I recently purchased a backup power supply for my father, since he uses his computer for business purposes, and thus cannot afford for his computer to suddenly lose power when he is performing important work. I noticed that the unit was extremely heavy, likely due to the batteries that it contains, which I discovered are sealed lead-acid batteries, which is something that I find to be very odd, given how popular and ubiquitous lithium-ion batteries currently are.
I know that lead-acid batteries are a proven technology that have existed for over a century and thus have had plenty of time to be perfected, but lithium-ion batteries offer numerous advantages over the older technology, most notably that they weigh less, can shaped into virtually any form factor, and are far more resistant to environmental factors, and I am certain that any differences in power capacity/energy density between the two technologies is minimal, at best. Therefore, why would manufactures still be using lead-acid batteries? Are they less expensive than lithium-ion batteries? What does everyone else say about this?