How To... Make Your Own Battery Cables.

[Deezelweazel]

No kidding.

Burned my UHF radio.

[junglejuice]

Oh please....

[oldon]

I thought a cable would only flow the power drawn by whatever you were running, providing the cable was big enough in the first place. To burn something usually you hooked up + to - reverse polarity or something else is wrong, maybe bad ground. I'm no sparky so I could be wrong, but blokes like JJ & RB with lots of experience are on here & always willing to help if someone has trouble. Hey Roler, in your line of work I think your brain & hands would be particularly well switched on, no resistance joins there mate. Regards oldon.

[Roler]

Haha, well, it does help being switched on during my work, yeah. And there is resistance too...just not where you would think

[Redemptioner]

Though I better pipe up and dispel a few "myths" in this thread

Originally Posted by Freetripper

Doing both crimping and soldering can create a high resistant join, do one or the other., and use the correct Crimper.

Incorrect, this is actually the best way of doing it and ensures a high current connection, the crimp holds the cable and the solder provides the connection. If you don't know how to do large diameter cable soldering then stick to crimping only but with the proper tool (needs to be hydraulic and apply a few tons of force) and use oversized cable. The whole idea of solder is to provide a low resistance joint capable of carrying a much higher current, say your cable is rated for 100amps and you are using the correct sized lug, the connection at the crimp using the correct tool only provides around 80-90% of the cable rating on average.

Originally Posted by Deezelweazel

As already mentioned crimping involves a hexagonal crimp around the cable.
This process is also refered as cold welding.
The even pressure guarantees a tight connection.

Using a vice is just squishing the copper cable even with the punch afterwards.
The pressure applied is simply not enough.

+1, the vice is a really bad idea, it's ok if you just use it to hold the cable while you then solder it (FYI you won't be using your 30watt Jaycar soldering iron to do the soldering with ).

Originally Posted by Deezelweazel

Use of solder leaves a lot of flux inside the core- that will cause corrosion. A not desirable state.

If this is happening then you are doing it wrong, certainly filling up a lug with solder then just jamming in the cable is definitely the wrong way of doing it, this will create a cold/dry solder joint which is very bad.

Originally Posted by Deezelweazel

Just a hint to remember. The diameter of the cable has to be choosen properly. If you increase the cable diameter to big- the current which can flow can and will burn up e.g a starter, or accessories.

Incorrect, the cable diameter sets how much current can be carried and has nothing to do with the amount of current the device drawing power will draw. If your cable is too small you will cause the cable to heat up and depending on how much higher the current being drawn is above the rating for the cable will dictate if the cable just gets hot or if it causes a cascading current overflow resulting in the cable failing and the cable melting/catching fire (as the cable gets hotter the resistance goes up and so will the current running down it, the increased current heats the cable up more making the cable resistance increase causing more current and more heat round and round we go). You can use as bigger/oversized cable as you want, technically the bigger the better, it will NEVER cause "can and will burn up" as a result, also remember the longer the cable the lower the cables rated current will be. Try aiming for a cable rated for 3 times the current you plan on running, if a device fails because "your cables are too large" then you are colour blind and should stop doing any electrical work (mixed the polarity up)......

Originally Posted by werd

So, for someone like me who doesn't have a lot of specialised tools, what's the best way to do it?

Either buy the correct tool or take the cable down to someone who does and don't buy supercheap cables

[Deezelweazel]

A good source (like a fresh battery) is able to provide about 3000A to 5000A.( very low internal resistance is a good indicator)
That combinded witha cable diameter big enough to flow that current will blow almost anything "if" demanded.

Typical demanding consumers are:
Starter and amplifiers. No matter if music or radio.
Have a nice day and try...

[Redemptioner]

and somehow your device just suddenly demands 3000 times as much current as it is rated for or needs to operate (without shorting out internally) just for sh$ts and giggles on a Friday night........ I think not. A little conmen sense would tell you tell you that an oversized/rated cable causes no issue else every time you plugged your 0.5amp charger into a power socket at home it would be destroyed, how many amps do you think the power lines out the front of your house are rated for, even the lowest current rated lines are a few hundred times more than 0.5amps.

But hey it sounds like a demonstration/example you can do yourself is in order. Go grab a little low current rated (in the milliamp range) 12V light bulb (not an LED), then take a short length of a nice thick cable, say like 10cm of 35mm diameter (like what you would use to join 2 battery negatives together in a 4x4 or run to your winch) or hell go crazy and get some 100mm cable, this cable in 10cm length is good for a thousand times what the light bulb could ever hope to draw in current even in its wildest wet dreams. Now connect you light bulb up to a decent battery using your 10cm length of cable and see what happens. (spoiler alert, nothing special happens, the light bulbs work as per normal, no black holes created).

The trick with high current rated cable is to ensure it is fuse protected as close to the battery connection as possible (well all supply lines should be done like this) to ensure if a short occurs the cable is protected, then any devices that are connected to it are then also fused protected individually but this time you want the fuse as close to the device as possible. The fuse near the battery is there to safe guard the supply cable from a short and the fuse close to the device is there to protect the device an other devices connected to the same supply cable from a short within the device (ie. if your radio shorts it does not take out anything else connected to the same supply cable).