18650 w.o. soldering pins - how to pack??

[Momato]

Hi all

Found a link to these http://www.dealextreme.com/details.dx/sku.5776
protected 18650 cells. I want to make a pack with a balancer wire attached, but how to connect in series and add balancer? - I do not have acces to a spot welder (which I read about somewhere)?
I guess it is not good to solder directly?

I only wanna do this because I have not been able to find a finished pack with balancer wires already connected.

Best regards, Morten

 

[Fallingwater]

You *can* solder to them, but it's bad to do it with a normal soldering iron, as it isn't hot enough and needs to be kept on the surface of the terminal for 8-10 seconds, which heats up the cell too much.
A much better idea is to use a soldering station set on its maximum temperature (450°C for normal units); this way you'll only need to keep the tip of the iron on the cells for 2-3 seconds per joint.

This is if you already know how to solder, especially to flat surfaces. If not, your best bet is to give the cells to a shop that will weld them for you.

 

[jzmtl]

There's a plan on how to make a capacitive discharge welder for less than $100 that's great for battery. It's basically a car battery charger and a car audio capacitor wired up. Can't give you a link, bookmark is on my home computer.

 

[rizky_p]

You can solder the cells directly using big cooper soldering head to maintan melting temprature while soldering. It works nicely in mine only 2 second and they make a good contact..but this is the dangerous approach.

For more money i recommends DIY spot welder like in this link.
http://www.philpem.me.uk/elec/welder/

thanks.

 

[mdocod]

please consider a better quality cell for use in pack applications, these trust-fires and ultra-fires are proving to be very potentially fiery indeed.

for protected cells get some AWs protected, for unprotected get some LGs or Panisonics, or Sony's or something like that.

 

[Fallingwater]

please consider a better quality cell for use in pack applications, these trust-fires and ultra-fires are proving to be very potentially fiery indeed.

As far as I can remember they have caused not one accident involving fire. Actually, they haven't caused any accident at all.
DX occasionally sends out a dud, but it's just cells reading 0V and/or with problems in their protection circuitry, and even then it happens rarely and DX replaces them.
I don't consider WhateverFire cells the best there is, but they seem quite safe to me.

 

[mdocod]

hehe.... we do this every time. How many times have we disputed the value of the "cheap" cells FallingWater? Ok... I'll give it another go...

We have in fact had a li-ion explosion in a 4xRCR123 powered Kai light that was being used with cheap no-name unprotected cells. What's amazing is that it's VERY RARE for Li-Ion cells to develop problems during a discharge, they almost always fail while being charged. point being, if they managed to make a Li-Ion cell so unstable and so out of whack that it failed on a discharge, then the likelihood of a vent during charging is in my eyes, substantially higher.

If someone takes shipment on a cell that has been resting in an over-discharged state for potentially years, they are putting themselves at risk even trying to use the cells, many around here have gone ahead and charged them up, only to find substantially lower than label capacity, the question then becomes whether the battery is suffering from low capacity because that is simply how it is out of the package, or if it is actually that severely aged fresh out of the package... Considering the number of these cells that won't even hold a charge over 4.10V new from the distributor, It's very reasonable indeed for me to point out that these are risky cells that are much MORE likely to vent-with-flame than a more reputable brand.

saying that problematic cells are rare is not really accurate, here's just a few examples from around here. Keep in mind that AW has been selling large quantities of cells to CPFers for a much longer period of time, and overall I think we still have less incidents with AW cells than we do with the ultra-super-trust-fire cells which are a relatively new thing on the market.

Here's a 900mAH rated 14500 trustfire cell that only lasted 20 minutes on a 0.94A load, Meaning it came in at less than half it's label capacity. I realize inflated ratings are common in all brands, but this is more than double, which can be very risky when trying to calculate even a ballpark maximum safe discharge rate.
http://candlepowerforums.com/vb/showthread.php?t=186042&highlight=trustfire

Here's an example of a failed protection circuit and 18650s coming in at about half their label capacity. Major heating problems during charging/discharging also.
http://www.candlepowerforums.com/vb/showthread.php?t=173760

Here's an example of more misbehaving cells, one of them won't even get above 3.5V, the risk of an incident with that cell was pretty high IMO.
http://www.candlepowerforums.com/vb/showthread.php?t=179045

here's something interesting, we have 2 very different specifications for what appears to be the same cell... now what do we know?!
http://candlepowerforums.com/vb/showthread.php?t=173341&highlight=trustfire

protection circuit on cheap RCR123 failed:
http://candlepowerforums.com/vb/showthread.php?t=181958&highlight=RCR123

Here's an RCR123 explosion with cheap unprotected cells:
http://candlepowerforums.com/vb/showthread.php?t=180597&highlight=RCR123
Luckily as I understand it, nobody was hurt, no fires were started, it was outdoors and the flashlight was tossed in snow which prevented a potentially worse scenario, Kai replaced everything if I understand correctly. So there's good an bad there.

Here's a strange problem, cell did get some good use for about a year before failing, but this one was borderline explosion, heated up to a very dangerous point.
http://candlepowerforums.com/vb/showthread.php?t=186165&highlight=ultrafire

Here's an example of some brand new 18650s that refuse to take a full charge and perform poorly compare to aged Panisonic cells. These cells will barely hold above 4.0V, suggesting that they are already nearly completely "spent" as far as cycle life is concerned.
http://candlepowerforums.com/vb/showthread.php?t=184062&highlight=ultrafire

in this thread:
http://candlepowerforums.com/vb/showthread.php?t=182643&highlight=ultrafire
LEDite points out that he has had hundreds of cheaper cells fail prematurely. Then 2 responses down, forum Member Mash points out that he has had a "dud" 18650 from DX.

Here's 2 out of 3 cells shipped dangerously over-discharged.
http://candlepowerforums.com/vb/showthread.php?t=180505&highlight=ultrafire

here's a 2xRCR123 setup where one cheap cell discharged to 0.8V while the other was still 3.8V, obviously this was also probably user error in conjunction with the mistake of buying unprotected cells, but the fact that the cells were so inconsistent capacity wise can be a major problem.... this is the type of situation that could lead to a cell be reverse charged and going haybonkers.
http://candlepowerforums.com/vb/showthread.php?t=176800&highlight=ultrafire





http://www.candlepowerforums.com/vb/showthread.php?t=169200
in that thread, you can get a better idea what you are getting for your money with the AW cell, his latest revision of the protected cells includes great reinforcements to protect the PCB, internal PTC as a backup measure, and industrial grade shrink-wrapping that in my experience is in fact very durable in compared to other cells. When you buy an AW cell now you are getting Pila level quality (possibly better in some ways) for half the price. That is great value and piece of mind.

 

[LuxLuthor]

While I admire Fallingwater's unending pursuit of low priced Lithium batteries and encouragement of soldering Lithium Cobalt cells, I have to again side with mdocod. The risks of exploding cells and hot burning Lithium metal and toxic fumes is well documented.

If I HAD to solder a Lithium cell, I would at least pick one of the new safe chemistry cells which I summarized in this thread.

I'm not at all confident after taking apart both the Pila and AW protected cells that their PCB (& protective cushion collar) would hold up to any soldering.