The Prius Is Very Nice But What If .............. ?

[Desmond22]

It will be time to swap my trusty Avensis before too long and a test drive in a Prius seemed a good idea. It was - super car, well equipped, not bad ride, road noise iffy but acceptable. In fact it appears to be everything I need as a low-mileage-blue-badge-but-not-slow driver. ;) So why am I hesitating? The mpg looks good, it's easy to drive, comfy seats, plenty of auto gizmos ............

The problem is this - confidence.

My car is parked on the drive all year round. If I have to leave the car idle for several days in the winter can I be sure it will be like my Avensis and start with no fuss even when covered in ice and snow?

Of course the dealers say "No problem". Toyota do not even mention the possibility, presumably they think that if they did advertise some charging socket or other that this would make people think it was actually needed and put them off buying the car. But there is this nagging doubt in my mind that an electric motor and all those gadgets need power on tap for 100% of the time.

I know there have been threads about power packs and chargers but my days of playing about in the wind, rain and snow with locks that don't open and searching for stuff under the bonnet have gone now. For this money and at my age I want a car that is going to run and run.

So will it? That is my question to you good Prius owners.

(If Toyota had put a charger socket in the boot for a 240v mains extension lead to plug in, I might already be a Priius owner and not be asking daft questions. :) )

[SilverT4]

Hi Desmond,

I have owned a gen2 Prius snce Jan 2004 when they first went on sale in the UK and it has now covered 80,000 miles.

It has been mainly parked outside overnight on the drive summer and winter and I have never experienced any problems with the electrical system. In fact the only real problem with the car has been failure of the air conditioning unit shortly after the warranty expired.

I'm not 100% sure, but I think if the Battery went completely flat, then the petrol engine would still start up ok and soon put a charge back in the Battery. The petrol engine uses the auxiliary Battery to start and is not dependant upon the hybrid battery.

I have left the car parked outside for seven days during a cold winter whilst on holiday and it started up ok first time.

In fact I have been so pleased with the car I have just ordered a new one.

[timberwolf]

<snip>

I'm not 100% sure, but I think if the battery went completely flat, then the petrol engine would still start up ok and soon put a charge back in the battery. The petrol engine uses the auxiliary battery to start and is not dependant upon the hybrid battery.

<snip>

Sorry, you've got your thinking on the two batteries muddled up. The HV Battery (High Voltage/Traction battery) is used to power one of the motor/generators and that spins the petrol engine. The Aux 12v Battery is a tiny Battery that does not have sufficient power to crank over an engine. The Aux 12v battery is used to boot up the various Prius computers (ECUs) and once they are "happy", then the 3 relays are energised to connect in the HV battery.

The HV battery isn't the problem and there is no need to plug the car into a 240v supply - not unless you plan to go for one of those 3rd party PHEV kits but then you would be installing additional batteries.

My car sits on my drive most of the week, and I am not at all concerned about the HV battery, but I am aware that the 12v Aux battery is probably going to have a shorter life.

[agfs]

I intend to go to the US for 4 weeks over Xmas while my Gen 2 Spirit is garaged. Is there any guarantee that the car will have enough power to start up when I return ?

[Ogo]

I intend to go to the US for 4 weeks over Xmas while my Gen 2 Spirit is garaged. Is there any guarantee that the car will have enough power to start up when I return ?

The are no guarantees in this world. Next week big asteroid might hit Earth if it will not be destroyed over the weekend by the Vogons to make way for a new Hyperspace Bypass.

4 weeks is no problem for High Voltage traction Battery. The only problem could be with small 12 Volt Battery. Especially if it is already 4 or more years old. You can increase the life of the latter by shutting down the smart key system if you have it in your Prius - there is little black button below the steering wheel for this and of course shutting all the lights in Prius and closing all the doors and hatch properly.

You can also increase chances that your 12 V Battery will not be dead after 4 weeks by properly charging it before leaving car unattended. If you drive every day for at least 30 minutes, latter is probably not a problem. If you drive only once per week for few minutes, than hooking it up to proper charger is the best as Prius's internal charger is not known as best performer on powering up chronically undercharged 12 V batteries. Slow death of lead acid batteries begins already at 12.1 Volts, while voltage drop below 10.8 V means quick and reliable death.

Prius's 12 V battery is so vulnerable to discharge and discharge related failure as it is small and has much lower capacity than standard car batteries. And Prius consumes some power even when completely shut down. The biggest consumer of electricity while Prius is shut down is the SKS system, but the latter can be manually disabled immediately or will be disabled automatically after several days of not detecting any smart keys close nearby. Other things which rapidly kill the battery are, leaving the headlights on, leaving doors open and any other "parasitic" stuff like badly designed third party electric accessories like alarms, which draw energy out of the 12 V battery.

Ogo

[timberwolf]

Mmmm, I think the Vogons destroy the earth on Thursday, as one of Arthur's immortal lines went something like, "It must be Thursday, I never could get the hang of Thurdays." A timeless classic except the phrase "How am I going to operate my digital watch now" - which doesn't make much sense now unless you know that the early digital watches used to display the time with power hungry, red, 8-segment LED displays.

