OPENUPS SMBus Pins Konfiguration

Hallo,

I want to let an Atmel microcontroller communicate with the OPENUPS via 
SMBus. The OPENUPS's slave address is 0x70. OPENUPS's pin "SMBUS DATA", 
pin "SMBUS CLOCK" and pin "GND" are connected the the uC's pins 
respectively. I left the "+3.3V" Pin unconnected. 5V from the uC is 
connected to a 10k pull-up resistor, the resistor is connected to the 
data line. 5V is connected to another 10k pull-up resistor, that 
resistor is connected to the clock line.

However, I've broken two OPENUPS in just two days... I used a multimeter 
to measure the GND, SMBUS DATA and SMBUS CLOCK pins, they are all short 
circuit!! I think maybe it's because the pin +3.3V on the OPENUPS is not 
connected, or maybe 5V is much too high for the OPENUPS? There must be a 
reason, why there is a +3.3v pin on the OPENUPS. However, there's no 
exact documentation describing OPENUPS's SMbus from the manufacturer 
minibox.

Thanks a lot!!

Jichun