HB404 DC Wattmeter

[chuckj3456]

I picked up this wattmeter and a 75mV/200A shunt resistor from lightobject. I have four 12V wet cell batteries in series connected to a 48V 7000W motor through a control solenoid and a speed control. I connected the shunt resistor from the positive lead of the first battery to the negative lead of the next. I connected terminal 10 to the low side of the shunt resistor using the small terminal screws, and terminal 9 to the high side of the shunt resistor. I connected the positive lead from the last battery (48VDC) to terminal 6 through a fuse. Since the application is an electric vehicle and I only had the batteries for power, I connected terminals 1 and 2 to the first battery through a 3A fuse. As soon as I made the final negative connection to the first battery, there was a spark and this fuse blew. When I disconnected all the leads and connected a 9V transistor radio battery to terminals 1& 2, the display did not illuminate. Since I have never seen the meter display when there is no power flowing through the current and voltage sense, should there be a '0' display when power is applied to terminals 1&2 even if the other terminals are not connected? Does the 9V battery have enough current capacity to power this meter? Per the specs, the meter uses 2W of power, which would draw 250mA @ 9V, and the battery has 1200mAh. Did I blow up the meter along with the fuse?
There is very little information to help you measure large current with this meter-- using an external shunt resistor. Does anyone have better information?
Thank you.