Which solar panel for my barn

[Beaver Cove Deere]

Tenders are fine, but I found just disconnecting the batteries and leave them alone worked for me. When I came back from Florida to Wisconsin after 4-5 months everything started right up. It maybe didn't crank like a new car, but it only needed to start.

Pull the negative cable and go.
I used to pull my 3 boat batteries and then got smart and just shut off the master switches and that was the end of that needless extra work.

 

[Milo]

...... It maybe didn't crank like a new car, but it only needed to start.

While your battery still had enough juice to crank your car its charge was surely somewhat depleted, which causes the plates to sulfate, which weakens and shortens a battery's life.

 

[SPYDERLK]

Tenders typically draw about 1/4 amp.

~ Max for a 2A intelligent charger ~30W input. When maintenance charging point is reached it would be much less because the maintenance output A to the batt is very low.