battery issue

dexter9 · Jan 30, 2012

I bought 10 2400mAh 18650 cells from ebay and i run 3 xml from 3P3S.
From fully charged batteries(4.07) after only 15 minutes burn time the voltage drops as low as 3.54 while in use, but if i turn it off the voltage per cell goes up to 3.7, and after a while it shows even close to 3.9, in the next cycle it gets to 3.5 in 5-7 minutes, then after 5..
Is it safe for the cells to run it if it shows less than 3.5-3.3 while running?
Batteries from hobbyking.com are high-quality? or "ebay-quality"? I suspect that my batteries are nowhere near 2400mAh.

betti154 · Jan 30, 2012

Lithium ion/polymer cells have a nominal voltage of 3.7 voltage. Fully charged they're 4.2v, though quickly drop to 3.7 under load and stay there for a while but continue to drop. Empty is typically considered 3.0v, some say 3.2 to be a bit more conservative (check battery specs and whether or not they're protected).

Depending on the current you want to run you 3 XMLs at, you may find 3S3P lithium ion to not be ample voltage if the LEDs are configured in series. e.g. At 3A XML U2s will require 3.337 volts each. So when the batteries are full you'll get full brightness, but as the batteries drop to below 3.3v your light will dim.

See cree calculate for specific voltage requirements. http://pct.cree.com/

DIWdiver · Jan 30, 2012

I would say that 3.5V after only 15 minutes at 1A load per cell is not good performance. That's only one tenth of the capacity, the voltage should still be higher.

As Damien pointed out, you can safely discharge them well below 3.5V. IIRC, many manufacturers calculate capacity by discharging from 4.2V to 2.7V. You might see if they hold out a lot longer going from 3.5 to 3.3. After that the current will be less and less, but that just makes the batteries last longer!

Which brings up another point, if they started out at 4.07V, that's a bit low. You will not get full rated capacity unless they are charged higher than that to start with.

I'm building a light now with one XM-L and one LiIon cell. I expect full output for 70-80% of the rated capacity, then reduced output for a while after that.

350xfire · Jan 31, 2012

I tried some of the cheap Ebay batteries a while back and they were a waste of money.

betti154 · Jan 31, 2012

I've been using these Tennergy 2600mah 18650s with success, though I've heard mixed comments. Time will tell I guess, particularly with the ones in my small video lights as they discharge at 2C.

I've just got a stack of Kallie's Custom 18650 3100mah (unprotected /w tabs) and am about to build a few larger packs (8S2P) as well as use a couple in standalone backup style lights (single 18650). Will let you know how I go.

dexter9 · Feb 1, 2012

i tried to go lower with my batteries, but after just 8 minutes i was at 2.8 volts, so those batteries were really a waste of money.

Klem · Feb 1, 2012

betti154;I've just got a stack of [URL="http://callieskustoms.com/CalliesKustoms-Batteries.html" said:
Kallie's Custom 18650 3100mah [/URL](unprotected /w tabs) and am about to build a few larger packs (8S2P) as well as use a couple in standalone backup style lights (single 18650). Will let you know how I go.

Interesting find. If true 3100 then that'll be terrific for your project.

Just clicked on their 'International customer' tag and suddenly the price skyrockets...YeeOuch! Where's my industrial tub of Vaseline?

betti154 · Feb 1, 2012

The reviews on various forums are very good, up there with AWs but I struggled to figure out where to buy them.

I bought 16 cells for $230 usd shipped to Australia. That's approximately double the tenergy 2600, so only time will tell if they are worth the it.

I'm building a pair of single cell 18650 backup lights using a triple XPG board + lflex driver /w piezo, as I flooded one of my rat jnr lights and no longer trust them. With variable power, at full 3500ma I wanted to get full intensity as long as possible, on med/low I imagine it'll go for 3-6 hours so I went for the best battery I could find (both reliability and capacity). For the size of this sucker (34x140mm) I think it will be an awesome little weapon at 1100 lm on high, though I concede this will decrease somewhat as voltage drops.

