Cleaning the Battery contact with fine sandpaper helps, using extra Flux is never wrong 
For nickel, steel and joints that are problematic i use some very old flux that i got from an work college (he is now over 75years old) it is some very old verry agressive stuff but it works perfect. The right solder is also a point. But i have not read a word about one very important point. How much power has your soldering iron?
If you are using a iron with not enough power soldering big things is a pain in the ass. And it is more likely that you damage something because you have to stay way to long on the joint until it is really hot enough.
I do not say everybody needs a 60 or 90W soldering station (if someone is willing to do it with a 25W iron and is also happy with the result thats fine), but the power defenitly helps! Today when i am soldering copper MCPCBs, Springs, batterys… . . (with a 90W station) everything works like it should. But i realy do not want to go back in time when i was using a small 25W Ersa station. It worked but it was not always fun.
pieman7, yes, I linked flat tops because the conversation was about soldering a bump on them to work in this kind of light. I like a flat top better, always looking for the least resistance and don’t like the added button top. Button tops are always an added aftermarket deal as the cells were originally made for packs and as such, are all flat tops.
For the same reason Dale said about button tops and resistance, taken a bit further I would rather have solder rubbing against a PCB then Steel!
And you don’t need to go crazy with the solder, just a dab will do you!!
+1 each there. Don't like those suspect button tops. I did buy a bunch of the 30Q BT's but didn't realize then it's not risky and pretty easy to solder the cell tops. True, they can be kept lean and mean, matter of clearance.
Do Sanyo GAs require solder blobs as they already have a raised top (though not a button)?
The GA's are the highest flats I've seen or gotten. They do protrude clear from the surrounding top and edges of the wrapper - least all the ones I got. I would feel better with a small dome of solder on them though, and as TA said, soft solder makes a better contact for a PCB than steel.
It depends on the light but for most they are raised enough.
Thanks. I was referring to the Q8.
when will this light be available?
Here is the stock PCB with pads added for modding to 4S or 2S. This doesn’t change any trace, only removes cover insulation to make pads. The green is where you would cut traces to mod it.
Strictly you only need the 8 pads left and right, but the top ones will help make jumps shorter and cleaner. Changing the one center bottom pad to two separated ones wouldn’t hurt either.
No plans on changing the ledboardnow that a copperDTPuad board has been made.
Still things to work on, it is the ld saying here: “it is done when it is done”
There is also another option to get a nice button top cell better than just solder
Sand or clean the contact and add solder paste or do a solder button
Get a 5x2mm brass pill 5mm x 2mm Brass Button
Get a bit solder or solder paste on one side of the pill
Get a burner heat up the pill a lot at least 450-500 degree celsius
Put the brass pill on the flat top
Sand the oxidation of the brass top
Keep in mind that a soldering iron tip is nickel plated,
so the problem is getting enough heat in the flat top so that the solder can stick to it
Gearbest has GAs again stocked up below 4.5$ a piece
17.39$ for 4 GAs
3€ is a bug if you order 1000 you are at 3.6€
P.S. if your outside EU you can check out 20 at 3€ nice bug
Yeah but for us EU nkon means € instead of $ and a 21%VAT
Changing the choice
For four
Gearbest GA $4,50 a piece
Nkon 30Q €4,45 + €0,93 VAT + €1 shipping = €6,38$7,- nearly twice
But I saw they have good AAA cells so might just order it anyway 
Need the best cells for reviews anyway.
TheOnlyDocc
I got your point, I have a 40W now with copper tip, I think I will buy a 60W one.
Lexel
Thanks. I’ll probably keep it simple and pay some extra for tabs.
The price doubles with GearBest's insane US shipping charges - GearBest is not an option from the China warehouse.
Not really changing the board there, just exposing the metal.
Post parcel, with full tracking, to the USA is only EUR 11:33; which should make this a nice deal for everyone in the US too.
OP updated!