18.5V 5 CELL & 6 Cree R2's.

[gav6280]

Can Anyone see any foreseeable problems using an 18.5V 15C 5 CELL 4000mAh Li-Po Battery with a Blue Shark driver from sandwiche shoppe to drive 6 Cree R2's in series with a nice big heatsink?

Expected max run time?

 

[gav6280]

Re: 18.5V 5 CELL & 6 Cree R2's will it fry..

Was just a bit concerned that the battery fresh of charge might be higher than the forward voltage of 6 Cree R2's (Not exactly sure how low in a worst case the Fv of the R2's could be?) which would fry my Blue Shark Driver i think???? As shark board is a boost driver.

Are there any regulators that are a buck and boost and are clever enough to switch over from one to the other?

 

[Greg G]

Depends on the actual front voltage of the led's. If they're at least 3.5 volts each at drive level that's 21 volts, which would equal the batteries resting voltage fresh off the charger. Assuming some battery sag and switch resistance you should be ok.

Of course if it were me I'd try to put a 7th led in there. :naughty:

 

[gav6280]

ah yes top idea, but i think the shark has a max output of 22v.

 

[Greg G]

Blue Sharks are rated for up to 32 volts. :twothumbs

 

[gav6280]

But the plan is to use this....

http://www.cutter.com.au/proddetail.php?prod=cut839

With this:

http://theledguy.chainreactionweb.com/product_info.php?cPath=48_49_61&products_id=1136

And finally one of these:

http://cgi.ebay.co.uk/ws/eBayISAPI....m=120333836422&ssPageName=STRK:MEWA:IT&ih=002

And then stuff the whole lot into a water tight case

 

[Greg G]

You'll have to get the battery, fully charge it, and measure its voltage.

This is a situation where about a dozen R2's and a power supply to check their front voltage, so you pick the ones with the highest number, would be required.

Is that a good battery? Do many people use it?

 

[gav6280]

The battery, well that doesn't really matter if it's a "Good one", it just has to work. Cant justify spending all that money on this kit and for it then not to work...

 

[yellow]

6 led with 5 Li-Ion cells in series + Shark is safe,

roughly, if that pack goes around 4000 mAh, runtime should be:
4000 / (led drive current / 5 * 6)

... better deduct at least 10 % of runtime to be on the safe side
... are there 5 cell protection circuits for the pack?
(just checked the link, these packs have no protection inside, I do give them one-use-till-dead if You dont put protection in
btw: I have very bad experiences with Li-Po. Imho that chemistry is "Diva" and not long-term rugged)

 

[gav6280]

To give it the best chance i have got a high tec slow balance charger. As for the protection i have little circuit that beeps loudly and flashes when the voltage drops to 3v in any cell.

 

[gav6280]

Ok.... I have been convinced more is better and i am going to go for it and do the 7 R2's as suggested. Good job im going to have the whole ocean as a heat sink to cool this thing...

18.5 lipo ebay battery and a blue shark.

Now i just have to get all of this inside a 63mm diameter heat sink...

Any ideas for some small form factor narrow beam inexpensive optics / reflectors?

 

[ledaholic]

I have the same basic setup in my Makita light with no problems so far.

 

[steve6690]

My dive light is 7 x Q5's driven by a blue Shark, fed from a 14.8v battery pack. No problems at all with heat. I used AA epoxy to fix the shark to a copper plate, then AA'd another strip of copper between the top of the switcher ic and the copper plate to wick away the heat. I ran it for 15 minutes in still air without probs, and 2 1/2 hours in the bath. Your shark should theoretically run cooler than mine as it has less boosting to do. My housing is 52mm inside diameter and I can fit 7 of these Fraen reflectors FRC-N1-XR79-0R Cree XR-E :

http://www.cutter.com.au/proddetail.php?prod=cut738

the biggest optic you can use and still fit 7 in, is 21mm diameter, which gives you a wide choice...

 

[gav6280]

Have you seen cutters shipping prices. OMG.... Ridiculous.

 

[steve6690]

I bought 20 of those Fraen reflectors from Cutter and total including delivery was 37.80 AUD or £18.16 which didn't seem bad really...