Regards,
Damien Siviero
http://damiensiviero.com

Klem · Feb 1, 2012

You want to use the Iflex with programmable settings...prolonged piezo? I live in Perth and source mine online from Everswitch, based in Oz.

Went prawing last night with a 75W HID which uses 15*18650's (in 3S5P). Got about 50 minutes out of it before it cut out...with 10 minutes of exit-finning still to do. It's those cheapy Trustfire 2,500 (stated!) from DX. The dilemma is, buy cheap and put up with the bullsh*t rating or go expensive and get a full dive.
Had a backup torch so never in any trouble but still, would be nice to control when the torch goes off! $$$$$$$$$$!!!!!

betti154 · Feb 1, 2012

Klem said:
You want to use the Iflex with programmable settings...prolonged piezo? I live in Perth and source mine online from Everswitch, based in Oz.

I've used the TaslLed drivers and Apem prolonged piezos in a variety of solutions, works a treat. I've been sourcing them from KD Fischer in South Australian, but they're about $40 each and have min order quantities of 10+ and lead time up 3 months (so a bit painful).

What are you getting from Everswitch?

H20doctor · Feb 1, 2012

i run 3 xmls on a battery pack of 10 cells.. 1.2 volts NiMH 3/AF 2600 Mah.. 14 volts fully charged.. and I get a 90 min burn driving them at 3amps on a sharkbuck driver

Klem · Feb 1, 2012

betti154 said:
What are you getting from Everswitch?

About $50 each when you factor in postage but at least they sell them individually. Last time I bought three so it brought it down to about $40 each. Only one colour in the Baran M16 prolonged...red.

Codiak · Feb 1, 2012

I've noticed an issue in real cold weather where my light doesnt respond to the switch real well....
Not sure what is causing the issue... But the APEM piezo is suspect right now.

Cold water is ice diving

betti154 · Feb 2, 2012

Klem said:
About $50 each when you factor in postage but at least they sell them individually. Last time I bought three so it brought it down to about $40 each. Only one colour in the Baran M16 prolonged...red.

Do everswitch have a website to order from? I couldn't find anything online other than USA site.

Regards,
Damien Siviero
http://damiensiviero.com

budynabuick · Feb 2, 2012

betti154 said:
The reviews on various forums are very good, up there with AWs but I struggled to figure out where to buy them.

I bought 16 cells for $230 usd shipped to Australia. That's approximately double the tenergy 2600, so only time will tell if they are worth the it.

I'm building a pair of single cell 18650 backup lights using a triple XPG board + lflex driver /w piezo, as I flooded one of my rat jnr lights and no longer trust them. With variable power, at full 3500ma I wanted to get full intensity as long as possible, on med/low I imagine it'll go for 3-6 hours so I went for the best battery I could find (both reliability and capacity). For the size of this sucker (34x140mm) I think it will be an awesome little weapon at 1100 lm on high, though I concede this will decrease somewhat as voltage drops.

Regards,
Damien Siviero
http://damiensiviero.com

Man i checked out the photos. Very nice work!

Keith

Klem · Feb 2, 2012

They also go by the name, SwitchesPlus
http://www.switchesplus.com.au/index.php

The switch is the Baran SMF6.
http://www.baran-at.com/s5.html

Part # 19020350 . You can have any colour... as long as it is red!

Dashrynn · Feb 3, 2012

betti154 said:
I've been using these Tennergy 2600mah 18650s with success, though I've heard mixed comments. Time will tell I guess, particularly with the ones in my small video lights as they discharge at 2C.

I've just got a stack of Kallie's Custom 18650 3100mah (unprotected
/w tabs) and am about to build a few larger packs (8S2P) as well as use a couple in standalone backup style lights (single 18650). Will let you know how I go.

I could source the Panasonic cells way cheaper than what you buy them for....issue is...I'd have to buy 1k American worth. Still around 8$ for one 3100mah cell is cheap.

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