Here is BA policy on this matter (since you are from UK): "Please note that you cannot travel with wet-cell batteries for any purpose other than for powering wheelchairs.", BA further requires that the battery be electrically isolated, and the powered wheelchairs are carried in the cabin, not as checked baggage. Most airlines have similar policies, though it does vary; the only airline that I know allows checked batteries is AS (needed for their Alaskan community service, where there is no road/rail access so AS carries all freight into those towns). Probably the same applies to Siberia and Africa for remote services.