High power soldering

[Theo Markettos]

I need to solder to the ends of some D cell NiMHs. I know you're not supposed to solder to batteries, but they have no tabs and welding them isn't an option. After some experimentation I'm happy that I can do it without overheating them if I have a large enough source of heat so I can do each job quickly (less than a second on each end).

I have a '150W' soldering gun. However it's pathetic. It takes maybe a minute of holding the trigger to warm up, and is incapable of melting 3mm thick leaded solder (just makes it soft like toffee). It can just about solder the batteries, but any time I want to put it down it needs a few minutes to warm again. I put it on a power meter and it's taking 60W in heat-from-cold no-load mode, so clearly something is very wrong. I've tried cleaning up the electrode terminals - helps for a minute or so but then they oxidise again and performance gets worse. A new tip hasn't improved it. I'm also not terribly happy with the way its performance depends on what metal is across the tip - put a blob of solder across the end, the resistance goes down and so the heating moves to the terminals and not the tip. Sounds like I was ripped off for the 2 pounds I paid for it :)

So I've been wondering about another iron. Alternatives seem to be a

100Wish 'conventional' pencil-type soldering iron, or a gas flame thing. I already have a 45W temperature controlled iron for the small stuff, so I just want something for beefy jobs. I'm unlikely to be soldering pipes, but will use it general metalwork (not necessarily electrical). Something relatively crude is fine - don't need temperature control etc etc. I know where I am with pencil irons, but have no experience of gas.

So any suggestions for what sort of iron to buy?

Thanks Theo

[Andy Dingley]

Antex, 100W, not temperature controlled, 15 quid(ish) from CPC

Or: The instant iron you have, with a chunk of copper or brass screwed / clamped / brazed to the tip. Don't make the thin bit too thin though, or else you reduce the power of the element.

[Andrew Gabriel]

There's something wrong with it, although a soldering gun has very different characteristics from a soldering iron, and you can't compare wattages. Soldering guns have very low heat capacity bits, since they have to heat them up each time you use them, but it shouldn't take longer than 10-15 seconds.

A 45W iron is more than enough to solder the batteries, but the heat capacity of the bit is more important than the power.

With a temperature controlled iron, I would use 800F which would do the job in a fraction of a second. Counter intuitively, the high temperature means you can solder much faster, and get less heat passed into the object. The power of the iron is irrelvant, it's the heat capacity of the bit which matters for this sort of thing.

[Dave Plowman (News)]

Sounds like a poor design. I have a Weller one which works well. Gets so hot the tips just about melt.

A bigger bit for your temp controlled iron, and turn it up a bit. That's what I do here for soldering cells.

[The Natural Philosopher]

The standard tool for this is a hammer (double) headed tip that goes on e.g. a weller. Its a massive copper bolt and takes an age to heat up,

When its hot you put the cells end to end in a spring loaded tray and,after tinning the facing ends, Insert the hammaerr head between the and when molten both sides, remove it and the springs (or a fast hand) slaps the cells together.

They key is a lot of thermal mass in te right shape, so the tip does not cool

They are available from model battery suppiliers.

If OTOH you are NOT making up series packs just go for am iron with a LARGE tip. Or one you can add a large tip too..the thermal mass is what you want.

Her are some useful guideline products.

uuou can source similar in the UK that will do the job.

Ultimately its best to spot weld to nickel cells if you can find someone to do it, but most people in the RC world have successfully soldered cells with a hot iron a big tip and a bit of skill. I've even solrdered aluminium electrodes on Lithium polymer cells..with the right flux. Evils stuff, but it does work.

[brass monkey]

Take more water with it ;)

[The Natural Philosopher]

Hehe. Not really. The fumes give you instant emphysema for about 4 hours. I will never fail to 'make sure you have extremely good fume extraction or are in a well ventilated space' again. :-)

[Matty F]

I made a solder pot that sits on a solid stove element:

don't you clip the batteries into battery holders?

[NT]

The most likely candidate would be an old 65w or more Solon soldering iron. Good for a variety of medium heavy soldering jobs, and often last a life time.

NT

[Dave Plowman (News)]

No use for high current apps. Like rechargeables are often used for.

[Dave Plowman (News)]

Technology has moved on a long way from then. My 50 watt low voltage temperature controlled iron will easily do what those could.

The only time a large wattage old fashioned iron is useful is for continuous use like soldering tinplate.

[NT]

Yes, its moved on, but theyre still perfectly good for what they were intended.

NT

[Dave Plowman (News)]

But no use for other smaller stuff - whereas a temperature controlled low voltage one is. Simply by swapping bits.

I've got a couple of those lying around somewhere totally unused. Unlike other tools which do get used once in a while.

[NT]

Tempco has certainly extended what small irons will do, but in the end theyre only 40 or 50w with a small bit. The old Solons are 60 to over

100w, so will do bigger workpieces.

NT

[Dave Plowman (News)]

There is no comparison between an old Solon and a decent modern iron in terms of how much heat it gets to where it's needed. Solons had a vast area which conducted heat away from the tip. A decent modern iron a fraction of that. You can tell by how long it takes to get it up to temperature. And a decent low voltage make will have a variety of bits available including larger ones.

As I said if you are regularly soldering large areas like tinplate or brass they still have their uses. But not for what most people solder these days.

[Bernard Peek]

Have you considered buying them tagged?

[Theo Markettos]

buying 20 cells :(

Theo

[Theo Markettos]

And no good for any kind of vibration, especially when they'll be used outside.

Theo

[Theo Markettos]

Thanks. It's a Weller TCP, the one with the magnetically controlled thermostat, on the standard 700F bit. So I think I'll invest in some 800 and 900F bits.

FWIW I'm not using unleaded solder... when I'm doing unleaded electronics work (on digital controlled irons) I find that I need at least 425C (ie 780F) to get anywhere at all. Some fine work recently I needed 460C. The higher temperatures really did make the job easier.

Theo

[Theo Markettos]

I saw one of those on a how-to-solder-cells youtube video... I think someone had made their own. Looks useful, but my pack is only one cell thick so I need to solder strips between cells. Chopped up bean tins seem to do the job well enough - with plenty of flux and making sure everything is tinned beforehand.

I think I'll give one of these a go:

(that's the biggest available tip for my iron, in 900degF flavour)

I started practicing with dead alkaline AAs from the recycling box, and have now graduated to zinc carbon Ds from Poundland. I think I've mostly got the technique now, but the Ds need a fair bit more heating (perhaps more than NiMHs owing to the big zinc case, I don't know).

Theo