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Old 02-13-2019, 04:35 PM   #1
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Default 12v thru Cat5 Cable-Harebrained Idea?

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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Old 02-13-2019, 05:45 PM   #2
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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.
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Old 02-13-2019, 06:04 PM   #3
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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.)
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Old 02-13-2019, 10:13 PM   #4
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Quote:
Originally Posted by rowiebowie View Post
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
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Old 02-13-2019, 10:48 PM   #5
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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*.
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Old 02-14-2019, 12:07 AM   #6
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Quote:
Originally Posted by markopolo View Post
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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Old 02-14-2019, 12:10 AM   #7
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Quote:
Originally Posted by Gryphon View Post
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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Old 02-14-2019, 12:16 AM   #8
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Quote:
Originally Posted by Boxster1971 View Post
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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Old 02-14-2019, 12:19 AM   #9
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Quote:
Originally Posted by booster View Post
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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Old 02-14-2019, 12:51 PM   #10
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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.
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