Hm. I’m keen to get an uninterruptible power supply (UPS) so that I can self-host more services from home, but I’m extremely worried about the fire-risk.
I’m afraid I know little about battery construction to know whether this is a valid concern, or what specifications/designs to look for. Do any of the battery experts of this thread have any advice?
There are some out there, but not at the commercial/industrial level. Like you said, higher risk along with added shipping cost keeps them out of the mainstream. Also the need for lightweight UPS systems for servers is pretty low. One bad thing if a lead battery is involved in a fire is the spreading of lead contamination, that's not cheap to clean up, but it's low probability.
I'm not a battery expert, but I have quite a bit of practical experience repairing UPSs. Battery failures are a very common problem, but battery fires are not. The most common failure mode for a lead acid battery is it just stops working. Sometimes some acid leaks out. Compared to lithium based batteries, they are very safe.
If you do buy a UPS, get one with a good warranty from a reputable supplier. In my (biased) experience, it's quite common for the internal electronics to fail. The repairs are usually pretty straight forward, but it's easier under warranty :)
I’m afraid I know little about battery construction to know whether this is a valid concern, or what specifications/designs to look for. Do any of the battery experts of this thread have any advice?