Where should I connect the Battery tender?

I hope you also get a reply from an owner of your model of Prius. I have the previous one. Anyway, what I understand to be true is that the 12 volt battery should only be connected to an external charger after having been first disconnected from the car. So you would work your connections from the back.

Second, however your battery tender works, it should not continuously apply anything more than 14 volts to the battery. Over the long run higher voltages will shorten battery life. If your device goes higher, you could operate it through a timer, set with just one "on" hour over 24. That would be safe for sure.

 

The Battery Tender Jr would probably work best if mounted in the rear hatch next to the 12 vdc battery, but then you'd have to snake a power cord in under the hatch.

It should work fine the way you propose doing it. Make sure to try it out to ensure it does properly keep a float charge.

tochatihu: the Battery Tender Jr is perfectly safe to leave plugged in 24/7. I use them at my hobby farm to keep the battery up in my old Ford truck and in my diesel tractor.

The Battery Tender Jr specs:

http://batterytender.com/product_info.php?...p?products_id=4

Some battery tender devices also promise to "condition" the battery, AKA "desulphate." These devices also work very well, but the battery has to be disconnected from the car electrical system.

A desulphator introduces a high frequency pulse to get the sulphur deposits off the battery plates. That high frequency pulse could harm sensitive electronics in the car.

 

I don't see why you couldn't hook it to the jump start teminal under the hood, especially if you hook it to a timer. If the battery is going to remain inside the car anyway, there is no advantage to hooking it directly to the battery terminals.

 

For a couple of months, I'd be somewhat concerned about the traction battery.