Lead acid is very cheap, electrically very easy to charge, safe and actually very recyclable.
That said, yes LiFePO4 is really coming down in price. In telecom DC power systems, I’ve been using 48V packs in some situations because the cost difference between lead acid and lithium is only about 20-30% more.
The big benefit of lithium is the weight and amount of cycles you can get out of them. The longer service life is also a factor, but they’re most useful in situations where you are cycling a lot (EVs, solar power systems) but UPSes aren’t really taking advantage of that unless you live in a particularly bad area for power, the UPS’s poor quality charging will likely damage the battery more than the cycling. It’s also nice that lead acid is so common that you can often just walk into most battery / auto parts stores with the cell and they’ll have something that will fit.
EDIT: I forgot to mention! There are some cheap 12V lithium UPSes out there for powering things like modems and WiFi routers. These are often a lot smaller than traditional UPSes, but since they’re keeping everything on DC power can mean you still have a decent amount of runtime.
I had one of these that was pretty nifty — you could pull the battery and take it with you as a power pack. Unfortunately like many cheap lithium implementations, running the battery all the way out came with a chance that it would refuse to charge again. Not ideal for a UPS…
Lead acid is very cheap, electrically very easy to charge, safe and actually very recyclable.
That said, yes LiFePO4 is really coming down in price. In telecom DC power systems, I’ve been using 48V packs in some situations because the cost difference between lead acid and lithium is only about 20-30% more.
The big benefit of lithium is the weight and amount of cycles you can get out of them. The longer service life is also a factor, but they’re most useful in situations where you are cycling a lot (EVs, solar power systems) but UPSes aren’t really taking advantage of that unless you live in a particularly bad area for power, the UPS’s poor quality charging will likely damage the battery more than the cycling. It’s also nice that lead acid is so common that you can often just walk into most battery / auto parts stores with the cell and they’ll have something that will fit.
EDIT: I forgot to mention! There are some cheap 12V lithium UPSes out there for powering things like modems and WiFi routers. These are often a lot smaller than traditional UPSes, but since they’re keeping everything on DC power can mean you still have a decent amount of runtime.
I had one of these that was pretty nifty — you could pull the battery and take it with you as a power pack. Unfortunately like many cheap lithium implementations, running the battery all the way out came with a chance that it would refuse to charge again. Not ideal for a UPS…