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  • 18650 Li-Ion batteries – are they solderable, and any experiences?
  • large418
    Free Member

    Hi,
    I need to build a 3 cell battery pack (11.1V), and am thinking of buying a couple of pairs of Ultrafire 18650 batteries on ebay. Will I be able to solder wires to them (some batteries I have bought in the past have been very difficult/impossible to solder to). Can't seem to find solder tag versions.

    And the 3000mAh version – anyone tried these and are the runtimes really 3000mAh, or is it Hong Kong seller optimism?

    Anyone got any experiences? Cheers

    Posted 13 years ago
    smudge
    Free Member

    Hi Large,

    I can build you a 3 cell battery no problem. It would be out of 2.6Ah cells so could build a 5.2Ah battery if preferred.

    If also have single cell 2.4Ah 'protected' Li-Ion cells that I can weld tags onto if you prefer to build your own.

    You will also need a 3 cell charger if you havent already got one? again I can help out if needed.

    Please feel free to email should you need any more info or help

    smudge

    Posted 13 years ago
    aracer
    Free Member

    I'd not recommend soldering directly to LiIon batteries – they're not the sort of thing to mess around with, given they can explode if mistreated.

    I'd also be very dubious about 3000mAh cells – that's higher capacity than anything I've seen from reputable manufacturers. Chances are something being advertised as that is nearer 1000mAh IME!

    You're definitely best off going to smudge IMO – he offered me good prices on cells (not something I took up – sorry for wasting your time, smudge – as I found some decent enough cells in some of my old cheapy ebay packs when I checked properly).

    Posted 13 years ago
    TheFunkyMonkey
    Free Member

    Hey smudge,

    I've got 5 18v Dewalt batteries, 2 of which are knackered and one is failing. I was just going to rebuild them with much larger 4ah nimh sub c cells. They'd cost about 45 quid.
    But for not much more, I could replace them with 18650 lion cells. I've had a peek inside a new 2ah Dewalt battery and a milwakee battery, both appeared to have 5 18650 cells in them.
    I was thinking of using 10 though, to put less discharge stress on the cells and double the runtime. The circular saw is probably the most demanding, pulling about 440 watts, equating to about 23amps. I think that current would kill an average lion pretty quick though.
    Anyhow, what do you think to a 10 cell pack, would it be up to it? And how much would it cost for you to build me one?

    I already have the multi chem lithium charger, but I don't know if it would be suitable for a 10 cell pack. As opposed to 5. Would I need a big fancy balance charger to sort it out every few cycles?

    Thanks in advance,

    Posted 13 years ago
    footflaps
    Full Member

    Answering the original Q: You need a Capacitive Discharge welder to connect up Li-ion batteries. Cost about £1k new or you can make one for a few £ but it's a bit fiddly…

    Getting them hot enough to solder with a normal iron would risk the cells catching fire / exploding…..

    Posted 13 years ago
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