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Ok, probably not the best place to post, but I'll try here before I run around trying to find electronics forums and doing the sign up stuff. Someone must know about this stuff.

I'm trying to make battery packs. 9xAAA batteries, bundled together to put out 8.4V for use in an RC plane. I bought myself a new soldering iron (50W) cos my old budget 35W one is crap, some solder tags and some solder, but I think it might all be wrong. I crank the iron up to max and heat up my battery terminal and solder tags, but can I get the bloody solder to melt? Can I ****!!!! I've always had problems with soldering ... getting the solder to melt, and heating up the components, and my soldering iron tips always get ruined within about 10 seconds and dont seem to conduct heat anymore, even when cleaning them as often as possible .... so I end up using parts of the soldering iron that just arent practical for heating up the components. I must just be useless at soldering.

Perhaps batteries suck up too much heat, so the iron cant get it hot enough to melt the solder? Is it normal for soldering iron tips to get skanked up, or are there technique to keep them clean? Anyone got any tips at all?

Edit: I just tried to heat up a solder tag on its own, and I cant get that bloody thing hot enough to melt solder on it! WHY IS SOLDERING TO HARD?!?!

You should file the end clean, then heat up and melt a little solder on to the tip. Now you're ready to start.

You should heat the item to be soldered, not the solder itself

As for soldering batteries, I'm not convinced it's the healthiest thing to do. I would imagine the end of a soldering iron is earthed, so at best you'll drain the battery and at worst you'll fry it.

You can get plastic battery holders in places like maplin. Then you solder the wire ends of the holder, not the battery itself.

" You should heat the item to be soldered, not the solder itself"

Just what I was going to say when I read the thread title .

You do get batteries with little tags to solder onto, I think the problem is that the batteries are conducting too much heat like you say. Have you tried soldering on plain wire?, there should be no problem with that as long as your iron is working properly.

Of course, lead-free solder is slower to melt too, maybe try some good old fashioned poison solder (but don't mix lead-free and old solder). Perhaps some flux would help, like a flux pen that you'd draw on the bits you need to solder, but at the end of the day soldering right onto battery contacts simply won't hold, the solder could be talked into falling off a smooth surface like a batter end (hence the tagged batteries you get from electronics suppliers).

Touch the iron to see if it is hot enough Kidding, don't do that!

Your solder should melt if its hot enough, so if the iron is hot enough, make sure what you have is actually solder, you might have been scammed, when I used to solder 3 years a go, when I made a weird little organ thing, I held down the component I wanted to solder with the iron, the put the solder to it. If you have a wet sponge, get the solder to the iron then cool it off on the sponge and make little solder balls you can throw at people if you get that frustrated working the thing.

Thanks for the input guys. Well, I knew that stuff, but you've helped me to realise what I'm doing is probably fruitless. Basically the packs I use on my RC plane are 9xAAA cells connected then rapped in insulating shrink rap. No plasic case or anything. The problem is, they're all 650mah .... 700 mah ... but I can buy AAA batteries with up to 1200mah, and today I even saw 1800mah AAA batteries on ebay (although I'm not convinced they'd be any good). So I wanted to make my own battery packs so I can double my 5-7 minutes flight time.

I think Van is right when he mentioned the solder tagged batteries. What I tried to do is solder together normal batteries with solder tags for compo use. Basically, I think what I'm trying to do isn't gonna work. It's a shame cos I bought 16xAAA 1000mah batteries for £11 delivered, where as a 700mah 7cell battery pack normally costs £12-£15. So if I could get it to work, I could've made 2 longer running packs for less cash than it costs to buy one.

I can't risk a dodgy solder connection either. If I'm diving to the ground and my battery shorts out, I'll be digging the fragments of my plane out of the field.

Anyways, cheers for the input. Gonna have a rethink. The idea of a plasic battery holder is good, but unfortunately it'll probably make the pack too big, and I doubt I'll find a 7-cell AAA battery holder.

A 50W iron will easily solder untagged AAA cells. Not the easiest thing for a beginner though as they will absorb a fair bit of heat.

Easiest way is to heat up the battery and melt some solder onto it. Then get some solder on the wire. Then heat up the battery solder again, position the wire and heat both until the solder flows which should happen fairly quickly.

I prefer using untagged cells and connect using small pieces of wire. Flexible wires give you a little movement so you don't have to be too precise with the connections.
The tags work better when spot welded instead of soldered.

Some other tips. When heating something up have some solder on the tip. The solder will conform to the shape of the component aiding heat transfer. Sometimes it helps to wiggle the tip a little while the component is heating up.
Don't turn the heat up too high. You probably want somewhere near the middle not the hottest temp. If it's too hot the flux will burn off too quickly.

The goal is to heat everything up quickly and put as little heat as possible into the components. A common mistake is to get distracted trying to make a joint and heating everything up far too much. If it isn't working stop, let everything cool and start again.

I'd avoid filing the tip as many are plated iron. If you file through the plating solder doesn't stick to the iron and flux eats it away.
All you really need to do to keep it clean is to clean off the burn flux occasionally when the iron is hot. A wet sponge is the proper method but any cloth that won't melt will work.