24 volt DC welding

Hi all;
As some of you may know, I am constructing my first batch box rmh.
With the style door frame I have built for it. I wanted to tack weld it to my floor channel to hold it in place.
Sadly being off grid, I have no arc welder here. I do own one but it lives elsewhere.
I really need this weld to happen "in place" so marking it and taking it to a welder was not a good option.
I looked into buying a 110 vt stick welder. Cheap enough, but do I really need one? And more important, Do I want to wait for it to get here?

Then my out of country consultant, also a fellow Rocket Scientist. Suggested looking at you-tube videos of 12 vt battery welding?
I knew they made "off road welders" I even looked them up, not cheap!  So how is this done?
Well, it turns out very easily!

The first video I watched, had a guy tape four 5 amp 12 vt battery's together... they fit in one hand... then he wired them in series to get 48 volts... Then before my eyes, he welded  with it!  Amazing!  
Next I watched a guy use three 12 vt car battery's wired to be 36 volts. He welded 1/4" plate ! Said it would cut up to 1/2" plate!! Wow
The last video was two 12 vt battery's wired to 24 vt. He laid four beautiful beads and then welded two brake rotors together! Said it welded 1/4" plate , no problem!  

So out to the shop I go. Grab a good car battery , hook my 25' long welding lead jumper cables to it. Take my 6" floor channel and clamp a piece of angle to it...
I have no good new welding rod but... I have funky 20+ year old rod been kicking about my shop.  I collect an assortment of sizes and number rod and bake them on top of the wood stove to remove moisture.
To weld, you use reverse polarity.  The positive lead is your ground! Connect the positive lead to your work.
You weld with the negative side! Clamp your welding rod with a pair of vice grips and then clamp your jumper cable to the vice grip.

I had to try using just one battery...No go, it sparks but will not hold an arc. OK ,out to a Subaru to steal/borrow a battery....
Back in the shop I connect both battery's in series for 24 vt output. Connect the jumper cables and its back to welding...or more sparking?

First I tried a small dia rod. It arced and although not pretty it puddled the metal.  I checked and sure enough it securely tacked 1/8" angle to 1/8" tubing!   How Cool is this !!!
Next I grabbed a full dia. stick of 6011 rod.  Not only did it arc but was doing a good job of it as well!
This is 20 year old rod I'm using... not properly stored at all!  I broke apart the welds to inspect and both had made penetration!
Wow, no need to buy a new stick welder... I already had one here all these years!
I'll be buying some new rod just to have on hand, but I can tack that door frame in moments as soon as I am ready!!!  WHOO-HOO

Children!  Do Not try this at home.
This is safe, if you use proper size connections and secure them well.
Done improperly, this can melt the posts off your battery.
Battery's can explode!

As a welder myself, it looks like you do not have enough power to do the welds correctly.
Thin plate 16g may weld, but that heavy section you have may be too much.
My gut feeling is you may wreck the batteries trying.
I also live off the4 grid.
I would drill holes and bolt the things together in your circumstances.
Have you consiered that?

Hi John;
Yes , I thought of bolts , but in this case you do not want anything disrupting airflow.
As a welder, if you saw the rod I was using today you would laugh.  Most of the splatter came from that small rod. The 6011 struck a good arc
I'll pick up some new rod soon and just lay some beads to demonstrate.
More photo's then.

Round headed bolts would not be a problem, plus we are not dealing with the air flow needed for an airliner, so anything may work.
Perhaps shorten your cables alot as well.

John has made 2 really good points Thomas. However, this is a rocket so it kind of falls into the airliner category  :)

I just studied the image of your battery connections as well.
The point contact you are establishing may also be a limiting factor
in the power supply availability.
Perhaps the use of proper terminals will help?

Hi All;
Finally back with an update.
Same setup of 24 volts, using new preheated 6011 3/32 rod.
Not happy at all with the results.  Might have worked better with larger rod.

Today I tried 36 volt welding. Same preheated rod.
It worked. I was happy with the bead I got.
What I was not happy with, was how quickly it would blow a hole thru 1/8" tubing!
Once you struck an arc if you didn't move quickly... you blew a hole! That fast!  That is serious amperage flowing.
This would work great if you needed to cut metal away! Also as a back country welder for repairs.

It is not good enough for my shop dragon. I don't care to risk blowing a hole in my door...
This morning I ordered a 110 vt stick welder.

Yup.  Used it to weld a tractor back together to back home and weld it right, but it is not a "controlled" arc.

Really short duty cycle before you can melt batteries, too.