Freedive/Spearfishing light.. advise please!

[Codiak]

Other's more knowledgeable will chime in but the buck driver is the limiter, the battery pack will shut down at it's limit both with overcharge and at the lower limit, and constant current isn't necessary but is used if your want ...constant current...constant brightness throughout the burn time rather than a longer burn time at decreasing brightness.

Maybe I'm just stating the obvious and haven't completely understood your question!

The buck driver is a voltage limiter, the issue with the SST-90 is that it can draw >10 A (which is above spec) even at lower voltages. So the watts=heat=thermal shutdown and/or burn out.

So it's not enough to limit the voltage, amp limiting is required as well.... least thats my layman understanding.

I look at this PCB and read that it limits to 10 A... still above spec but well below the 12-13A the LED has be shown to draw.
Is this a good short term solution while we wait for a more "traditional" driver?

With Canister based lights we have the advantage of additional space and PCBs ;-)

 

[Codiak]

Regarding needing to go to a cannister design to get 3+ hours, that isn't the only option.

Unless you are on a rebreather you probably aren't underwater for 3+ hours at a time..

He's free diving... definately not rebreathing

Seriously, I'd want 3 hours because I may go out all day and don't want to fiddle with extra batteries..... oh and I am on a rebreather ;-)

 

[gcbryan]

Ah, you're right. I'm still not up on all the driver details! I knew a buck driver brought the voltage down and I knew that current was key with led's and I knew that direct drive is the most efficient when battery/led vf can be matched and I understand constant current but I wasn't considering that buck drivers don't also address current.

Electronics...so complicated.

 

[Codiak]

Ah, you're right. I'm still not up on all the driver details! I knew a buck driver brought the voltage down and I knew that current was key with led's and I knew that direct drive is the most efficient when battery/led vf can be matched and I understand constant current but I wasn't considering that buck drivers don't also address current.

Electronics...so complicated.

We do what we can or risk becoming a jack of all trades and master of none.

 

[Codiak]

He's free diving... definately not rebreathing

Seriously, I'd want 3 hours because I may go out all day and don't want to fiddle with extra batteries..... oh and I am on a rebreather ;-)

Yuck, requirements for 3 hours at 10A ~= 12 x 18650 pack....oh the pain of reset expectations.

 

[Codiak]

Okay, so as I understand the real issue with Current is the SST-90 draws more as temp increases. So why worry about constant current below 10A if the LED can handle it? What we really need is a limiter? Do I correctly understand the issue?

If so, as I read the details for this board, current is limited to a max of 10A. Note: it doesn't say cut-off/shutdown... just limited... isn't that what we need?
http://www.batteryspace.com/pcbprot...r2cells60vlifepo4batterypackat10alimited.aspx


Are we good with this coupled with a good buck driver?

Techjunkie contacted BS, turns out this is just a polyswitch... damn fools gold.