Here's Marko welding a giant sports car rotisserie using the solar welder.
These panels charge the cart at about 3 amps. Welding or driving draws up to 150 amps, but only in short bursts.
To my surprise I have to disconnect the panel after a day or two to keep from overcharging the pack. I probably only charge one day a week. I better add an inverter so I can power my office and other tools from this thing.
This thing is so damn cool you'll smile too much and hurt your face.
I probably should have put the cover back over the batteries before he started welding, cuz batteries can make hydrogen which can go pop.
You're smart kids, you can figure out other safety warnings for this thing.
Step 1: The Panels
To my surprise most of the panels worked okay and the seagull poop cleaned off pretty well, althought the aluminum frames were pretty corroded.
These are 20 watt panels that produce an open-circuit voltage of about 18 volts. That's about right for a 12 volt battery, which is what they were made for. We wired up three of them to charge the 36 volt golf cart battery bank. Then I wired another three the same way to double the amperage. I tried them all in series, but it didn't work nearly as well. Only about half as many amps flowed.
Step 2: State-Of-Charge Indicator
To make sure I didn't over-overcharge, I got a $3 alternator tester from harborfreight.
It has a series of LED indicator lights showing 5 ,12, 12.5,13,13.5, and 14 volts.
I wired that to two adjacent 6 volt batteries in the bank. When it gets over 13 volts I'll pull a cap on one of the cells. If I see bubbles I unplug the panel. Then I watch the battery voltage and when it gets down toward 12 I'll plug the panel in for a recharge.
Over-discharge is a lot worse for a flooded lead-acid battery than overcharge. That's what wrecks most car batteries.
Step 3: Panel Plug
Step 4: In the Beginning...
It had four totally flat tires and six totally bulged and dried-up batteries.
One of the tires wouldn't hold air no matter what so I bought a new one for $40.
I should have just bought an innertube for it. Anyone know a good source for golfcart innertubes?
The differential plug was out and the diff was low on oil. I added some and made a new plug from a lobster buoy.
All the controls needed some lubing and working. I put my good batteries in it and drove it around on my cleanup errands til I was sure it was reliable.
Step 5: What angle for the panels?
If you can't move it you'll calculate the proper angle for your sun vs load curves and build your house with the roof facing that way.
We were planning to make a tilting roof that could be aimed at the sun, but when Franziska and I started taking off the old frame, it suddenly looked really good, so we bolted it back on looking all rakish like this, and decided to just point the vehicle at the sun. That made the rest of our job really easy. We attached the solar panel frames to this frame with hose clamps.
If you want independent angle control for your panels, this vehicle at makerfaire 2008 should be good inspiration.
Step 6: Panel Frames
Here's Marc Lander at work cutting mitered corners with the cold saw. We welded up the frames with the homemade AC stick welder.
Then he marked the hole locations with a spring-loaded centerpunch, drilled 1/4' through holes with a hand drill, and cleaned up the corners with a flap disk on an angle grinder as seen in the next photos.
Step 7: Shock Mounts
Step 8: Painting
Here's my mom painting a frame with shiny zinc paint. The frame is propped up on nail boards so we can flip it over and paint both sides without messing up the paint too much. You can also hang parts from wires, same intent.