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Thursday, July 16, 2020

Doug's Domain

Doug Vetter, ATP/CFI

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Friday, September 27, 2013

Crimping Lugs for Audio System Test

In prep for a full bench test of the audio system I needed to crimp a couple lugs onto some #2 welding cable to supply a single amp with power from a 100Ah AGM battery. I ordered the lugs from Mouser along with some other stuff I needed for unrelated projects.

The lugs aren't cheap -- about $5 each for the #2 and $6 for the 1/0 versions, so I bought what I needed plus just one spare of each type in case I screwed up the crimping process. Fortunately, the very high quality Greenlee crimping tool I originally bought to crimp the 4/0 cable in my emergency battery plant came in handy again and firmly attached the lugs to the cables.

If you look closely at the pictures you'll note a number "2" embossed in the lug by the crimping process. For the best quality crimp, the wire, lug and die used to crimp them together should match, and this feature of the Greenlee crimping dies allows independent verification of the proper crimp.

To insulate the exposed portion of the lug I applied some heat shrink tubing. Heat shrink is generally overpriced when bought in small quantities so I decided to pick up a few 50 ft rolls of 2:1 Polyolefin heat shrink from buyheatshrink.com. While their website looks and feels like it's firmly stuck in the late 90's I'll credit the company with a smooth transaction. The box arrived from Florida quickly and the prices were reasonable considering the amounts involved.

All heat shrink must be purchased carefully as the nominal and shrinked sizes can be radically different based on the shrink ratio (2:1, 3:1, etc.). This company was one of the few that clearly indicated the size of the product before and after the shrinking process. I purchased 1/2", 5/8" and 3/4" nominal sizes knowing that I'd have to deal with a couple different wire sizes and some experimentation might be necessary. I applied the 5/8" heat shrink in this case and the result looks perfect.

For those that are cringing at the idea of using two black cables for both positive and negative leads, allow me to allay your fears. This is only for the bench test and done for practical reasons -- I don't want to waste wire or expensive lugs. When the amps are installed in the car I intend to use black for negative and red for positive leads. Additionally, while I have to connect the negative lug of the amp to the negative terminal on the battery during the bench test to complete the circuit I will NOT be doing that in the car. Instead, these leads will be cut as short as practical (a few inches at most) and bonded with the car body in close proximity to each amp in order to reduce the resistance to ground and thus the potential for ground noise.

Check out the video I took during the crimping process.

Mileage: 240000