I agree with Glider. The Battery Tender is different than most because it actually uses a micro-controller & firmware to determine state of charge, unlike almost all normal trickle chargers that will continue to charge batteries even after the battery is fully charged.
There is only 1 question that I wonder about using the Tenders Charges. As far as I know, the firmware is written to only accommodate the charging characteristics of typical lead acid batteries. I don't know how it will handle dry spiral & paste batteries like the Odyssey or Optima because the final charging voltages on these batteries are slightly different than wet cell batteries. I have been meaning to call them and ask because I can't see how 1 software program would work for all types of batteries.(?)