Help needed with system configuration for a wireless repeater and cable modem.

[austin.colby]

Hello,

I am new to the solar world and will be slowly working on taking my house off the grid. For my first project, I need to build a system to power a cable modem and wireless CPE 802.11b/g/n repeater. Basically our cable company wants to charge around $7000.00 to run a 1400' coax to the house and I really have no desire to pay that especially since I only am interested in the internet service. Below are a few things that I have put together so far but am stuck on whether or not the system will work since I am unable to do the math properly for the load calculation.

Equipment:

Motorola SB5101 Series SURFboard® Cable Modem
DataSheet
Input Power: 105 to 125 VAC, 60 Hz
Power: 9W (Nominal)

Ubiquiti Nanostation LOCO M5 Outdoor MIMO 2x2 802.11n 5GHz
DataSheet
Max Power Consumption: 5W
Power Supply: 12V, 1A (12 Watts). Supply and injector included

Location is in Keedysville, Maryland and have a pretty clear property. I plan to mount the panels on top of a 10' aluminum pole and then mount a weather tight box about 4' from the bottom to house the battery and equipment in. I have come up with many different panel size requirements using a few of the calculators on the web (anywhere from 15W-193W panels) and just need some advice regarding the optimum setup for the two pieces of equipment above. I might be adding a wired camera to the equipment that has a max power consumption of 12V DC or 24VAC @ 500mA.

Currently I am looking at purchasing two 50W Monocrystalline Solar Panels, 10A Solar Charge Controller / Regulator 12V / 24V, 200W Power DC to AC Inverter along with a deep cycle marine battery but think it might be overkill.

Any help would greatly be appreciated!

[Sunking]

Read this thread and then go get your solar insolation for December here.

[austin.colby]

Read this thread and then go get your solar insolation for December here.

Alright - so with some initial math, here is what I came up with...

The modem and router take approximately 14 watts total (9W Modem and 5W Router)
Total watt hours: 360
Fudge Factor: 540 watt hours
Solar Isolation: 3.1
Size of Array: 174.19 watts
Battery size: 1800 watt hour (75 amp hour at 24VDC)

Now, I would assume that this is close to being correct but can't determine that for sure from the datasheets provided since they are quoting some power usage at 12VDC.

175 watt panels seem overkill for such a low power system. Is there something that I fudged somewhere?

[Sunking]

Alright - so with some initial math, here is what I came up with...

The modem and router take approximately 14 watts total (9W Modem and 5W Router)
Total watt hours: 360
Fudge Factor: 540 watt hours
Solar Isolation: 3.1
Size of Array: 174.19 watts
Battery size: 1800 watt hour (75 amp hour at 24VDC)

Now, I would assume that this is close to being correct but can't determine that for sure from the datasheets provided since they are quoting some power usage at 12VDC.

175 watt panels seem overkill for such a low power system. Is there something that I fudged somewhere?

Depends what kind of charge controller are you using. For PWM you need to generate 720 Watt hours, and for MPPT 540 Watt hours. So if you use a PWM controller you need 720 wh / 3.1 h = 240 watts, and for MPPT you need 540 wh / 3.1 h = 175 watts. You are right on the border line economically. Price both PWM and MPPT to see which is less expensive.

Battery is easy as you need a capacity of 360 wh x 5 days = 1800 watt hours. At 12 volts that is 150 AH, and at 24 volts is 75 AH. Last word on the batteries use flooded lead acid. Less expensive and last longer.

[Naptown]

Just finished one up in Keedysville.
Beautiful country. Needing only one panel and minimal charge controller and battery this is actually an off grid project that makes economic sense. If you go PWM controller look for 36 cell panels. If you go MPPT you can use either a 60 or 72 cell panel. What you will find is the 60 cell panel will be less expensive than a 36 cell panel for the same watt rating but the MPPT charge controller will cost more. Which works to your advantage will have to be priced out component wise.