# Solar Kit for Tool Shed



## Jonathan (Oct 26, 2011)

I feel like I unintentionally hi-jacked another thread, so I thought I would start a new one to avoid taking that one farther off topic.

I plan to buy a small solar kit to power a tool shed. The primary use will be for lights (a couple of CFLs or maybe a halogen shop light), charging batteries, and maybe a small fan or radio. The lights are likely to only be used for an hour or two maybe 2 - 3 times per week. I would also like the ability to power a circular saw for the times that my cordless saw isn't sufficient. The saw I have now is 12 amps, and I would only need to use it for a few minutes. Anything beyond that I would use a generator.

I was considering buying the 45 watt kit from Harbor Freight and adding a 1500 or 2000 watt inverter and a decent battery (maybe something like a 12 volt 55AH). Everything other than the saw would do fine on a smaller inverter, so I may hold off on that purchase for a bit.

I'm hoping to not sink too much money into this, since it is really just to experiment with. I've looked at a few kits other than the HF kit, and was hoping that someone here might be able to make some suggestions (I've received a few already). If you were in my shoes, what setup would you go with? What other costs should I plan for (wiring, etc). Any specific suggestions on batteries, etc is also welcome.

Thanks


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## wy_white_wolf (Oct 14, 2004)

Everything may be doable with the HF kit except the saw. 

That small of a battery can never provide a enough power to run it. It would exceed the stable output rate it could provide. You have to remeber that 12amps at 120v would be over 120amps at 12v. It just can't supply that much power.

Also the 45 watt kit would take 2 to 3 days to replace what the saw uses in 5 minutes.


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## Jonathan (Oct 26, 2011)

So here is what I was thinking with the saw. 12 amps @ 120 volts would be the equivalent to 1440 watts. A 12 volt 55AH battery could provide a total of 0.660 kwh of power. Assuming the battery is not discharged below 50%, and assuming 80% efficiency of the inverter, the battery should be able to power the saw for 10 minutes or so. Sounds like I'm missing something regarding the stable output the battery can provide. Would you mind to explain that? Also, what type of battery would you suggest for powering the saw?

As far as the recharge, I figure on an average day the panels would produce somewhere around 180-200 watts. If the battery is kept at 50% charge or better it should take, at most, 2 days to charge the battery (assuming idea conditions). So, if I used the saw today for 10 minutes, I definitely wouldn't be able to use it again tomorrow, but should be able to use the lights if needed to. I wouldn't be able to use the saw again for probably 2-3 days, which should be no problem since I wouldn't use it often anyway.


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## 12vman (Feb 17, 2004)

In Ky, during the winter months, you can figure ~ 3.5 hrs. of charge time during a good day. That's only going to produce a little over 9aHr. of charge.

Deep cycle batteries are designed to supply current for a longer length of time than a standard car battery. Car batteries will supply high current to start an engine for a short duration but doesn't like to be deep cycled many times.

A 55 aHr. battery alone will not supply 120 amps on a surge or hold it for any length of time. It might supply most of it but the voltage is going to drop dramatically, well below the inverter shut down voltage.


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