Problem assembling LiIon battery pack

[Don Se Wion]

Hi all,

I got some of these batteries Tenergy Li-Ion 14500 Rechargeable (http://www.thecustomsabershop.com/Tenergy-Li-Ion-14500-Rechargeable-AA-size-37V-800mAh-P480.aspx) from the store to be assembled in a custom pack but it turned out a real nightmare.

Basically, it seems I'm simply unable to solder a wire to the positive pad.
I already tried all known tricks (to me at least) like scratching the pad surface, using flux and 60/40 lead solder, but it seems that regardless all my efforts the lead doesn't want to stick to the pad at all.

The worst part of the whole story is that the negative pad did accept the lead right away, only the positive doesn't.

It's not the first custom pack I'm building, all the sabers I built so far have a NiMh packs.
This time I'm going to use a CF so I chose the LiIon, but these are the first batteries that really don't want to cooperate.

Do you have any additional suggestion to try and solve the problem ?

[Takanis]

The "flat top" batteries are tricky. Basically, you need to use a higher heat setting on your iron (if able). You don't want to keep your iron on the surface for too long; just a second or so. Also, try making some small circles with your iron when heating the surface. This allows the heat to be evenly distributed.

[amwolf]

You're not the first person to have this issue or comment on it... personally, it's a problem I still haven't figured out. You can always look for batteries with tabs "elsewhere" if your blood pressure gets too high. Feels like such a defeat though...

[Don Se Wion]

You are right, it feels just like a defeat.
However, looks like I found a local shop that seems to be willing to apply the tabs on my batteries.
In the end I think I'll follow this way, but it's kind of a shame.

[Ari-Jaq Xulden]

Don't feel as a defeat but as an outsourcing avenue. I long ago gave up trying to 100% fully solder my own packs. I too use a local company that solders the tabs on for me using a a solder welder. I have gotten to know the owner and he knows what I use them them for so he is very accommodating. With his help I can create packs I can't get anywhere. This is another reason he was willing to be so helpful, once he realized this was the only way he could meet any of my needs, thus acquire my business.
In this example I explained the type of pack I wanted to build and he even did an accordion type tab between the two cells and a connected common tab, and negative tab all to come out of the top for my connections to the pcb which I will take care of. This is a 7.4v pack consisting of 2 18350's next to a single 18650 for size comparison.

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I could have never done this small of a 7.4v stick pack on my own.My attempts were much larger.


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