I can't believe I never knew that Medela offers a car lighter adapter for their pumps! I just saw it on Amazon for the first time. I've been spending tons of money on batteries for this monster and the power is dismal on the batteries. Ugh.
So, I am going to buy the lighter adapter. The question is...they sell a 9v one and a 12v adapter on Amazon. Which one do I buy for the Medela PISA? How do I know?