# Solar power question



## cobracon2 (Oct 27, 2014)

If the grid is down and all is lost, what happends when your batteries die? What could you power with a solar panel ? Sorry if it's a stupid question, but batteries don't last forever.


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## HuntingHawk (Dec 16, 2012)

You could still power stuff threw the "dead" batteries. The batteries just wouldn't store power for later use.


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## Dubyagee (Nov 9, 2012)

Someone would have taken over battery manufacturing by then or learn how to make batteries. 

Direct solar cell power would have to be regulated somehow to be useful and still would be an erratic source of power.


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## cobracon2 (Oct 27, 2014)

Maybe some kind of regulator or filtering device. You think homemade batteries will be possible?


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## Maine-Marine (Mar 7, 2014)

The power could still be filtered through a controller..same as when the batteries are good

two ways... 
1 as mentioned above keep the batteries and let the power go through them ie solar connected to solar, battery to battery, load to load

2. solar to solar, then device (like a light or radio) to battery connection and nothing on the load...


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## 8301 (Nov 29, 2014)

I think Cobracon2 means the batteries need recharging and is asking about how much energy a typical Solar Panel makes. I've built small solar setups (less than 500 watts) and hydro generators so let me see if I can keep this simple.

Just remember that "watts" is the measurement for energy and we are going to ignore parasitic losses for this discussion. Don't let volts and amps confuse you at this point, let's just focus on total power amounts measured in watts. If you make one watt for 1 hour you have one watt hour. 
A 40 watt lightbulb needs 40 watts to light up and 40 watts fed to it for as long as it is on. 
A 1000 watt microwave needs 1000 watts (1kw) to run at full power. If you run your microwave on full for 1 hour you will need 1 kwh. This is how your electric company measures the energy on your bill, kilowatt hours or kwh
A 3 amp refrigerator at 120 volts needs,,, 3 (amps) X 120 (volts) = 360 watts to run but like most electric motors may need a bit more than 360 watts when the motor first starts up.

Solar panels come in many sizes and voltages but the voltages tend to be around 20 v which is good for charging a 12v battery. You can hook the panels in series to raise their voltage for charging a 48v battery bank. Solar panels usually aren't running at full rated power so in average sunlight you may see a 100 watt panel putting out 90 watts in the middle of the day. If it's cloudy I've seen my panels putting out just 10 watts and on super bright days at noon I've seen over 110 watts from a 100 watt panel.

So, Assuming you have a good location a 100 watt solar panel can run 90 watts of lightbulbs for as many hours as it has good sunshine. If you were trying to charge up a 12v battery and your area averages 5 hrs of strong sun a day (that's the national average) it would look like this. 90 (average watts) X 5 (hours) = 400 (average watt hours a day) per panel.

Since we are using this 100 watt solar panel to charge a 12v battery your 90 (average) watts it looks like this. 90w divided by 12v =7.5 amps feeding your battery. If the sun shines for 1 hour you will put 7.5 ah (amp hours) of charge into your battery.

You will want a solar charge controller (cheap ones cost around $30) to keep from overcharging your batteries. You can find a fuller and maybe easier to understand explanation using hydro power on my business website Water Wheel Electricity


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## budgetprepp-n (Apr 7, 2013)

There will be good car batteries around for a long time and they would work in a pinch


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## paraquack (Mar 1, 2013)

I used a pair of golf cart batteries (true deep cycle) in my RV for house batteries (not for starting the engine except in an emergency). With proper care and feeding, this pair lasted me from the summer of 2000 until I sold the RV in February of this year. While dry camping, even tho they were nowhere near 100% they still managed to supply the periodic power to the hot water heater, bathroom ventilator fan, freshwater demand pump (low demand on 12 volt power), the inverter to watch TV for 3 evenings, the 2.5 Amps to my fridge, 24/3, and the lights I needed at night without nearing discharge. IMHO, knowing the limitations of the batteries prevented me from prematurely destroying the batteries by fully discharging them thru out their life. The proper type of charging system, weekly checks on water level (probably could have been done monthly) and using only distilled water to fill top off the batteries added up to a long life span. The biggest killer of lead acid batteries is the complete discharge multiple times.


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