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Can I make a solar power source with a car battery, 5 watt 12v solar cell, and 12 volt to 110 vac 400 watt inverter? Answered

The title sort of says it all but what I am wondering is  if the solar cell can keep up to the inverter...


The solar cell charges the battery slowly over the course of the day, and the battery supplies the power to the inverter when the 110 v load is running.

The solar cell will put out 5 watts, and I assume that this is only under conditions with good sunlight. So, if the conditions are correct for getting the max out of the panel, the largest 110 volt load that would be powered would be 5 watts, minus the inefficiencies of the inverter. 5 watts isn't much for trying to power 110 v electrical appliances directly, unless they are just computer peripherals or other small devices.

In a setup like this, the solar cell keeps the battery charged, and the energy stored in the battery is used by the inverter to supply much larger loads. Depending on how large your load is and how long it will run per day, this setup might work fine, but you don't get that specific. if the battery is in good condition and charged, it can easily supply the 400 watts the inverter is capable of, but the solar cell will not be of much use powering the inverter directly.

If the load is large enough and runs long enough, the battery will will discharge to the point where the inverter will not function properly and will probably go into an overvoltage shutdown. The solar cell will not be able to keep up, as it can only supply 5 watts.

what I wanted to do was have the solar cell charge the battery in the morning and when I turn on power to the inverter (whenever it gets dark out) for my lights and then turn off the power when I am using no power.

Also I could gladly buy another solar cell for a longer discharge time but would I have to buy another battery too?

Adding more solar panels or a higher output panel would allow you to charge your battery more quickly, but the amount of time your loads can run will depend on your battery capacity.

Charging during the day and only using the inverter at night should work with this setup, but the energy accumulated would be fairly low. The length of time you can run your lights will depend on the wattage and how long you need to power them. If you got 12 hours of conditions sunlight sufficient to make your panel output 5 watts, you could store 60 watt hours of energy, some of which would be lost due to inefficiency of the battery and inverter. 60 watt hours isn't a whole lot of energy. It would roughly power a 60 watt bulb for one hour. That wouldn't be enough to supply a homes lighting needs for several hours in a evening.

If you do plan to add more panels for faster charging or more batteries for greater storage capacity make sure you interconnect them properly. I'm not an expert in solar systems by any means, but there are right and wrong ways to interconnect solar panel arrays and battery banks. For example, multiple cells may not be able to be directly connected in parallel, as the one which produces less may act like a load to the other panel.

A good resource on solar and other renewable energy systems is www.homepower.com.

+1. Great explanation.

Whenever it comes to simple capacity problems I always equate it to the water analogy (oversimplified, yes, but gets the point across)

If you fill a bathtub with a trickle (5 watts) then you can totally 'drain' 400 watts out the large hole in the bottom, but only for a few minutes before it's dead, even with the panel trying to keep up.

Can you help me about how can I charge a laptop by a 5watt solar pv panel(an concept or design)what kinds of battery, solar charge controller & inverter I should use? Thank you so much

I am doing something exactly like this with the 400 watt. I have 12 volt 5 watt solar panel and a car battery. would the battery run longer if i use a low amount of wattage in an inverter? such as 100 watt inverter or even a 75 watt inverter?
Plus a have one more question, Is this true: "The higher the amp in the rechargeable battery, the longer it takes to charge fully?"

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Yes. With the 100 watt inverter every 20 minutes of full capacity charging will give one minute of energy. For 75 Watt, you'll get one minute for every 5 minutes 20 seconds. The statement is true.

1. If you connect batteries in parallel, you get same voltage but higher amps?
2. Is it possible to somehow connect two of the same 400 watt inverters in parallel, or something, to get higher wattage?

Yes, and yes. Both assuming that your wire can handle it.

how would I do that? Just connect positive to positive and negative to negative?

Yes. You would get more power if you put both inverters' outputs in parallel. The reason being some inverters are regulated hence double amps in the input would give the same output.

Thanks! I'll put it to the test when the inverter comes. I might even post an instructable about it if there isn't one already. Thanks

Yes you can.
But appreciate that for every minute you run the inverter at 400W, the panel needs to have been charging at full output for 20.


wouldn't that be 80 since 400 / 5 = 80?
and if I added a second solar cell and put in 10 watts would I only need to charge half the time to get the same amount of power?

Erm, yes. What was I doing there..?
10 watts would be better.