I built this for my telescope and as i told my wife, and portable charging station for cell phones in an emergency.
It turned out the learning curve was fun, but a bit pricey as i got more into building it. I ended up spending about 75ish in parts, if you were to total the whole thing, it'd probably be over 100 with ammo can cost in it. But it works. The next one i build will be larger to hold eyepieces and filter along with light sticks, wiring cables and whatnot.
Please read on and enjoy. If you have a question please ask.
I used lots of dangerous toys and supplies on this. If you are not able to work without adult supervision please dont attempt this project.
Step 1: The Box - or How to Build Something That Will Get You Cavity Checked at Airport.
When i bought my telescope i was happy to find a nice GOTO that was within my price range. However I figured out quickly that keeping 8AA batteries in stock and fresh for when i wanted to go observing was annoying. Who ever has fresh batteries when you need them :)
Also, when using the scope on the cheap AA batteries i noticed that it seemed that the motors where laboring to get enough current to move the scope when it was cold or really warm outside (read - Texas summer night hot)
For those that haven't already done the math, 8AA = 8x1.5v= 12V.
Ok, i thought, what are my 12v options for power. Car adaptor? yeah, but thats not gonna reach to my back patio. 12v convertor for wall outlet, nope, not paying 25$ for one. Plus who wants to have your wife trip over the cord when you finally convinced her to come away from the kardashions for 10 mins to see a view of nature. Not to mention ripping the cord out of the wall, ripping the cord out of the scope, knocking the scope over etc. You get the picture.
I saw the Celestron Power Tanks. Nope, ugly and expensive. Not to mention, design was a bit superfluous.
I thought I can do this cheaper and cooler looking.
Wire, solder, heat shrink, soldering iron, drills, grinders, voltage meters, sweat , burnt finger tips.
Ok, Truth part. If you don't know what you are doing with this stuff, leave it alone. All you'll most likely accomplish is a fire, you might hurt yourself or others. Be safe. Be smart.
Step 2: I Gotta Fix My Multimeter.
I found my multimeter, it'd been sitting in a drawer for a while. Turned it on, and of course. Dead battery. I start to change it and one of the terminals had corroded to the post. Tried to get it off, but only succeeded in tearing the terminal off the 9v connection. Gotta replace it first.
I know my soldering jobs aren't pro level, but if it works and its ugly who cares.
Got a new connector, stripped some fine wires, and got to work.
I do a Western Union pigtail connection for wire to wire connections like this.
And then put a drop of solder on the joint. I don't care that wires will be hanging out, i lost the battery cover a long time ago.
Step 3: Defining Boundaries
I had picked up some 6v's at Harbor Freight for about 2.50 ea.
Some electrical tape and routed the battery for 12v. I'd already taped the batteries use in V.01 where i was using alligator clips and a plug to the scope before. That was the real reason for building this beast.
I sized up the batteries in the ammo can (US .30cal belt) and marked out my holes. I used google sketchup and did a base hole chart. My original plan had been to have dual 12V meters left and right, but as with so many things built from scratch plans change mid-stream.
Step 4: Should Have Gone Plastic or Admire My Monkey Feet, Admire!
Ok, after drilling base holes in side. Its time to size them. The meters and 12V and USB sockets advertise 1 US inch. Make a note now, A US inch does not equal a chinese inch!
The biggest drill i had was a 1/2 carbide. ( I really didnt think about this till I drilled about the 3rd hole).
The meters / USB / 12v were 1" , how was i going to turn a half inch hole into a 1" hole, With a dremel tool.
The first 1" hole took 1.5hrs. Build Note- real ammo cans have f'n hard steel. Go plastic on next one.
The other 1" holes my neighbor had a fix for, he thought. He has a commercial size drill press and just happened to have a 1" carbide end mill bit. Not the safest, but it worked. Should have gone plastic. Even with the mill bit, and one person steadying the press, the other trying to work 1" bit into a 1/2" hole. It still took about 30 mins per hole to open them up. Go plastic. Please wear safety glasses during this. This stuff is really flying fast when it hits. And its all hot and sharp.
Step 5: Building the Harness.
By this time, i've gotten the holes to 1" and can see how the wireing needs to go.
I start with the negative harness. I wanted to just be able to drop it in, and then plug and play so to speak.
I used a lot of heat shrink to manipulate the wire direction and insulate against friction. Tedious, overkill, but was a good education in design and follow thru.
Design at this time was still a 6 piece installation. So i wired for 6 connection points. 3 per side.
I used a piece of coat hanger wire for a frame and then built wire to frame. I worked very well. I didnt have to change any wires once installed. For this part i'll put build notes on individual pics. If you know how to build this you'll follow ok.
Step 6: Lexan, Roof Flashing, and More Heat Shrink - Building the Battery Trace.
How to manipulate the battery current. I used a piece of 1/4" plywood scrap and cut some ribbons of roof flashing (from another project). Drilled out the holes and then made the contacts insulated them and eventually encased them ( not very well, but i learned how for next project) in a covering of 1/8" lexan sheet.
Notes on pics.
Step 7: Testing for Magic Blue Smoke Failures. Its Alive!
Time to start showing that you actually know what you're doing.
Wired up batteries. 12v cig lighter socket in place. Got the meter out and lets see whats gonna happen.
I grinned, and said, see it didnt explode and it works the first time. Its alive!
Step 8: Show Time
Pics for details at this point.
After using it for a couple months i found that while adequate during the summer the cheap carbon batteries really labored in winter. Since I first built this, i have upgraded the battery to a 12v 9a rechargeable. Noticeable improvement in long cold run times.