12v thru Cat5 Cable-Harebrained Idea?

rowiebowie · 02-13-2019, 05:35 PM

I have a disconnected Cat5 cable (previously used to power the now disconnected Sunexplorer solar monitor) that runs from the power side of my Avenue to the other side where I'd like to install a USB charger outlet.

I really don't want to "do it right" and try run new wires across the van to the opposite side because the difficulty just wouldn't be worth it in my opinion. Would the 8 wires within the old Cat5 (ethernet) cable provide the 2.4A required to power the USB outlet?

If so, how would I wire it since the 8 wires are individually insulated? 4 for positive & 4 for negative? All 8 positive and find a separate ground?

If this is the most stupid post you've ever seen, you can tell me. I'll only cry a little bit.

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markopolo · 02-13-2019, 06:45 PM

Is it a single 2.4A 5V USB outlet? How long will the wire run be? Can you see what AWG is marked on the individual wires?

I took a quick look at a couple of parallel conductor calculators and both indicate 4 x 24AWG in parallel would equal approximately 18AWG which would seem to be fine.

Maybe see if anyone else here has an opinion on the idea.

Gryphon · 02-13-2019, 07:04 PM

It's not a stupid idea, but I'm not sure it will work in this case.

There are electrical standards for supplying Power Over Ethernet. The critical thing is not drawing too much current through those small wires. The "type 3" standard appears to be using two wires for the + side and two wires for the - side, with a maximum total current of 600mA per pair, or 1.2A total.

Your 2.4A USB charger is supplying 12W of power, which means at 12V it's drawing at least 1A (probably higher due to losses in the charger). That's pretty close to the limit. Before you go ahead, be sure to measure the current being drawn by your charger when it's under full load to make sure it isn't going over 1.2A.

I'm assuming here that your charger has a single outlet. If your charger has multiple 2.4A outlets, then the maximum current drawn will be too high. A dual 2.4A charger will be drawing at least 2A under full load, which would be well over the limit.

(The "type 4" standard allows for 960mA per pair, but the caveats about "temperature planning" makes me think that there are issues with heat, and an RV isn't really a temperature controlled environment.)

Boxster1971 · 02-13-2019, 11:13 PM

Quote:

Originally Posted by rowiebowie

I have a disconnected Cat5 cable (previously used to power the now disconnected Sunexplorer solar monitor) that runs from the power side of my Avenue to the other side where I'd like to install a USB charger outlet.

I really don't want to "do it right" and try run new wires across the van to the opposite side because the difficulty just wouldn't be worth it in my opinion. Would the 8 wires within the old Cat5 (ethernet) cable provide the 2.4A required to power the USB outlet?

If so, how would I wire it since the 8 wires are individually insulated? 4 for positive & 4 for negative? All 8 positive and find a separate ground?

If this is the most stupid post you've ever seen, you can tell me. I'll only cry a little bit.

.

I agree with Gryphon - not a stupid idea. But powering a USB outlet is likely too much for the fine wires in a Cat5 cable. I've used a abandoned Cat5 cable in my van to power a small LED indicator light, but it only draws 1.5mA. This is the LED I was powering...

https://www.bluesea.com/products/817...2_24V_DC_Green

booster · 02-13-2019, 11:48 PM

According to the link in this discussion

https://electronics.stackexchange.co...-on-cat5-cable

you would be right on the edge for 24ga wire. .577 X 4 2.308 amps plus 4 wires in a bundle will run hotter than a single wire in air. I don't know what the temp rating on Cat 5 is, but maybe 90*C or even 75*.

rowiebowie · 02-14-2019, 01:07 AM

Quote:

Originally Posted by markopolo

Is it a single 2.4A 5V USB outlet? How long will the wire run be? Can you see what AWG is marked on the individual wires?

I took a quick look at a couple of parallel conductor calculators and both indicate 4 x 24AWG in parallel would equal approximately 18AWG which would seem to be fine.

Maybe see if anyone else here has an opinion on the idea.

Sorry, should have provided more information in the beginning.

The outer sheathing states 26AWG wire. Although the USB outlet is just across the aisle, I estimate the length of wire to be maybe 12-15ft max in length as it appears to cross underneath from side to side.
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rowiebowie · 02-14-2019, 01:10 AM

Quote:

Originally Posted by Gryphon

It's not a stupid idea, but I'm not sure it will work in this case.

There are electrical standards for supplying Power Over Ethernet. The critical thing is not drawing too much current through those small wires. The "type 3" standard appears to be using two wires for the + side and two wires for the - side, with a maximum total current of 600mA per pair, or 1.2A total.

Your 2.4A USB charger is supplying 12W of power, which means at 12V it's drawing at least 1A (probably higher due to losses in the charger). That's pretty close to the limit. Before you go ahead, be sure to measure the current being drawn by your charger when it's under full load to make sure it isn't going over 1.2A.

I'm assuming here that your charger has a single outlet. If your charger has multiple 2.4A outlets, then the maximum current drawn will be too high. A dual 2.4A charger will be drawing at least 2A under full load, which would be well over the limit.

(The "type 4" standard allows for 960mA per pair, but the caveats about "temperature planning" makes me think that there are issues with heat, and an RV isn't really a temperature controlled environment.)

