Isn't hydrogen produced only while the battery is charging, or at worst, when discharging? If so, this still makes them much safer as they're otherwise inert while not in operation, compared to lithium-polymer which contains materials flammable at all times.
LiPo and LFP are very different things. LiPo is probably the biggest fire risk battery chemistry in common use today. LFP is pretty safe. LTO even more so.
Yes, I am aware of other "L" batteries that are safer. I was just commenting about how lead-acid is still relatively inert compared to the "fiery" kind of L batteries.
