before figuring out what charger you need, you first have to find out what kind of power supply is available in your building. Obviously you have 110v, but that is realy not the best way to go. Do you have 208v, 240v, or 480v service in your building? If you have any of these power supplys in your building (in single or 3 phase)you can use them to power a commercial grade charger. Most commercial chargers are convertable to work on any of those three power sources. They can't be converted to different phases though; a charger made for single phase can't be converted to 3 phase and vice versa.

next as already stated you have to match the chargers a/h out put to the battery that you are charging with it.
Hopefully both of your machines have simmilarly rated batteries so that one charger will work for both lifts.
Try to find a local fork lift service co. to sell you a used charger, they are genneraly not to expencive.