You can get a welder that operates directly off of lead-acid batteries
and (reportedly) works well. I'm too lazy this morning to google it
for you.
Paul Mathews

RoyJ wrote:
Welder typically runs around 25 volts while welding (open circuit
voltage is a different story) with reasonable efficency. That would put
your max power at around 4kw. But you can do nice stick welding of 1/8"
6013 at around 110 amps, 3/32" at 80 amps. Depends on what you are
welding. Big problem is when you stick the rod, it pulls the full
amperage setting.

I did a quick search, it's not clear if the Kemppi is an inverter unit
or a transformer unit. (If it's heavy, it's a transformer!) I would NOT
want to feed an inverter welder off of a square wave inverter, too much
chance the circuits will start fighting each other. A transformer welder
MIGHT work on an inverter, depends on how well the inverter takes to the
heavily reactive power factor as well as the inductive surges you will
see. Net: I don't think I'd chance it on your inverter, even at low power.

I run both a 120 volt MIG welder and a 225 amp (dialed down of course!)
AIRCO stick welder off of a 5kw generator. Works ok, either one will
load the generator quite heavily.

Nigel wrote:
I have a Kemppi Master 1400 Stick welder that I'd like to be able to use
aboard my boat
I have a 2400w inverter fitted that I think is a square wave, might be
modified square wave.
or... I do have access to a 3.5kv generator. would either of these run it.
The Kemppi has a maximum output of 140amp, but at what is the voltage, how
many watts do I need to strike the ark etc

thanks