New user getting started with pi.

[apopleptic]

Hello, I am new here, just got my pi. Hopefully I'll find some helpful people here as I really have no recent programming or linux experience. back in the 90s I studied programming, but I haven't done anything at all since 1999.
Excited to use this little thing, hopefully going to end up with several doing several things in different places.
My main purpose of purchase was to replace my aging surveillance system. When my house was robbed, the one camera didn't capture a good enough quality picture to use to catch the thief. The other wasn't aimed right to capture the license plate information, and even then would probably have been blurry. pan and tilt on the one would be nice.
I also have plans to use one for temp/humidity and possibly another to detect if there is a leak in my basement.
End goal is probably 4~6 of these, and I would like to run them all with wired ethernet, using the brown/whitebrown pair for power so as to only run a single cable.
Anyhow, getting started.
I downloaded the installer for raspbian and got a bunch of errors that eventually seemed to say the mirrors no longer serve that version of linux.
Next I downloaded an image for raspbian and put it on the card. Brought it to my living room to try to install it and my wireless KB isn't working.
I get the multimeter and read between TP1 and TP2 and see that it is saying 4.2v so I assume that my wallwart is of poor quality (thanks HTC).
I connect a 12v SLA battery and a DC-DC Buck Converter Step Down Module LM2596 and adjust until the output reads at 5.2v and reconnect the pi. Measure TP1 and TP2 and show just over 4v again. I adjust the LM2596 until we are showing 5.2 under load and it seems like it boots so I power it off, build an injector, connect the battery and the LM2596 in my server room to my living room and connect it to my tv via hdmi and power it up and it goes through the startup until it gets an error. I assume that it's due to a bad poweroff so I put a fresh image on the sd. When I power it back up I get to the setup screen and no network lights and my keyboard isn't working.
I turn everything off, disconnect the injector test the network cable and it is working, reconnect the pi with a different KB and still nothing. I measure the voltage and it seems to be fluctuating from 5.3v down to 3.8v averaging 4.4v most of the time.
I've turned everything off at this point. Wondering if the cause is the resistance of the wires. The cable is about 60' if I remember right from when I installed it. Maybe I need to move the LM2596 down to the end of the cable that the pi is on and run the full power of the battery through the line before stepping it down right before the pi. I was hoping to be able to run multiple devices from a single LM2596 but maybe that won't be possible.

Can anyone point me in a good direction? or am I looking in it already?
Thanks!

[Tarcas]

The Pi has very tight voltage tolerances. The 5.2 that you were reading at once point, I believe is the top end of what is acceptable. You will definitely have problems with resistance of the Ethernet cables unless you're using a step-down located at each Pi. I've seen people with issues using USB cables over 6 feet, so your 60 feet is definitely going to add too much resistance. If you have to use power over Ethernet, try running the highest voltage that your source and LM2596 can handle over the wire and step it down right at the Pi with your LM2596.

Also since you read 5.3 at the Pi at one point, do test the Pi. That's definitely out of spec and I would be concerned about damage. Do test it on a known-good power supply before you spend more time on the PoE solution.

[apopleptic]

A slight update.
First I replaced the battery with a new one that I know is good. Then I moved the LM2596 to the end so that 12V is being carried then brought down at the pi. I adjusted the voltage so I was getting 5.18V at the LM2696. Powered up the pi and read it on the board and it was dropping down to 4V.
It seems as though the issue was a bad usb cable. I had been carrying it my work bag and it must have been damaged.
I replaced the USB cable with one from my car and I now have the miraculous ability to boot the pi and get online with ethernet and wireless keyboard.
If I unplug the cord at the wall here it disconnects the power so it is an open circuit and as far as I know that means no drain on the battery without having to go upstairs.

Looking forward to playing around now that I can boot.
I will continue this thread as I learn the pi and move closer to the end goal of my projects.
Pictures will follow for the power injectors and etc.