The laptop batteries tend to go bad(either just stop working or expand and become a major fire hazard) after a year or two as they are not built to be fully charged for years on end. I tried doing it twice and that is what happened both times.
Would not recommend; if you want a UPS just buy one, the small ones are not that expensive, like 70 USD.
Would not recommend; if you want a UPS just buy one, the small ones are not that expensive, like 70 USD.