Bought 3 cheap garden solar lights, each < 1.00 Eur just to see how do they work. One did not work from the start. Another stopped working after a weak. Third worked well during all summer.
One had: circuit with a chip marked 5252F 1109, Ni-MH battery 2/3AA 300mAh 1.2V. Another with YX8018 0157 chip, Ni-MH battery 2/3 AAA 300mAh 1.2V.
Some Googling for those chips leads to these similar circuits:
Lamps by them self, nothing special to disassemble, just few photos: