My neighbor's car battery was dead so I lent her my battery charger. When I got it back BOTH of the alligator clips had slipped off of the wires. Although the charger is decent, the wires were clipped and not soldered to the wires. Lame and hazardous. When I soldered the wires on, I had to guess which lead was positive and negative because I my multi-meter is dead. I guessed the wire with the white stripe was + , but no way did I trust my guess enough to hook it up to my car.
I did some searching and found a TEST that worked: Electroplating!
Ingredients:
* Vinegar
* Salt
* A glass container (Pyrex measuring 2 cup)
* a penny
* a brass key
I clipped the penny to positive and the key to negative. Then I taped the wires to the outside of the glass so they wouldn't move and the electrodes just touched the bottom of the glass. In another container, I mixed salt in the vinegar to maximum concentration (no more salt would dissolve) and decanted about 1cm of electrolyte into the glass cup with the electrodes.
CAUTION!: THIS EXPERIMENT WILL PRODUCE EXPLOSIVE HYDROGEN AND OXYGEN. I PUT IT NEAR THE WINDOW FOR PROPER VENTILATION.
I set the charger to minimum (12V @ 2A) which turned out to be extremely high and plugged it in. The experiment bubbled, steamed and I could see the gases rising. The instructions said after about half an hour one should see pitting and discoloration on the penny and copper on the brass key. In my case half the penny was GONE and the key was black. I guess this test was meant for a 9V battery electronic current and I was doing it with car battery level current. Ooops!
So what have we learned today kids?
Never lend out your tools or you may blow up your house.