SSC P7 direct drive w/3 AA NiMh should I use a resistor or diode?

I'm assembling a SSC P7 direct drive w/3 AA NiMh should I use a resistor or diode or will the internal resistance of the switch be enough.

If I need a resistor my guess is that I would use something around 1 ohm at 10W. Has anyone found one small enough to fit in a mag D

If I use a diode to protect from reverse voltage and add a slight voltage drop what are the ones that are commonly or successfully used?

With a Seoul P4 at 4x AA NiMh I used big wire wound resistors (5 watt, 0.47 Ohm and a 10 watt 1.0 ohm) in series to get the amp draw down to 1.0 +/-.


Here are my testing results from that setup. I don't know if it will help you or not.

https://www.candlepowerforums.com/threads/246884

for what it's worth, 3x AA NiMh directly connected to the P4 gave:

4.19 V (pack resting voltage)
3.66 Vf (forward voltage)
1.44 A (including the resistance present in the diode protected switch on my light)

sbelyo said:

I'm assembling a SSC P7 direct drive w/3 AA NiMh should I use a resistor or diode or will the internal resistance of the switch be enough.

If I need a resistor my guess is that I would use something around 1 ohm at 10W. Has anyone found one small enough to fit in a mag D

If I use a diode to protect from reverse voltage and add a slight voltage drop what are the ones that are commonly or successfully used?

Click to expand...

You can safely direct drive a SSC P7 with 3xAA NiMH cells without using a resistor or diode. Just make sure your P7 is of the "J" voltage bin. For example if you had the choice between a DSWOJ and a DSWOI go for the DSWOJ. The J at the end refers to its voltage. You will get enough sag with 3xAA to protect your SSC P7. Just make sure you have a good heat sink and the emitter is well connected to said heat sink with a good thermal epoxy.

thanks guys... I'll give it a try

sbelyo said:

thanks guys... I'll give it a try

Click to expand...

Hey just to beat it to death. Direct drive is fine with 3xAA NiMH cells with a "J" SSC P7. Some of the guyz even direct drive them with 3xD NiMH cells. Just a word to the wise I would not direct drive a SSC P7 with 4 NiMH cells regardless if AA, C or D is used. At this point you could and probably would damage or destroy the SSC P7.

OP, 3s is a great set-up for your P7. No resistor needed for long-term use.

Now cover your ears, the rest is a bit more 'advanced' stuff: I"m not saying you should, but I've run a P7 off 2 cr123's (6.0v) while testing an optic. No long term effect on the emitter.
Read jtr's Whiteledtesting for P7 performance well outside the listed specs.
Again, I'm not saying plan for it, but I am saying you won't definitely won't fry the led connecting it to four 1.5v batteries.
If you want to destroy the emitter, don't give it a thermal path and just let it cook until it turns angry blue, then cook some more. You'll deform the surface and wreck the bond wiring.

Thanks for your help guys....

My short 1D digi camo is alive and bright as hell!

My first led is a success and out of the way.

It's almost as bright as my M6 running an 1185 bulb @ 11.1 V for like 1/3 the money. But then I can always say I own an M6

with only 3xaa ni/mh you dont need resistor, it can work direct drived

Here's some pics

Hi all

I got myself a DSVNI binned P7 from litemania. Is this DD'able with 3 D NiMh ?

THanx

I would have to look at the max forward voltage. If it's in the 3.6 - 3.7 range you're fine. When I measured the actual voltage that my pack was putting out under a 2.8A load it was 3.2 - 3.3 so if you can measure the same for yours, you'll have a better idea.

barnefko said:

Hi all

I got myself a DSVNI binned P7 from litemania. Is this DD'able with 3 D NiMh ?

THanx

Click to expand...

Yes you can. I've built a number of lights with both I and J binned forward voltage without a problem in C and D Mags. My personal light that I use almost every day is an "I" running DD from an IMR18650 at 3.4 amps in a C cell mag. It was built last winter and works great ever since. And a D cell will run cooler than my C.

Everyone seems to be fussy about the vf on these builds but I don't recall anyone frying one because of this.
Please correct me if I'm wrong.

And a great job on your P7 sbelyo! I love those camo lights!
If you ever get bored with the P7, build your next
one with an SST-90.