solar panel to charge 12v deep cycle battery?

sup guys i am using a computer for about 3 hrs every night, it has a 400 watts power supply. I am also using a wood lathe which is has a 1\2 horse power motor for about 1hour of use. I want to use a solar panel to charge a 12 v battery (car or deep cycle battery, i have a use car battery as for now) so i would like to know how much power solar panel i would need running all day to keep the battery charge so when i come home at night to use my computer for 3 hrs.also i would like to know if the car battery with a 400 watt inverter will keep the computer running for 3 hrs only and then its off and the panels can recharge the battery next day till i come home again.

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• Seth
Lv 4
7 years ago

A 400 W supply doesn't really say what the average power consumption is. But if we assume that you are operating somewhere near 400 W total, including losses due to the inverter and battery, then this is 1200 WH. You probably won't get more than the equivalent of 6 hours of direct sunlight per day, which means that you would need about 200 watts of solar panels. This would not account for variations in sunlight, which could significantly reduce the stored energy. But you may not be using a full 400 W, so you may not need quite that much either.

If possible, it would be MUCH better to use a laptop versus a desktop computer if you need to run it off solar power, since the power consumption is far less.

And the lathe might add another 400 WH or so, so for that you would need at least another 70 watts of solar panels, probably more due to inefficiencies.

• johnm
Lv 7
7 years ago

The PC will use only 150 watts unless you run a gaming graphics card, then the wattage will be 300 watts. So 150 watts x 3 hours is .45 Kwh per day. The lathe uses 745 w / 2 = 372 watts. So 372 x 1 = .372 Kwh per day. Total = .822 Kwh per day.

The solar panel needs to be at minimum .822 Kwh / 8 hrs sun = 103 watts capacity. But since the battery, inverter, and solar strength are not 100% efficient, figure about twice that size. A 200 watt panel should work.

Use a deep cycle battery of around 200 amp hrs for storage.

• 7 years ago

My computer used to have a 150 Watt power supply and when it burnt out I bought a 400 watt replacement. I plugged one of those Kil-A-Watt meters into my power strip to measure how much power my computer was using (Dual Core 2.0 MHz each core) and it rarely even made it to 100 watts and that was when using the DVD.

Your problem is going to be getting a battery because that car battery doesn't take deep discharges well at all. It will take maybe 50 deep discharges (50% of capacity) and the plates will just get heat warped because they are so thin.

If you turn on your headlights, they use about 120 watts of power on high beams. See if your battery will last for 3 hours running your headlights. Probably close, but they will go bad quickly if you pull them down that far. It is better to get the deep discharge or trolling marine batteries, which have less capacity but can be run down real far without damaging the lead plates.

Maybe two 500 amp-hr batteries and at least a 100 watt solar panel running all day and you should have no problem even in cloudy weather.

The lathe has a motor that would use 400 watts at full load, but if you take it easy on the lathe it will only draw 100 watts or so.

You really ought to buy one of those Kil-A-watt meters, because they tell you exactly how many watts anything you plug into it is using and it also runs a kilowatt hour running total so you get a much better idea of the power requirements of both the lathe and the computer. Plug those into one and run it like you wanted for those three hours and it will give you an exact kilowatt-hr number so you can calculate how much storage and solar cells you would need

• 4 years ago

You are using 400 watt-hours at night. At best you may generate 50 watt-hours during the day and more likely half that amount. To be resonably secure, you will need about 100 watts of generating capacity at a voltage of 18 or greater. Panels marked nominal voltage of 12 volts will usually produce in excess of 20 volts. You will also need a charge controller. The 100 watt panel will generate 100 watts at noon when perpendicular to the sun. Derating by 50% should put you in the ballpark. So, 8 hours times 50% times 100 watts equals 400 watt-hours or about your nightly use. By the way, a deep cycle battery means that it will recover from deep discharge. This is the proper type of battery to use with solar installations. A regular car battery is not deep cycle. They are designed for high starting currents, not deep discharge.

• Anonymous
5 years ago

There is a step-by-step video guide online right now that can show you how to reduce your power bill by making your own solar panels.

Take a look at it: http://tinyurl.com/Earth4EnergyRew

Why pay thousands of dollars for solar energy (\$27,000 average cost) when you can build your own solar panel system for just a fraction of the retail cost. You can build a single solar panel or you can build an entire array of panels to power your whole house.

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• 3 years ago

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Source(s): Homemade Solar Power Videos : http://Solar.eudko.com/?lMl