ENEDED

You could just disable LVP by drastically changing the voltage divider to never enter LVP. Or in the firmware I think there is an option to disable it actually.

The voltage sag could easily be 0.2-0.4V after the resistive losses are taken into account on turbo (aka, the voltage lost in the springs ect).

For this MT03 TA driver, it is R5 which has 4.7ohm.
I have replaced the R1 and R2 with 1% resistors. I use 357k ohm for R1 and 46.4k ohm for R2. Voltage measurement of this hot MT03 is much better now. LVP still alerts earlier than the other MT03 though, but I think that is due to higher current draw causing voltage sag.

I was hoping to disable the LVP via UI, but could not find any info on it. When you say firmware, you mean modify the source code and recompile it right?
Ya, I was thinking if there is another path reaching the batteries for voltage measurement, could it be better for LVP feature. It will measure without resistive loss.

Last night I make a swap on battery tubes between my two MT03. The one with higher brightness is still about 10-15% brighter as shown in lux meter. Visually it is obvious too when shoot on wall side by side. I think it is due to two things below:
1.It has 6 wires into MCPCB while the other has 2 wires into MCPCB
2.It uses Infineon BSC009NE2LS5ATMA1 while the other uses Vishay SIRA60DP

Yes, those 2 things would cause a difference in output for sure. I would not worry about it too much or you can upgrade the dimmer one with thicker wire and the better FET.

Also, the XHP70.2 tends to loose some lumens over time, so the more used light will generally be a little lower lumens.

That is the dilemma I am having.
I like the brightness but it really heat up very fast. Play time is really short. Also it has this earlier LVP alert thing.

May I know what is the value of R1 or R2 that I can change to make it offset like say 0.3V? Just to compensate the resistive loss during turbo mode.

But one thing is that the voltage of HKJ graph is voltage under load. Of course it shows it still have way more juice left since it can still discharge for another 23 minutes. If the test stop at 3.7v, its resting voltage will be much higher than 3.7v for sure.
Mine is resting voltage that I measure with multimeter. But my charger indicates it charges them to full with about 1400mAh of charge.

I was actually mistaken, the XHP70.2 MT09R uses the 360k/47k voltage divider, it is the XHP35 that uses the GT buck config.

In this case you could increase the 47k to around 51k and that should reduce the LVP around 10% I think although I have not done the calculations.

Thanks. I made some calculation below, I will try 50k ohm first.
Basically i try to make mcu seeing 0.693v that FW will take it as 6v, hence 3v LVP alert and step down.
With R2 as 50k, 5.7v will make the resistor divider having 0.695v, MCU will think it is 6v although it is already 5.7v, that is 0.3v below 6v.
Hope this theory works. I think best way is to have different LVP limit or offset level for turbo mode especially for flashlight having 10+A current draw.

Now it blinks 4 for 3.8v batteries and blink 4.4 for 4.14v batteries. R2 50k ohm makes it having 0.2-0.3 offset.

Update:LVP kicked in, blink and step down from turbo, take out batteries and measured 3.22v. Last few minutes of turbo were not crazily bright like fresh batteries though.

Great, glad it worked!

Yeah, after the normal LVP kicks in the power drops off really fast, which is why I am not bothered by the early LVP. If I really need the light on that long, I would rather extend the time I have it for vs a little longer at max power. But to each their own, nothing wrong with your setup if that is what you like.

Ya, by default MT03 TA LVP is finely tuned.

The thing is I use its turbo only, the FET mod and 6wires make LVP kick in very early, end up charging battery at 3.8v.

I mod the other MT03 TA with 4 wires, also changed R2 to 50k ohm. Don’t have suitable thicker wires, so have to squeeze 4 wires there, very close to shorting with reflector.

What battery are you using? You might want to try a higher drain like VTC5A or 20R.

You can also use Teflon coated wires since the insulation is thinner. Or use a single thicker wire like 14ga, etc…

Did you already bypass all of the springs?

I use VTC6, 30Q, HG2. VTC6 give best performance. I have enough high drain batteries, still have 20+ new batteries unused. So I am not getting any battery soon.
I have thicker wire but they are not rated as 200 degree c. I am using silicon wire that can withstand high temperature better. That’s why i squeeze 4 of them there. Springs are not bypassed, what i afraid bypassing spring will cook something because the current will be very high.

Using extra led wires has a similar effect of bypassing the springs, it reduces resistance and allows for more amperage to pass.

Ya, it has to balance, overdo will cause too high current. The FET and wires method is proven by my other MT03 TA, so i chose same method. Also i don’t like to mess with springs.

I’m curious. Do you know there is teflon treated fiberglass wrapped wire that can go very, very high temperatures?

I think it’s about 250c continuous. I have it in one of my heating platen on equipment i built back in the 90s. Still have some hanging around somewhere.

I definitely don’t have those. Is it soft and flexible like silicon wire?

It’s stiffer than silicone.

Silicone wires are really the best for our mod i guess. Inexpensive, soft, high flexibility and temperature resistant. I bought a few meter of black and red color many years ago and can’t finish them at all.

There are pros and cons to each. The Teflon insulation is thinner, so you can get more wires together without adding bulk and it can withstand higher temperatures. You see it used in high temp appliances like stoves, dryers, etc… the down side is it’s stiffer.

Silicone can’t handle the same high temperatures and is thicker, but it’s much more flexible.

It’s definitely better than the average low temp wire insulation you see on cheap wire.