Selected Honda HRR216 and HRX217 electric start mowers have a battery that is usually charged by the engine. Honda offers an optional wall charger, should you need to charge the battery but not want to run the engine.
Below is a link to a easy, 1-page instruction on how to correctly connect and use the optional charger:
It's important to note the above procedure applies ONLY to the following models: HRR216VLA, serial numbers MZCG-867001~9349370 HRX217VLA or HRX217HZA, serial numbers MAGA-2200001~2369999 HRX217HZA, serial numbers MAGA-2370001~2417294
The serial number is located on a sticker near the back edge of the mower deck:
The optional wall charger can be purchased from any Honda dealer, part number 31570-VL0-W01, list price $36.84. Google the part number to find a dealer selling online, or use this link to find a local Honda dealer in your area: Find A Honda Dealer