I think you posted a couple links for spot welders designed for batteries. The prices for both of those were right in the ballpark of a digital soldering workstation, maybe even a bit less expensive than some workstations. I'd probably go with the heavier duty model that can handle more than I intend to use, as long as it's not too powerful for the batteries you intend to spot weld, or if the power is adjustable. I wouldn't want to run a lower powered model higher or at max, would much rather have a heavier duty, higher-powered model that I could turn down. I like having room for more, in case additional projects surface that require more than the lower powered version. You can always turn down/adjust higher power models, but you can't increase a lower powered model beyond its limit.
Just like an outboard boat motor. I wouldn't choose a horsepower rating that just gets the boat up on plane and running but constantly need to be run at high rpms to provide any useable speed. Instead, I'd get a higher-powered motor, higher than what I need to get the boat up on plane. That way, I can cruise at a decent speed with the engine running at 75%, which gets better gas mileage and helps preserve internal parts. But I know that I have that additional power available if needed, like when trying to outrun a thunderstorm to get back to dock fast, lol. So, your call, but might be a better play to spend a few more $ today to get the higher-powered model, that could provide more versatility and come in handy for other projects down the road. And IIRC, the higher-powered model didn't look to be much more expensive than the lower powered model. So, a few extra dollars spent today, could save you a lot more dollars down the road from needing to buy a more powerful model.
