How long can a Prius go without being used

i think 6 months is about as long as you would want to leave the traction battery, and only a few weeks on the 12v without a smart tender.

 

The computer is always on to sense the key fob and probably other status items.

 

Here's a good article regarding the discharge of the Prius 12 volt battery over time.

Leaving a Toyota Prius Undriven

The article calculates that the nominal 36 mA load for an unpowered Prius will permit the car to sit for 32 days before the 12 volt battery is drained. Your results may differ due to different equipment and the only way to know for certain is to measure the quiescent current of your particular vehicle. Not difficult to do, but the answer is still going to be measured in weeks, not days. The only reason you might want to do this is if you're planning to leave your Prius undriven for close to a month.

Please note the date of the article - it is obviously written regarding an earlier model Prius. However, the underlying rationale remains solid.

 

Like -most- "modern" cars, the Prius has several microprocessor systems. They, like any computer you may own, are never really "off", unless you unplug them and remove the battery (if a laptop or tablet).

This is a "good thing" (tm) as the car is always ready for you. The only downside is the 12V battery will -slowly- be discharged. It's about a 38 A-Hr battery, and it doesn't need a lot of charge to "start" the Prius, though other cars do need the battery to be "mostly" charged. The Prius only uses it to "boot" the system, which takes one or two 50A 1/2 sec. pulses. You can actually "boot" a Prius with AA cells (NiMH).

Soooo, if you "take care of" your 12V battery (never let it fully discharge), it -could- last 1000 hrs with a 38 mA load, though that would be to fully discharged state and that probably wouldn't get you to "ready". That's 41 ish days. Hence, we estimate 30 days for safety.

Yes, this "problem" is worse for some other cars!

If you are worried about this, and have access to a 117VAC plug where you park the car, in a semi-secure environment, get yourself a "battery tender" or "battery minder". There are many manufacturers of these devices. MAKE SURE it's designed to be left on indefinitely! Most are designed for ATVs and motorcycles and they will work just fine. You can't just use a "charger" as it will "overcharge" the battery and shorten its' life (by causing water to be lost - which you can't easily add back).

I use one on Pearl S in the "dead" of winter, and it's currently on my FJ Cruiser, which I avoid driving when possible as it uses, yup, THREE TIMES as much fuel as Pearl S. It's tough sledding season so I don't need the FJ for most trips.

 

Ours was manufactured August 2009 and we bought in November 2010. It had about 10 kms on it. The 12 volt was dead as a door nail, but the hybrid battery has been champion so far, no unusual behaviour.

 

You imply a set say 12 or 13 AA 2000mah NIMH batteries connected in series would boot up a Prius with a dead 12 volt but fully charged HV battery. That is very interesting! Has anyone actually tried this? Because I have to take 1-2 month trips and may have to leave Prius in parking lot, so may have this problem. I could series connect some Eneloop AA NIMH batteries I have hanging around for an emergency boot battery if this actually works.

 

Or just get one of the cheap portable jump starters and keep it in the car.

 

I'd probably disconnect the battery and have a jump-starter at the ready too.

 

Good solution and I have had those in other cars, but they tend to be big, bulky, and heavy with lead acid batteries. If I found a small cheap one with NiIMH or Li-ion I would buy that for sure.
But the Eneloop NIMH batteries have a very low self-discharge rate and would thus be good to store in the tub underneath for the dead 12-volt emergency situation.

 

the 12v is very small, and takes great exception to being deeply discharged

 

Best suggestion IMO is this. If you are going to leave your car for over two weeks, DISCONNECT the negative lead of the battery cable at the battery in the back end of the Prius. Make sure you have the back seat folded down and the little cover underneath the floor boards removed so you can open the hatch from inside when you are ready to reconnect the battery. As far as the "traction battery" is concerned, just try to have it close to 5 or 6 bars on the SOC readout on the dash. Like other's are saying, the traction battery rarely goes dead. It's the 12 volt that gives folks a lot of trouble over time. I myself have a battery charger/maintainer and a portable jump rig. If I go out of town, I simply throw the portable jump in the back end. It always seems that someone needs a jump at times. I have not had to use it once on our Prius, but have helped several others in the past.

