Reversed Biased MOSFETS & BJT's?

I'm working on a battery charger / discharger design.  There is always the 
possibility that someone will connect a battery reverse polarity.  I don't

want this to destroy the charger.  I remember the stuff about correctly 
biasing transistors but how will a BJT or MOSTES act if you have Collector

Emitter or Drain Source reverse biased?  I'm trying to avoid diodes in the

discharge circuit unless the are required as I want to be able to dicharge

to 1V while measuring current and voltage.

I tried this on simulation and it seems to work (not conduct) but I don't 
know if the simulation is realistic with reverse bias.  I can also get a
1A 
diode to work at 500A in simulation.

Thanks!

RogerN