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Author Topic: Wire Sizes for Battery Cabling  (Read 208 times)

richald

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Wire Sizes for Battery Cabling
« on: May 19, 2019, 09:29:01 AM »

I need to extend/connect up a couple of 2S or 3S lipos -
what wiring size do people use, or would recommend? -

I cannot for the life of me figure out the AWG system!
Richald
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Tug Fanatic

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Re: Wire Sizes for Battery Cabling
« Reply #1 on: May 19, 2019, 09:45:16 AM »

We need rather more information. Voltage (2S 3S) is largely irrelevant here.

What current (amps) do you need the wire to carry?

If you don't know the amps the size of the lipos (mah) and the motors to be connected would help.
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richald

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Re: Wire Sizes for Battery Cabling
« Reply #2 on: May 19, 2019, 09:58:24 AM »

30A ESC + 2450KV motor (recorded as pulling 27A max in use)ESC Specification: Weight: 25g Dimensions: 45 x 24 x 11mm
 Firmware: Hobbywing
 Power input: 5.6V - 16.8V (2-3 cells Li-Poly, OR 5-12 cells Ni-MH Ni-MH / Ni-Cd battery)
 BEC: 2A
Constant current: 30A (Max 40A less than 10 seconds)


battery size 3000MaH -5000MaH
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Tug Fanatic

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Re: Wire Sizes for Battery Cabling
« Reply #3 on: May 19, 2019, 10:12:06 AM »

Component Shop rate their 10awg silicone wire as being suitable for a continuous 65amps, 12awg for 45amps continuous and their 14awg for 32amps.
https://www.componentshop.co.uk/cable/silicon-cables.html

I would use 12awg as a minimum although 14awg may well be enough. You can go bigger (bigger means a smaller awg number) with the only penalty being cost / weight.
https://www.componentshop.co.uk/12awg-silicone-cable-wire.html

Make sure that any connectors have a suitable current (amps) rating.
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malcolmfrary

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Re: Wire Sizes for Battery Cabling
« Reply #4 on: May 19, 2019, 10:16:35 AM »

It depends on the maximum current that will be drawn, and the length of the extension.  The longer the extension, the thicker the wire needs to be to minimise the extra volts dropped under load. 
If it is a short exrension, the same as the existing wire is practical, much longer, go for twice as thick.  Losses are inevitable with longer wires in a DC circuit, you just can't get away from Ohms law.
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richald

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Re: Wire Sizes for Battery Cabling
« Reply #5 on: May 19, 2019, 10:19:04 AM »


The connectors will be Deans type.
From measuring the existing cabling I had settled on 10AWG (or 11AWG if this is available)so 12AWG is a possibility.
I have asked this time, having been caught out and buying far too heavy a gauge cable in the past
and then struggling to solder it.

Thanks for your help
Richard
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Re: Wire Sizes for Battery Cabling
« Reply #6 on: May 19, 2019, 10:21:28 AM »

It depends on the maximum current that will be drawn, and the length of the extension.  The longer the extension, the thicker the wire needs to be to minimise the extra volts dropped under load. 
If it is a short exrension, the same as the existing wire is practical, much longer, go for twice as thick.  Losses are inevitable with longer wires in a DC circuit, you just can't get away from Ohms law.

Have you ever had a wire long enough in a model for this to be a problem if you select a wire with spare headroom in the first place? I haven't.
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richald

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Re: Wire Sizes for Battery Cabling
« Reply #7 on: May 19, 2019, 10:21:50 AM »

malcolmfrary

The extension will only be 5cm for each battery - I like to keep all the wiring as short as possible!

Richard
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Re: Wire Sizes for Battery Cabling
« Reply #8 on: May 19, 2019, 10:23:01 AM »

The connectors will be Deans type.
From measuring the existing cabling I had settled on 10AWG (or 11AWG if this is available)so 12AWG is a possibility.
I have asked this time, having been caught out and buying far too heavy a gauge cable in the past
and then struggling to solder it.

Thanks for your help
Richard
:-))
Sounds like your soldering iron isn't powerful enough for heavier wire.
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DaveM

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Re: Wire Sizes for Battery Cabling
« Reply #9 on: May 19, 2019, 10:38:50 AM »

Richard
I run several brushless motors of more or less the same spec as yours and I've never used cable thicker than 14AWG. I have a soldering station with an 80W iron and I use a 5mm-wide flat bit at 400C. An old-fashioned resin-cored solder containing lead is the easiest to use; lead-free solder takes more heating.
DaveM
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richald

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Re: Wire Sizes for Battery Cabling
« Reply #10 on: May 19, 2019, 10:39:28 AM »

Tug Fanatic

No - it was down do using crap (probably lead free) solder.
 I've just bought some Weller stuff and it is a gazillion times better to use!

Richard
Edit: DaveM re: the lead free stuff - it was always sludgy, even at 400C
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DaveM

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Re: Wire Sizes for Battery Cabling
« Reply #11 on: May 19, 2019, 11:39:09 AM »

Edit: DaveM re: the lead free stuff - it was always sludgy, even at 400C
I've been using the stuff to assemble ACTion units since 2007 - that's several hundred-thousand joints - but I've never had any that was sludgy. I use Wartons lead-free solder and it's fine for batch production, but you can't beat the leaded variety for free-flowing and bright joints. Unfortunately it's not legal for commercial use.
BTW There's a table of AWG sizes and current capacities here https://www.modelboatmayhem.co.uk/forum/index.php/topic,62828.msg663563.html#msg663563
DM
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malcolmfrary

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Re: Wire Sizes for Battery Cabling
« Reply #12 on: May 19, 2019, 02:23:52 PM »

Have you ever had a wire long enough in a model for this to be a problem if you select a wire with spare headroom in the first place? I haven't.
Neither have I, but then again, the length wasn't originally stated.  You get away with a lot more on two inches than you do on a couple of feet.
Now that the length is known, more sensible answers can be (and have been) given.
As DaveM said, a hot enough, big enough iron is needed.  Hot enough to do the job, a tip with enough heat reserve to avoid having the heavy wire cool it to the point where the solder and flux can't do their job.  Given that, the iron can be in and out quick enough that the heat doesn't travel up the wire and frazzle the insulation.  A tip that cools too quickly is just one of the many causes of poor joints.
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