Another option for rarely used car batteries — but don’t skimp

Dear Car Talk:

Love your column!

Recently, you gave a reader three suggestions for keeping his rarely used Toyota’s battery from dying while it sat.

You recommended: A. Disconnect the negative terminal with a wrench (messy), B. Hook up a plug-in trickle charger, or C. Use a compact jump starter.

I hereby recommend what I believe to be the best choice D: Buy a car battery terminal quick cut-off disconnect master kill switch.

The one I got costs $9 for one or two for $10, and it’s simple to install. It connects and disconnects your negative terminal with a simple, easy-to-use thumb screw.

You’ll need to access your battery, so you need to keep your hood unlatched or have access to your car with a key (a key fob might not work if the car’s battery is fully dead).

What do you think?

— Bob

Yes, a cut-off switch definitely is an inexpensive option, Bob. And it does work.

There are two things to keep in mind about these “cut-off switches.” One is that many of them are really cheap junk. I see a lot of them that are flimsy and prone to failure. And if it fails and disconnects your battery when you don’t want it to, your car will stop running. So, if you’re going to get one, get a good one.

The second issue is that they don’t fit in every car. They require a certain amount of room and not all cars have enough. Some batteries are mounted right up against the inner fender liner and that doesn’t leave room for a switch.

As far as ease of installation, for some of these switches, you simply remove the negative battery cable and tighten the switch right onto the negative terminal. Then you attach the negative cable to the switch. That’s easy to do yourself if you have the room under the hood and paid enough attention in school to know the difference between positive and negative.

Other units require you to sever the negative battery cable and, essentially, splice this thing in. If you’re buying one of those, I’d have a mechanic install it. That’s not a do-it-yourself job for most people.

But your recommendation is a good one, Bob. We’ll add “D” to the list of options. As long as you get a well-made switch and have enough room to install it, a negative terminal cut-off switch will stop any parasitic power drain while your car sits unused.