“Not enough for that LED” implies that the CFT90 only works above 10A. Mine works in moon mode to Turbo mode, so I know that isn’t the case. Whatever is “locking” Turbo mode is a driver related issue more likely as compared to emitter or cell issue.
Multi-cell parallel configurations are usually easier on a cell because the load is shared between the set. It’s really difficult to push an emitter that the forward Voltage goes up to 4 or above with a single cell because by itself Voltage sag under extreme load keeps that lone cell from meeting the high amp drain Voltage needs of such an emitter… like the CFT90 or SBT90.2.
With 4 parallel cells the 25A needs of this kind of emitter can be supported while each cell only supplies around 6A, low enough demand individually to allow Voltage to stay relatively high, at least for awhile.
This set of cells, though, ( a battery if you will ) takes a beating trying to run the demanding emitter over time, running deeper cycles in shorter times, perhaps, than other less hard use lights. Remembering that a cycle is a full discharge and recharge, the hard use emitters are likely to run the battery through more cycles faster, thus reaching EOL sooner.
I built a lot of small 2S 18650 lights back in the day, MTG2’s in single 18650 lights, and those small cells got beaten down quite quickly!
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How come it works with brand new batteries as I mentioned?
Maybe the driver recognizes that it’s not able to push the original amps with these older 30q, and it steps down immediately? 
Just to reiterate, the initial step-downs are all from turn on .
The odd thing to me is after 6 or 7 step Downs it locks in. But it never stepped down with new batteries until they’re depleted.
Thx
If you remember back when we started building High amp triple S2s with a fet driver – The MCU would go crazy and reset with certain LEDs ---- I’m thinking this is more of a voltage problem – The voltage sag of an older cell is greater than that of a new cell
Cochise – with new cells-- how far ( voltage) can you run them down before the Turbo acts up – If I had the light and hooked it up to my adjustable power supply – I could tell you exactly when and why it’s doing it’s dance
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I bought this light used when it was about 6 months old. I have no idea what kind of driver it is. All I know is it’s custom made by that VIN guy but mostly by Richard from Mountain electronics.
A DMM measures resistance by outputting power with a fixed, known quantity (either current or voltage, i don’t know which) and then measuring the resulting voltage (if current is fixed) or current (if voltage is fixed) in the component, and the resistance of the component is calculated from the two values using Ohms law.
This only works on passive components, it can’t work on a component which introduces it’s own power into the circuit, such as a battery, and connecting a battery to the DMM’s resistance measuring circuit which is not meant to take power input may have consequences.
Hopefully your DMM has built in protection to prevent damage from such a connection.
The internal resistance of a battery can be determined using a DMM and a resistor of known value (with correct power handling capabilities for the power that would be delivered to it), known as a ‘shunt resistor’.
The battery’s voltage both with and without the shunt resistor connected across the battery is measured, and as the difference between the two voltages is be due to battery’s internal resistance this can be calculated with a formula derived from Ohms law.
There are caveats to ensuring as accurate a value as possible, HKJ’s article here contains detailed info on the above, including the formula:
https://lygte-info.dk/info/Internal impedance UK.html
There is also a thread here which shows thefreeman’s solution to making 4 connections to the battery: https://budgetlightforum.com/t/measuring-battery-internal-resistance-always-around-50-60-mohms/65680/7
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As I mentioned it only acts this way with aging 30q’s and the first batteries I put in brand new ga’s or MJ ones could not handle the load.
Immediately after activation it starts stepping down.
With new cells it won’t step down until it’s at about 3.50 to 3.55 volts. And this is measured after I get home when they’ve been resting for 20 minutes. So they may have been down to 3.2 3.3 volts I have no idea.
I also repeat this again. There was zero issues when the 30q’s were new and when I put in brand new VTC 5D or Samsung 25s. So the solution is simple, new batteries which I’m going to do.
I’m just trying to have you guys who know more about this give me ideas is why it does that?
Looks to me like the low Voltage protection is at work there. The aging cells immediately sag far enough to trigger the low Voltage step downs. The issue is from the comparatively high Voltage needs of that emitter.
