I can resist myself to buy a solar power garden light which so cheap. I was thinking to use the solar cell for my electronic project.
How can I know the output amp from the solar cell?
probably its very little. those lamps just feed the batteries power until it is dark.
...But you can probably up the amp/volt a little if you built one of those Miller Solar Engines. However, the power would be in pulses.
As said, you really are not going to get much power from these solar lights. Their solar cell is on ly used to trickle charge the battery to run a LED for 8 hours and the design is optimized (cheapened) to the max by the chinese engineers.
You are much better off buying some commecial cells.
As a gereral rule, count the number of stripes adnd multiply by 0.6 to get the voltage.
You only get the maximum current in full direct sunlight. It drops off drastically in other light levels. Indoor light may only be 2% of direct sunlight.