Yeah. Once that battery fully charges you should be good to go. The one you borrowed from a friend wasn’t going to cut it
So with single layer cells any thoughts on welding the nickel strips sideways to a copper bus bar and just folding it over on top of the P cells. Assuming welding nickel to Cooper goes well. That way each nickel strip can handle the individual battery and the copper bar can handle the P group.
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Nickel on copper is possible…yet difficult to do and not good quality. I suggest to solder instead. If that is not an option make many welds to leave it as firm as possible. The neodinium trick is always a safe bet too.
Link doesn’t appear to work for me
just joined to boss spot welder’s club, finally put things together yesterday and was doing test welds today.
i scavenged some cells from an old build and put together a 3s12p pack made with 25r cells. on paper, this pack can output 240a comfortably, almost 400a burst.
i’m finding, however, that the recommended timing isn’t working at all. that is, 4ms for .15 nickel to steel weld isn’t doing anything. i’m about doubling (8ms by 2x) the time to get a solid .15mm nickel to steel weld.
for a .15 nickel to nickel weld, i’m having to up the weld time to 16ms by 4x.
is this the result of my pack not being able to deliver enough amperage? i was sure a 12p pack would suffice.
put a giant heat sink on it so temp hasn’t gone above 28c yet:
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I was thinking about buying this!!! What battery do you use?
i described in the post above
@thisguyhere those settings seem high. Probably the batteries. I’m using 8000mah lipo and I downed it to 1.3 because it was doing holes at 1.4. I wonder if the nickel strips aren’t letting enough instant amps through.
Also that’s a monster heat sink
yea, that’s what i’m thinking, the liion pack isn’t cutting it (despite having worked on it for like 5 hours).
gonna get a hold of a lipo pack and compare.
heatsink: https://www.amazon.com/gp/product/B00UVPT0CS/ref=oh_aui_detailpage_o00_s02?ie=UTF8&psc=1
I picked up two smaller heat sinks with a fan to put on top. But I still haven’t seen much of a temp rise. Only did like 100 welds so far.
drilled out 0.25" wide holes, maybe 0.25" deep.
problem is those screws are buried inside the heat sink.
but the thermal silicone adhesive isn’t permanent and can be cleaned off so it’s still possible to service this thing if need be.
yea i think this bigass heat sink is overkill.
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The new version is more resilient to 4s lipo. I’m not sure but maybe the side effect is that requires a better 3s lipo. I used a top lipo since day one and the flux times always were as posted at 1st post. I can’t edit it anymore but seems I have to recommend the best possible lipo now on.
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I was researching another arduino spot welder that runs on 3s, and he’s measuring 1000-1500 amps for a pulse. 25r also have relatively high internal resistance, I think, which will hamper performance.
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So from what I’ve noticed
-frozen weld cables or cold weld cables need less MS and less multiplier as the resistance is lower. -as the weld cables get hotter the resistance increases, making the MS and multiplier higher. -having a big pack helps(I use a 32Ah 4s 10C - which can easily do 320A continuous) -less batteries being welded requires less timing. Ie when I weld a 5p pack vs a 2p pack. I lay the nickel on and then hold it down across. Resistance changes the welds. Ie for 5p, on a 4s power supply, 4.5ms x2 works well, but if I used this setting on a 2p pack I would burn a hole. The 2p on 4s power supply needed 2.5ms x1.
Basically you need to account for temperature (air) as well as relative humidity, temperature of the welding wires, the resistance of the material (nickel), and the resistance of the pack surfaces (how many cells are attached to the strip).
About the humidity, below 45%RH, is considered dry, and air is likely to hold static charged ions making burning holes with to much power even more likely. Weld in 55-65%RH and it will suppress the extra sparking from charged ions in the air.
Regarding heat of the fets…I easily got the fets upto 48c cutoff after 30-40 welds in a row… I added my plates and highest I’ve seen is 31c after 290 welds in about 20 minutes. Basically I put this thing through the paces hard lol.
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good to know, to start i’m putting a 2p pack together and welding 40 x 10 x .15mm nickel so don’t think material resistance is the culprit. and environmental conditions are ideal.
aside from the battery, only other bottleneck may be the 10awg wires coming off the battery, it’s about 18" in length, maybe that’s adding too much resistance? i could probably double that up and see if it makes a difference.
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Maybe I’m not sure my wires from lipo tab to welder are about 11".
A test you could try, if you have some dead VESC laying around… Add a cap rail right by the input of the welder… Then you can rule out whether it’s length of wire or C capability… As the caps should fix anything if it’s from resistance during the burst current.
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