Acebeam x70

I don’t think active cooling reduces power consumption. It very slightly increases it.

No, I meant that if the light is regulated at a certain brightness level, active cooling will decrease power consumption compared to no active cooling due to the fact that the forward voltage of an LED going up as it heats up. So active cooling will actually decrease the power usage by maybe 10-15W if done right.

Hmm… maybe this whole fan thing is what’s holding this light up. Especially since I’ve been hearing that the x70 is suppose to keep its max turbo for 1/2 hr just rumors for now…

I think I understand what you’re saying, but you might be saying it in a way that’s a little confusing to me.

Flashlights are not capable of monitoring there output in lumens. To do that would require some type of optical feedback loop which isn’t practical at all. So all the driver can know is how much amperage is going to the emitters. It’s up to the designers and engineers to use enough amperage to generate the amount of lumens they want.

I don’t think the designers and engineers have to take into consideration the changes in the forward voltage as the light heats up. If they measure the output using ANSI-FL1 standards, then they measure at 30 seconds.

So I assume there’s no power usage decrease due to the active cooling. This is a bit beyond my knowledge, though. Maybe someone like Lexel or DEL (a driver designer) could go into more details.

I’m sure it is. It held up the X9R for a very long time until they scrapped the active cooling. It adds a tremendous amount of complication plus Olight and Acebeam also have to worty about their warranties. I know Olight has 5 years warranty, but I’m not sure about Acebeam. I assume it’s pretty long, though. It’s hard to keep the fans working well in dusty, dirty or wet environments for the duration of the warranty period.

I don’t know if the X70 can do 40k lumen for 30 minutes, but I did crunch some numbers and the batteries seem capable of handling it. I think the triple fans might be able to just barely handle the heat load. I think it’s physically possible it can do that, but can Acebeam build it to do that? We will have to wait and see.

Even if it can only sustain 30k or even 20k lumen that would be record breaking. Right now 10k lumen is the record and I’m not even positive that light is doing 10k. It has not been tested. It’s rated at 10k.

Hmm.

Doubt it could physically run 40k lumens for 30 min.

Well, being a 40000 lumen light and having 12x XHP70.2s, it must be pushing out about 3400 lumens per XHP70.2.

Knowing that an XHP70.2 consumes 22W at that power level, it means that the light is consuming at least 270W of power at max brightness.

Even if you were using NCR18650GA and not taking into account internal resistance, you would have at max a battery capacity of 100Wh. Meaning at 40k lumens, you would have a max, down to 2.5V, runtimes would be a max of 20 mins, not 30 mins. That would be even less down to 3V and counting internal resistance, and that the cells are probably 30Qs and VTC6s, not 3500mAh GAs.

It is physically impossible to get 30 mins even with an 8 cell battery pack at 40000 lumens. Maybe 30000 lumens, but not more.

It would need 30Q’s not GA’s.

I was saying it is possible to run in turbo for 30 minutes. I don’t think it will maintain the 40k, though. As voltage drops, the output would drop.

Hmm… nice points… I hope they pull it off; groundbreaking if they do…

Hmm you missed the led in the middle…

I know.

But it would not matter much anyways.

Vf goes down as the LED heats up.

Wut.

Thank you. I always thought it was the opposite, since in my LED builds, using my constant current supply, as my LEDs heated up, so the voltage went up.

Is there a reason for this?

Never seen that happen. Did you measure with a DMM from the LED wires instead of trusting the PSU?

me to I thought the same thing

Another test with another LED where I turn the heatsink fan on at 10 minutes.

Well this one makes sense…

You can even use diodes (which LEDs are of course) as temperature sensors, because the relationship between temperature and forward voltage is pretty linear (for Si diodes at least, don’t know about LEDs).

That’s true, for example the Nichia 144A is very linear from 20°C upwards. Use a very small current not to heat up the LED itself much and it can be used to estimate ambient temperature.

The exact reason “why” is pretty much a entire undergrad class in silicon junctions. Needless to say it involves quantum effects with the bandgap. I guess an ELI5 answer would be that the increased thermal energy can give lower voltage electrons a push across the bandgap? That is probably wrong on several levels though.

The effects of a falling Vf are huge though. It is why LEDs need current regulated supplies. Otherwise you get a thermal runaway and the LED destroys itself.

Anything with a negative temperature coefficient will need regulated current. Very few things have negative coefficients and voltage regulation is sufficient.

On a related note I’m always kind of amazed that direct drive FET lights work at all. The wires and contacts and the battery itself form a positive coefficient that magically balances out against the LED that is trying to self destruct.

Thanks to you all for the answers.

The reason I thought forward voltage of an LED would go up is because of my experience in CPU and GPU over clocking.

See, when you up the voltage and frequency beyond its normal parameters, as you may already know, the additional power creates more resistance, and therefore more heat.

Then, what happens of this effect is that it accentuates electromigration since electrons have less incentive to stay inside of the silicon transistors, and if there is too much electromigration, boom! a crash even before speed ans temperature were a limit for the chip itself.

I had noticed this on my GPU, when I kept temperatures below 40°C, I could achieve massive frequencies and push voltage to its limit without any crashing.

Once I reached even 1°C above that threshold, it crashed. And observing the voltage and current behavior, I noticed that voltage slowly upped as the temperature went up, as well as current. Lowering the fan speed did this and if the voltage was not locked, this is what would happen.

Thanks for the explanation everyone again!