roterabe

joined 1 year ago
[–] roterabe@discuss.tchncs.de 2 points 2 days ago

Recently got good in making sourdough. But I could also add plastering walls. I'm semi-decent at it.

[–] roterabe@discuss.tchncs.de 4 points 10 months ago

The smoke is from the rosin core and flux. Lead free is equally bad for the lungs.

I wouldn't eat after touching Lead though.

[–] roterabe@discuss.tchncs.de 1 points 1 year ago

Yeah, just gonna chime in here real quick.

I went down this road just as you. I found out that most MOTs are rather weak for 18650 nickel strips.

You need a transformer rated around 1500 watts. Most are 700-900 watts. I ended up wiring 2 transformers in parallel. Also, make sure to remove the transformer's shunts. They are a form of current limiting and will impact your amps at the end.

Finally, make sure to carefully regulate your pressure with the copper tips. High pressure does indeed equal a weaker weld.

AC in general is also not the best for very short pulses of welds. I have found that 40-60ms work best for 0.2 with around 1000amps. Anything less didn't weld tbh and the MOT couldn't pull amps fast enough. I tried all sorts of windings and cable thicknesses. I finally chose 6AWG and I'm happy enough with 2 transformers.

[–] roterabe@discuss.tchncs.de 1 points 1 year ago

Yeah, that seems like a good way to go. 65 degrees at ground level is what I'd also expect. My assumption up top would be close to 90/95 degrees. Driving the pump more often would be interesting.

[–] roterabe@discuss.tchncs.de 2 points 1 year ago* (last edited 1 year ago)

Could you send it over? Seems good to check it out. I'll be on the lookout for a more powerful transformer in the meantime. I also went out and bought a more reputable SSR still rated at 40 amps.

[–] roterabe@discuss.tchncs.de 1 points 1 year ago (2 children)

Hmm, the heater element being controller disregarding your will is a bit of a bummer.

Thanks for clarifying, so you are indeed circulating the water itself, it's not a separate line used as a heater. In this case you really are at the mercy of either your pump, pipe length, ambient temperature, insulation and/or sun intensity.

Have you monitored the temperature at the panel on the roof itself? Also, what type of insulation are you running on those pipes?

[–] roterabe@discuss.tchncs.de 2 points 1 year ago (2 children)

Hmm, maybe I should have clarified. You would be correct if I was talking about doubling the overall power. I meant simply adding another turn to my secondary coils so as to raise the voltage and lower the amps a bit or to connect the 2 transformers in series.

Caps seem like a decent idea actually. The house is rated for something north of 40 amps so I should be fine for a ms load.

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MOT spot welder / discussion (discuss.tchncs.de)
submitted 1 year ago* (last edited 1 year ago) by roterabe@discuss.tchncs.de to c/electronics@discuss.tchncs.de
 

Would anyone like to chime in. I recently made an MOT spot welder for 18650 nickel strips. I can reliably weld 0.2mm nickel. Although I do need a slit if I'm doing nickel <--> nickel (stacking for more amps).

My main problem here is that I had to use 2 parallel transformers since I can't source a single more powerful one e.g. 1500w

The current ones are around 700 and 900 watts. Together, they manage around 20 amps from the wall 220v, that's about north of 4kW, so I'm guessing 2000 amps at 2 volts in theory.

In practice, I'm probably closer to 1000 amps due to heat and smaller electrode tips near the end for the spots.

Any ideas if raising my voltage to 4 volts would help with welds? I might also switch out my SSR since it seems to be sagging on that end. I measure more amps on the free directly connected cable from time to time, versus the one coming from the SSR.

Edit: The cables on the secondary windings are 16mm2 or around 6AWG. I'm confident they can handle the load since I can't really feel any heat in them. They barely heat up after 5 seconds of a constant short. I'm doing mostly 50-60ms pulses for the welds.

[–] roterabe@discuss.tchncs.de 1 points 1 year ago (4 children)

OK this is interesting, but also differs. If I have read correctly, you're circulating the water in the system as a whole.

I'm also using a solar setup, but I'm using a serpentine coil running a separate coolant liquid. The coolant is used since winter goes from -10 to minimim -20 degrees celsius.

What are your coldest months like?