The outlet is a double 2.1A USB. But I can find a single for that outlet so it is not overloaded.
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rowiebowie · 02-14-2019, 01:16 AM

Quote:

Originally Posted by Boxster1971

I agree with Gryphon - not a stupid idea. But powering a USB outlet is likely too much for the fine wires in a Cat5 cable. I've used a abandoned Cat5 cable in my van to power a small LED indicator light, but it only draws 1.5mA. This is the LED I was powering...

https://www.bluesea.com/products/817...2_24V_DC_Green

Your LED light is similar to one I wired earlier as an indicator for my battery disconnect to show when the battery is engaged. I agree it is very low draw compared to what I'd use the wiring for.

It's not a "need" but rather a "wish". I'm really just looking for something productive to do with the old Cat5, since the install of my new Victron 75/15 solar controller with bluetooth will make the old Sunexplorer monitor unnecessary.
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rowiebowie · 02-14-2019, 01:19 AM

Quote:

Originally Posted by booster

According to the link in this discussion

https://electronics.stackexchange.co...-on-cat5-cable

you would be right on the edge for 24ga wire. .577 X 4 2.308 amps plus 4 wires in a bundle will run hotter than a single wire in air. I don't know what the temp rating on Cat 5 is, but maybe 90*C or even 75*.

Turns out the cable sheath reads 26AWG and length is an estimated 12-15ft. So even combining wires is a no go? What about going down to a single 1A USB port?
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markopolo · 02-14-2019, 01:51 PM

All 8 x 26 AWG wires in parallel would give an effective AWG of 17 according to a calculator I looked at.

4 x 26 AWG wires in parallel would give an effective AWG of 20 according to the same online calculator. It comes down to your comfort level with using parallel wires. Is there a 12V wiring code to refer to?

Using 20AWG at 15' 1-way distance (30' round trip) with a 1 amp load results in only 1.64% voltage drop using this calculator https://www.powerstream.com/Wire_Size.htm . I don't know how much current at 12V a single 1 amp 5V USB outlet would use. We don't know the loss with the conversion. 1A at 5V = 5W 1A at 12V = 12W

Is there movement at both ends of the Cat5 cable if you pull on it? If so, maybe it could be used to pull new wires through.

rowiebowie · 02-14-2019, 04:00 PM

Quote:

Originally Posted by markopolo

Is there movement at both ends of the Cat5 cable if you pull on it? If so, maybe it could be used to pull new wires through.

Ive pulled on the Cat5 (but I haven't pulled too hard yet) and it seems fixed in place. It could be just bundled and zip tied somewhere, but it could also be compressed behind a cabinet, so I don't believe it is a candidate for fishing a new wire in it's place. Darn tight spaces in a class b.
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HarryN · 02-14-2019, 07:58 PM

A bit complicated, but if you use a 12 - 24 volt converter, push the power through at 24 volts to the other side, that doubles the power for a given current.

Blue sea makes some 24 volt in / USB outlets.

The downside is that since it is unlikely for that cat 5 wire to be inside of a protective sheath, if it wears through and shorts it wouldn't be ideal.

It might be cheaper and easier to buy one of those portable USB batteries that charge from an existing source and then power what you need.

rowiebowie · 02-14-2019, 08:14 PM

Thanks.

Thinking now of just putting a cheap battery monitor there that tracks voltage. I just couldn't justify the $$ Victron wants for their monitors, and their bluetooth system should give me much more information (without the need for a separate monitor). Still, I like having some battery information at-a-glance.
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HarryN · 02-14-2019, 08:58 PM

Panel volt meters are fairly accurate.

Bogart makes some nice SOC setups.

llemberg · 02-21-2019, 06:24 PM

You can safely run 12V through an unused ethernet cable. The question is how much current will it carry? The answer is, it can handle what you want to do. You should remove the ethernet connectors at each end. Tie four of the wires together and use them for plus 12V, mark them with red tape. Make VERY sure you tie the SAME four wires together at both ends of the cable. If you don't, you will see lots of smoke when you hook it to the battery. Tie the other four wires together and use them as the Ground or return, mark them black or green. Four 26AWG wires tied together in parallel can handle the current of a single 20AWG conductor, which is 1.5Amp for Direct Current. At 1.5 Amp, the voltage loss across 15 feet of this cable is less than 1/2 volt, leaving 11.5V available for your USB, which is plenty. Your USB converter will convert the 11.5V to 5V for the USB device plugged into it. If that device tries to pull more than 1amp of current through your 1amp USB converter, the USB converter will either fail or protect itself from overload and shut down, but the wire will not be an issue.
Lars

avanti · 02-21-2019, 06:28 PM

Quote:

Originally Posted by llemberg

Tie four of the wires together and use them for plus 12V, mark them with red tape. Make VERY sure you tie the SAME four wires together at both ends of the cable.

....or:
Tie all 8 wires together and use the chassis as ground.

JohnnyFry · 03-12-2019, 12:53 AM

That is about the best idea...8 #awg 26 wires work out to 1 #17 awg.

Yoshimura · 03-12-2019, 09:51 PM

Could you not pull a new cable using the Cat5 cable as a fish?

rowiebowie · 03-12-2019, 10:15 PM

Quote:

Originally Posted by Yoshimura

Could you not pull a new cable using the Cat5 cable as a fish?

No. there was no "give" on either end even after I unbundled the CAT wire from others nearby. It runs under the floor from street-side to curb-side, so I was not surprised the wires were not pulling freely.
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chris_g19 · 03-14-2019, 12:08 AM

Using the cat 5 as a feeder line to pull through a rope or string. Then use that line to pull the cat 5 and a thicker guage wire through.

If I were you, I would be pulling off panels and putting in the proper line to prevent fire hazard, but I know it's lots of work.....

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