I've had my HD tender since 2006, use it regularly and still working great.

 

maybe it is the battery?

 

Just my opinion, but I only use the junior on my bike. My car that sits on one is always hooked up to a Battery Tender Plus. I personally think the 750 MA junior is too small for a large car battery, especially an older one. Even the junior seems to run warm all the time on the small bike battery, figure it would be worse on the big battery.

The only one that has ever failed was the one I crushed when I drove over it when I forgot to unplug it.