Help with sst-90 homemade

[NewKind]

Hi, I need some help with a project for school. I would love some help.

Im going to build a flashlight with one sst-90, and I think I'm going to use these batteries:
http://www.bmsbattery.com/index.php?main_page=product_info&products_id=9

And this driver:
http://www.powerconversion.com/assets/ldo10c_1191530952.pdf

I would like it to work for like 3 hours if possible.
How should I wire them? Is it possible to charge them in a mounted battery pack? With a modern RC-lipo charger.

With how high voltage and current do you think I should use when charging?

Thanks!

 

[gt40]

It depends what you want. If you are trying to run the light at 9-10 amps, the light would have to be massive to handle the heat. I have built several sst90 lights and they get pretty hot at these power levels. I made one with a giant head to hold a 75mm aspheric, thick walled tubing and powered by 2 26650 4000 mah batterys and it still gets hot so 3 hours run time at high is probably not realistic for continuous run time.

With the battery you are looking at, you would need to run 2 to get the voltage up enough to run at higher levels and match the vf of the led. Then you have driver issues. You can use the ldo10c or Lineage Power Naos Raptor. Both will allow you to run at 10 amp levels assuming you have a big heat sink and the light will still get hot. You can also go with dwdiver's driver if you can get one.

I was going down your route but decided on the batteryspace 26650 (2) because of more compact form factor.

Good luck with your build.

 

[alpg88]

you picked wrong driver, and wrong battery, and you never mentioned what flashlight you're trying to convert, also heat sink for sst90 is the most serious issue, no way in hell you'll run it at full power for 3 hours, even for 30min, unless your heat sink is 5lb chunk of copper.
use search box here and read existing sst90 threads. we have it covered plenty of times.

 

[PMM]

Heatsink as mentioned needs to be good

Nowt wrong with the LDO10C - driver I use for my own SST90s but you'll only be able to drive it to about 2000 lm at a 8ish amp rate and you will be pulling about 30 watts factor in some driver inefficiency and lower than rated real batt. capacity you can put together a nice light while keeping things safe and in limits.

Batteries... well you want 4 of them to get the capacity and voltage for the driver.

You should be able to get your 3 hrs.. you'll have around 100watts battery capacity using 4 & SST90 @ 8ish amps is 30watts so there is more or less 3 hrs.

 

[NewKind]

Thanks for replies.
If I lower the amps to between 6 to 7, is the heat still such a big problem then?

 

[MikeAusC]

If you run it at 6 amps, you'll have about 2/3rds of the heat at 9 amps - still a lot of heat to move out.

 

[Walterk]

See it like this: 4 volt x 9 amp = 36 watt.
Try to hold tight a light-bulb in your hand, it wel get to hot soon.
And that is confined in the head of the flashlight where the heat cant go away, but gets new heat added.

With 60 degrees Celsius the flashlight is to hot to hold.
With 120 degrees the Led and all solderings will give away.
The colder the Led the better, preferred is roomtemperature but that's ideal.

You need good thermal contact and surface area to the open air.

 

[CKOD]

Thanks for replies.
If I lower the amps to between 6 to 7, is the heat still such a big problem then?

Yep, this light

which is a SST-90 driven at 6.6A on high, overheats in still air from room temp in ~7 minutes. The driver board is set to cut back when the drive board reaches 60C The driver is on the back of the heatsink, so the LED is much hotter then that, and the whole front end is somewhat uncomfortable to hold. It folds back to its "medium" setting, which is 1.6A. However hanging out the car window at 30 mph it runs just fine on high constantly

 

[AnAppleSnail]

However hanging out the car window at 30 mph it runs just fine on high constantly

Are you developing an emergency car headlight or something?

NewKind, I think you might be getting ahead of yourself with the design here. What sort of light output are you after? Lantern, spotlight, floodight? Different LEDs (of equivalent cost) may be better for your goals.

What kind of light? Portable, pocket rocket (no 3 hour runtime), tethered, or spotlight size?

What fabrication can you do? Lathe? Epoxy things together? Solder?

What's your budget? You can do really neat things with more money, or save trouble the same way.

If you want a portable light, you're limited in the power you have on hand. A 2D mag lite is about as big as most people consider handleable, which gives you something like 40 watt-hours if you use three of these D-cell-size Li-Ion cells. 3.7v, 4Ah, rated for 10 amp draw. A very few high-power driver options exist for 9-Amp draw. If you're careful, you could set up a direct-drive ONLY IF you put 3 of these in series. The voltages come out nearly right. It will get dimmer as the batteries discharge, but be hellishly bright if you don't fry the LED. Of course, a bigger light gives you more power. At 9 amps and 4v on the SST90 you need at least 36 watt-hours for every hour of runtime.

With LEDs, more power gives you less more bright. Derating them is where the fun is - an XP-G driven at 750 mA gives around 250 lumens, while at double that you only get 200 more lumens. To the eyes, it'll look somewhat brighter, but take twice as much heatsink and twice as much battery to run the same way.

In a portable light, heatsinking is the challenge. Metal is very conductive, but air is not. So you see big lights with big fins, trying to heat more air. A hand is a good heatsink, but at this power level on a warm night you'll want to hold a cold drink in your other hand. That's why Coleman's LED lanterns are so big - no hand to take heat away.

Tell us more!

 

[MikeAusC]

I wouldn't plan on using an LDO10C unless I had one in my hand - I paid RScomponents for one in June - they've justa greed to refund me because they won't be able to supply until March 2011.

LDO10C is not a good choice fo LED driving - it's only constant-voltage.

The PTH08T240W also does 10 amp but can do Constant-currrent - it's twice as big as the LDO10C.