Well, I'm going to step way out on a limb with this one. First of all, I have no idea about the 25V welder boost. I'm certain 25V DC is not a problem boosting a 24V system, one volt doesn't seem a big deal when your alternator puts out 26 - 28 volts while charging, I'm more concerned about the amps the welder would put into the batteries. Maybe someone else out there knows. Now to step out on a limb. I've worked for many years around contractors type equipment, which is 12V. I've worked more around heavy equipment for the last 2 1/2 years, which is 24V, and that would be in a shop/yard environment. I deal with my dead 24V machines with a monster garage booster I built with 4 group 31 batteries, that thing will make any dead beast come to life. But you guys out in the field don't have that luxury. This thread made a light bulb go off in my head, the limb I'm going to step on. A 24V system is generally (2) 12V batteries wired in series, making the master positive and master negative going to the starter 24V. Your typical support trucks are Ford/Chevy/Dodge F350/3500 series trucks, diesel engines, which have (2) 12V batteries wired in parallel making the master positive and master negative going to the starter 12V. Now, how do we boost a 24V system with this? Here's the limb, maybe someone's done this and can let us know. You need two sets of jumper cables. Connect one set from one battery of your truck to one battery on your machine. Connect the other jumper cable set from the other battery of your truck to the other battery of your machine. Be very mindful of connecting positive to positive and neg to neg with your jumper, very critical. Your saying, "but it's a 24V system." It's only 24V at the master positive and master negative. Don't believe me? Take a multitester and read the volts on one of the batteries on the machine, it will read 12V. Go to the other battery, check it. It will also read 12V. The 24V only happens in the final output of the batteries wired in series at the starter, where master positive and master negative meet. Now, this is in theory in my head sparked by this thread and the need to boost 24V machines in the field. I think it would work, maybe someone has done this and would let us know. There it is, let's noodle it out. I'm sure a lot of guys have dead machines right now, it's going to be 5 degrees here tomorrow morning.