Can I get some feedback on my spot welding for my 18650 pack

Hello all, I am building a 10s 4p pack from 18650’s. I have my batteries and supplies, but I want to get some community feedback before I weld together the rest of my cells. Here is picture of my practice welds on some dead cells I had:


Can you rip them off?

I’d like to hear as well. Just got a new spot welder and my settings don’t leave the burn looking marks and the welds hold great.

It is very difficult to pull them off with pliars

What welder are you using?

sunko 788H

If you can’t rip the welds off, you good. Welds look overdone.

Go slow on the sunko 788H if using the 120V AC version. I’ve read plenty of review on Chinese spot welders I came to a conclusion these units are not designed to handle the higher current on 120V. Blown triacs or copper traces and stuff. I have something similar to yours, but the 240V with that 50hz transformer because my house is wired for both 120V/240V. The funny thing about using a 50Hz transformer on a 60Hz mains is you lose 20% of peak flux density and the built-in transformer runs cooler as a result of that. You can’t run 60Hz equipment on 50Hz mains.


yea i think the pulse length is too much, there shouldn’t be haloing around the welds.

try backing off a bit.

1 Like

So with the Halo around the welds that’s just additional heat going into the cell correct?

imagine that the burn marks look about the same underneath the battery pads - you don´t want to damage your cells with puncturing it with to much current. Just try to tweak the settings a bit with old cells. You can also rip off the nickel after a try to see how your cell looks like under the nickel. My welds look like this:

1 Like

Hi, @TarzanHBK which spot welder do you use?


these are mine, arduino welder with 2x 3s lipos in parallel.


I´m using a selfmade arduino based on KaptainBalu´s Version

Do you where could i buy it?

Welds seem very good, try with lower current it is almost burned thru

These weld spots look almost like through holes. Either the current is too high or the material could be nickel plated steel and not pure nickel. How’s the spark development looking like. I did some test welds with mu-metal (nickel-iron-copper) and got similar holes and massive sparks …

I got the previous version to this one:

You can get a full kit from him i think

You can, I got the full kit with case & foot pedal, should be here monday…


The sparks only show up every now and then. Most welds are uneventful.

Yours look strong but a little over done…

1 Like

Why are you covering everything around the welds with kapton tape but not the welds themselves?