They are not safe as the lithium-ion batteries are all prone to thermal runaway and can catching fire and explode, which is why they are not allowed in checked airline luggage and why the new Boeing Dreamliner jets were grounded for months to fix problems with the plane's new bleeding edge lithium-ion batteries.
I use them in my cameras as there is no other choice. I use NiMh for all my other electronic devices as it is much cheaper. If I was going to buy a large lithium-ion battery it would be for a boat or a trailer where if it caught fire I would not destroy my truck or my house if the truck was in the garage.
All the lithium-ion batteries I have used required special chargers to avoid overheating and the chargers in an RV are not going to be engineered for this type of battery nor will automotive or solar chargers.
