I use B&C specialty, BC110-1, 12V, 28 AH, RCG battery, mounted behind the
passenger seat in my LNC2.  No out-gassing from these batteries.  Contains
no free liquid.  Some say that they can get 6 to 7 years service life from
them.  I believe it, if you keep it charged and don't replace it before it
dies.

An equivalent rated battery  can be purchased from Digi-Key (a Panasonic)
for a better price ($56) as compared to $108 for the B&C battery.  Can not
vouch for lifetime of the Panasonic.

Bob Jude
N65BJ