Battery tag welder from China - Page 1
Forum section: electronics / testgear

author: Fraser
author_rank: Super Contributor
timestamp: February 17, 2013, 11:37:08 am
content: 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.l2649Instructions are here:http://www.alibaba.com/product-gs/667411556/Micro_computer_control_Lithium_battery_welding.htmlVideo 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.l2649Buying 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 spaceFraser

author: Dagon
author_rank: Regular Contributor
timestamp: February 17, 2013, 12:18:01 pm
content: 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.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: February 17, 2013, 12:18:35 pm
content: Internal pics please...!

author: amyk
author_rank: Super Contributor
timestamp: February 17, 2013, 12:21:38 pm
content: From the link to the instructions above:Quote

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: February 17, 2013, 12:29:03 pm
content: Quote from: amyk on February 17, 2013, 12:21:38 pmI think they mean voltage...I have some very old electrical engineering books that refer to "electrical pressure"

author: Fraser
author_rank: Super Contributor
timestamp: February 17, 2013, 01:19:19 pm
content: Be assured...the unit will be opened and photographed before I plug it inIf I find the 220V connected to the welding tips via a resistor and an SCR... I will have serious egg on my faceI 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.htmlA video guide for a similar, but not identical unit called an AD-10aodal 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

author: firewalker
author_rank: Super Contributor
timestamp: February 17, 2013, 01:41:10 pm
content: Probably a capacitor bank with some mosfets.Alexander.

author: Fraser
author_rank: Super Contributor
timestamp: February 17, 2013, 02:52:27 pm
content: 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

author: SeanB
author_rank: Super Contributor
timestamp: February 17, 2013, 02:55:30 pm
content: That looks just like a Mag Lite battery pack.

author: Fraser
author_rank: Super Contributor
timestamp: February 17, 2013, 03:07:08 pm
content: Hi ShaunB,Really? ... I will investigate that lead. Thank youI 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-14279Take a look here:http://www.hk-md.cn/show.asp?id=4305&lang=2Looks 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.

author: Spawn
author_rank: Frequent Contributor
timestamp: February 17, 2013, 03:22:17 pm
content: 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:QuoteSorry for the quote didnt want to dirt your topic with youtube video.

author: Fraser
author_rank: Super Contributor
timestamp: February 17, 2013, 03:31:20 pm
content: 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

author: Spawn
author_rank: Frequent Contributor
timestamp: February 17, 2013, 03:42:02 pm
content: 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.

author: Fraser
author_rank: Super Contributor
timestamp: February 17, 2013, 04:11:04 pm
content: There is some good food for thought here:http://www.turtlesarehere.com/html/cd_welder.htmlIts 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 loadI wonder how long my Chinese 'budget welder' capacitors will last ?Fraser

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: February 17, 2013, 04:36:55 pm
content: Quote from: Aurora on February 17, 2013, 04:11:04 pmI 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.

author: nctnico
author_rank: Super Contributor
timestamp: February 17, 2013, 04:58:08 pm
content: 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.

author: Fraser
author_rank: Super Contributor
timestamp: February 17, 2013, 05:12:08 pm
content: 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' insteadAt 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 cellsIf the $120 Chinese black box contains some magic sparks that enable me to do that, I will be happyFraser

author: SeanB
author_rank: Super Contributor
timestamp: February 17, 2013, 05:33:44 pm
content: I got everthing bar the brass electrodes ( but have brass rod and must practise with the lathe a little) and I can make one.

author: IanB
author_rank: Super Contributor
timestamp: February 17, 2013, 05:54:03 pm
content: Some general info here:http://www.sunstonespotwelders.com/spot-welders-capacitive-discharge.phpIt 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.

author: IanB
author_rank: Super Contributor
timestamp: February 17, 2013, 06:01:39 pm
content: Looks very nice, but I don't think I want to know the price:http://www.sunstonespotwelders.com/spot-welding-applications-battery-packs.php

author: robrenz
author_rank: Super Contributor
timestamp: February 17, 2013, 06:28:54 pm
content: Quote from: SeanB on February 17, 2013, 05:33:44 pmI 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.

author: robrenz
author_rank: Super Contributor
timestamp: February 17, 2013, 06:34:38 pm
content: 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?

author: Spawn
author_rank: Frequent Contributor
timestamp: February 17, 2013, 06:40:14 pm
content: Quote from: robrenz on February 17, 2013, 06:28:54 pmI 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)

author: robrenz
author_rank: Super Contributor
timestamp: February 17, 2013, 07:09:15 pm
content: 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.

author: IanB
author_rank: Super Contributor
timestamp: February 17, 2013, 07:26:20 pm
content: Quote from: robrenz on February 17, 2013, 07:09:15 pmTake 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.

