Stall-out/Recall

Car needed jump start and dealer says it was the battery, but you are sure it was the water pump? Had you checked the date on the battery, it may have been older than 5 years. Prius owners especially need to keep their batteries fresh. Testing voltage at 4 years really should be considered essential. Pushing the limits is foolish for our computer controlled cars.

 

I think you will be good after replacing the 12V battery. I suggest that you fully-charge the new battery prior to installation.

Yes, it is a reasonable conclusion that a failed inverter coolant pump led to the warning lights and shutdown while the OP was on the highway. That failure required the 12V battery to provide power to the 12V bus which it can only do for a short period if in marginal condition.

 

"A little low" as in time to replace? You certainly don't need to buy a charger to install a new battery. If the battery tests low, just run the engine/drive for 30 minutes.

 

30 minutes is not enough time to provide much of a charge to the 12V battery, might be 2 or 3 Ah if you are lucky, while the charging current will diminish over time as the battery starts to charge up since the 12V bus is regulated at ~13.8V. The battery capacity is ~40 Ah.

If the OP does not wish to invest in a battery charger, I suggest he will need to leave the Prius READY for 8 hours or more to ensure the battery will be fully-charged. If he does invest in a battery charger, I suggest charging at a 4A rate.

 

no, it is not safe. if you can't safely leave it outside, buy a charger. you never know when it will come in handy.

 

Yeesh, If your brand new battery is that badly discharged, return it for a new one. 8 hours of charging is crazy.

 

This advice will do little or nothing for the battery. In 30mins at the maximum charge rate of the Prius "4amps" the battery will have received a 2 amp charge minus the initial start up loads eg running the brake pump at about 50amps then booting up the ECU's. The car does not have to be driven the engine does not directly charge the 12volt battery by an alternator as with a normal car. all that is required is the car be made ready and leave for about 4hrs to give a reasonable level of charge.

John (Britprius)

 

Now I'm fully geeked and piqued! What exactly does "be made ready" mean in plain speak?15 minutes of highway driving fully charges the HV battery and a brand new, 12v battery probably gets a decent charge in a half hour. The question for most drivers is how long it takes to charge a Prius 12v battery, sans chargers. Surely you, too, are not suggesting that a new, unused battery needs to be charged for hours before install. Suggesting anyone idle their car for 8 hours to charge a new battery is absolutely insane.

 

A "new unused" battery may have been sitting on a shelf for a year or more without being maintained, as people on PC have discovered by purchasing batteries that have charges below 50%.

Being made ready is a term used throughout Priuchat, and is entered by putting your foot on the brake and pushing the start button so that the word "ready" appears on the dash panel. This is all that is required to keep the HV battery in a healthy state of charge to be able to maintain the charge to the 12 volt battery, there is absolutely no need to drive the car.

An AGM battery "the batteries fitted in the Prius" has a self discharge rate of about 3% a month and the battery supplied could be many months old. Your recommendation of driving the car for 30mins will put back into the battery being generous 1.5 amps not allowing for charging losses or about 3.7% of the battery capacity.

Your method of driving the car for 30mins on the highway will use more fuel than leaving the car in ready for 4hours. Your method is for those cars that have alternators that push out 70 or 80 amps something that would destroy a Prius 12 volt battery.

"I cannot see in my post any reference to 8hours but agree even this is not unreasonable and will still use less fuel than your method. Of course using a charger is preferable than the above method but the OP did state they do not have a charger.

The Prius if left in ready mode does not! idle continuously as stated by you, it only runs to maintain the state of charge of the HV battery "rated capacity of several KW HRS to charge the 12 volt battery rated at about 400 WATT HRS.

John (Britprius)

 

My post #7 above made reference to the potential need for 8 hours of charging, i.e., overnight. This is validated by my experience charging the Prius 12V AGM battery using a constant current (4A), then constant voltage (13.8V) charging procedure with a lab power supply, similar to what the 12V battery will experience in the Prius. The battery needs to be charged until the charging current stabilizes, typically to less than 0.1A with a battery in good condition.

It is far better for the owner to be conservative regarding the length of time needed to charge the 12V battery - than to be optimistic, charge for a very short duration, and then be surprised when the car doesn't start.

There have been numerous recent posts from members who thought that Optima was a quality brand and purchased a new battery. They then found the new battery to be unsatisfactory, needing replacement or at minimum substantial charging.

 

Gentlemen, I fully appreciate your math, but question your practicality. Changing the battery does not require a degree in engineering. Prius owners (who tend to be very smart consumers) are best advised to simply buy a new battery that is not an old battery! Consumers can/should check the date on any battery to make sure that it is fairly new (less than 4 months old)! All the extra charging will be avoided. I'm sticking to my guns that it's safer to use the car normally and let it charge itself, rather than wasting gas and the greater danger running a car for any amount of time, in a closed garage.

 

Surly Prius owners are smart enough "by your own words" not to leave a car running in a closed garage and I cannot see that recommended in any of the posts. Taking the car on the highway for a half hour run will use far more fuel.

John (Britprius)

 

John, you seem to be forgetting that the OP asked if it was OK to run his car in his garage with the door shut:
"Is it safe to leave the car READY while parked in an attached garage with door shut? Do I need to worry about CO build-up?" He also didn't know that cold temperatures severely affect the strength of a battery. These kinds of questions must be answered correctly, without endless hyperbole. I think we can agree that running the car on the street (highway or local) for a needed trip is still the best use of fuel. Much as I enjoyed your keen arguments, in this case, you made some errors in judgement. You should have remembered to Keep It Simple!

 

Post #9 was an immediate response to the OP's question, indicating it was unsafe to leave the car READY in an enclosed space. The OP found his new battery was full-charged and was willing to buy a 12V battery charger if needed, so this discussion is now moot.

A hypothetical: If the OP did not wish to buy a battery charger, found his new battery measured low (for example, only 12.4V), wanted to ensure that his new battery was fully charged, and had no need to immediately drive his car somewhere for an 8 hour period:

Then, much less fuel is consumed leaving the Prius READY and parked on the driveway for 8 hours, vs. actually driving around for that same period of time. Hence I would not agree with your assertion regarding the best use of fuel, given the above hypothetical circumstances.

 

Does it really take a full 8 hours from a Prius engine to charge a battery from 12.4v or is that the time it takes from your suggested "lab power" charger? Is there no difference in charging time between idle and higher RPMs? And do you still think it is good advice to have anyone run their car for eight hours, consume gas and pollute the air rather than use the car normally and wait for the car to slowly recharge the battery over the course of a few days? Or better yet, return the battery for a new, properly charged one?