Battery tag welder from China

[Fraser]

Hi all,

I have lost count of the number of times I have had to hunt around for Ni-Mh cells, or other battery technologies, that may be bought with solder tags pre-fitted. They usually cost more than the plain untagged cells as well.

I then have to solder the cells into a battery pack formation and it all takes time and can be a real PITA. Recently I have taken to buying premade battery packs and modifying the cells configuration to meet my specific battery shape needs. That seems the cheapest way to get tagged cells but the quality of the Chinese cells has been very variable to say the least.

Well I have another battery pack that needs a rebuild and I found a source of competitively priced 2000mAh Panasonic untagged cells so I bought a bulk load of them with a view to building a DIY Capacitor Discharge battery tag welder. After some research I discovered that the large capacitors required for such a project are not easy to find at wallet friendly prices in the UK and there is no guarantee that they will take the abuse that will be heaped upon them in such a high stress application.

Here is the theory of tag welder operation:



I have bitten the bullet and purchased a budget battery tag welder from China. The seller appears decent and accepted my offer of US$120 (~10% discount). The unit may be found here:

http://www.ebay.co.uk/itm/300832562092?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

Instructions are here:

http://www.alibaba.com/product-gs/667411556/Micro_computer_control_Lithium_battery_welding.html

Video of it working is here:



It is a budget model so will be limited in its capability, but I use thin nickel interconnects and mainly low current application AA or similar cells. You can use these units to do other metal on metal welds as well. i.e refitting the earth tab on a hot air gun heater tube. It is single sided welding so has many possibilities. Making tagged lithium coin cells will be very useful as I seem to be replacing many of these in equipment that is over 10 years old.

Nickel interconnect strip consumables may be bought here:

http://www.ebay.co.uk/itm/400398300016?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

Buying this unit is a calculated risk but hopefully it will be adequate for my modest needs. If not...I will modify it !

I would be hard pushed to build such a device to a good standard from UK sourced parts so it looks a reasonable deal to me. The time taken for a DIYbuild would cost me more than this unit in commercial terms. There is very little information on these units so I cannot comment on the technology inside it. It does weigh a healthy 6.5kg though. I will advise on performance when it arrives and will have the covers off to check safety etc.

Watch this space

Fraser

[Dagon]

Let us know how it goes. I was batting about the idea a of getting something similar. I'd come across those but wasn't sure about the quality, not that you'd expect miracles for that price.

[mikeselectricstuff]

Internal pics please...!

[amyk]

From the link to the instructions above:

C. High pressure inside the chassis . Do not open it.

[mikeselectricstuff]

From the link to the instructions above:

C. High pressure inside the chassis . Do not open it.

I think they mean voltage...
I have some very old electrical engineering books that refer to "electrical pressure"

[Fraser]

Be assured...the unit will be opened and photographed before I plug it in   

If I find the 220V connected to the welding tips via a resistor and an SCR... I will have serious egg on my face 

I am expecting a capacitor discharge circuit. I found a manual for a similar type of unit that appears to show just such a design.



The following web page also mentions a self discharge during 'boot' that would appear to indicate capacitors in use.

http://www.aliexpress.com/item/High-quality-Pulse-Metal-manual-for-Mini-Micro-Spot-Welding-Machine-Battery-Spot-Welding-for/657536077.html

A video guide for a similar, but not identical unit called an AD-10

aodal AD-10 spot welder use guid AD-10?—?—???


A scary quality video ! The AD-10 doesn't look too great as the power setting entry seems a little eratic, lets hope my unit is better ! It could be poor user input however !
Note: I would discourage direct hand holding metal strips whilst welding them, as in the video...a daft act if ever I saw one.


Fraser

[firewalker]

Probably a capacitor bank with some mosfets.

Alexander.

[Fraser]

One of my first challenges will be to rebuild my Tektronix THS battery pack. A somewhat ornate design needing a welder to reproduce it well.

I attach some pictures of the challenge.

Fraser

[SeanB]

That looks just like a Mag Lite battery pack.

[Fraser]

Hi ShaunB,

Really? ... I will investigate that lead. Thank you 

I tried to get a rebuild done by a German battery rebuild 'specialist'. He chickened out when he saw that it wasn't a simple 'stick' battery. It was the charging band around the lower cell that scared him off. I can't say that I like the design either.

I have just found a pretty good site for a battery welder that looks to be the same as mine. The MingDa MD-14279

Take a look here:

http://www.hk-md.cn/show.asp?id=4305&lang=2

Looks pretty versatile in the pictures.

UPDATE: Sadly my battery is a little different to that of a Maglite ... it is 4 x full size 'C' cell, with charging ring fed from positive of battery. Not difficult to make except for that charging ring. I was/am going to transfer the ring from the old battery to the new one and spot weld it to the positive battery nipple.

[Spawn]

Very interesting Aurora, every time I have to spot weld a battery package for some power tools from Bosch and other brands, I Google my eyes out but at the end I get batteries with solder tabs on them. I have two packs waiting here, each with 20 batteries to weld. I am really interested to see if you are pleased with the welder when you get it.

Time to time I check on DIY spot welders like this one here, but I want a professional looking device on my bench, if I had the sources like I had before I can make one nicely:

Sorry for the quote didnt want to dirt your topic with youtube video.

[Fraser]

Hi,

I have already seen that video and have the following comment:

For metal to metal spot welds you can be pretty crude and brutal in the application of high currents. Many such heavy continuous current welders have the metal glowing cherry red and things get pretty hot around the weld point.

