The best replacement for battery tender is trickle charger.

The best alternatives to battery tender are rated as following:
★★★★★  trickle charger
★★★★  ctek
★★★★  batteryminder
★★★★  battery charger
★★★  battery tender jr
★★  battery minder
★★  yuasa
★  schumacher
★  noco
★  battery maintainer
★  float charger
★  optimate
★  maintainer
★  noco genius
  minder
  battery tender junior

Your alternative for battery tender is not listed? Suggest!
Speaking about battery tender, one probably shouldn't forget about agm.

Other search terms related to battery tender and their ratings are:
★★★★★ agm
★★★★ shorai
★★★★ agm battery
You have in mind a companion for battery tender and it is not yet here? Propose!



Google Trends

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battery tender
trickle charger
ctek