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Drive belt changed on 2006 prius

Hi, just went to dealer to have oil changed. They said that I needed a new drive belt. They also said that I should have the two coolant systems flushed, since I had 100k miles on the car. I pointed out that they had just replaced both water pumps 5k ago, and the coolant systems had to have been flush out then. I did have them replace the drive belt. Two days later, I took the car to work. When I left work, the car was dead. AAA, jumped the car, and ran a check on the battery, which they said was fine. Took the car to be detailed today, and it went dead, with the car doors open, in the detail shop. Could an improperly installed drive belt, cause this? Never had a problem before this.

I doubt the trouble is with the drive belt. I think you probably need a new battery, your car is almost 8 years old, original equipment batteries tend to have a service life of about 5-7 years.

I’m not talking about the hybrid battery pack. Your Prius still has a conventional 12 volt battery like other cars do. Leaving the door open and the dome light on at the detail shop probably shows how weak that battery is.

Thank you. The AAA guy ran a test on the battery before charging, and it was 7.83V.


I might add that almost nobody but the Toyota dealer has the correct 12V for your Prius

So, if you do need a 12V battery (and I believe you’ll find out you do), save yourself a bunch of phone calls and go straight to the local Toyota dealer

The reason is this: the battery is such a small battery, and such an oddball size, that the Prius is the only vehicle that uses it. Therefore it’s not really worth it for Autozone, Pepboys, etc. to have those things in stock.

So you have a failed battery. I assume the AAA guy did more than just test voltage on the battery. You should have gotten a reading of available cranking amps and battery state of charge.

Results: Voltage 7.83, measured 67CCA, rated:450CCA. Time to charge: 7 hours@ 6A, 4 hours@10A, 2 hours@20a.
Not sure what it all means, but never had a problem, until the first day I used the car, after the drive belt was replaced. I was told that if the belt was improperly installed, that it would affect the alternator. Then told, the Prius doesn’t have an alternator, but has an inverter, instead.
I plan to call the dealership, in the morning, but I want to have some idea of what I am talking about.
I have been bringing the car in for oil changes, every 5,000 miles. Each time, they find something that needs to be replaced, to the tune of $300-$900. This time, they also recommended that I change my spark plugs. They said they could do it for $265.00. That seemed high to me. After many of the estimates that they have given me for work, I have taken the car elsewhere, and had the work done for 1/2 the price.
I want to be reasonable, but not stupid.


I’ll cut to the chase . . . those numbers tell me your 12V battery is toast

Like I said before, install a genuine Toyota 12V battery . . . nobody else will have it in stock

I appreciate it. Thank you.

I fully agree with db4690 on this. If the accessory drive belt were installed wrong you would have several problems such as power steering, cooling system etc. One belt drives them all. However I am not sure about the alternator part.

An inverter is used to convert DC to AC. Your engine has three transmissions attached to it, one of those drives a three phase AC motor generator the charges and uses the large 480 VDC drive battery. when in motor mode, the inverter takes the DC from the battery and converts it to a three phase AC to move the vehicle.

They could use a step down transformer and a diode pack to charge the 12VDC accessory/starter battery so I don’t know on this one. Outside the Toyota dealership, there are very few people who have had the training necessary to maintain one of these. But if it does use a conventional alternator for the 12 volt accessories and battery, then it is driven by the accessory drive belt.

I don’t know why the AAA driver told you that the battery was still good. You can’t get a valid test on a battery until it has been recharged. You might get an indication as to good or bad, but it really must be charged up first and then load tested. But any battery that is below 10 VDC in open circuit condition is usually unrecoverable. a battery that is that low can also damage your alternator, so if you have a separate alternator, you should get it checked before putting in the new battery. The Toyota dealer should be able to do this for you.

Like the others said above, the battery is bad. Available amps=67. Rated amps=450. So your battery is at 15% of it’s original capacity. Time for a new one. Batteries have a finite life span, be it the battery in your smartphone, tv remote, camera, or car. Yours lasted 7 years, about normal. Replace it and move on, nothing unusual about your battery failure. The drive belt on your Prius has nothing to do with the battery.

Cranking amps don’t apply since this battery doesn’t start the engine.
A 12V battery at 7.8V has a state of charge of less than zero.

On a Prius, it does. You must be thinking Honda.

Nope, on a Prius one of the large electric motors starts the engine, using the large battery pack, not the 12v battery.

That’s what I thought too, but I was in the service department of the Toyota dealer where my daughter bought her new car and a guy brought in his Prius that he had to get get a jump start on. I asked the tech that came out to look at it how it could be jump started and he told me the starter is a 12v conventional starter.

Nope. Here’s an explanation from Priuschat:
“The Prius has two motor/generators, called MG1 and MG2. When you first power up the car, MG1 starts turning and begins spinning the engine. When engine RPM and oil pressure reach acceptable levels, the engine lights, generally several seconds after startup.”

Just another example of gross ignorance on the part of a dealer…

However, a dead 12V battery (which powers a lot of systems) could keep it from starting. So there is that for confusion.

Here’s another explanation, in more detail:

It appears that you are absolutely correct, my bad and the dealers bad, however a Prius will not start if the 12v battery is dead. If the 12v battery is dead, it can be jump-started, but if the polarity is accidently reversed, the consequences are disastrous in this vehicle.

It also appears that there isn’t a belt driven alternator either, the 12v battery is charged by MG1 also. So changing the accessory drivebelt for the engine has no affect on the battery.

I stand corrected.

BTW, if the original battery is a 450 CCA, that’s the capacity as the battery in my riding lawn mower, you don’t suppose…