Valhalla,
I need to be able to take my RV out of storage and drive it, with full battery banks. Since I need the batteries to work in the -30 area only one Li format would work. If you wish to donate "to the cause" then send me funds to buy them, I'd be quite pleased to accept.
I am not willing to put any large capacity battery of any chemistry in the living quarters, because I believe it is a safety issue. If others wish to do so that is their affair. It is -34 C where my RV is right now, and it did get to -41.