I'm looking to buy an extra MBP battery, because one just won't cut it. I'm in a situation where I need to use my MBP for 8 hours straight without any power outlet at my disposal. Now I was wondering if there's an alternative way to charge an MBP internal battery, externally? Because it would be a real pain to change batteries each time I want to recharge one of them. Or, are there any alternatives you know of to suit my needs? Thanks in advance!