samsung 18650 2600 battery power source

SNORKY

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Dec 7, 2012
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Hi All,
My Name is Snorky and this is my first post , im wellimpressed with the website and the expertise people show and are willing toshare ……I have read reams and reams on the safe use and charging of the notorious18650 battery (un protected ) …some posts make me shiver with fright and otherposts make me feel I have hit the jack pot with the batteries I have scavenged outof some dell lap top battery packs …I dare say each user has a different reasonfor using this cell …..so I would like to run my reason to use these to see ifanyone can guide me on the best use of the cells I own
Ok I have just followed some instructions to make a head torchfor night time MTB’ing ..its a COOL item….but getting the correct power sourcewill make all the difference
Ok …im running a single 3W XRE CREE LED 3.7 V FORWARDVOLTAGE …SOMETHING LIKE 100 LUMENS @1000MA……now will 1 Samsung 2600 mAh batterybe sufficient to power my led for 3 hrs safely …what I am concerned about isthe discharge issue of the battery ….will the led take the battery passed thesafe point and into the danger zone …remember this cell is not protected…thegood thing is the led housing is free of the battery (the battery is in a casein my hydro pack)….will it be safe to put 2 batteries in parallel (I think)….youknow +/+…-/- so having 2 batteriessupplying 4.2v @2.6a …is it better to guarantee the constant supply of voltageand current this way ….or can anyone seeany pitfalls ……..i have loads more questions but I will leave it there for now
Snorky
 
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SNORKY

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Hi There ,
Thanks for the reply ….yes the light it self is custom made …..the LED sits in its alu housing with a trailing lead waiting to connect to the power source …..the led has no pcb controller as yet (awaiting delivery from DX)….the driver pcb I have ordered is a standard 5 mode driver 1000mAh 3.7v
Regards Snorky

ops sorry the LED is 3watt........not 5W
 
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Thr3Evo

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The mAh (milliamps per hour) rating of the cell states its capacity. Like mpg(miles per gallon) ... how many miles you cover with one gallon.
In your case 2600 milliamps in one hour. If your driver pulls out 1000 of these per hour then you do the math.
However these numbers are theoretical only since efficiencies and internal cell resistances come into play. But it's a good rough estimate.
Running them in parallel will be the only way to get that sort of a run time from those cells with that driver.
And since these were pulled from a pack, chances are they were already hooked up in such a way, so the answer is yes, it is okay and safe to do so. Just make sure to use cells with same voltages together. Rule for li-ion parallel hookup is to always use identical cells, in chemistry, power and age.

Oh and looking around at your posts I see the lack of use of the space bar. Please pay attention when typing as it's treacherous reading this way.
 
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moderator007

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Divide your current draw from the mah capacity of the battery. 1000ma / 2600mah = 2.6hours or multiple x 60 = 156 minutes. If you will use a panasonic 3100mah or 3400mah 18650 cell you will achieve your 3 hour run time from a single cell.

If you are going to be using 2600mah unprotected cells then run two in parallel will give you a run time of 5.2hours. As the battery voltage decreases you should notice a dimming effect. This is a good indication of the cells needing to be charged before any harm is done. With two in parallel this effect is decreased because each cell is drawing 500ma each less voltage sag so the cell is drained lower in voltage before you notice the dimming.. In parallel the current divides between the cells.


In my oppinion for this to work properly either add a protection circuit to the parallel cells or buy a driver with a low voltage cut off protection. Or use a single protected panasonic cell. The insurance of the protection circuit in this is well worth the piece of mind and safety.

Also a cree xp-g might be a better choice with greater efficency and more floody type beam. Just my two cents.:)
A xre R2 should make around 270 lumens at 1000ma. A xpg should make around 350 lumens at the same current with the benefit of a lower vf. Should stay in regulation longer unless the driver is both boost and buck. I am assuming your driver is a linear driver?
 
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SNORKY

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Dec 7, 2012
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Hi and thanks for the reply…..i don’t know why I’m gettingthe words blending …it types ok but when I post some connect …I don’t know why
snorky
 

SNORKY

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Joined
Dec 7, 2012
Messages
21
Divide your current draw from the mah capacity of the battery. 1000ma / 2600mah = 2.6hours or multiple x 60 = 156 minutes. If you will use a panasonic 3100mah or 3400mah 18650 cell you will achieve your 3 hour run time from a single cell.

If you are going to be using 2600mah unprotected cells then run two in parallel will give you a run time of 5.2hours. As the battery voltage decreases you should notice a dimming effect. This is a good indication of the cells needing to be charged before any harm is done. With two in parallel this effect is decreased because each cell is drawing 500ma each less voltage sag so the cell is drained lower in voltage before you notice the dimming.. In parallel the current divides between the cells.


In my oppinion for this to work properly either add a protection circuit to the parallel cells or buy a driver with a low voltage cut off protection. Or use a single protected panasonic cell. The insurance of the protection circuit in this is well worth the piece of mind and safety.

Also a cree xp-g might be a better choice with greater efficency and more floody type beam. Just my two cents.:)
A xre R2 should make around 270 lumens at 1000ma. A xpg should make around 350 lumens at the same current with the benefit of a lower vf. Should stay in regulation longer unless the driver is both boost and buck. I am assuming your driver is a linear driver?

Thanks for the reply …..nice info on the led cheers …I haveordered from ebay (hopefully ok) a double cradle that holds 2 cells that equateto x2 current @3.7v with built in protection
The driver I have is a 5 mode pcb type from dx, [email protected]
Snorky
 
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