4pyros, math errors happen to the best of us! And far more frequently to people like me =)
yusuf, there is no simple way to do what you want, it's not very practical either considering the Lithium cell actually has more energy storage capacity than the lead acid pack does.
To make a practical emergency recharger the simplest method is to use a higher voltage battery with a regulator and set the regulator to whatever the phone chargers voltage is and allow it to charge itself from this supply.
You could probably directly wire the lead acid battery to the Lithium cell with a current limit resistor can get SOME kind of charge into the Lithium cell but I wouldn't image it would be enough to be useful, and the voltage dip of a lead acid pack during discharge would quickly drop to the point where it wouldn't be able to charge the Lithium cell LONG before it reached a full charge state.