Off grid Wireless hotspot

Hi Paul - the best thing to do is take a quick look at the numbers. You note that the radio required 2 amps of 5 volts DC, and the wireless router 500mA of 24 volts DC. So from a device point of view, this is 22 watts.  Assuming you go the inverter route and use the power supplies provided (wall wart for the 5v and a tabletop for the 24V, most likely), you will need about 30 watts AC to run the setup.[IMPORTANT NOTE: Steve seemed to think your numbers were too high - it is absolutely critical to get the correct power requirements in order to size the system even for ballpark analysis - I am using your numbers for now].

For the Albuquerque area, if you run the available solar energy models, you will find that in the winter months you can expect to get about 12.6 kWh usable at AC (accounting for typical weather as well as inverter performance) per month from a 100W solar panel.

This is about 420 hours per month (12.6 kWh/30W). Divide by 30 days and you can run for 14 hours per day.�  This seems to work assuming you shut off the system between 10PM and 8 AM as you mentioned (you obviously don't have teenage users of the system.. although you could shut it off between 2 AM and noon and they wouldn't know the difference....). A nit is that an inexpensive timer on the output of the inverter to shut off the loads won't shut off the inverter so you will have a small (but non-zero) drain on the batteries from the inverter overnight; this can be minimized but not totally eliminated with the correct choice of inverter; for now I am ignoring this loss).

Storage should be a couple of days, so you might get by with a 100 amp-hour AGM battery (better would be about 200 amp-hours of capacity to reduce the depth of discharge for a very long battery lifetime).

Total costs would be on the order of $1200 (sorry this is about twice your current budget).�  We have found that taking short cuts with minimalized systems leads to poor/unacceptable performance. But if you can live with less hours per day you might get by a little cheaper (i.e. closer to your $600 with a smaller panel and only one battery).� 

If you want to discuss further please feel free to post and/or provide contact information.�  Best regards -

Tom Hardy, PE
HVTA, Inc.

Thanx for the information.  I believe the values are the rated  values from the transformers, not the measured...having said that I think the performance and reliability should error on the high side, so all your info (I believe) is right on target.  The timers as you suggested are perfect...didn't think of just using those cheap timers.  I will post the results as they develop.  Thanx again... Paul

P.S.  You guys are great and I really appreciate the info as it cuts time and money from the project...I believe that I would have had more maintenance and power problems that would have tripled my budget...I think your analysis will save me in the long run.

Hi Tom

Didn't see this as I haven't been watching for responses to this thread anymore.

You mention a load (8 watts), but are you intending to run this 24/7?

Also, where are you located?  Makes a big difference in power availability.

Finally, I have used a 5V supply running off the 12V nominal supply (11 to 15 or so volts) and can provide you with a suggested vendor for that. 

Let me know your location and the expected hours per day and I can run some models and provide suggested panel and battery sizing. 

Regards -

Tom Hardy, PE
HVTA, Inc.