prevent dead battery

Toyota's guideline is that a Prius being stored should be made READY at least 30 minutes every two weeks to keep the 12V battery and traction battery charged.

If your 12V battery is original equipment it may need to be replaced now.

 

The 12V battery is the small auxiliary battery that is required to power up the ECUs and start the Prius. With that battery, low annual mileage (like your case) usually means a shorter service life. This is because voltage on the 12V bus is fixed at ~13.8VDC, when the Prius is READY, and it takes a long time to charge the 12V battery at that charging voltage.

The large traction battery is the one that will power the powertrain when you are driving on electric power. It also powers MG1 (via the inverter) to spin up the gasoline engine when it is time for the engine to run.

The traction battery has a dedicated ECU that keeps track of the traction battery's state of charge. Based upon the battery's SOC, the hybrid vehicle ECU will allocate more or less gasoline engine power towards recharging the traction battery.

Hence, the traction battery is able to tolerate very low miles being driven, as long as you drive your car periodically to give the battery a chance to be recharged by the engine spinning MG1.

 

The small 12V battery carries a load when the Prius is powered down, but not when the Prius is Ready. It's not really a matter of miles but age that kills the 12V battery. If you drove your Prius constantly, the 12V battery would last almost forever. Parking it as you do, the 12V battery will suffer an early death.

Tom

 

If you have the smart key option (the one where the doors open when you approach, it has little black buttons on the door), you should disable it if you are not using the car for a while. That will significantly reduce the drain on the battery, and allow a longer interval between needing to run the car. It is a small push button under the dash to the right of the steering wheel. There is one next to it for resetting the tire monitoring system.

 

Since your battery is 4+ years old it may need to be replaced soon. If you have access to a battery charger this would be a good time to hook it up overnight, using the 2A position. If not, maybe you can leave the car READY for several hours in an effort to charge the 12V battery.

 

The first winter with my '04, I had problems with my aux battery. It was literally a Perfect Storm to kill a battery: commute 15 mins, at -40, headlights on, Max Heat, electric defrost on, etc.

I finally put in a VDC Electronics Battery Minder

BatteryMINDer® Plus 12 Volt 1.33 Amp Charger-Maintainer-Conditioner (Desulfator) | All | Battery Chargers by BatteryMINDers.com

which I hardwired directly to the aux battery





When I sold the Prius last summer, the aux battery was still in perfect condition. If a Prius is used in something like Taxi duty, and kept in Ready 16-18 hours a day, the aux battery will last a long time

A Prius rarely driven, especially with those low miles, you MUST use a battery tender. Never leave a conventional battery charger hooked up all the time, you will ruin the battery

 

If a Prius is used in something like Taxi duty, and kept in Ready 16-18 hours a day, the aux battery will last a long time


I do hope so

I would have thought that all the additional power drain from the meter, two way radio and despatch computer running all the time (even if in Ready mode) would have a negative affect on the 12v battery.

 

No. Once the Prius is READY, it is up to the DC/DC converter to maintain voltage on the 12V bus at 13.8V. The output of that unit is fused at 100A. While the Prius is READY, the 12V battery does nothing other than receive a charge.

 

Since the owner in this case lives in an apartment, an extension cord may be problematic, one solution I've read others have tried is wiring a 12 volt solar charger directly to the small battery in the rear ( the cabin 12 volt power plugs are off/ disconnect electrically / when the car is off) .

 

Still using original 12V battery which had been very abused for the first couple of years. It sat on the dealership lot for a good six months and needed a jump so I could test drive it. Then I had it down below 9 volts a couple of times after that (a slow learning curve on my part). I took Jayman's advice just over two years ago, purchased a couple of VDC Electronics Battery Minders for my vehicles, and have had happy batteries since.

I don't use the Prius except for trips (cycle and walk locally), so it sits for periods of up to a month and a half without starting. I installed the connections for the Battery Minder under the hood (bonnet) on the Jumper Stud in the fuse box and a ground stud on the side of the Inverter. A simple install that doesn't interfere with anything. Attached pictures should illustrate installation, but if any questions, just ask.

Wayne

 

Note that it doesn't actually have to be driven to charge the battery. Merely turning it ON as though you were going to drive, but leaving it in Park instead, is sufficient. Do that for 30 minutes once each week and all will be well.

 

Duffy's Taxi here in Winnipeg is one of the pioneer hybrid taxi operators in North America. Winnipeg is a harsh environment, winter temps can reach -40 C, summer temps can reach +38 C

About Us - Duffy's Taxi - 1100 Notre Dame Avenue

I haven't heard of any Duffy's Prius taxi's actually wearing out. They usually get totaled in crashes with stolen cars, or get carjacked in a violent manner

Do immobilizers lead to taxi carjackings? | Winnipeg | News | Winnipeg Sun

Pregnant woman involved in taxi crash | Winnipeg | News | Winnipeg Sun

If you play the following surveillance video, you will notice a Prius holds up well in a crash

Taxi driver dodges death | Winnipeg | News | Winnipeg Sun

Winnipeg is a very violent city, with a lot of gang subculture. It's considered the homicide capital of Canada, in addition to the car theft capital of Canada

Perspective: Chill. Thrill. Kill. - Winnipeg Free Press

so the fact a Prius holds up considering the climate and crime, is pretty amazing

Much easier than wiring it up directly to the battery