Disconnect the proximity sensor. Then try to flash/boot/run your N9. I found out that the proximity sensor was the cause on three N9 to cause the SU_PARAM_BATTERY_LEVEL error message.

If it works after disconnecting the proximity sensor, you have to find out yourself what is the reason why it doesn't work with it. I'm not sure if there's a general issue, but I hardly can believe it broke on three devices just like that.