How to sharpen blade 36V Lithium-ion Cordless Lawn Mower?

Blade sharpening (fig. below)

Keep the blade sharp for best performance. A dull blade does not cut grass cleanly or mulch properly.
Warning! Always make sure that the safety key is removed. Warning! Wear proper eye protection while removing, sharpening and installing a blade.
Sharpening the blade twice during a mowing season is usually sufficient under normal circumstances. Sand causes the blade to dull quickly. If your lawn has sandy soil more frequent sharpening may be required. 

Replace bent or damaged blades immediately. When sharpening the blade:

• Make sure that the blade remains balanced.
• Sharpen the blade at the original cutting angle.
• Sharpen the cutting edges on both ends of the blade, removing equal amounts of material from both ends. To sharpen a blade in a vice (fig. below)
• Release the bail bar to turn the lawnmower off and wait for the blade to come to a complete stop.
• Remove the safety key and the battery pack and turn the lawnmower on to its side.
• Remove the blade from the mower, see the instructions for removing and installing blades (in attached instruction manual)

To sharpen a blade in a vice (fig. below)

• Release the bail bar to turn the lawnmower off and wait for the blade to come to a complete stop. u Remove the safety key and the battery pack and turn the lawnmower on to its side.
• Remove the blade from the mower, see the instructions for removing and installing blades.
• Warning! Wear proper eye protection and gloves and be careful of the sharp edges of the blade.
• Put the blade in a vice.
• Carefully file the cutting edges of the blade with a fine tooth file or a sharpening stone, maintaining the original cutting edge.
• Check the balance of the blade, see the instructions for blade balancing.
• Install the blade on the mower and tighten securely, see the instructions for removing and installing blades, (in attached instruction manual)