Hand crank battery charging circuit build
First, you really, really need to check how well your generator works when under load. 

As brhans pointed out, you've got your battery connected wrong. Fixing this and adding a MOSFET will produce







simulate this circuit &ndash; Schematic created using CircuitLab

M1 is a p-type MOSFET, and when the generator output is zero the FET will be turned on. When the generator is charging the battery, the gate of the FET is high, and the FET is turned off. D4 compensates for the voltage drop in D2, and keeps the FET gate voltage from going the wrong way.