s also possible, but highly unlikely, that the wrong resistors got used.

3

Ok, thank you for the possible explanation.
But does the Biscotti driver shuts down the light without blinking?

4

OT here,but not really!

Did you know that Biscotti means “Biscuit” in Italian!! It was also the name of the doctor who delivered me!! lol! I am sure you are all thrilled,hey, you learned the meaning of it,BISCUIT DRIVER! :sunglasses:

5

Yes, I do, Wolfdog! Thanks! :slight_smile:

6

Yup. Biscotti has the step-down blink commented out.

// See if it's been low for a while, and maybe step down
if (lowbatt_cnt >= 8) {
   // DEBUG: blink on step-down:
   //set_level(0);  _delay_ms(100);
7

Somewhat related… I just received a couple biscotti drivers from aliexpress. I goofed and ordered from a different seller instead of Simon directly, because I found a lower price. One of them is of course defective, it doesn’t change modes at all. I took a closer look at it and it’s missing the little capacitor on the lower left of the driver. Does anyone know the value of that capacitor in case I want to try to repair this driver? I’m looking at another biscotti driver and that capacitor has no markings on it.

8

They’re typically 10uF 0805-size

9

On my driver is written: convoy v 2.
Is that the correct marking?
Also, the spring is narrower.

10

The V2 is the newer one that fixed the “running too fast” problem and potential memory mode issues of the first gen biscotti driver. I’d rather have the V2. Simon apparently just has a giant pile of old and new mixed together and grabs them randomly.

I have two of each currently.

11

I just de soldered an identical looking smd capacitor from an old broken dvd player and soldered it to the driver. No idea if it’s the right value, but size wise it’s pretty much identical. It actually worked. All the modes work. I tested it staring right at the bare LED like an idiot and now I may be blind, but it works. I’ll build a light with it when my hosts finally show up and see if it dies again.

12

Haha glad it’s working. That particular cap isn’t very sensitive to what value you use.

13

Nice fix Jason. :slight_smile: