Small spot welder for Lithium battteries in 2026 recommendations?

[nightfire]

Situation: I want to repair and/or refurbish some battery packs of photo equipment, where buying genuine manufacturer stuff will be a mixture of overpriced stuff and things, that were manufactured long ago and since then stored somewhere...
So I want to be able to replace the Lithium cells of some battery packs (probably mainly 18650 or 14500), which means I will have to spot-weld them.

I checked for recommendations in the forum, the last thread dealing with this topic seems to be from 2022, so I would rather open a new one for a lookout on which models of spot welders would be ok to use in 2026?

From what I read and concluded:
- Power supply is very important, as it will have to provide a very big current in a very short time
- foot pedal ist nice to free up the hands
- regulation of duration of burst and/or energy is something the smaller sub-100 $$/€€ units struggle

Also having read https://www.keenlab.de/index.php/portfolio-item/kweld/  , it seems that in the region I want to work, some smaller device with capacitors and 230V supply would be the way to go.
I am located in germany, so I would like to buy something that can be purchased within EU.
(Fun fact: I lived some years in the same city as the guy that developed the KWelder, as I was a student back then...)

Ok, so:
a) Are there any devices in the sub-200 €€ region that can be recommended?
b) I would be ok with buying used quality gear from trusted sources
c) I would be happy for some links detailing the calculations used for the thickness/ampere used in welding the battery connections, to get some feeling for the materials I would have to weld and or buy

[thm_w]

https://www.eevblog.com/forum/manufacture/spot-welders-for-18650-batteries/

If you want it to last more than a year or two, don't get the li-ion based units. There are quite a few supercap based units available out there, I'm not sure what is good or not, eg https://www.aixun.com/product/f3000-farad-capacitor-spot-welder/

[nightfire]

From what I have seen on Amazon or with research on ebay etc. in germany you can whether get the Kweld system, or the brand names AWithZ or Seesii would show up- everything else below 200 Euros seems to be wether some stuff with integrated batteries, without energy buffer at all (not that bad, but you would have to provide your own energy source which will drive the price up again and leaves margin for error) or you would get some "pseudo-brand" names...

What looks nice and probably would fit the niche I would work in could be the "AWithZ model UKF10", which is charged via USB-C (another version (UF20) has integraded 230V power supply), has capacitors inside, can weld 0.2mm Ni strips with 1000A.
https://www.amazon.de/Punktschwei%C3%9Fger%C3%A4t-AWithZ-Farad-Kondensator-UKF10-Drehknopfbedienung/dp/B0FJ1Z644K?ref_=ast_sto_dp&th=1

What I see, is that those sub-200€ devices would have static timings, whereas only the intensity of the current flow can be adjusted, the KWeld is able to do some finer adjustment of power delivered.
Question here would be, if this would be worth nearly double the price, if a Kweld unit is ordered with the extra capacitor module.

[Finderbinder]

This is exactly the topic I was going to start
I googled few days already and now am torn between two choices:

1) kWeld kit with 2 kCap.
Pros: innovative approach; consistent welds; probably powerful enough for 90% of situations with Lithium cells (mostly for power tools rework); EU business support.
Cons: quite few improvements, upgrades after many years; no case choice to fit complete kit; still stuck at 2000A; modular design, but lack of remarkable choices, ex. 2000A, 5000A, 10000A.

2) AWithZ P120D.
Pros: complete, compact device; just nice design; quality brand; fresh model; probably most powerful and capable for similar price by now (7000A, 69kW).
Cons: old school approach; not upgradeable; CN business support.

3) kWeld Pro?
Pros: more power than non Pro?
Cons: when? really?

For me the choice is totally equal: consistent welding with minimum effort but limited to some point by power OR more hit and mis welding but without limit in power till farther point? Or third choice, when and what if at all?
Price vise I may accent any, but no way both - the bench has limited area

[nightfire]

As the AWithZ welder is considered of the more powerful species of its trade, Question here: What do you want to weld, and which reliability of those welds do you need?

2mm metal thickness is serious stuff, in my application profile i would weld smaller battery packs, so I am probably fine with 0.2mm- very different use case...

[Finderbinder]

For main use with power tools battery packs kWeld is probably sufficient (not sure, because I only own battery operated DX10 from Aliexpress, which is barely sufficient for laptop cells).

Big power of AWithZ P120D will probably be used rarely. But if you pay similar price why not to have that bonus power. As it is capable of thick steel you may find another use for it: metal parts, enclosures, etc.

And then we come back to kWeld pros