Battery Cables

[Vector4fun]

Anybody have any experience in making up new cables for Cessnas or similar? I have an (owner assisted) annual comming up next month, and I'm replacing the battery. Some of the original cables are looking pretty old. (1972 C-172) I can order a new set of Bogart (Bogert?) cables for around $150, but wondered if making up our own set wouldn't be just as easy and much cheaper? Swage or solder the terminals? 6ga or 4ga?

Wisdom appreciated.

 

[erj-145mech]

Follow the manufacturer recommendations in the service manual. Personally I would swage vs solder the connections. Soldered connections are too brittle in a vibration environment. If the original cables are aluminum, and you are replacing with copper, you're going to have to rework the weight and balance, copper is much heavier.

 

[Vector4fun]

Thanks,

I just looked at my copy of the service manual, but didn't find anything about repairing/replacing the battery cables. The wiring digrams though, did call out 4 ga wire, so I figured that much out.

About swaging the terminals, I'm beginning to suspect that requires a special tool to do properly, and the tool costs twice what new cables cost. Correct?

 

[erj-145mech]

I got a battery cable sized swager from one of the electrical supply trucks that sell ty-raps and terminals and such. Its the type that looks like a "C" frame and you smack the piston with a hammer to swage the terminal on the wire. As I recall, it wasn't that expensive.

 

[avbug]

While crimped connections are generally preferred to soldered connections, for the battery, I'd sweat the cable before putting it in the ferrule end...it helps prevent corrosion from building amid the strands of the wire. If you're not moving the cables much, then putting solder in the ferrule end isn't going to embrittle anything or hurt it. I'd run in the solder and seal it over with a double layer of shrink wrap.

Check your mx manual(s), & AC43.13.

 

[Jeff Helgeson]

Borrow tools for free at the autoparts stores

Thanks,

About swaging the terminals, I'm beginning to suspect that requires a special tool to do properly, and the tool costs twice what new cables cost. Correct?

Try some of the autoparts stores to borrow tools. It's free with a deposit. I am sure battery terminal crimping tools are on the list.

 

[avbug]

A lot of pilot owners believe that auto parts and tools are interchangable...sometimes the tools are (sometimes the parts are...another long discussion, I'm sure). I watched a private pilot crank his battery dead recently. I opened the battery compartment, and found the terminal end staked on apparently with a cold chisel. I've seen folks squeeze terminals to death...aviation mechanics use ratcheting crimpers that put a set crimp, consistently, every time...auto mechanics seldom use anything but a sears craftsman style hand crimper...how much pressure you put on the terminal is entirely dependent on how many wheaties you had this morning.


Sealing the terminal end in with solder means good connectivity and less chance for corrosion to enter the terminal barrel. Finishing the job by sealing the work to help prevent corrosion is is a good idea.

Staking the cable in the terminal end isn't rocket science, but it should be done properly. Don't jump on the chance to use automotive tools or parts until you've verified that they will do the same job, and are approved for the function you intend.

 

[Vector4fun]

Thanks 'Bug. I'm trying to track down a proper crimper right now, like the one ERJmech mentioned. I've found them on the 'net for around $50, but asking around to see if someone has one to borrow at the airport. I can get the 4ga aircraft cable and AMP terminals at Aircraft Spruce.

 

[avbug]

It hasn't been mentioned yet, but now is a good time to replace all the grommets where the cable passed through baffles, formers, bulkheads, etc. I like to replace the grommets, adding a little adhesive or PRC to keep the in place, and to surround the cable or line with a wrap such as PVC, spyral wrap, tygon, or other tubing that fills the hold completely and keeps the cable immobile. This prevents chafing and damage to both the cable and any structure through which it passes. Any runs of any significant distance I like to see secured with tie string or other restraining devices such as insulated adel clamps (I don't like tie wraps in aircraft). Might as well hit it all while you have the cable out. It doesn't cost hardly any more to do the job 100%, and you're always better off.