author: robrenz
author_rank: Super Contributor
timestamp: February 17, 2013, 07:34:31 pm
content: Quote from: IanB on February 17, 2013, 07:26:20 pmUnderstood, but when you spot weld two .003" thick pieces of metal together do you think the melt can be controled to not reach the surface that is touching the electrode?

author: IanB
author_rank: Super Contributor
timestamp: February 17, 2013, 08:12:19 pm
content: Quote from: robrenz on February 17, 2013, 07:34:31 pmI think maybe it can be so controlled, but it requires very precise control of the weld parameters: energy, maximum current, pulse shape, pulse timing, etc. I think a good weld requires about the same amount of precision that you demonstrate in your machining videos...

author: robrenz
author_rank: Super Contributor
timestamp: February 17, 2013, 08:21:45 pm
content: Thanks, yes probably doable but you will need something with more finess than a $200 chinese unit

author: nctnico
author_rank: Super Contributor
timestamp: February 17, 2013, 08:24:51 pm
content: Quote from: robrenz on February 17, 2013, 07:34:31 pmIf you have precise control over the welding parameters you can make excellent spot welds. I have worked on spot welding control systems which keep the weld invisible on one side for manufacturing cars. Not hobby stuff by far though.

author: mzzj
author_rank: Super Contributor
timestamp: February 18, 2013, 12:27:46 am
content: 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)Copper melts to other metals as well, they even use copper plate/shim for serious high current battery packs. Obviously spot welding copper is royal pain, but doable with right equipment.I was less than satisfied with pure copper electrodes, too soft and tends to stick to workpiece. Copper-molybdenium and copper-tungsten should be better alternatives but availability is not that great..Next I was planning to try 4mm pure tungsten TIG electrodes.Another way around capacitor problem is to use 350v caps coupled trough transformer. Much easier to get required energy this way than with 12v caps. 350 to 450 volt inverter electrolytics are much easier to find and biggest ones put out serious punch. Also easier for your thyristor/igbt.Transformer coupling also has its problems, like redesign the windings for short duty pulse and if you use toroid transformer you probably have take care of the core (pre-)demagnetizing before each shot.

author: ftransform
author_rank: Frequent Contributor
timestamp: February 18, 2013, 12:53:03 am
content: Quote from: robrenz on February 17, 2013, 06:34:38 pmor some kind of fast relay? Modding a real welder would be highly favorable

author: robrenz
author_rank: Super Contributor
timestamp: February 18, 2013, 12:59:03 am
content: Solid state relay with flywheel diode with 555 timer for pulse length?

author: nukie
author_rank: Frequent Contributor
timestamp: February 18, 2013, 03:55:51 am
content: EDIT: Apparently this is no good for materials other than steel. So it isn't very helpful.This is nice but limited adjustabilityhttp://www.robbe.de/welma-2000-punktschweissgeraet.html

author: Marco
author_rank: Super Contributor
timestamp: February 18, 2013, 04:32:46 am
content: Those big spot welders do work with transformers, but I doubt the ones for the battery tabs do ... a cheap electrolytic capacitor can disintegrate a screwdriver, I think it can make a spot weld on a battery tab.

author: mzzj
author_rank: Super Contributor
timestamp: February 18, 2013, 01:48:12 pm
content: Quote from: ftransform on February 18, 2013, 12:53:03 amRequired power levels make direct ac powered battery spot welders impractical. We are roughly speaking about 1 to 10 ms pulse duration with 200-400 Joules of energy. Even the low end gives 20 kW of pulsed power and upper end is 400 kW !

author: robrenz
author_rank: Super Contributor
timestamp: February 18, 2013, 03:00:30 pm
content: IMHO the portable spot welder will definitely work. It is meant to have intermittent primary energization as that is how you control the spot weld time. It uses a finger controled switch on the primary already so putting a SSR with pulse timer on the primary is not a big deal as long as you don't violate the 50% duty cycle which should not be an issue for sub second weld times. The secondary current with 6" long tongs is 5500 amps and would increase if shorter adapter bars made to hold the small electrodes were used. As you can see the secondary current is affected by the tong resistance. To get optimum current for battery tabs It may require using even more resistance than the 18" long tongs. In that case welding cable could be used with the optimum length/Ga to get a hand held probe unit that would be easier to manipulate and have the right current. Most quality spot welders use a two pulse setup with one light pulse to clean/establish good contact then the actual weld pulse which could be impimented here also.The weld shown is .006" steel shim stock and the weld time was me just bumping the finger switch as fast as I could. You can see by the peel test that these are good welds andnothingabout this setup is optimal. Remeber this thing is capable of welding two pieces of .062" steel easily with 12" tongs so I dont think power is an issue.Edit:At 42 µOhms per 12" of the .625" diameter copper the current drops 950A per 6" change in tong length (2 tongs x 6" = 12") so it will be easy to drop to even lower currents if that makes the weld easier to control. But I think a very short higher energy pulse is more desirable as there will be less heat affected zone and heating of the battery in general.

