MacBook mid 2010: battery problem

I would make an appointment and take it to the genius bar. Some folks are getting their batteries replaced after the update. Look in the "More like this" box to the right of your thread.

Without addressing the EFI update itself, what does your MacBook show you about the battery...go to the apple in the left corner of the menu bar, About This Mac, More Info, System Report, Hardware, Power and what is given for the Battery Condition, Charge Cycles, Charge Remaining, Capacity, and Voltagge? Voltage is given in mV so the decimel moves over three spades to the left.

That info says there is nothing wrong with your battery; condiditon is Normal which is what you want to see. Charge cycle count is great, only 140 cycles, should be good to 1,000. The battery is at 98% charge, 4341/4430. and the voltage is right where it should be, in the range from 11.5 to 12.5 is normal on a MacBook or MacBook Pro.

At this point, run through a couple cycles and see how it behaves. If it keeps doing a fast discharge take it to an Apple store genius bar and see if they can roll the update back...users cannot do so.