Well, still no luck with finding a good way to ship this thing back to get fixed without it costing more than just buying a new one in the end, lol. I think I'm gonna give up on that for now... and just try to fix it myself (assuming I can identify the problem.. if it's a blown MOSFET... or multiple.. shouldn't be that hard to figure out). The only thing holding me back was that I didn't feel like breaking anything more trying to take this thing apart. But from what I can tell, I should just be able to remove the solder from the pins connecting each layer to the next, and then separate the layers... which will give me access to finally test each MOSFET.
On a side note, partially due to me wanting to also be able to weld some copper ideally... I've been looking into other DIY spot welders... it's pretty amazing how many they are (most following the same principles... with certain design differences). I'm actually pretty amazed that these LIPO batteries are capable of producing so much power to work for spot welding (and you can get some pretty damn strong LIPOs if your device/circuit can handle the power). I've also seen quite a few designs utilizing capacitors (either 1 huge one, or a bunch of relatively large ones combined)... this seems to give you the benefit to use a range of different power sources... and with enough capacitors (or just large enough ones) seems like you could easily produce as much power as you would ever need for a spot welder. I'm sorta leaning in that direction.. BUT.. like I said, you can get some pretty serious LIPO batteries with extremely high C ratings... seems like I should be able to get a strong enough LIPO, and would just need to build a circuit that can handle the power (ie. more mosfets, or better ones... bigger bus bars, etc). On the other hand, using capacitors, an AC to DC converter/power supply.... could probably build a pretty serious setup that's self contained and has no need for a battery. Has anyone done much research on this... is there a compelling reason to go in one direction or the other?
Here's a few different spot welder designs I've been looking at...
This one I'm sure many of you have seen... seems like it's actually very comparable to this welder for the most part (and if you look at the prices that the guy is selling the parts... the PCBs and Aluminum plates.. it's very reasonable). I'm not exactly sure how this one's capabilities compare to the BOSS welder, I'm gonna guess they are very close.... if I wanted to make a stronger welder good for copper, I'm guessing I would probably have to beef up the design... but still probably a good starting point: http://www.instructables.com/id/DIY-Ard ... ot-Welder/
Here's one that is EXTREMELY simple... really a great example to understand the core functionality of any of these spot welders... but this one doesn't have any form of microprocessor controlling it... so there's no dual pulse, and no real configuring of settings... just how much you charge the capacitor seems to be close to all the control.... This is also a cool example because it's using just one HUGE 1.2F capacitor.. and some seriously thick copper bars: http://www.instructables.com/id/Tutoria ... 0-Battery/
Then there's this one, which is kinda in the middle of the above two. It does use an arduino, BUT it seems like it's a much more basic program on the arduino... it has a display, and 3 pots to control 3 settings, and a foot switch. It's display simply shows the values set by the 3 pots (the 2 pulse widths, and the dwell width) and the current voltage on on the capacitor (plus there's a buzzer to indicate the welder's state while use, so you don't have to keep checking the screen during use)... it uses a bank of Capacitors + MOSFETs (One cool thing with the PCB design for that part, you can basically choose how many of these PCBs you want to chain depending on your needs... pretty cool idea). Plus he even put everything into a nice package, utilizing an old broken UPS case. I actually really like this one... it's simple and straight forward, but seems like it does exactly what you need (with the exact options you'd want) with basically nothing extra. There is definitely no confusion of how to use the settings, or what things do... you basically have the option of how powerful you want to go based on the number of PCBs you chain, and it's got a few diodes thrown in there for protection. It feels like a minimalist approach, that doesn't cut any corners, just does exactly what it needs to. I do wonder if there is a benefit/need to utilize a bank of capacitors, instead of one huge capacitor like the first example... I'll have to look into this more, maybe one reason is that it's a dual pulse not a single pulse per a weld... and also could just be for the benefit of giving the builder the option of scaling up or down... I'm not entirely sure. One thing tho, considering you gotta get the PCBs built for the capacitors/mosfets already... I feel like I'd probably end up also making the rest of the circuit into a PCB... to both reduce space and keep things clean (my assumption is that he didn't because this was a prototype, and being so simple, he built it as he went, and only needed one, so never decided to get PCBs built in the end). http://www.instructables.com/id/Capacit ... tery-tabs/
As you can probably tell, I'm liking the third design... and considering trying something similar. BUT the first thing I really need to figure out... is there a reason/need to go with capacitors... or can a high power LIPO battery do everything I need. And, if I were to go with capacitors... does it make sense to have a bank of smaller ones... or just 1-2 giant ones.
If anyone can help elaborate, especially on my major questions, that would be amazing. I do think I might try to build my own... while I think the BOSS welder is great, and I'll likely get a lot of use out of it (and it's portability is a huge bonus)... I'm thinking it would also be really nice to have a non-portable "home" welder, that has the potential to do more (specifically handle spot welding copper without a problem).