NOTE: When disconnecting the 12 volt, it is simpler and easier to remove the bolt that clamps the negative cable to the frame of the car rather than fiddling with the battery clamps themselves.

Ron (dorunron)

 

I've had mine sit for a month with no troubles. Just be sure that no key fob is close to the car.

One member here changed their 12 volt battery and thought that something was wrong with their replacement.

turns out that they parked the car along the same outside wall where just inside they always put down the car keys. Hence, the voltage would drop a little faster with that new battery than they thought it should... but it was the SKS repeatedly waking up in the car plus an over emphasis placed on voltage levels that caused this person to question the new battery.

With mine, I could see that the car had indeed put the system into sleep mode, despite it being parked on the busy sidewalk and road outside my home with other cars and people with rf keys no doubt passing by all day and night. I had to touch the door handle twice to first wake the system back up, then again to have it unlock the door.

I think the Prius is really not much different in this regard to many new modern vehicles. Lots of little gadgets lead to some power loss due to inactivity. If you can, get somebody to fire it up if you tend to leave the car for extended periods, or get a maintainer or disconnect if it is most appropriate in your situation, but it is not a problem really.

Roland

 

If you want to try to use AA cells, it's very important that the holders are robust. Most plastic ones are not. They have fairly high contact resistance (nickel plated steel contacts and nickel plated steel springs). To do this properly the best practice would be to use spot-welded tabs on the cells, second best, the aluminum holders that use nickel plated brass contacts (no springs - the aluminum holder is the spring). They are made by Keystone.

The easiest way is still to disconnect the 12V negative lead. If you have one of the portable "boosters", you can connect it to the "boost point" under the hood when you return to the car and then open the hatch normally without having to crawl into the back, to reconnect the negative lead.
This procedure will prevent the damage to the 12V battery that would result from allowing it to discharge fully.

 

Thanks for info and ideas--will look for Keystone units.
Drove thru Edmonton 1 month ago and THOUGHT I was seeing air pollution. Is that true? Do you have air pollution there in summer? Is gas "re formulated" as in US?

 

Ours has been sitting idle at the dealer for 6 weeks now waiting for an inverter. I fully expect the 12 volt to need to be replaced after this ordeal is complete. Hopefully Toyota will pony up for a new one for the inconvenience . I can only hope that traction battery will be fine years from now.

Normally our Prius can go 3 weeks sitting. Our RX400h can't sit more than 2 weeks without killing its 12 volt battery. Long term parking at the airport is a risky proposition .

 

The problem disconnecting the 12v battery would be the computer will lose it's OBD data. Won't it have to relearn over the next hundred miles or so and give you worse gas mileage? This will also cause problems if you have to get an emissions test - there won't be any data as the computer won't be in Ready mode for emissions.

Trickle/float charger or a solar charger if it's sitting outside with no 120V nearby (like at an airport). I have three Battery Tender units with extensions for my vehicles. These will charge but never overcharge

 

Loosing the very limited data the computer stores is not a problem. It learns it back in a week or less.

If the traction battery -self- discharges (not from a load), it won't shorten its' life. NiMH batteries can sit fully discharged pretty much indefinitely. If you have a PIP with lithium batteries, not so much. They can be permanently damaged if they are discharged too far just once. But this is something we don't really have to worry about. The car won't let you discharge either type of battery too far.
If the car sat for several years without being used, 12V battery disconnected or not, you would have to replace the 12V battery and probably get the National Toyota special charger and charger person shipped in to recharge the traction battery. I suspect the cost would be in the $1000 range.

Yes, we had a very unusual two to three weeks of high humidity, "high temperature" (for us - 28-30C), with forest fire smoke and trapped particulates LA style this summer. Like the song says, "it's all over now". But as we all know, "global warming" is a myth perpetrated by, -us-. The oil companies and far right must be right!

 

We've had quite a few days here where it's like sunset all day, due to Washington State forest fires I believe.