Will a 300000mah solar panel charge a 20000mah battery?

Will a 5v /300000 mah solar panel charge a 12v lithium battery?

H Carr, please move this to the Electrical category.

Not to mention this sounds like a homework question.

No, it won't. The capacity of the battery in mAH has nothing to do with whether it can be charged by a particular source - the important thing here is the voltage. The voltage of the output of the solar panel must be greater than the nominal voltage of teh battery you are trying to charge. And I don't understand the use of mAH terminology as you've applied it to the solar panel - the proper units is watts (i.e. power), or mA at 5 volts, not mAH. I suspect what you are looking at is the rating of a solar-powered charger with an integrated battery - so this is the energy that can be contained in that battery. In essence you are asking about using a battery to charge a battery - is that really what you want to do?