The Prius 12v Aux Battery question is a tricky one to answer for a two year old car. A brand new 12v Aux Battery, fully charged, will be fine for four weeks. About 4 years seems to be the typical life of the Prius 12v Aux Battery from those people who have posted about a problem (but this is sort of like the 8 out of 10 cat owners who stated a preference said...). How gracefully does a 12v lead-acid battery degrade? Does it just die giving a long standby capacity right upto the end? Or does it degrade and as the years progress so does the standby capacity reduce?

[agfs]

Thanks guys for your advice, Will certainly give the car a 30 minute drive before departure. Luckily I'm only about 1.75 miles from a Toyota agent so should be able to get help from them is anything is amiss on my retirn.

[Ogo]

Mmmm, I think the Vogons destroy the earth on Thursday, as one of Arthur's immortal lines went something like, "It must be Thursday, I never could get the hang of Thurdays." A timeless classic except the phrase "How am I going to operate my digital watch now" - which doesn't make much sense now unless you know that the early digital watches used to display the time with power hungry, red, 8-segment LED displays.

The Prius 12v Aux battery question is a tricky one to answer for a two year old car. A brand new 12v Aux battery, fully charged, will be fine for four weeks. About 4 years seems to be the typical life of the Prius 12v Aux battery from those people who have posted about a problem (but this is sort of like the 8 out of 10 cat owners who stated a preference said...). How gracefully does a 12v lead-acid battery degrade? Does it just die giving a long standby capacity right upto the end? Or does it degrade and as the years progress so does the standby capacity reduce?

Performance of 12 Volt lead acid Battery slowly degrades over time. So it is basically loosing its capacity of retaining energy as time goes by.

Things get worse faster, if the car is not used much and therefore Battery is almost never fully charged. Please note that 12V lead acid Battery needs quite long times to get fully charged, usually around 10 to 15 hours from full discharge. So if you use your Prius only 10 minutes per week, 12V battery will never be fully charged, increasing chances of quicker performance degradation due to constant undercharge.

High voltage Ni-MH traction battery is completely different story. It can be charged with currents over 100 Amps - 20 kilowatts during regenerative braking, and over 20 Amps - 4 kilowatts during normal forced regeneration charging, so Prius can charge it up within minutes. It is also totally disconnected when Prius is powered down and has extremely low self discharge rate, so it can survive with no harm for months if not even years. ;)

Ogo

[Desmond22]

Thanks greatly for the replies, much appreciated - I've learnt a lot about batteries there but I do have a couple more questions arising from the comments.

Is there any benefit to keeping a spare 12v Battery charged up?

How easy it is to replace?

[agfs]

Degredation of Prius 12 volt Batteries.

According to my local Toyota Agent,

“the 12 volt Battery, unlike in other cars, will not degrade over a period of 4 weeks if the car stays in the garage for that amount of time”

Nevertheless I will drive it for at least 30 minutes prior to departure and then let you know if it starts OK when I come back in January.

[Phoenix999]

Degredation of Prius 12 volt Batteries.

According to my local Toyota Agent,

“the 12 volt battery, unlike in other cars, will not degrade over a period of 4 weeks if the car stays in the garage for that amount of time”

Nevertheless I will drive it for at least 30 minutes prior to departure and then let you know if it starts OK when I come back in January.

I think the Toyota agent meant 4 weeks and not 4 months :o

[agfs]

Ummm, I think I did say 4weeks rather than 4 months.

[timberwolf]

What does your Toyota dealer thinks powers the standby current for things like the alarm and remote key wireless systems?

Just in case, I'd suggest testing that the key from the remote fob works in the drivers door lock.

[don21]

Sorry if this appears pedantic but why would you want to spend so much money on a hybrid like the not inexpensive Prius when you drive so few miles.

Surely the figures would just not add up.Of course you may be retired with a huge pension and a low boredom threshold.............

Sorry,do not mean to be offensive in any way but surely unless you are doing serious miles it just does not make sense?

Regards.

[Cyker]

You can also ask why people by giant 4x4's and flash sports cars when they are only going to be driving through tiny congested streets!

[agfs]

Before buying my car I read the drivers handbook. I could find no reference to the necessity of driving the car on a regular basis just to keep the 12v Battery charged, but I may well have missed that item. Neither is there any reference that I could find to illustrate that keeping a car garaged continuously for 4 weeks would be a bad thing.

After all, I have done precisely that with other cars at least 16 times in the last 10 years,

So why is the Prius any different and, if it is, why are there no instructions on that subject in the drivers manual ?

My local Toyota Tecky says that leaving the car garaged for 4 weeks will not make any difference to the 12v Battery. Is he wrong ?

Has anyone experience garaging their Prius for 4 weeks and could give therefore give an experienced view rather than stating perfectly understandable logical theories ?

Surely the state of the Battery prior to garaging the car would have some effect on how long the battery will last ?

Has anyone experienced finding a dead 12v battery and can explain why it died ?

[Ogo]

Well, Toyota assumes that most of the people buy Priuses for driving and not for keeping them parked for weeks and then driving them only for few minutes.

Otherwise you do not need to actually drive your Prius to charge up the 12 Volt Battery. Enough is to put the Prius in "Ready" mode when parked. When in Ready mode, hybrid system will go online and will charge both the 12V and the big high voltage Battery if needed. Internal combustion engine will be used on demand while in Ready mode, so this should be done in well ventilated area. ;)