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Magicshine mod for run-time (weight no object)

2201 Views 14 Replies 7 Participants Last post by ortelius, Jan 13, 2010

pswann

Discussion Starter · Jan 12, 2010

I know you're probably all getting sick of Magicshine questions, but I think this one is a little different from the norm.

My buddy is a marathon canoe racer and is going to be competing in the Texas Water Safari this year. He'll be on the water for 4 days and nights and needs lights that will give him about 200 lumens for the longest time possible without carrying a garbage bag full of batteries. Also, the batteries should be as waterproof as possible (I think this might be the ***** in the armor here).

Is it possible to rig up a ~5v pack for the Magicshine that would allow it to run for 10 hours at roughly 200 lumens? Small form factor is not that important in a canoe like it would be on a bike. It would be great if it were not an anvil, but it doesn't have to be just tiny either.

Thanks in advance for any info you can share.

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J_Hopper

· #2 · Jan 12, 2010

From poster rfxc in this thread: "I tested the amp draw from my battery in each of the various modes ( I have the 3 mode light). High draws roughly 1.5 amps, with a range of approx 1.4-1.6. Low mode draws .5amps +/- .1amps. Flashing mode (highest brightness but flashing) draws about .75-.85 amps. Roughly speaking then, Low mode should last 3 times as long as high, and flash mode should last about twice as long as high. Or to calculate theoretically runtime, take the total amp-hour rating of your battery (I think 4.4ah or 4.400mah for included battery) and divide by the amp draw of a particular mode. IE, 4.4ah divided by 1.5amps drawn in high mode = approx 3 hours of runtime with the stock battery."

Seems like low should last about 9.5 hrs and be around 200 lumens.

Re: waterproofing: I used silicone caulking to seal mine. Then, I got the crazy idea to get some Plastidip. I put 3 or 4 coats of Plastidip on it. I have no doubt my Magicshine battery is waterproof.

vroom9

· #3 · Jan 12, 2010

I'm not really sure that a magic shine is really the way to go. While I have not seen one I would really worry that it is not waterproof enough. The Magic Shine is a 600 lumen light, not a 200 lumen light. A more proper light for your 200 lumen requirement could be a single XP-G R5 bin at 700ma or so.

How will the light be used? I'm thinking helmet light. Is that correct?

Just how many hours does the light need to function for? Just take some guesses. For example how about 6 hours per night for three nights. That makes for 18 hours. A number like this is needed to select the battery required to get the job done. A single XP-G will need 6 hours * 700ma = 4.2 amp hours through it. A XP-G has a low enough forward voltage that a single cell could power it using the 7135 linear regulators. If you made a battery with 2 of the 2500mah 18650 cells in parallel, it should run for at least 6 hours. It will need one battery for each night.

Another possibility would be to just use a couple of flashlights. There are some XP-G ones on DX now for between $20 and $25. Most flashlights have decent water protection. And with high/mid/low modes may even last for several hours of mid and low. Just carry enough pre charged batteries in a waterproof container to get you through. I would attach some flotation to the flashlights so they float.

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pswann

Discussion Starter · #4 · Jan 12, 2010

Thanks J–Hopper and Vroom9. These are all good suggestions. I will pass them on to my friend. I don't know what he's going to decide, but from what he's told me of his needs, it seems to me the flashlight idea might be the most flexible choice. It will be a helmet-mount application and will need to burn for about 7 or 8 hours a night. Since the flashlight batteries are small and cheap, this seems like a good option to me. They carry water sensitive stuff in small Pelican boxes so I could see them having one dedicated to batteries. I'll be interested to see what he decides.

Thanks for taking the time to answer so thoroughly.

lidarman

· #5 · Jan 12, 2010 (Edited)

vroom9 said:
The Magic Shine is a 600 lumen light, not a 200 lumen light.

It is a 200 lumen light on low mode--draws around 450 mA on low.

And the head is definitely water-resistance and even waterproof--even if submerged (no idea on the depth though but someone posted a video of one being submerged in a swimming pool). The window is sealed with O-rings, the button is sealed and the power cord is grommeted. If one uses the magic shine on low with two battery packs, it will do the job--I would go with three to make sure.. And as stated above, the battery packs can be sealed. I would add some RTV to the grommet are just to be sure.

If you wanted a custom pack, you can buy a connector and something like

http://www.batteryspace.com/customi...tterypack72v9ah648wh2xlm-er26500endtoend.aspx

However, it's probably easier to just buy magic shine replacement batteries as spares. In fact, It might be a good idea to have two full magic shine lights plus one extra battery, not to use at once but to have a backup.

gmcttr

· #6 · Jan 12, 2010

lidarman said:
...I would add some RTV to the grommet are just to be sure....

