# solar power

i am trying to setup a 900mhz ap and a 5.2 back haul on a small tower in which i have no way of getting electric to it what is the cheapest way to do solar how big of a panel do i need and how many batteries and what kind do you suggest? i live in upper mid TN

kenny
Info-ed Inc.

A. Add up all of the power requirements for the equipment. (including battery charging)
B. Calculate how many amps you will need to make it through the hours of darkness
C. Get batteries that will store at least the amperage of B
D. Find a solar system that generates more then enough for your given light levels

There is no easy canned answer. It takes a complete understanding of DC electrical, solar generation, and electrical consumption principals and the exact needs of your system.

I have a site that is solar it consists of a cmmmicro 1 900 connectorized AP 2 5.7 AP’s and 1 2.4 BHS. I did all the calculations like ahull described and ended up installing 2 12v pannels in series for 24v i will get specs for you a trace charge controller a low voltage disconnect and 2 batt. It was a learning experiance. everything was fine till the system got loaded. I did learn that the whole system will work all the way down to 12volts and pass data. That means that both batteries got all the way down to 6 volt each. I lost both batteries and they are not cheap. Thats why i suggest a low voltage disconnect. Any how everything worked fine. got customers on it still fine. Until the rains came. I had it calculated just like ahull said wrong. their were days when i never saw the sun. That is my point dont just calculate for 1 night. I have it set now to go a whole week without sun just incase with 2 300 amphr batt. Good luck.

i forgot to mention once you figure out how mutch capacity of the batteries get big enough pannels to charge them in 1 day say like 5 hrs.

well i just want to put a 900ap and a 900 sm i am gonna do that until i can afford a back haul i am just gonna have about 15 to 20 subscribers so i dont think the extra delay will matter that much just for them right now.i can always beef it up a little later on.

info-ed inc…

attitude0330 wrote:
2 300 amphr batt.

Dang. Those batteries must be enormous!

We use 2 12V 72 amp-hour batteries in ssries as battery backup for our towers and those were pretty hefty. I can only imagine those monsters.

I completely aggree with you on the low voltage shut down.

their pretty big. just a little bigger than one you see in an 18wheeler. Our main business is rf we use them on 100watt repeater sites so i had a pallat of them in the shop already.

We use 12 - 2 volt flooded cells (6 in series, then paralled) for 12 volts - 100 amp hours each. The damn things are 100 lbs a piece. With our load (also mostly VHF and UHF repeaters) we get anywhere from 10 hours to 24 hours of backup. All of those sites have utility power to them.

I have one solar site that has 2 - 45 Mbps backhauls, 6 - 2.4 AP’s and one 900 AP. We also have a PTZ camera, LED lighting, and and RTU for site SCADA. (approx. 10 A @ 12 V continuous) not much load in my mind. The same cells there float at 13.6 V and last about 18 hours (down to approx. 11.2 V).

We have approx. 1300 W of panels to charge with - on a good day we get over 60 amps of charge ( we want as much as we can get if the sun comes out). We have the same problem of not seeing the sun every day. We also have a gas generator up there that we can start remotely via the SCADA if the sun isn’t giving us any charge. Power company has told us Dec. 4 they’ll have utility power to us - I hope so.

Aaron