On August 13, 2011, about 1400 Pacific daylight time, a Cessna 210L, N732FY, collided with terrain at Boeing Field, Seattle, Washington. The pilot/owner was operating the airplane under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The private pilot and two passengers were not injured; the airplane sustained substantial damage by impact forces. The cross-country personal flight departed Friday Harbor, Washington, about 1330, with Seattle as the planned destination. Visual meteorological conditions prevailed, and an instrument flight rules (IFR) flight plan had been filed. The pilot stated that the airplane was on approach to runway 13R, and prepared for landing. She lowered the flaps to 10 degrees, and placed the landing gear lever to the down position. As the gear was coming down, the airplane lost all electrical power. She quickly verified that there was no electrical power available for the gear or radios. Since she had been cleared to land, she felt that the safest course of action would be to land in the grass on the infield between the runways. She didn’t think that there was time to manually pump the landing gear down. She didn’t want to be distracted trying to lower the gear, while trying to fly the airplane, and prepare her children for the landing. The pilot stated that with the 10-degree flap setting, the airplane was a little faster than her normal approach. The landing was smooth, and no one on board was injured. The airplane sustained substantial damage to the horizontal stabilizer. Maintenance personnel from American Avionics, Seattle, examined the airplane under the supervision of the Federal Aviation Administration. The original battery was depleted. Maintenance personnel jacked the airplane, and performed a landing gear retraction and extension with an auxiliary power unit connected. They then installed a shop battery and successfully completed normal retraction and emergency extensions. Maintenance personnel discovered that the landing gear warning horn did not sound at reduced throttle settings. They did a ground run of the engine, and discovered that the overvoltage light was not functional. The AMP meter was not functional; it did not show negative or positive amps when the alternator was turned off and back on under high current loads.