I assume its a lithium battery of some description probably a lithium ion battery same as you get in mobile phones.
It really depends on the quality of the battery, some batteries that are sold as generic are actually identical to the manufacturers ones just with different labels but come from the same factory, some are actually better quality.
Risk? Unless theres something wrong with the battery theres no risk as far as I am concerned as the charge rate for devices such as these are low.
If the device used a fast charger of some description then I would be more wary however.