I've had this saw on my desk for weeks and didn't exactly know what to do with it. I get fixit projects from coworkers and those were not worth doing because of the cost. A leaf blower/weed whacker combo with failed batteries was cheaper to discard than replace even one battery. The plasma tv I got needs a main board but led tvs that size now are the same price as the board and internet capable, so the broken tv is going in the trash.
The Craftsman battery powered saw I found in my church dumpster was missing the battery (of course) and the charger, but the saw looked almost new. A quick check on eBay showed it was not economical to buy another battery and charger. But the only circular saw I own is full sized and won't run from the inverter I have in my car.
I converted a variable speed drill to run from my car battery, so I thought maybe this saw was worth converting.
Step 1: Testing the Saw on 12v
I tested the saw with a worn out 12v 17 amp hour battery I have sitting on my desk and the saw spun up. There are no electronics inside, just a trigger lock. The motor is a fixed magnet direct dc motor and those are not very picky about voltage. A decent car battery would put out more voltage and current, esp. if the motor was running when using the saw, so I figured this would work.The saw gear box was clean inside, but I added some grease to pack it tight since I had the saw apart. The country of origin on this saw is China, but it has the fit and finish of a Craftsman tool. Kind of a shame since Sears is closing down in Canada this spring.
Step 2: Wiring It Up
I had a cheap spare set of car booster cables. The wires inside are so small that I don't need big cables to prevent voltage drops, but I did notice that the drill using the dash power port works poorly compared to running it straight from the car battery so I chose to force myself to lift the hood and go straight to the car battery when using this saw. I just cut the original battery clips off the saw and one end of the booster cables and used wire nuts to made the connections.
Step 3: Testing the Cut
The saw came with a Craftsman blade. 1mm thick with 2mm carbide tips. That blade is the secret to making this saw work with the removable battery. It's sharp and thin so it removes very little material to make a nice clean cut.
I also had a 2mm cheap stamped steel blade from another compact saw, and with a shim was able to make it fit the Craftsman saw. Becasue this is a dc motor, if the blade you use is accidentally mounted upside down all you need to do is reverse the cables. I found even the cheap rusty blade would cut wood even spinning backwards.
I made a cuts to a 1x2 with the original blade and with the older one. Both cut well. Even the rusty blade cut a 2x4 in decent time, so I'm happy with the result and the saw in now going in the car with me in case I need it for a quick job