I have a CFT90 in a light I built from scratch but I honestly haven’t used it at length to see what happens to the cell… I run it on a 6,000mAh 32650.
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As I thought, the CFT90 has high forward Voltage demands….
Typical at 3.5V, under high amperage up around 4.2V, or equal to/over a fully charged cell.
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That makes sense but I still don’t understand how come all the sudden after a half dozen or so stepdowns from initial activation, it’s able to lock in then and run until the batteries are depleted?
Bypasses lvp?
Richard would be the one to ask since he builds Vihn’s drivers.
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Ok. Thx
As a vague idea it may be that going to turbo triggers an impulse-like voltage drop which is just enough to cause the driver to drop out of turbo, and that after several activations warmer components or residual charge in components reduces that impulse voltage drop just enough to avoid the drop out of turbo.
You could leave both the torch and the 30Q to rest and then try triggering several turbo stepdowns with a different battery in the torch, and then inserting the original 30Q to see when turbo locks on.
If it locks on immediately it’s the torch that’s changing, if you still need several stepdowns with the original 30Q following several stepdowns on a different battery it’s the battery that’s changing.
I contacted him through Mons Pura recently — Still as friendly as ever with me
It is simply the batteries or how the driver reacts to worn down batteries. There is no triggering turbo on brand new batteries. It won’t step down until the batteries are depleted.
I just remembered it does have a thermal step down that was set very very high, but that has never been activated. The only step-downs with new and functioning batteries are when the batteries are depleted. And of course you have the step-downs immediately with older worn down batteries for reasons yet unknown.
What is happening with the 30Q’s seem to be unknown and are educated guesses my members more educated on flashlight Electronics than myself.
New batteries are the solution.
Thx
Yes, and my suggestion is to help you narrow down which one it is.
If by ‘triggering turbo’ you mean ‘triggering turbo step down’ then that’s right, i know your high current batteries don’t step down until they’re too depleted to re-engage turbo. But in the first post you say you have MJ1s, GAs, and P26Aa that all step down in the same way as the 30Qa? You could use any of those?
I understand enough about internal resistance and voltage sag to know why your 30Qs and lower drain batteries won’t sustain turbo mode, i am specifically looking at why turbo mode can become sustained by your 30Qs after several unsuccessful attempts as this goes against basic logic.
I also know that the characteristics of electrical components can change with temperature which means the driver spec changes slightly as the components warm up.
My thought is that the 30Qs in their current state are just under the threshold of being able to systain turbo, and that several bursts of turbo result in that threshold changing enough for turbo to now be sustainable.
If this is the case then it doesn’t matter which batteries are used to provide those turbo bursts, hence my test suggestion.
If the changes are due to heat then just running the torch on high for a while also produce the same result.
Battery characteristics also change with temperature, though i don’t know enough about how to know if this could be the answer.
The Vf of an LED reduces with heat too, so it may be that the several turbo bursts are heating up the LED enough to allow the 30Qs to sustain turbo.
The point is that the 30Qs repeatedly drop out of turbo, and then illogically they don’t.
So the repeated turbo activations are changing something but we don’t know what.
It makes sense to me to narrow down the area of change, my suggestion was intended to help with that.
Apologies if it doesn’t.
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No worries. I know you’re trying to help.
I wasn’t clear enough in the first post about my p26a, mj1’s and ga’s.
I started with MJ1 and GA’s when I got the light about 4 years ago. They were new and didn’t have the power to maintain Turbo and kept stepping down from the beginning just like my older 30qs. The p26a on the other hand we’re just like the 30q’s in a sense once they got older 2 years or so they could no longer sustain Turbo when I turned on the light.
My solution arrived in the mail today a present from my brother. 
He heard me b**** about the light a few weeks ago and things aren’t that great with me. Been out of work for a while. I now have 4 X P28A BT from Liionwholesale being charged and then the capacity test on my opus. Runtime test tomorrow and on the trail with them on Wednesday evening.
Thanks for your help.
Cheers
P.S.
I still have the ga’s and MJ ones. They are in different lights that don’t require a lot of amp draw. They are doing well for 4 years old.
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Are those Grade A cells
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I’m curious how matched the resistance is 