Disabling battery

I am going to assume you mean the 12 volt battery, the easiest way is to unattach the negative cable at the body connecton, back right.

You lose all your presets.

 

Probably the best way is to put an AC powered Battery Tender on the 12vdc to maintain the battery

 

+1 for using a Battery Tender or Battery Minder trickle charger to keep the battery topped up. Once in maintenance mode, trickle chargers use only pennies worth of electricity.

The Battery Minder chargers also will desulfate the battery automatically. All lead acid batteries accumulate a layer of sulfate on the plates when left to sit without charging.

 

If you don't want to hassle disconnecting the neg cable (and you will loose various settings, sort of reset the car), and if you have a secure garage, leaving it permanently hooked up to a smart charger (as others have said) is THE way to go. You want to use a smart charger, they will run through charging session, then fall back to just sending a little "spike" of charge occasionally.

That's what I'm doing with ours, which sees use every 2nd to 4th day, on average.

 

How is the v's 12v battery difficult to access? Pull up the trunk floor and prop it up, Remove one plastic piece. So far no tools needed. Battery now stares you in the face. Been there when a bottle of wine broke broke lose, broke and flowed under the battery. The good news is it was cheap wine.

Why a maintainer on a battery that will sit for 2-4 days? The 12v will last for much longer than that. I don't worry until the number of days gets to be 12. I used a maintainer on a 12v that I expected to sit for a month or two in an ICE car. So I'm not unfamiliar or opposed to the concept. But 2-4 days?

 

Another +1 on the battery tender. Motorcycle riders in the north have been using them forever. Some people disconnect the negative cable also, but really not needed when keeping a trickle charger on it.

I have a snowbird friend who leaves his van here in FL in the summer and cuts the power to his house. He has a heavy duty knife switch that he installs while he's gone. The people who check his house once or twice a month close the switch, run the van for about 15 minutes, and then shut it off and open the switch. He's been doing that for many years. I haven't thought through how that would work with a Prius, but if you're not shutting off power, it's not worth the bother.

I use this once in a while, just for preventative maintenance.

 

How about a battery that sits 2~4 days, then the car goes maybe a couple of kilometers on a milk and bread run. Then sits another 2~4 days, before it sees use again. Relentlessly, month after month. We do the occasional good drive, but they're sporadic.

It takes me about 60 seconds to hook up my charger, from the opening the door to the garage to done, lol.

Also, regarding 12 volt disconnect: I've had to disconnect the 12 volt negative cable, a couple of times recently, once for a brake inspection, the other time to wire in my charger's quick-connect plug. Afterwards, besides the zeroed trip meters, lost radio presets and so on, I also noticed some weird engine revving, like the car had to relearn some things. For the first couple of start ups and drives. I'd prefer maintainer to disconnect, for that reason.

 

i leave for 5 weeks every winter, my 12v is now 5 years old, no issues. how long are you gone for?

 

Typical for the ECU to resort to using presets before a few start-run-stop cycles where it learns what are normal sensor readings for the specific engine and its current condition and then it can better adjust the air/fuel mixture.

Re the guy who starts the car and runs it for 15 minutes, I've been told by guys who build engines for a living that that is the worst thing you can do. All it does is insure that you frequently wash the oil off the cylinder walls starting it and don't get the engine oil hot enough to burn off the water vapor in the crankcase. My rule of thumb when I was running a car with a $30k engine was get the water temperature to above the thermostat open setting for 5 minutes even if I had to drive to a further grocery store. Then on the trip back, make sure the RPMs exceeded 6k for a few minutes to make things super hot and give the oil squirters that oiled the rod bearings and cylinder walls a chance to feel some pressure. If I wasn't able to do that, I took the car with the $3k engine. And left the expensive one on a cTec maintainer. I don't do that in the Prius but, if it is a shorter distance than will take the car to warm, I walk. And the nearest anything store is 5 miles so I'd have 10 miles of warm up.

 

I'm sure he knows his stuff. But in 15 minutes running in FL summer heat, it's good and warmed up. He also runs the A/C for a few minutes. The van has about 175,000 or so miles on it and must be at least 15 years old. It's his car, so I just let him do what he wants. And I would think 6k rpm would be well above red line on that old thing.

 

Yeah we walk a fair bit, avoid super trivial short trips. And try to consolidate car chores. Our case is maybe not as bad as I paint it: I was trying to justify my charger use, lol.

 

Of course, if you have a PiP or a Prime and you have the time (wow, I made a rhyme), you may want to keep your errands within battery range, come home, recharge and go out again. That is, if you have time for that and your electricity is enough cheaper than gas to make up for the extra miles. I sometimes do morning errands, come home for lunch while the PiP charges, and then go out to do more errands. But it's rare that I have that much running around on the same day. My electricity is about 40% cheaper per mile than gas.

 

If it was me, I'd just use a trickle charger like the Battery Tender or something. Not need to get fancy, but that is enough time that your 12V is likely to be pretty flat when you get home.

 

For long term, I think fancy is better. Safer: the smart charger will not overcharge, it's monitoring the battery's charge. Once the initial charge session is done, it just gives a little nudge every so often. And it will need that nudge: any modern car makes light but persistent demands on the battery.

 

2 months, yes I'd maintain it. But the challenge is to get the cord into the area of the battery without messing up the weatherstripping. Maybe someone else can suggest a way that doesn't let critters in. I might even take the 12v out and just live with the loss of presets. (On the one I had hibernating, there was cutout in the door weatherstripping. And to make it easier, the charge point was a lighter socket on the dash. There were times I just unhooked the extension cord and left the maintainer sitting on the passenger floor while I took the car out for a run in between snows.)

 

I've let the Prius stay parked for 3+ months, didn't even disable the SKS system. No problem.

 

Connect it under the hood. There's plenty of room in there for a small charger and the cord can just hang down below the car if you don't want to close the hood on it. No need to remove the battery unless the car is outside and you're concerned about vandals cutting the power cord.