It depends on the battery type. Alkaline batteries can be stored in the cold to extend their usability. For a rechargable lead acid battery, no. Just keep it trickle charged indefinitely.
The space shuttles have 64,000 NiCad batteries on board and after each launch, they remove every one, discharge them to 0v using a specific procedure, wrap them in plastic and store them in cold storage until the next usage. Geesh... and i thought i had some battery maintenance to do
What did you buy for your replacement aux battery ? Type/size/vendor/price? i'm thinking i may be about ready for a new aux battery myself.