Power Macbook Air with Early 2008 Macbook Pro

Question

I have two batteries from my old 15" Macbook Pro Core 2 Duo (Early 2008). It's a non-unibody (discrete) model. Anyone know of any way to use these batteries to power my 2nd Gen Macbook Air? An external battery costs ~$300-$450 and it seems kind of unnecessary if there is an adapter or some hack job way to make the old batteries work.

Note: I'm not talking about replacing the macbook air batteries, I'm talking about using the macbook pro batteries as an external battery connected to the magsafe power port.