I have just bought a ubiquiti Airgrid m2 hp router and would like to run it on batteries. Has any body carried out such a modification to the Poe.?

I would caution you to verify the pin out of your POE injector.  There are several different schemes in use and if your injector puts the voltage on the wrong pins it releases the "blue magic smoke" that makes the nodes work.

I have used several ubnt nodes running of a 12 vdc battery with no problems.  If you are using 12v I would suggest you keep your cable distances shorter.

Clint, AE5CA

Thank you both for your replies. Being a novice I am assuming that an injector is a device which plugs into the Poe  which allows a way of feeding power to the system from an external source. This is an excellent way of doing it but I would have to ensure the pin connections are properly observed. To date I have not found ubiquiti as being forward in providing technical information on their products. Can you suggest a site I can use for the purpose.

having said this the second option of feeding the node with 12volts or 24volts for that matter, need a detailed explanation of how to go about it. I would be obliged to receive more information regarding the matter.

thank you again.

chris 9h 1bw.

The Ethernet cable connected to your AirGrid has 8 wires.  They are grouped as 4 twisted pairs.  10/100 Ethernet only uses 2 of the 4 pairs for data.  Actual data will only be on pins 1 & 2, and 3 & 6.  This leaves the other two pairs available to supply power to the AirGrid.  POE means we are sending Power over the Ethernet cable.

On page 5 of the AirGrid Datasheet available at http://dl.ubnt.com/datasheets/airgridm/airGrid_HP.pdf, It states that the Power Method is "Passive Power over Ethernet (Pairs 4, 5+; 7, 8 Return)".  The POE adapter that comes with the AirGrid takes 120 VAC and converts it to 24 VDC.  It then places the positive output on pins 4 & 5 of the Ethernet cable and the return on pins 7 & 8.

The POE injector that Andre referred to replaces the POE adapter that came with your AirGrid.  Instead of having a power supply build into it, there is an input for power that can be connected to a battery or an external power supply.

While it is hard to find definitive data, my research has found that there is no problem powering a ubnt node with 12 VDC.  You just need to supply that power to the node with the positive on pins 4 & 5 and the return on pins 7 & 8.

When I indicated verify the pinout of your device, some POE injectors reverse this polarity or may use a different set of pins.  There are multiple versions out there.  

You may want to also look at this thread from the forums:

http://www.broadband-hamnet.org/hsmm-mesh-forums/view-postlist/forum-794/topic-794-emergency-power-and-poe-for-ubiquiti.html.

I wish people would quit calling this stuff "POE."  POE is a standard that is "safe" in that it handshakes before sending the voltage.  

If you plug a standard gigabit ethernet device into one of these bogus "POE" cables, you'll smoke the device.   Gigabit ethernet uses all 8 wires in the CAT5 cable.  Gigabit ethernet is getting a lot more common in laptops, desktops, and other devices. 

Like it or not, "Passive PoE" is an industry standard term, Cisco has been using the technology since before 802.3af was created. Passive PoE has existed longer.

Plugging a gigabit laptop into the network side of a Passive PoE injector is safe, the injectors split the wire and do not back feed down the network side of the port (unless it was poorly made but I've NEVER seen that ever)

Plugging anything on the POWER side is the same thing as plugging into a wall outlet,  you should be careful (I recommend using a colored tag if you are worried or colorized tape to signify the line is HOT).  This is same concern as wiring up your radio in your car, or a tnc, don't plug the power cable in the wrong place.

That said I've plugged the injector HOT/Powered side into gigabit switches accidentally and not fried anything yet, I sure would not recommend doing it regularly but it's not a guaranteed death sentence either.