wanting to make a battery pack....

[Swallow]

I have previously purchased ready made battery packs from batteryspace - all well and good. However seeing as they are made from cells, and cells are cheap at dx, couldnt I make my own?
Can anyone tell me if this is a good idea or a bad idea?
I was thinking of using eight Ultrafire 3.7V 2400mAh LC 18650 Protected Batteries
in the hope of ending up with a 14.8v 4800mAh pack.
Any suggestions as to the feasibility/wiring/assembly of this much appreciated - I am an electronics novice to say the least. I have made a set of bgike lights with the help of CPF and am now addicted. This pack will hopefully power a helmet light I am working on. Would it also be possible to charge the pack as a whole or do the cells need charging individually? DX seems a good option as it is free shipping to th Uk as well as pretty cheap already.
Thanks in advance for any help, but please keep the language simple as, as I say, I'm no expert.

 

[yellow]

seems expensive for me,
+ I give You (as a novice) no chance to solder these cells together without damaging them, I would not try it.

Better get 2 packs of BP491 rechargeable camcorder packs from E-Bay, so You end up with 12 similar batts. Good for one of the packs You want + an additional 4 in-a-row small pack. They have connectors mounted and its way easier and safer to solder at these as on the batts.
negative: You have to get an additional circuit for over-/undervoltage protection of the packs.

PS: the most difficult thing in doing such is, that the batts have to be EXACTLY in the same stage imediately be4 soldering them together. Easiest way to achivie this is to solder "+" of all the packs together and then all the "-" (at beginning with a small resistor (~10 Ohms) put in between, after a day directly connected. And have this rested for some days so they all end up with the same voltage). Then hurry quick to solder the pack together and watch out not to short any cell

 

[Swallow]

seems expensive for me,
+ I give You (as a novice) no chance to solder these cells together without damaging them, I would not try it.

Better get 2 packs of BP491 rechargeable camcorder packs from E-Bay, so You end up with 12 similar batts. Good for one of the packs You want + an additional 4 in-a-row small pack. They have connectors mounted and its way easier and safer to solder at these as on the batts.
negative: You have to get an additional circuit for over-/undervoltage protection of the packs.

PS: the most difficult thing in doing such is, that the batts have to be EXACTLY in the same stage imediately be4 soldering them together. Easiest way to achivie this is to solder "+" of all the packs together and then all the "-" (at beginning with a small resistor (~10 Ohms) put in between, after a day directly connected. And have this rested for some days so they all end up with the same voltage). Then hurry quick to solder the pack together and watch out not to short any cell

so maybe better to stick with the ready made batteryspace packs? only problem is the shipping to the UK they charge as well as the tax - everything in the UK is a comparative rip off! Thanks for tips though!

 

[LEDependent]

Psst... LuxLuthor just got a spot-welder for making packs...
http://www.candlepowerforums.com/vb/showthread.php?t=166954

He may consider helping you out for a few $$

 

[LuxLuthor]

Yeah, like they said because of the plastic spacer/separator parts, explosive/thermal runaway dangers of most Lithium cells, it is not safe to solder their terminals (which can be done with NiMH or NiCad). Even those AW Li-Ion cells with protection circuit PCB chips in the Neg end are endangered from heat.

The only option, and what you see in various computer, power tool type Li-Ion packs is to use a "contact spot welder" which fuses the Nickel contact strip with the metal below....but only in tiny spots, so virtually no heat is transferred in the process.

Newer Lithium chemistry is now being developed as in the "A123" (Saphion) & Emoli brands, that are no longer explosive or at risk of thermal runaway, but they are very limited in their sizes/shape/mAh....and mostly used in either Dewalt or Milwaukee power tools.

Depending on the voltage of a pack, there are different thickness and width of the strips (or multiple strips) that are used to contact weld them. One thing I like about the strips once attached to any battery type is there is flexibility of battery configuration angles, ability to attach battery pack voltage balancing wires, etc. etc.

I'll set up a way to do this for members at a nominal fee so it remains a hobby/community service. I have no idea how to set it up/ forum category with all the new Marketplace rules, as I have never sold anything here before.