A recent answer at a sister site suggested disconnecting the battery routinely.

I often disconnect my battery before embarking on a hike. Especially if I am in a remote location. This is a nice way to ensure there is no slow electrical drain that may discharge the battery. Additionally, it would hamper a would-be thief’s efforts at stealing the car.

Back in the old days, when my vehicles were built in the 1960s and 70s I would usually instal a 'marine battery terminal connector' to make it easier to connect and disconnect the battery, for very similar reasons as the OP in quote above.

But today my vehicles are made in 2010s and have significant on board electronics. I know the drivers door can be unlocked with a key when the battery is dead, and the inside hood release will also work. Functionally this is potential possible, but are there any negative side effects from disconnecting the battery routinely?

Related questions, that don't seem to address this:

Note In the 60s and 70s, this was not a good anti-theft solution, opening the hood, and using a wire and screwdriver where all that was required to start the car. At this point the thief would just connect the battery. Hidden disablement switches were the inexpensive deterrent of choice.


For theft-prevention, this doesn't make any sense on any modern car. They have immobilizers. Practically the only possibility to steal the car is with a key. If the thief has the key, it's possible to reconnect the battery. So, you are mainly looking at drain prevention.

For drain prevention, you need this only if you leave the car unused for many, many weeks (over a month or so), if the battery is in prime condition. The small continuous drain is optimized to be so small that it won't typically be a problem. Cars with smart key system have larger drain, but even they have optimizations (such as only the driver's door working after parking for week or two).

An alternative would be a trickle charger. Does your car have electrical outlets nearby? If so, I would use a trickle charger.

The drawback of disconnecting the battery is that you forget many settings in electrical devices such as the radio presets. The engine control system may also need to re-learn some parameters, so the car may run a bit rough after disconnecting the battery.

None of this of course is something that you absolutely must avoid. E.g. for airbag replacement (which I had due to a recall in my past car, a 2011 Toyota Yaris), the battery must be disconnected. So nothing is going to break by disconnecting the battery. It's just going to be a major inconvenience.

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On my vehicles, the only “side effect” is I have to reset the clock, as it defaults to 12:00 when the battery is reconnected. I find this only a minor inconvenience, outweighed by the knowledge that I will return to a vehicle with a working battery. I have done this with a 2017 Chevy Trailblazer and not had any bad effects. One thing to consider though, is the keyless entry. You might need to lock/unlock the vehicle with the key, as the remote lock will be non-functional.

As far as drain protection, I have found that even small drains such as the indicator light on a phone charger left plugged in, can drain the battery after a couple of days. Also, there may be unknown shorts in the system that cause drain. During daylight, it can be hard to tell if an overhead light is accidentally left on, so disconnecting the battery is a nice way to make sure nothing will discharge it while you’re hiking. The 30 seconds it takes to disconnect/connect the battery is worth it if you are in the wilderness away from jump starts, roadside assistance, or cell service.

As far as theft protection, though it might not be necessary in modern cars due to the RFID chips in the keys, many people, especially hikers use “hide-a-keys”. Loosing your keys while hiking would be a disaster, so I usually hide a key under my car. Sure a thief who finds the key might be smart enough to pop the hood and re-connect the battery, but it does provide one additional layer of security. Or, perhaps I get robbed while hiking/camping, and the thief steals my keys. Again, my hope would be that he is too dumb to figure out that I disconnected the battery.

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