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How to design a Li-Ion battery charger to get maximum power from a solar panel

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The challenge on tempered latitudes is frequently another one...
Laszlo.Lebrun   7/29/2017 5:41:13 AM
The challenge on earth is frequently another one: how to get the maximum power out of solar cells *on rainy days*.

A typical 5W, 7V solar pannel will really deliver  around 4,5v@800mA in bright sun, which is perfect to load a LiPo Cell in a few hours. You don't really need to optimize this.

But on rainy days -frequent here- that same panel will only deliver 40-60mA and the real challenge is to get *this* optimized.

The best is then to feed everything available to the cell as directly as possible, avoiding converters, which will take to much power for themselves.

The other problem is on sunny days, once the cell is full, the IC does not load the cell any more, its voltage clims to up to 8,5V which is out of specs for many cherger ICs, I've senn them overloading the cells to a dangerous 4,5V.

I am currently considering a circuit to "waste" to useless energy once charged, at best with a fan, which isn't even useless considering that the case will be quite hot exposed to bright sun.

Alternatively, it could be a good idea to massively overdimension the cells compared to the cell power to harvest whatever is available in sunny conditions for the "bad" days...

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re: How to design a Li-Ion battery charger to get maximum power from a solar panel
zman_tekinsil   3/19/2009 3:57:23 PM
Basically, a solar cell comprises a p-n junction in which light energy (photons) causes electrons and holes to recombine Should replace "...electrons and holes recombin" with "...electron-hole pair generation". One needs to generated these charges that lead to the current, and that's the purpose of the light excitation! Recombination is a process to reduce or eliminate for high efficiency PV's

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