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Batteries!!

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Hi, sorry if this was discussed somewhere else already, but I'm looking at buying my batteries on Ebay because you can get way better bulk deals with chargers. Anyways, Since there are so many different ratings of 18650 batteries, and I'm new into this game, i was a bit overwhelmed. My question is, for something like a 405nm 400mW Violet Laser Pointer, can using a higher mAh battery like a 3000 vs 4200 cause problems with the laser, or would it just have a longer run time? Also, tab or no tab?, protected or unprotected?? Does it matter?? Iv been pretty much educating myself off this site alone hahaha :thanks:
 

qumefox

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Keep in mind that >2800 mAh batteries generally are rated in 'chinese mAh'.. Meaning, they just make numbers up.

It's hard to find reputable name brand (samsung, panasonic, etc) li-ion 18650 batteries higher than 2800mAh because that's pretty much the upper limit for capacity in that size cell. But other than that, 'capacity' won't hurt a laser. It just affects how long it will run on a charge.

Generally to use in flashlight hosts. You want them without tabs. Protected vs non-protected also just depends on your application as well. A lot of protection circuits in cheap cells are crappy and can cause more problems than they prevent. And some lights (like the sipiks I use as hosts) won't work with protected cells due to the added length. (generally 2-3mm longer than non-protected cells)

Personally I pretty much just use non-protected cells in pretty much everything. But that's mainly because I have a metric buttload of them that i've scavenged out of laptop battery packs.

Quality protected cells are 'safer' in that you don't have to worry about running them down too far, or drawing too much current from them. But they are longer than non-protected cells, and in cheap cells, the protection circuits have the chance of not working properly.

Quality non-protected cells are easier to find (laptop battery packs, etc) cheaper generally, and actually 65mm long so they'll work in pretty much anything that takes 18650's, but you have to make sure you don't run them down past 2.8V, and don't draw excessive current from them or there's the chance of them overheating and venting.
 

LarryDFW

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ShambhalaRaver;

I suggest that you only buy brand-name 18650 cells.

I have been building commercial UV lights and lasers for several years,
and have used hundreds of 18650 cells.

I now only use name brand 18650 cells like Panasonic, Samsung or LG cells.

Typical capacities for reasonably-priced cells are 2600-2900 mah.

Internal resistance is a measurement of how much voltage drops when you have a significant load on the cell:

http://laserpointerforums.com/f67/how-healthy-your-batteries-how-measure-internal-resistance-57576.html

LarryDFW
 
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qumefox

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The downside to name brand batteries is they pretty much will always be non-protected, since they were manufactured pretty much exclusively to be used in laptop batteries.
 

qumefox

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AW's are good. And Shambhala.. the phrase 'you get what you pay for' very much applies to batteries.. Providing you stick to known good brands. It's possible to pay too much for 'junk' as well. I've seen new chinese '3000mAh' 18650's that have had actual capacities as low as 1200mAh before..
 
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Good to know. Well its a good thing I opened my mouth before clicking the mouse because i just about bought a bunch of GradeA china junk.
 

qumefox

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Not all chinese li-ions are total crap. However when the mAh rating is above 2800 on them, facts are usually being stretched a bit. When in doubt, just order a couple, then charge and test them and see how long they last on a known load. If they're good, order more.
 

qumefox

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The ones below 2400mAh have generally been regarded as 'ok' I believe. I know the 3000mAh ones have proven to be 'nowhere close' though.
 
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The ones below 2400mAh have generally been regarded as 'ok' I believe. I know the 3000mAh ones have proven to be 'nowhere close' though.
Yea that sounds about right, I use the blue skin 2400mAh ones and they have always been good for me.
 
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On my 445nm survival laser running at 1.1W I usually get over 1 hour to an hour and a half with two of the blue skinned ultrafire 18650 cells.
 

qumefox

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How much run time you get off any battery will depend on the load applied. so sopark's answer probably wouldn't realistically have much applicable use to you unless you were using the battery in the exact same kind of laser.

For example. I have a battery that will run a 1.2W 445 for a little over 2 hours. Yet that exact same battery will run a 260mW 660 build for well over 5 hours. It all depends on your load.

You really need some kind of reference to get any meaningful information.

On my 445nm survival laser running at 1.1W I usually get over 1 hour to an hour and a half with two of the blue skinned ultrafire 18650 cells.
Hmm. Then assuming your laser is drawing around 1.3A after driver losses, that puts the capacity of them somewhere around 2000mAh.
 
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