Tagging Button Cell Batteries

[JohnInStockie]

Hi Everyone

I wondered if anyone had found any animations or vids or pics on how to tag button cell batteries.

I was planning to go seeking some advice on using button cells in Twist battery case.

I would assume that the case may need some slight widening, and there maybe some other steps required to be taken.

Any tips, links or advice very welcome indeed.

Thanks

John

 

[flecc]

The only option is soldering onto the cells John, but to do that does carry some risk, especially of you are not very experienced with soldering. The case wouldn't shut fully so that might cause a problem if the base area ends up too wide for the platform on the bike.

I think it could be a difficult option, and I'd hesitate to try fitting button cells in there. I guess that you might have been attracted to those Ebay 11 Ah cells at very low prices? Bear in mind we know nothing of their quality or discharge rate capability.

If you do take the risk, use a hot soldering iron of at least 25 watts and minimise the soldering time to avoid heating the cells. Follow the same linking formation as the existing cells, and use wire of at least 16 amp capability. It's essential that you use a suitable card layer with holes punched through at the soldering points to prevent any chance of your links shorting into the next cell casing. This can easily happen if a wire link melts through the plastic coat on the cell when the cells get very warm under charge or discharge. There's a real possibility that the battery meter won't work afterwards, it won't work with all cell types.

Definitely not a recommended thing to do, and I think a spare battery "Grandad" fashion is better for extra range.
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[JohnInStockie]

Yes Flecc you read my mind

 

[BigBob]

If you do take the risk, use a hot soldering iron of at least 25 watts and minimise the soldering time to avoid heating the cells

Could I just add the warning that it isn't only the soldering iron wattage that is important it's also the size of the tip. Apart from needing sufficient power (watts) it also needs a large enough tip to prevent a dip in temperature when it is applied to the cell.

Having soldered cells together for many years in another context, it is generally accepted that any contact between the iron and cell of longer than ~3 secs can start damaging the cell. The reason you need a large enough tip is that the cell acts as a heat sink once the iron is applied, cooling the tip. It then needs time to regain it's temperature and heat the cell sufficiently to melt the solder.

The iron I've used for many years is only 55w @ 12v (mainly because it's used in the field away from mains supply) but it has a tip approxiamately 25mm long and 15mm in diameter - sufficient to act as a heat 'reservoir'.

The other thing you need to careful of is to clean any remaining flux off thoroughly - as it tends to be acid based it can cause problems with the connection in a surprisingly short time.




BB

 

[flecc]

Quite right Bob, at least a 4 mm tip on small cells and allow heat to recover with each contact. I got lazy as I've given this advice so many times before in here!
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[Ian]

On the subject of soldering cells I (and others) have found modern lead free solder to be greatly inferior to the old 60/40 alloy, amongst other factors it has a higher melting point and I wouldn't recommend it for soldering cells. Tin/silver alloy solder is superior but expensive, but good old fashioned 60/40 alloy is often available from ebay sellers, I recently bought a large roll of 60/40 on ebay for less than the price of a small coil of lead free from Maplins.

 

[BigBob]

On the subject of soldering cells I (and others) have found modern lead free solder to be greatly inferior to the old 60/40 alloy, amongst other factors it has a higher melting point and I wouldn't recommend it for soldering cells. Tin/silver alloy solder is superior but expensive, but good old fashioned 60/40 alloy is often available from ebay sellers, I recently bought a large roll of 60/40 on ebay for less than the price of a small coil of lead free from Maplins.

Another instance of older being better I actually bought several dozen smaller rolls from a discount shop for 25p ea a few years ago and am still using it.

The other problem you tend to find with Tin/Silver is the melting point tends to be higher leading to a higher liklihood of damge to cells.

Another thing I've found is that some/most silicon sealants can cause corrosion on cells and it pays to use a specific electrical sealer or even a hot glue gun where the sealer may come into contact with the connections.


BB

 

[Baboonking]

YouTube - Making Custom battery Packs

Battery Pack Building: end-to-end soldering

Easy once you get the hang of it. Use lots of old nonrecharable batteries to practice on first

I've just discvoered the illegal lead ebay stuff too , much easier to use. though i've used the legal lead free solder for battery soldering and it worked fine for my battery packs.

 

[Ian]

I don't think the solder itself is illegal, it can be legaly used to repair non RoHS equipment imported before July 2006, or so my employers tell me.

 

[JohnInStockie]

Thanks for the info guys, and that video is excellent BaboonKing. Watching a vid like that shows me exactly what you mean (I'd never seen a iron head like that before).

Is the technique roughly the same for buttoned batteries then?

 

[JohnInStockie]

Whats that braid thats being used to connect the cells. Could you use insulated copper wire (like from normal electricity cable).

PS - I have never soldered anything other than a Gameboy control once (about 3 years ago) so all tips on soldering welcome.

 

[flecc]

Your Twist cells are a completely different formation John, as seen on this page, so as you've guessed you'll have to use linking wire or strip. The method is to use as large an iron as possible to tin both the button and cell end, doing all the cells first.

Then having made up the links, tin the ends of those as well. Then the amount of heat needed to join the links to the cells will be minimal.

If using cable, make sure it has a minimum 15 amp rating. Bear in mind what I posted earlier, it's important that you make up a card insulating layer over the cells with openings through which to solder, or insert card strips under the connecting wires. Don't rely on the thin plastic coat on the cells and the insulation on the cable to prevent shorting of button to cell casing via the cable links, since they will soften when the battery is getting hot internally. You'll also need a card layer on the sides of the made up pack to insulate it from the connection cables passing it.

Also, have you checked the case will shut when using button cells plus the thickness of the soldered connections, insulation layers, and cables passing over the surface for the connections to the terminals and battery meter? I don't think it will be able to anywhere near close from my experience of using flat cellpacks in these Twist batteries, those being very much slimmer.

P.S. If you're making up an auxiliary pack ignore the comments on the Twist case and cell formation of course.
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[BigBob]

Rather than cable it may be worth trying de-soldering braid as it's flat. Just need to be particularly careful with the insulation you use on the cells



BB

 

[Ian]

All the advice given has been of the highest quality but it seems an awfull lot of trouble when a ready made pack that can easily be transplanted into the Twist case can be bought from Powacycle for what is likely to be a slightly cheaper overall price. I have used those ebay cells as part of a pack and they do work, but I can't verify that the capacity really is 11Ah, especially under the discharge conditions on a bike, remember many things on ebay are not what they seem.

 

[JohnInStockie]

Could I just add the warning that it isn't only the soldering iron wattage that is important it's also the size of the tip.

I have managed to buy a twin mains set from Aldi compring of :-
- a 25W iron with a screw held pointy tip,
- an 80W iron with a screw held bent screw driver tip,
- 100g 1.5mm Flux cored general purpose lead based electronic solder,
- 20g Flux,
- 1.6m 2.5mm Desoldering braid,
- iron stand,

All in a plastic carry case for either 4.99 or 6.99, which seems agood deal (I think knowingnothing about soldering).

Any tips where I can get a large tip/bit thingy to go into the 80W iron?

John

 

[flecc]

The tips are specific to each manufacturer's irons John. I can't suggest where to start looking because I don't know that iron.

That said, I think that 80 watt iron should be ok as it is for soldering braid links, I certainly wouldn't hesitate to use it as it's heat recovery time will be quick. I normally use about a 25 watt with a 4mm tip with no problems in many years of soldering cells of various types.
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