author: Marco
author_rank: Super Contributor
timestamp: February 18, 2013, 03:36:44 pm
content: It will certainly work, question is whether it's economical or smart ... the copper in a mains frequency 1.5 kW transformer and the electrodes is probably worth more than the entire machine the OP bought. You still of course have to remove those ridiculous electrodes from the spotwelder as well and bodge something like the pressure activated electrode system from the OP's machine.For the price OP's machine makes perfect sense to just outright buy ... if you're determined to DIY it's a big enough project mechanically that you can probably put a little more effort into the electronics as well (charging a capacitor to a variable voltage and discharging it through a thyristor and an aircore coil isn't that much harder than modding a spot welder).

author: robrenz
author_rank: Super Contributor
timestamp: February 18, 2013, 04:03:17 pm
content: I am not saying what the OP has purchased is bad. I really hope it works and If so it is probably the most economical way to get a tab welding system.I was simply suggesting a much simpler approach than the DIY capacitor discharge units mentioned in this thread. All of the ones I have studied on the web are monumental projects with lots of tweaking and a huge amount of time and money and smoked components involved. I paid $100.00 for the Dayton unit pictured and the Harbor Freight unit is only $160.00 in the US. Add some weld cable, electrodes, SSR with simple pulse timer and foot switch and you have a funtional unit. All the DIY units I have seen apply pressure to the two electrodes by hand.

author: Marco
author_rank: Super Contributor
timestamp: February 18, 2013, 04:48:51 pm
content: Here's a pretty simple one (if the SCR is big enough the inductance of the welding cable is enough to limit dI/dt I guess, with an inductor you could use higher voltage electrolytics though).http://www.philpem.me.uk/elec/welder/http://www.rcgroups.com/forums/showthread.php?t=763308

author: sorin
author_rank: Frequent Contributor
timestamp: February 19, 2013, 04:28:56 pm
content: how about using mosfet??

author: Flávio V
author_rank: Regular Contributor
timestamp: February 19, 2013, 07:35:46 pm
content: Would medium sized super caps(+-500F) be good for the battery welding?(i have 2 maxwell 350F ones so well...interested)

author: IanB
author_rank: Super Contributor
timestamp: February 19, 2013, 07:48:06 pm
content: Quote from: Flávio V on February 19, 2013, 07:35:46 pmIt's not about power, it's about control. For a battery tab weld you need a small amount of energy that is controlled with great precision.The aim is to make a tiny little weld, not to explode the battery into a glowing fireball

author: Psi
author_rank: Super Contributor
timestamp: February 19, 2013, 07:51:58 pm
content: I've tried welding battery tabs with some maxwell caps and couldn't get it to work reliably.I think you need PWM control of the current to make it work.However, i didnt have those battery tabs with the slot cut in them to force the current through the battery metal which would probably make it easier to do.

author: robrenz
author_rank: Super Contributor
timestamp: February 19, 2013, 08:00:26 pm
content: In looking at the sunstone units 100 watt seconds or joules is more than enough to do tabs.The spot welder above is 1.5kVA so it isroughlycapable of 1500 watt seconds.

author: Marco
author_rank: Super Contributor
timestamp: February 19, 2013, 08:11:53 pm
content: Sorin, a 5$ thyristor can handle a kA surge current and is trivial to drive (you just have to be a little careful with dI/dt). With MOSFETs you need a more complex drive and much much more silicon (IGBTs too, although cheaper than MOSFETs).Flavio, the balance of voltage/capacitance/ESR for a supercap just doesn't work. If you want high currents you need to charge it to near it's max voltage, at near it's max voltage it takes way way too long to discharge when you short it through the battery tab (destroying the cap in the process). They could work with MOSFETs or IGBTs I guess, 800 amp short circuit current will be able to get things hot, but as I said Thyristors are cheaper and easier so better to use electrolytic capacitors.

