Could use almost anything. Depends on what you have available. i.e. Just have normal power, a normal UPS will work great. a 650 watt unit will hold 3 RB532s with radios up for many hours.
If you only have solar or something else like that, then you will have to determine what options based on what the power system is. But other than that, normal UPS's are the way to go.
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