Originally Posted by tcdrvr
From what was explained to me the Zero-Thirty discharges at 30 amps per cell, is not polarized and does not require an external power supply unless you want to run the two fans at a constant speed. I could be wrong about the discharge rate. But with the smart tray if your batteries are put together the wrong way you may have to flip the solder tabs on the pack. I've had both for about a year and I've used the Zero-Thirty a lot more than the smart tray. Also the smart tray was $90 when I bought it and the Zero-Thirty was $50.
Just depends on what type of cells you use. I have the IB3600's and they don't like to be discharged below 0.9v per cell. So the SmartTray is the one for me. I only use it just before I charge my packs - so they are equalised.
If you have GP3300's then they are happy to go onto a zero volts tray before charging.