author: sorin
author_rank: Frequent Contributor
timestamp: February 19, 2013, 10:54:08 pm
content: Quote from: Marco on February 19, 2013, 08:11:53 pm50RIA20 cost $15

author: Psi
author_rank: Super Contributor
timestamp: February 19, 2013, 11:42:32 pm
content: Quote from: Marco on February 19, 2013, 08:11:53 pmThe maxwell caps i tried to use are rated to 600A max discharge.I tried various combinations of 9 caps (series/parallel) with the wire length/gauge to the weld point chosen to limit shortcircuit current to 600A / 1200A / 1800A (parallel caps)

author: Marco
author_rank: Super Contributor
timestamp: February 20, 2013, 12:32:21 am
content: Quote from: sorin on February 19, 2013, 10:54:08 pmThis one isn't though :http://www.digikey.nl/product-detail/en/S4065KTP/S4065KTP-ND/967811

author: robrenz
author_rank: Super Contributor
timestamp: February 21, 2013, 01:55:18 pm
content: After some more research on the Sunstone welder site:They make transformer style welders also and 1.5kVA is the rating of their smaller unit and the duty cycle is the same at 50%. The weight of my spot welder is 28 lbs and their unit is 31 so that means the spot welder I have should be a good match (similar weight in copper and laminations). They fire the primary in whole multiples of line cycles from 1 to 100 and also have multi pulse modes.Tungstenisthe higher performance material for electrodes as opposed to copper.I won't post any more on this thread I will start a project thread when I get the time.

author: firewalker
author_rank: Super Contributor
timestamp: March 06, 2013, 02:07:50 pm
content: Nice! Enjoy it! I am also expecting waveforms!Alexander.

author: robrenz
author_rank: Super Contributor
timestamp: March 06, 2013, 02:13:08 pm
content: Great! very interested to see how they control the triac with an inductive load. Yes please show waveforms.

author: robrenz
author_rank: Super Contributor
timestamp: March 06, 2013, 07:14:31 pm
content: Nice pictures and the unit looks pretty good also. Makes me very confident that my spot welder will make an awesome tab welder. My problem may be taming the output down enough for small parts. More resistance on the secondary does reduce the output current so it might just be using longer runs of #1 welding cable to the actual welding probes. Since yours is transformer based you dont have to worry about capacitor recharge times but you still have to watch out to not exceed the duty cycle whatever that is. My spot welder is only 50% duty cycle but that should not be a problem.I would be very interested in the triac input as to whether they are using zero turn on and random turn off so they can just energize the primary for a certain number of milliseconds duration to control the weld power level. And is the lowest power setting less than half of a line cycleAlso have read about dual pulse where the first pulse is set just low enough power to barely stick the parts together but establishes a more consistent contact resistance for the main pulse that actualy does the final weld. (supposed to give more consistent results) I figure initialy I will just fire the SSR I end up using on the primary of my spot welder with my DG1022 and I can just make arbitrary waveforms to control the dual pulse durations.If you have a differential probe for your scope or if the secondary is truly isolated you could connect to two points on one side of the secondary acting as a shunt and read the current waveform of the weld pulse.

author: mzzj
author_rank: Super Contributor
timestamp: March 06, 2013, 07:34:37 pm
content: Seems to work better than I expected.How thick Nickel strip You can do? High power battery packs(ie portable drill, rc-toys ) with 30-50 Amps of current would need some thickness...

author: SeanB
author_rank: Super Contributor
timestamp: March 06, 2013, 08:56:51 pm
content: Pity he will not ship to my country.

author: firewalker
author_rank: Super Contributor
timestamp: March 07, 2013, 11:44:17 am
content: Are you going to investigate the way they control the transformer to control the current?Alexander.

author: nukie
author_rank: Frequent Contributor
timestamp: March 07, 2013, 01:36:03 pm
content: Try aluminiumor copper.

author: philpem
author_rank: Frequent Contributor
timestamp: March 08, 2013, 01:36:55 am
content: Quote from: Marco on February 18, 2013, 04:48:51 pmHeh, I didn't expect to log in and see someone talking about one of my projectsFor the record, the welder works pretty well - I used it to build a NiMH pack for a Psion Workabout and rebuild several laptop LiIon packs. That said, it really needs its own PSU, a case, and dual-pulse welding (which means swapping the SCR for a MOSFET).The 50RIA20 makes a good SCR, I haven't managed to blow one up yet. All the wiring is car battery power cable (6AWG or something like that, possibly thicker) on copper busbars (thick copper sheet from the local hobby shop, cut into strips).

author: robrenz
author_rank: Super Contributor
timestamp: March 10, 2013, 09:30:59 pm
content: Glad it worked out for youI know you are busy and bought this as a tool not a project. And you have no obligation to satisfy every forum members whim. But if you ever open it up again to investigate and are feeling generous, I would be very interested in the triac input on time relative to the current settings. As a guess it may be the current power number is equal to the number of line cycles of on time on the primary. You mentioned it was dual pulse so it would be interesting to see what the ratio of first pulse to second pulse on times are.Even if you never get to the above, thanks for the thread because I now know I can mod my spot welder to do the same.

