Any Disadvantage of cheap/pseudo PoE Adapters from ebay/Amazon if power is below 10Watts?

[Baum]

What is the disatvantage of using these cheap "Power Over Ethernet" Adapters with an old Router that takes 5V at around 4Watt to 7Watt

Is it possible that the cable degrades over time?

Does the link speed go down from 1Gb/s to 100MB/s ?

 

[Bill_Bright]

What is the disatvantage of using these cheap "Power Over Ethernet" Adapters

Compared to what?

Sorry but how are we supposed to know anything about those cables by looking at a picture? You didn't include a link to them. You didn't include the specs, brand or model numbers. You didn't include any alternative solution to compare those cables to in order to determine what, if any, disadvantages (or advantages) they may have.

What makes them cheap? Do you mean cheap as in "inexpensive" compared to other PoE cables? Or do you mean cheap as in "poor quality" compared to other PoE cables? If you mean poor quality, how do you know they are of poor quality? And what does that even mean? Lousy manufacturing techniques and poor quality control? Low quality parts? How are we supposed to know?

Should I get this power cable?

See what I mean?


FYI - "all" cables degrade over time. Degradation will happen more quickly if the cable is exposed to direct sunlight, the weather or other physical abuse like teething puppies, people tripping over them, etc.

 

[Count von Schwalbe]

I was under the impression PoE was a 48v standard. Looking into it, it looks like those are simply taking a pair of wires to transmit 5VDC, which is not true PoE.

If that is the case, it will limit you to 100Mbps. Also, your cable length will be quite short (voltage drop). I find it hard to understand the purpose of those cables.

 

[Solaris17]

This looks and smells like a fire hazard and is 100% not spec at all.

100% would not connect to literally any equipment.

If you want something powered over POE look for "POE Injector" there are plenty of actual products that conform to spec that can do this.

 

[Operandi]

I was under the impression PoE was a 48v standard. Looking into it, it looks like those are simply taking a pair of wires to transmit 5VDC, which is not true PoE.

There are different versions and revisions of PoE but yeah whatever that is isn't part of any of them. The more advanced versions communicate and negotiate the correct type of power which obviously this isn't doing. If its cheap stuff you don't care about and you know what you are powering is supposed to accept passive PoE (which I think is one of the standards?) then it might ok but I wouldn't use anything like that.

 

[thewan]

While passive POE is not a part of any standard, major networking brands have been using them for a long time, such as Ubiquiti and Mikrotik for example. The main drawback of it not being a standard is that passive POE is dumb, it directly injects voltage in one side and expects the other side to accept whatever comes out. So for passive POE you need to ABSOLUTELY KNOW WHAT YOU ARE DOING. If you don't, you risk frying your equipment and burning your wires, creating a fire hazard.

If you bought networking equipment that was made for each other, lets say you use a Mikrotik Switch that can be powered via passive POE with a Mikrotik passive POE adapter, then you are fine, those companies know what they are doing. They do this to save costs and pass the costs savings over to the customer. But if you don't understand how electricity works, please do not attempt this.

Active POE, which is the main standard, requires negotiation between the two points. Without this negotiation, POE won't be activated for safety since too much voltage can damage the device and cause a fire hazard. Which is why Active POE is preferred over passive POE. In fact Ubiquiti mentioned that they stopped using passive POE and are switching to Active POE for this very reason, safety.

Also there is an issue with passive POE, at low voltages, it can't go too far. If you are trying to input 5V one end, you wont get 5V at the other end, theres too much voltage drop around right before 5m I believe?. For long distances you would have to send a higher voltage from the source, and then convert it to 5V at the destination before plugging into your device. If you don't know what is all this, do not attempt it.

Active POE does this automagically via its negotiation, which is why it is more expensive to implement.

 

[Operandi]

Yeah I knew Ubiquiti used it in the past but that was before my time using their gear. All the other equipment I've used has been active PoE including Ubiquiti. In the switch it will actually say what voltage and how much power the device is using. Speaking of switches thats by far the best way to get PoE devices up and running, individual PoE injectors are expensive and I only use one to test devices when running cable to a switch isn't practical.