I hate it when I disconnect my battery when I am working on my car, and when I am done I have to put my radio presets back, adjust the audio controls the way I want them, reconfigure my nav, and lose my trip milage and trip computer data. So I made a tool to help with this. This is pretty simple stuff and for those 'practiced in the art' you won't learn much, but since I was making it I thought I would take a few pictures in the hope that someone might benefit. There are certainly other ways to do this, but I made it from parts easily found.
First, I got together some parts. These can certainly be purchased at Radio Shack, but I have the benefit of a Silicon Valley electronics surplus store close by.
Parts:
-Two 4-cell battery holders. I used C-cell, but D-cell or AA cell will work fine.
-Wire, 22 gague or larger. Some red and some black would be best, but any color will work
-Two electrical clips with insulators. You really want to get one red and one black.
-One diode, I used a part # 1N4006, available at Radio Shack. It should be rated at 1A or more.
-Miscellanous tape, solder, etc.
Pay attention to the diode. There is a stripe around the body of the diode near one end.
The idea is to make a circuit that looks like this:
Solder the diode to one of the clips. Turn it so the end of the diode with the stripe is attached to the clip. Position it close to the clip, cutting off extra lead length.
Solder a length of red wire to the other end of the diode. Solder a length of black wire to the other clip.
If you want to be neat about it, wrap some tape or shrink tubing around the solder joints.
Slide the clip insulators over the clips, red to the clip with the diode, black on the one with no diode.
Arrange the two battery boxes. The ones I used were easy to place back-to-back with the terminals aligned. I stuck them together with some double sided tape. Each battery box will have a + terminal and a - terminal. Solder a wire between the + terminal on one box to the - terminal on the other box. Solder the wire with the diode and red clip insulator to the remaining + terminal on one box. Solder the wire with the black clip to the - terminal on the other box.
I neatened it all up, and put some tape over the ends so they can't short anything out. When you store the tool, clip the clips onto the wire so they can't short out. Shorting them out is not dangerous, but will run down your batteries in a hurry and the batteries will get warm.
You should test it before attaching it to the car. Load the batteries and get a small 12V light bulb, like a marker light or interior light. Touch the clips to the two terminals of the bulb and it should light up. If it does not light up, double check the connections and the direction of the diode.
To use the tool, before disconnecting the battery, clip the red clip to a hot terminal and the black one to a ground. These are the points I use. The red goes to a stud in the engine fuse box.
I put the black clip on the ground wire next to the driver's side strut tower.
Now, you can disconnect your battery, negative first. After you reconnect the battery, remove the tool and your presets will still be there.
Warning: While the battery is disconnected and the tool is in place, do not turn on any electrical loads. Don't turn on the key, headlights, or step on the brakes. If you do this, it is not dangerous, but it is likely you will lose the presets as it will load the tool more than it can supply.
I considered adding a 1A fuse in series with the red lead, but ran out of steam and got too lazy to chase down the parts. Without the fuse there is a slight hazard that the diode will be destroyed if the leads are shorted. You could add this to make it more fool proof.
First, I got together some parts. These can certainly be purchased at Radio Shack, but I have the benefit of a Silicon Valley electronics surplus store close by.
Parts:
-Two 4-cell battery holders. I used C-cell, but D-cell or AA cell will work fine.
-Wire, 22 gague or larger. Some red and some black would be best, but any color will work
-Two electrical clips with insulators. You really want to get one red and one black.
-One diode, I used a part # 1N4006, available at Radio Shack. It should be rated at 1A or more.
-Miscellanous tape, solder, etc.
Pay attention to the diode. There is a stripe around the body of the diode near one end.
The idea is to make a circuit that looks like this:
Solder the diode to one of the clips. Turn it so the end of the diode with the stripe is attached to the clip. Position it close to the clip, cutting off extra lead length.
Solder a length of red wire to the other end of the diode. Solder a length of black wire to the other clip.
If you want to be neat about it, wrap some tape or shrink tubing around the solder joints.
Slide the clip insulators over the clips, red to the clip with the diode, black on the one with no diode.
Arrange the two battery boxes. The ones I used were easy to place back-to-back with the terminals aligned. I stuck them together with some double sided tape. Each battery box will have a + terminal and a - terminal. Solder a wire between the + terminal on one box to the - terminal on the other box. Solder the wire with the diode and red clip insulator to the remaining + terminal on one box. Solder the wire with the black clip to the - terminal on the other box.
I neatened it all up, and put some tape over the ends so they can't short anything out. When you store the tool, clip the clips onto the wire so they can't short out. Shorting them out is not dangerous, but will run down your batteries in a hurry and the batteries will get warm.
You should test it before attaching it to the car. Load the batteries and get a small 12V light bulb, like a marker light or interior light. Touch the clips to the two terminals of the bulb and it should light up. If it does not light up, double check the connections and the direction of the diode.
To use the tool, before disconnecting the battery, clip the red clip to a hot terminal and the black one to a ground. These are the points I use. The red goes to a stud in the engine fuse box.
I put the black clip on the ground wire next to the driver's side strut tower.
Now, you can disconnect your battery, negative first. After you reconnect the battery, remove the tool and your presets will still be there.
Warning: While the battery is disconnected and the tool is in place, do not turn on any electrical loads. Don't turn on the key, headlights, or step on the brakes. If you do this, it is not dangerous, but it is likely you will lose the presets as it will load the tool more than it can supply.
I considered adding a 1A fuse in series with the red lead, but ran out of steam and got too lazy to chase down the parts. Without the fuse there is a slight hazard that the diode will be destroyed if the leads are shorted. You could add this to make it more fool proof.
