The APC Back-UPS 600VA BE600M1 was introduced in 2016 as the replacement to the APC Back-UPS 550VA BE550G that originally came out in 2008. I actually bought the old APC Back-UPS 550VA nearly a decade ago and it just recently started giving off an alert that the battery was on it’s last leg. The battery life in one of these units is generally 3-5 years and I basically got double the advertised life from the original battery. No complaints there and the replacement battery for the BE550G is sold under part number APCRBC110 for $35.14 shipped. So, the question that I was stuck on was having to put a new battery in my nearly 10-year old unit for $35 or getting a newer model like the APC Back-UPS 600VA BE600M1 for $56.89 shipped.