AEP coiled cable lipo conversion Amp rating

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emit

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I've wired a mosfet in the grip of my JG V61 and wanted to run it with a lipo stored in a pouch by connecting it through a coiled cable.

I bought a coiled shaver charging cable, wired it with deans and connected it to the 7.4V lipo battery and mosfet.

The gun fires fine when the battery is connected directly to the mosfet but it doesn't fire when connected through the coiled cable. I checked the positive and negatives are soldered the right way. 

I can feel the coiled cable getting very hot and suspect the few wispy strands of wires are too thin to carry the 20-30 Amp rating of the battery.

Trouble is that going by this I would need a 2.5mm core cable to carry 20-30 amps https://www.energy-solutions.co.uk/technical-information and I can't seem to find reasonably priced coiled cables that thick.

I think the default cabling in most AEGs is 18AWG which is 0.75mm square and 16AWG is 1.5mm.

What coiled cables is everyone else using that work?

 
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Is a very interesting question to which I didn't come up with a great answer with I considered doing this myself, for much the same reason: most coiled cables that I looked at were intended for very low amperage applications, and thicker wiring isn't as easily available in springy coils.

You could form your own coil by winding some higher rated cable around a mandrel (and a heat cycle would probably help), but a coil will add significantly more length of wire than you actually need, with resistance scaling with length.

So if I were to do it now, I reckon I'd just use a straight run of mains power cable (an old kettle lead or similar) starting from my shoulder as a simple lanyard, rather than a coil.  As I already use a lanyard with pistols anyway, it would just be a matter of switching from paracord to cable.

 
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Don't know if they would be any good but may try looking at good headphone spiral cables. They always look for low impedance so good for little loss. Just not sure how well they will take the heat.

 
Keldon said:
Don't know if they would be any good but may try looking at good headphone spiral cables. They always look for low impedance so good for little loss. Just not sure how well they will take the heat.
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They won't handle the current.

@emit I do wonder why you want a coiled cable in the first place to be honest. I'd go for a silicone insulated normal cable (they're more flexible than PVC) and maybe consider sheathing it in some mesh cable tidy braided tube. As you've discovered, 30 Amp coiled cable is expensive (and heavy on account of the sheer amount of cable involved).

 
Yeah, coiled cable sounds like a good idea but in practice the resistance is too high and it would become a nightmare with the coils getting twisted out of alignment like the old telephone cables.

 
I ordered a £10 coiled cable with 2 cores of 0.75mm diameter each. Will provide an update on how it works once I install it.

 
A pistol lanyard would be a better option that a spiral cable. You can do it in a paracord sleeve with a core to prevent snagging and yanking on the cable.

I've done a few for lights, switches and some that include a step down for running 4s lipos in 2s systems (fpv goggles)

Have a good silicon shield cable slightly longer than the paracord outer, I use 550, then feed the cable as a fine paracord through the middle. Once the all threaded through melt the paracords together and add a little heat shrink. Then its just soldering the wiring together.  And the battery goes in a pocket/pouch next to the lanyard fix point.

 
concretesnail said:
A pistol lanyard would be a better option that a spiral cable. You can do it in a paracord sleeve with a core to prevent snagging and yanking on the cable.

I've done a few for lights, switches and some that include a step down for running 4s lipos in 2s systems (fpv goggles)

Have a good silicon shield cable slightly longer than the paracord outer, I use 550, then feed the cable as a fine paracord through the middle. Once the all threaded through melt the paracords together and add a little heat shrink. Then its just soldering the wiring together.  And the battery goes in a pocket/pouch next to the lanyard fix point.
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Do you have a photo of what the end result looks like?

 
Lozart said:
You've already found out that 0.75mm cable is too small, why buy something you know is too small?
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The one that didn't work was definitely not 0.75. It looked like it didn't have more wire strands than a signal cable on a mosfet and a fabric string intertwined.

 
emit said:
The one that didn't work was definitely not 0.75. It looked like it didn't have more wire strands than a signal cable on a mosfet and a fabric string intertwined.
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I was referring to the information you found regarding the size of wire needed for 30A being 2.5mm, not the cable you had already tried.

 
I installed the coiled 2 core 0.75mm cable and although I can now hear the motor labouring to turn it doesn't quite manage to compress the spring.

1mm core might be the minimum.

 
Just save yourself the hassle and install a lipo where the old battery was. It will last much longer than the nimh if the same size. One around 1000Mah should fit and will give you ~1500 shots.

 
Samurai said:
Just save yourself the hassle and install a lipo where the old battery was. It will last much longer than the nimh if the same size. One around 1000Mah should fit and will give you ~1500 shots.
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I did that in the end, I popped in a 500mah lipo.

 
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