Below are instructions taken from the user guide of the Plexus MV 1000VA UPS from Ebuyer:

When you find the battery is badness (for example: the time of power supply are being shorten), you should change it on time. Please contact with the dealer, and assure whether being needed to change the battery charge. The process of changing must be operated by eligible people. Pay attention to the following matter: the battery charge may bring to the electrical shock and short-circuitry, so when you operate, you should pick off the watch, ring, or others mental goods. You should use the tool with the insulated handle. Not to throw the wasted-battery charge into the fire, for the battery may be easy to explosion. You don’t open or destroy it, because the liquid in the battery is rodent, and it is harm to your skin and eyes. Please take the wasted-battery charge to recycle station or sent it to our company for recycling.