Electricity in Sierra Leone is 230v, 50hz. Supply does not keep up with demand, especially outside of the larger cities. An Uninterruptable Power Supply (UPS) is recommended for sensitive electrical equipment, especially computers and printers. When you purchase a UPS, make sure that it is intended for 50 to 60hz, particularly if you plan to run a 110v computer off a transformer.
Before plugging a UPS into an outlet in Sierra Leone, check with a voltage meter to ensure that the polarity of the transformer or outlet is correct. If the outlet is incorrectly wired, the UPS will be destroyed. You may prefer to have an electrician check the system for you.