Can't you use a diode in series with the battery to prevent that?

 

Can't you use a diode in series with the battery to prevent that?

Could you confirm the location of the diode in the schematic attached,D1 is the diode for protecting the lower FET from the battery and D2 is the fly-back diode to ground negative voltage from the inductor

 

D1 looks good.

 

Thanks,

But i just realized another potential problem.When lower FET is turned ON ,the negative current from the inductor,may not flow through the fly-back diode D2,it may flow through the lower FET,depending on which would offer the least resistive path,and it could blow up the lower FET.Would it be a better idea to place D1 to the left of D2 to avoid this situation?

 

Check the datasheet for the FETs. The body diode hopefully can cope with a current equal to the battery charging current, but D2 can probably be chosen to offer a lower forward voltage drop than the body diode, so that D2 hogs the current.

 

the forward bias voltage of the diode is lower than that of the body diode of the FET,so it shouldn't be a problem.I'll try out this configuration and get back with the results.