Solar Power Calculators

[thedudex2]

Recently, has anyone took apart a solar power calculator and used the solar panel for any sort of a project? I am curious because I just did. Looking at it, it charges one of those large watch batteries. Eh probably to low of a power to do anything. I would be interested if someone has used it. Any kind of project that involved a solar panel cell from a solar power calculator.

 

[Sceadwian]

You could probably use it to power a simple digital watch like a potato clock only with the solar cell instead, but nothing that uses more power than that, they produce nearly unusable amounts of current. Modern calculator ICs however are so low power they don't need much, they'll run off the battery just fine until you lose the calculator, the addition of the solar cell helps keep the battery topped off from it's own natural discharge because that's higher than the power draw of the electronics.

 

[Hero999]

I don't think the battery backed calculators I have use rechargeable batteries but I've never had to replace them. Most of the time the calculator is powered from the solar panel, it only very rarely gets used in low light conditions which cause the battery to be used. The main function of the battery, is to back up the memory so the settings and variables are saved.

 

[Sceadwian]

They're powered by both Hero, if the solar cell is in direct light it will produce a higher voltage than the coin cell, if not the power comes from the battery. All battery types can be re-charged to some extent but the power those solar cells can produce does little more than keep the leakage current low when it's not in use, that's why you never have to replace the batteries.

 

[thedudex2]

I am measuring 3.36 Volts to 3.35 Volts when I have the panel under sunlight. I could do a simple project with it and 2 LEDs just for kicks. But now I kinda want to see about storing that power when I leave it out all day. That would be interesting.

 

[Sceadwian]

And what's the short circuit current under direct sunlight? I'd be surprised if you could measure it.

 

[thedudex2]

No clue what you mean. I can still get 2.35 Volts at night under a lamp.

 

[Hero999]

He means, connect a current meter across the panel to measure the short circuit current, it'll probably be a couple of mA, at most.

You could connect a super capacitor across the solar panel, the problem is, it will take awhile to charge up before the calculator will work.

 

[Sceadwian]

The voltage a solar cell puts out means absolutly nothing if it can't put out a useful amount of current thedude.