>… the two batteries will be in different states of charge/sulphation etc. The tender
>will not know what to do. Maybe best to get two tenders? >

 

Jim -

Digi-Key sells a dual-output smart battery charger. Just connect one output to each battery.

 

http://rocky.digikey.com/scripts/ProductInfo.dll?Site=US&V=195&M=3212

 

-Adam Molny