Convoy 17/22 mm SST40 Driver temperature protection removal

Interesting, understandable, logical. The temperature protection gets activated by the resistance reduction in the NTC. If the NTC is removed the resistance “gets high” and cannot change. The temperature limit is thus removed.

Concerning the ramping driver, I modified a ∅22mm unit for a little bit more current (8.8A theoretical, 8.1+A measured) and two ∅17mm units for less current (5A and 4A, hitting ≈4.75A and 3.8+A when measured). The ∅17mm unit set for 4A had a small problem, with the first seconds of the ramping unseen and the 3rd mode setting clicks also unseen. Couldn't investigate the issue, the flashlight was for a colleague and he came home, got it and went away despite the thing.

The ramping driver has a weird UI which may not be everyone's liking.

Can you explain how you made the ramping driver less current? Would it be possible to run at 3A for an XML2? If you had to swap out chips then I won’t be doing it

I like the 6A driver but wish I could make it ~7.5 - 8A :confused:

By swapping out the sense resistor stack. Comes stock with 5mΩ, this means 40mV theoretical (I = R × V) sense voltage, although seems to be a bit less in practice (?). I added an R050 on top of the stock R005 in the “stock 8A” ∅22mm driver which ended up measuring 8.1+A. Concerning the smaller drivers I installed two stacked R020s in the one I set for “4A”, and for the one I set at “5A” I went with an R010 plus R050 plus R200.

For 3A effective a couple R025s may do.

Wed, 08/21/2019 - 11:43

1 Thank

@Barkuti what do you think if I just bypass “5mΩ” with the wire to run XHP50.2 3V I’m not sure if it a good ideal.

Barkuti, which component is the sense resistor stack? I think I see the R005 on the ramping driver, but do you know which it is on the 6A driver? I assume R010?

So what I’m understanding is that more resistance = higher amperage… Now to work out the right number to hit ~7.5A :slight_smile:

Edit: I’ve found a similar driver to the 6A one, but this is apparently 7A: https://www.aliexpress.com/item/33005190273.html - looks like it uses R015, but there’s a few other components of different values, too.

No, by adding the same resistor on top, your total resistance will be half of the value.
(Electronics series parallel basics) This will increase current output, many people did this with the L6 resistor mod (R100 or R120)

If you do that the driver won't be able to regulate at all. This means no ramping and no modes. I haven't tried it, though.

You still need to tweak the sense resistor stack value for it to work. You could try an R004 on top, it could work well or it may not. Add some heatsinking to the thing in such a case, as you'll be above the maximum power rating for single 1206 resistors (a couple stacked one doesn't changes this significantly). A good mound of thermal glue above sense resistor and MOSFET could help.

If the driver uses R010 for 6A this means sense voltage is Vsense = R × I = 10mΩ × 6A = 60mV. If you want to add 1.5A, you need Rextra = V / I = 60mV / 1.5A = 40mΩ or an R040 in parallel with the existing R010.

I have not measured how that driver behaves actually but if you really want to be sure to hit 7.5A, add some more conductance is my advice. I'd look for an R030, which would raise the maximum current to 8A theorerical (6A + 2A), albeit it would leave the actual figure in close proximity to 7.5A effective due to MOSFET heating, imho.

Thanks to you both :slight_smile: I did some electronics courses a very long time ago, so I’ve basically forgotten everything I ever learned…

Will buy that driver today!

Is it possible to do this with the 17mm version?

Yep, just gotta do the calculations and get the right resistor. Looks like an R010 on it, and max of 5A. Depends on how far you want to go, as to what you need:

6A total: Add an R050
7A total: Add an R025
7.5A total: Add an R020

And I don’t suggest going much further than that :slight_smile:

I was meaning removing the NTC on the 17mm version to disable thermal management

Oops. Sorry, forgot that’s what the thread was about.

I believe this is the 17mm driver:

It’s the bigger one in that circle (at the top of it).

Thank you guys!!
The only thing that was turning me away from this driver was the overaggressive thermal throttling!
Now a way to get a bit for regulated current out of it? SWEET

Thank you!!

Just ordered one driver for my Convoy M2

I have a couple ∅17mm units right here, I can confirm the matching board layout.

Overaggressive throttling? Could you or someone else explain this a little bit better?

We’re near, I’m from Molina de Segura, Murcia :smiley:

In what reviews I spotted of the SST40 based S21A, when you engage Turbo Mode, it almost immediately starts stepping down, pretty much negating anything useful of that mode.

I might do a runtime test of my S11 w SST40 that I’ve taken to 7.2A…

Cant wait, will do mine once resistors arrive.

Already removed NTC.