It shouldn’t draw this much current. I think some MOSFET on the board is probably burned for some reason. You should submit a support ticket.
By the way, if you plan to use OpenSprinkler for non-latching valves, you should consider OpenSprinkler 3.0, now that it’s available. OSBee is primarily designed for latching valves, and is not expandable. OpenSprinkler 3.0 uses the same ESP8266 chip and same OLED display, much more powerful and expandable.