This solar unit is supposed to put out up to 2.4 amps power - I agree with you that it should be able to - 2.4 amp is 2.4 amp. I do have a 20000 mAh battery pack here and it's a nice and sunny day - I will try to charge the battery and see if it will charge to full. It is possible they were referring to their 2.1 amp solar panel model. I will look into this more and try charging this battery and reply to you here later today with what i've found - and edit the post if needed. Thanks @darth-azrael