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solar question for mini pop

[ Edited ]

Hi all;

 

I was wondering if someone can make a suggestion for me. We're experimenting with solar deployment mini pops at 12v

on utility poles.

 

Our test scenario is

 

2 Litebeam ap

1 PBE5AC

1 Edgepoint R6

1 12v to 24v step up converter

2 250 watt solar panels

1 Lite midnite solar charge controller

 

We would like this site to stay up for atleast 3 days without sun. We get an avg of 6 hrs sunlight a day.

 

Can anyone make suggestion as to size ot battery bank? and are we better off using step up converter over a 

12 v to 110 ac inverter. Suggestions for this small site are welcome.

 

Thank You,

 

RJ

Established Member
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Re: solar question for mini pop

Have you checked out the solar point yet?

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Re: solar question for mini pop

The solarPoint really is on the verge of being under-sized for the proposed scenario unless it is located in the desert. 

 

For the proposed constant load of ~24 watts and 3 days of autonomy you need at battery bank of 288AH @ 12 volts.  So, essentially 3 group 27 or 29 size deep cycle batteries. 15~20 amps of charge would be needed to keep the batteries healthy.

 

Absolutely use a step-up converter as opposed to an inverter.  Why convert from DC -> AC -> DC and suffer the losses?

SeaKay Broadband
http://seakaybroadband.net
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Re: solar question for mini pop

Well the solarpoint is just the controller to eliminate a couple of devices, it has nothing to do with how long the site would stay up.
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Re: solar question for mini pop

The problem with the solarpoint is the 7A charge that it can produce into a 24v battery.  If he were to add another battery to make a 24v bank in order to keep his desired days of autonomy, he would run the risk of chronically under-charging his batteries, leading to sulfation and early failure. 

 

For two radios the solarpoint would be a better fit.  Add the third radio and the router, and it can't efficiently charge a battery bank large enough for his stated needs.

SeaKay Broadband
http://seakaybroadband.net
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Re: solar question for mini pop

[ Edited ]

We use:

 

1-2 Litebeam AP or RAC-Lite w/ Omni

1 PBE5AC

1 Edgepoint R6

1 Tycon Solar SCPOE-2424-HP

2 HQST 100 Watt solar panels in series

6 35ah AGM

 

We are in the central Midwestern US and get about ~6 hours of sun per day. We found that monitoring the batteries and occasionally swapping them with charged batteries is the best way to go for us. We only have to do this from about mid December until the first few weeks of February. We have a custom PCB that monitors voltage, temp., etc. It's based off an arduino but could easily be duplicated with off the shelf parts. We tried the Solarswitch but it limits a lot of the control vs what we can do with our current setup. The batteries start loosing capacity after about 6 months. We use the 35ah batteries because of the $/ah and they are available pretty much anywhere.

 

If you wanted to maximize the sun you could use 4 panels and face one set 45* to the east and the other 45* to the west. Just wire them the 2 sets together in parallel and you will be able to take advantage of that max charge rate for a longer portion of the day. Everything with solar is a trade off, just try it and see what works for your situation. Good luck!

 

EDIT:

I just looked up the cost of that charge controller, and thats more that the total equipment cost for one solar towers. Even if you are using 2 250watt pannels your only need ~20 amps for charging. There are plenty of 24v 35amp chargers for under $50 if you decide you need those.