A lot of the electric cars available today (except Teslas) have too small ranges. Inspecting them I see a lot of trunk that I might want to relinquish in exchange for extra range. However I don't see any official (i.e. without losing warranty, without DIYs) options for doing so. The only exception, as stated above, is Tesla which offers different battery packages.
Do the other manufacturers (Nissan, VW group, Renault etc) offer any such options?
I know about range extenders (that use gasoline for that) but I'm looking more into more battery mass.