what's wrong with this circuit?

Clearly less, since the battery voltage is more.

John

The subject being discussed is charging a battery from a single-cell solar cell.

Fred's statements violate COE. I suppose you'll take his side.

John

A flyback boost converter raises voltage at the cost of current. You

Jeroen Belleman

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Yes, but that current is derived from the charge stored in the capacitor as well as a small amount from the solar cell during disacharge- solar cell is in series with battery during flyback. JL is the creating a straw man again- who would say energy is not conserved? Based on the choice of L and C, you could pump charge into the battery at any rate you like during the flyback.

efficiency

Sure, but why? If efficiency matters, you want to optimally load the cell and pump as much average charging current into the battery as possible. Peak current isn't the point.

But straw man? Where?

You told me that "you miss the fact that the battery is being charged with carriers at the same average rate as they are produced by the solar cell" which, if I understand what you mean by "carriers", can't be true, because it does violate COE.

John

Maximum efficiency counts if you're running real world products and have to allow for something like five days cloudy weather between charging weather. I've notices quite a few newish solar powered devices conking out during the first cloudy day, that's poor design somewhere. Efficiency should be encouraged. That means keeping the solar panel nears its best operating point, not practically shorting it out each time you transfer energy to the battery. MPPT has been around for years, why?

Grant.

Splendid. If we can agree on conservation of energy, then we agree that by raising the voltage, we reduce the current and thus that the charge going into the batteries is less than the charge dispensed by the solar cells.

Case closed.

Jeroen Belleman

Except when his-two-faced-ness decides that charge is not conserved :-) ...Jim Thompson

You don't believe in that sort of classical-physics COE?

COE is invaluable in circuit design. All sorts of intimidating math can be beautifully simplified by invoking COE. We use it all the time around here.

You can also arrive at all sorts of interesting insights about noise, optics, filtering, all sorts of stuff, based on COE.

John

All of the charge harvested from the solar cell is injected into the battery.

How is this possible? Assume a 1.2v solar cell producing 1 amp. Assume a lossless boost circuit charging a 12V battery. The current into the battery is .1A.

I=dq/dt or, in this case using one second, Q=I.

So, in one second, the solar cell provides 1 coulomb. In that same period, the battery receives .1 coulomb.

Please point out my mistakes.

Thanks, John

Another who doesn't believe in CoE. How is this possible? You intend to harvest 1 coulomb at .5V from the solar cell and pump 1 coulomb into a 4V battery? Why not use a 100V battery? 1000V? You could sell it to Obama! You can't get any greener than this!

C'mon, you arguing for the sake of it? Put a model in LTSpice and watch where the voltage goes when you're charging a battery, if you model the battery as a voltage source with low resistance, the flyback V has to jump to > battery V before current flows out of the inductor. But you know that. Can't get that voltage boost for nothing! I think that's what the reference to CoE is about, no?

Grant.

I'm a bit confused here, Grant. If you look at my numbers, you will see that energy is conserved:

12V x .1A for 1 sec = 1.2W*S

And I *did* say a loss less boost, yeah?

Where is the problem?

John

You're too kind! Smelled like dog poop to me :-) ...Jim Thompson

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SHUT UP FOOL...YOU'VE MADE A DATE WITH THE GRIM REAPER... YOU WONT ESCAPE FOR LONG, YOU CRIMINAL HACK!

TGITM

Crud, you can't even design your own insults.

John