Such design is to be used with great caution (better, not at all) when welding cells. The heat produced is so great that it can destroy the battery seals or boil the internals. Not a good idea. Capacitor discharge welders use high current for very short periods of time and do not produce the very high temperatures in the work pieces except at the point of the weld and even then for a short duration only.

You do need to be very careful when welding batteries as they are of fragile, temperature sensitive construction, especially Lithium types.

Fraser

[Spawn]

True, I am aware it can punch a hole in to the battery.  The video was for reference, there are couple others on youtube which are better build for battery welding, but to be honest I like the one you got there. So waiting eagerly on your findings.

[Fraser]

There is some good food for thought here:

http://www.turtlesarehere.com/html/cd_welder.html

Its a DIY welder but it looks well formed and may be a basis for improvements to my unit if it does not perform well enough in standard form.

Take a look down the page at the dissection of the cr*p Farad capacitors that he discovered during his tests. They are tarted up to look big and beefy, but are in fact total trash and departed this earth once asked to do a decent days work ! They look like Audiofoolery type ICE capacitors to me. All flash and no bang !

The capacitors do provide substance to my concerns about sourcing decent capacitors in the UK though. I would probably have bought some ICE capacitors just like this chap did, and they are not cheap ! Even a decent capacitor is probably less than thrilled to be exposed to the brutality of a CD welders instant high current load 

I wonder how long my Chinese 'budget welder' capacitors will last ?

Fraser

[mikeselectricstuff]

There is some good food for thought here:

http://www.turtlesarehere.com/html/cd_welder.html

Its a DIY welder but it looks well formed and may be a basis for improvements to my unit if it does not perform well enough in standard form.

Take a look down the page at the dissection of the cr*p Farad capacitors that he discovered during his tests. They are tarted up to look big and beefy, but are in fact total trash and departed this earth once asked to do a decent days work ! They look like Audiofoolery type ICE capacitors to me. All flash and no bang !

The capacitors do provide substance to my concerns about sourcing decent capacitors in the UK though. I would probably have bought some ICE capacitors just like this chap did, and they are not cheap ! Even a decent capacitor is probably less than thrilled to be exposed to the brutality of a CD welders instant high current load 

I wonder how long my Chinese 'budget welder' capacitors will last ?

Fraser

I wonder if the issue if finding caps with good enough discharge characteristics could be solved simply by using a  large number of low-cost electrolytics in parallel, using their lead resistance to control the peak current out of each one.

[nctnico]

Using capacitors is a bad idea IMHO. The simpler industrial spotwelders (still up to tens of kA) use a big transformer and a big triac to let the mains conduct for a short time. If you make sure the output pulse is always positive you don't need a rectifier diode.

[Fraser]

Very true.

BUT it is the transformer cost that is a killer for 'off the shelf' welders, rather than DIY's using an old microwave oven transformer. Copper costs are high and the weight of the transformer can make the shipping cost prohibitive. I personally like the idea of a transformer based, controlled output, design but it would appear that the budget end of the market uses capacitor discharge instead. Or should that read 'Capacitor abuse' instead 

At the end of the day, I am not a commercial user and just need a relatively cheap way to safely tag my AA, Sub-C and C cells    If the $120 Chinese black box contains some magic sparks that enable me to do that, I will be happy 

Fraser

[SeanB]

I got everthing bar the brass electrodes ( but have brass rod and must practise with the lathe a little) and I can make one.

[IanB]

Some general info here:

http://www.sunstonespotwelders.com/spot-welders-capacitive-discharge.php

It seems the design of a spot welder will vary a lot according to the intended application and using capacitor discharge is quite appropriate for battery tab welding.

[IanB]

Looks very nice, but I don't think I want to know the price:

http://www.sunstonespotwelders.com/spot-welding-applications-battery-packs.php

[robrenz]

I got everthing bar the brass electrodes ( but have brass rod and must practise with the lathe a little) and I can make one.

I suggest tungsten electrodes used for TIG welding instead of the brass. Most weld shops would give you the stubs that are too short to use in the TIG torch anymore but would work for you.

[robrenz]

How about using a hazard fraught portable spot welder and making electrode holders to go where the tongs go. Then use controled timing of the on time of the primary AC input to control the weld pulse duration?

[Spawn]

I suggest tungsten electrodes used for TIG welding instead of the brass. Most weld shops would give you the stubs that are too short to use in the TIG torch anymore but would work for you.

I did TIG welding myself but I am not sure what the characteristics are with a tungsten electrodes, it could stick on the batteries with high temperature and the arc, brass or copper on the other hand wont melt in to another metal, that’s why welders use copper plate if they weld two pieces and things get to hot on a metal work table or in a narrow spaces.
But since you are the real mechanist, I stand corrected if I am wrong  (so... covered my arse if i am wrong)

[robrenz]

I don't know for sure either, just thinking out loud.  Tungstens melting temp is around 6300F so I thought it would probably not alloy with the nickel at weld temp.  Brass will wet to other metals at a relatively low temp as in Brazing.

[IanB]

I don't know for sure either, just thinking out loud.  Tungstens melting temp is around 6300F so I thought it would probably not alloy with the nickel at weld temp.  Brass will wet to other metals at a relatively low temp as in Brazing.

Take a read of my Sunstone links above. In a spot weld the metal is only supposed to melt at the contact surface of the join. It shouldn't melt where it contacts the electrodes.