Forget sealing the grommet. It just provides some strain relief and it's location has no ability to seal the case.

You would need to remove the base (single screw) and seal the light head where the cable enters.

With a little work the MagicShine would be a cheap possibility.

However, If I was looking for a waterproof light for 4 days on the water, I would be looking at the Baja Designs Stryker.

MtbMacgyver

· #7 · Jan 13, 2010

To maximize runtime, you want a light that's capable of a lot more than 200 lumens and you want to run it on a lower setting. That's much more efficient than running a 200 lumen light on full power. You also want multiple battery packs from a reliability perspective. Actually, you may want 2 complete systems so you have a good backup. Especially if you go with the Magicshine.

I think you should also consider the Dinotte 400L. The 4-cell pack running at 50%, 200+ lumens, runs for 10 hours. Two or possibly three 4-cell packs should give you what you want. They also offer a headband mount if that's needed.

http://store.dinottelighting.com/sh...t2=949912667&ProductID=90&Target=products.asp

The Magicshine with two or three packs will work as well, but I think the Dinotte will have much better waterproofing and reliability.

Keep in mind speeds will be low in this application, so light cooling is also a factor. The magicshine will probably be fine on low, but it'll likely overheat on high.

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lidarman

· #8 · Jan 13, 2010

MtbMacgyver said:
To maximize runtime, you want a light that's capable of a lot more than 200 lumens and you want to run it on a lower setting. That's much more efficient than running a 200 lumen light on full power.

You realize the MS runs in low by using a 1/3 duty cycle PWM right?

lidarman

· #9 · Jan 13, 2010

gmcttr said:
Forget sealing the grommet. It just provides some strain relief and it's location has no ability to seal the case.

You would need to remove the base (single screw) and seal the light head where the cable enters.

You are correct. And that reminds me, one probably ought to seal the screw too.

MtbMacgyver

· #10 · Jan 13, 2010

lidarman said:
You realize the MS runs in low by using a 1/3 duty cycle PWM right?

Yes, I do and that's part of why I was recommending the Dinotte.

gmcttr

· #11 · Jan 13, 2010

lidarman said:
You realize the MS runs in low by using a 1/3 duty cycle PWM right?

I googled PWM and now understand the concept. How is this good or bad for dimming LEDs to lengthen runtime?

TIA

MtbMacgyver

· #12 · Jan 13, 2010

gmcttr said:
I googled PWM and now understand the concept. How is this good or bad for dimming LEDs to lengthen runtime?

TIA

LEDs are more efficient at lower current. For example an XPG R5 produces 132 lm/watt at 350ma but only 105 lm/watt at 1000ma. Since PWM reduces the apparent light output by rapidly switching a high current on and off, you don't see all the efficiency that you do if you actually run the LED on a constant lower current.

lidarman

· #13 · Jan 13, 2010 (Edited)

MtbMacgyver said:
Yes, I do and that's part of why I was recommending the Dinotte.

No problem if one likes to throw cash at things.

I suppose the OP didn't seem to mention cost as a criteria, but I assumed so since anyone who talks about MS, usually does so because of the cheap price.

So when someone asks for advice, I try to keep that as the context. But that is just me. I'm certainly not going to suggest a $250 10 hr batter pack as a solution to make a MS last 10 hrs.

MtbMacgyver said:
LEDs are more efficient at lower current..

Yes, but a moot point with the Magicshine. The MS produces the lumens for at a cost way below other lights. So what if they are driving them a little too hard. This is not a NASA project here.

I see the Magicshine to lights as RAID to computer storage. Cheap and redundant versus expensive and reliable....but it's still yet to be proven that MS lights are not reliable.

But please, pick your way of doing things.

MtbMacgyver

· #14 · Jan 13, 2010

lidarman said:
If you wanted a custom pack, you can buy a connector and something like

http://www.batteryspace.com/customi...tterypack72v9ah648wh2xlm-er26500endtoend.aspx

Still seems a good bit cheaper than your suggestion of a non-rechargeable lithium battery that's only available with a minimum quantity of 25 and therefore a $650 price tag. That's a lot of money in throw away batteries....

ortelius

· #15 · Jan 13, 2010

MtbMacgyver said:
Still seems a good bit cheaper than your suggestion of a non-rechargeable lithium battery that's only available with a minimum quantity of 25 and therefore a $650 price tag. That's a lot of money in throw away batteries....

And with max discharging rate 400 mA.

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