M140 Vf @ 1200?

Hey guys. It's been a while.
I have 2 ben-boost drivers here collecting dust.

I want to power an M140 diode with one set at ~1200mA.
I want to use a single 4.2V 18650.
While looking for info on the ben-boost I came across someone reporting an issue when using this driver with a 445nm diode with the driver output V less than the driver input V.

Now my issue is that I can't remember the Vf of the 445nm diodes. Something like approx 4.0V @ 1000mA?
Will this combination damage the driver if the Vout < Vin?
It seems like the most common use of this driver is for 445nm diode... but maybe that's because everyone runs them at 2A these days so Vf is higher?

Does this thread belong in the 445nm diode section or the drivers section? :thinking:

That benboost will only stay in regulation about a second at that current I don't care how you sink it.
Your better off getting a foulmist boost unit set at that current. Sorry for that... And hey man I haven't seen you around late.

It will be fine you can go ahead and build it no problems.

At least I've tried it & had no problems... You will need massive heatsinking though for the driver

Hm. Two ideas that contradict each other.
Can I get a third opinion?

@jander: yo. I've been busy with school and trying to spend more time practicing my other hobbies... drawing, photography, adventuring...

That current is nearing the claimed maximum that driver can handle (1.25A), so a lot of physical conditions, component quality, and margins of operation may come into play. Maybe consider using two Ben Boosts in parallel instead of a single one running at its maximum capabilities.

Lame. I didn't realize this was the upper limit. IIRC they were offered preset at this and higher currents. I wonder why if it's not going to perform well at this setting.

Read up on the open source "benboost" thread it ends in some sorts of desoldering a cap IIRC.
I'be never run them in anything above 945mA due to heat.