Wherever I go on the internet, I see different methods for charging NiMH and NiCd batteries. These range from NDV charging to just putting a battery in parallel with a power supply and putting a diode in series with the battery to prevent current from going backwards. I have seen NDV all over the internet. I saw the simpler charging setup in a old craftsman electric screwdriver that I opened up earlier this year. There are other methods that I have heard of too such as putting the battery in parallel with a power supply and limiting the current with a resistor. Which of these will charge a NiMH battery without destroying it. I am looking to make a simple USB powered AA charger and I would prefer to use the simplest charger that won't damage batteries even if it's slow.