Hi!
From what I understood, you want to power a toy from a solar panel, but you don't know the size of the solar cells.
For an exact power, the size of the cell is highly dependent on it's quality.Higher quality results in a more compact cell. I found something that can be suitable for your application here:
https://www.aliexpress.com/wholesal...11131&origin=y&SearchText=solar+cell+for+toys
( I haven't bought from here yet, however, considering that most of the toys, including the solar ones, are made in China, the price is pretty good. The only bad thing is the delivery time that can range from 2 weeks to 2 months, 2 months is the guaranteed delivery time. You can also search on
www.solarbotics.com for solar cells, but the prices are higher...)
As for the batteries, maybe some supercapacitors ( 1 Farad or more) can be the solution, because, unlike the NiCd or NiMh, they charge a lot faster and they can keep the toy on for a few minutes (it's highly dependent on the capacity). Also they can be charged and discharged more times than a normal battery. This is what I am talking about:
An example of supercapacitor.
And, finally, the circuit needed is a SOLAR ENGINE. It charges a capacitor with a solar panel, and when a certain amount of energy is present, it releases all the energy to the load. It uses few components and its easy to build. The only disadvantage is that the load receives no energy during charging. I played with circuits like this, but not using supercaps, only ordinary ones.
The supercapacitors combined with the solar cells make the ultimate combination when it comes to solar energy!
This is my idea. You can agree with me, you can diasgree... And if I said something wrong, announce me!
Andrei