author: robrenz
author_rank: Super Contributor
timestamp: March 10, 2013, 11:20:54 pm
content: Thanks, and obviously no rush

author: Spawn
author_rank: Frequent Contributor
timestamp: March 12, 2013, 11:00:05 am
content: LOL AuroraHe wants the Fluke CNX3000Ontopic again, I still have a lot batteries to weld, but hobby budget of the month went in to another things so I am trying to avoid this topicBut it is looking good, thanks for the photo’s Aurora

author: ConKbot
author_rank: Super Contributor
timestamp: March 13, 2013, 04:29:50 pm
content: Hmm, this thread is relevant to my interests... and timely too.Though obviously I'm going for the CD route instead of using a step-down transformer.

author: entoni
author_rank: Newbie
timestamp: March 15, 2013, 01:37:23 pm
content: Quote from: Spawn on March 12, 2013, 11:00:05 am

author: nukie
author_rank: Frequent Contributor
timestamp: April 02, 2013, 06:36:24 am
content: Very nice to know there are people who makes custom tools in small quantities these days. I have a manual lathe, the time and material cost definitely more than 2 pounds here in ozland. Looking at the part, it will require at least 3 tool changes and soft sticky nature of copper makes it hard to machine.

author: SeanB
author_rank: Super Contributor
timestamp: April 03, 2013, 04:15:47 pm
content: The fuse blowing is most likely because of inrush current, and using a standard fast blow fuse ( common on plastic sealers, which use the same style of construction. They should use a slow blow fuse of 8A, but it is more expensive. 1kVA is common as inrush power, big transformer and low resistance windings. On the plastic sealers the transformer is 56V unloaded, around 2V when heating the strip, though this is incredibly sensitive to the temperature of the sealing strip. I modify the controllers by adding a 100k resistor across the pot outer connections, so that when ( it always will be) turned up to max nuke it is only half the time. 8 seconds of heat is enough to melt a 5mm plastic strip, never mind a 100 micron plastic baggie.

author: robrenz
author_rank: Super Contributor
timestamp: April 15, 2013, 01:40:18 pm
content: @ Aurora,Thanks for taking the time to do those measurements. I had a preconcieved idea that the power would be controled by the portion of/number of powerline cycles fed to the primary of the transformer. I believe that is how the sunstone units control the power levels. But I dont see any significant difference in the voltage pulse length on your traces but the amplitude changes and they all are just one line cycle (first pulse on the top of the sine wave and second on the bottom of the sine wave). I think the high resistance of the scope connection (= no load) is keeping us from seeing the real weld pulses. When I get to experiment with this I plan to use two differential amplifiers connected to portions of the input cabling and output cabling acting as shunts. That will let me see the actual input/output current waveforms including whatever inductive kicks are happening.Thanks again, robrenz

author: bgeery
author_rank: Newbie
timestamp: November 10, 2013, 08:50:09 am
content: Any update on this welder? I was looking to buy one ASAP, so the info would be timely and helpful?

author: Fraser
author_rank: Super Contributor
timestamp: November 10, 2013, 09:47:09 am
content: Still working well. No complaints.I have welded tabs onto all manner of cells and not a single failure in service to date.The only problem I have has is that if I use a current setting above 50 I trip the whole house RCCD ! The welder passes the tests on my Seaward 2000 PAT tester so it is not faulty.....it just upsets the sensitive house breaker at high instantaneous currents. I normally weld at level 25 to 30 so all works fine.I purchased the correct thin zinc battery tab material and highly recommend you do the same rather than trying to improvise. The come in strips and individual tabs in various widths and I bought all mine from China very cheaply.Would I recommend this welder to a friend? YES. For the money, and my lightweight application, it is excellent.

author: turbo!
author_rank: Regular Contributor
timestamp: November 14, 2013, 01:58:33 pm
content: I recall seeing a "spot welder" at Harbor Freight. You could also make one yourself with a set of capacitors and control the available energy by setting the voltage you charge the capacitors to.

author: macboy
author_rank: Super Contributor
timestamp: November 14, 2013, 02:44:11 pm
content: QuoteOne concern about putting many caps in parallel is the failure mode.You will be subjecting these caps to very high stress and failure will happen eventually. Consider what will happen when a capacitor fails. You have say 10 or even 100 caps in parallel. One fails, short circuit. What happens? The other 99 instantly discharge through the shorted one, andKABOOM! You will see an explosive failure which could not occur with just one large capacitor.