Prius Series 3 12V Battery

[inspiredron]

My Prius is now just over 2 years old. After I returned from holiday at the end of September I became conscious that the READY light was taking far longer to come on and consequently the car did not go into Drive. The fault was somewhat intermittent and I mentioned it when the car went in for its two year service in mid October. When the car was finished I was told "no fault found and no diagnostic codes". Returning to the car it was again reluctant to show its READY light. Back into Reception and a mechanic came out, whereupon the car refused to misbehave. He did however mention that there was a possibility that the 12V Battery was discharged and might need a boost - however he gave dire warnings about doing this without disconnecting the Battery.

This week the problems escalated and so I measured the 12V Battery voltage which was 10.33V. I went to the garage (Jemca Croydon) without an appointment and told them that either the battery had a duff cell or it was not being properly charged. They fitted a new battery but I do not know whether the charging mechanism was checked so will be keeping an eye on the voltage. It has completely cured the problem and the READY now comes on within moments.

Although Jemca dealt with the problem quickly on my emergency visit I am peeved that they ignored it when I had the car serviced. It took me 5 minutes to check the battery voltage when the problem became critical and I would have thought this was an obvious check.

I have to say that I regard only 2 years life as PITIFUL performance from a battery that does not have to cope with the load from a starter motor and I am conscious that, as an early Series 3 purchaser, my next replacement is likely to be outside the 3 year warranty.

And what does this mean for the probable life of traction battery? Please also see my separate post on this.

[Flaninacupboard]

Don't worry about the traction Battery, really. the lead acid 12V is small, and not very good. If mine dies outside of warranty i will replace it with a larger, better one.

It may be your use is punishing it hard, do you do lots of short trips, or sit in accessory mode a lot? I also always wait for the brake accumulator pump to stop (it starts when you open the drivers door) before starting the car to make sure there's minimal load on the 12V.

[cootuk]

Doesn't the MFD have a magic code where it will display various things like Battery voltage?

That would only take a few minutes to check.

[inspiredron]

Doesn't the MFD have a magic code where it will display various things like battery voltage?

That would only take a few minutes to check.

What do you mean by "magic code"? What sequence do I have to press on what buttons to access hidden menus? It would be really good to be able to check that without having to access the Battery or jump start terminals

My usage is fairly hard with lots of short journeys but no different from my old Volvo where I needed a new Battery every 7 years - and they had to cope with the demands of a starting motor. A small Battery does not mean it should last less time before dropping a cell - assuming that was the fault - an only time will tell.

[timberwolf]

Doesn't the MFD have a magic code where it will display various things like battery voltage?

That would only take a few minutes to check.

What do you mean by "magic code"? What sequence do I have to press on what buttons to access hidden menus? It would be really good to be able to check that without having to access the Battery or jump start terminals

My usage is fairly hard with lots of short journeys but no different from my old Volvo where I needed a new Battery every 7 years - and they had to cope with the demands of a starting motor. A small Battery does not mean it should last less time before dropping a cell - assuming that was the fault - an only time will tell.

On the Gen 2, the "magic code" involved pressing different areas of the touch screen in sequence to enable a service mode, and from there the Toyota mechanic could select various diagnostic screens mainly concerned with the audio or sat-nav. It isn't that useful for measuring the 12V battery, because the conventional advice for attempting to determine the health of a 12V battery is after it has rested for a number of hours and isn't on load. I don't know if the Gen 3 has a similar service mode.

The 12V battery has been a weakness in all the Prius models. With a conventional car, the 12V battery has to be large enough to crank over an engine, so the standby current needed to run the electronics for the alarm and remote locking is only a tiny fraction of that needed to crank the engine. On a Prius, the 12 battery is small because it only has to power up the various computers, energise 3 relays and run a few pumps, so the standby current to keep the alarm and remote locking is much more significant drain than if a larger battery had been used.

It is also claimed by some owners that the charging system used in the Prius, does not really do a good job of keeping the battery fully charged. Interestingly, Toyota USA have a Technical Service Bulletin that detailed how the dealer was meant to charge the 12V battery before the car was delivered to the customer. In the UK, I got blank looks from the both sales and service when I asked my local dealer if they were going to my car before delivery.

[johalareewi]

Doesn't the MFD have a magic code where it will display various things like battery voltage?

That would only take a few minutes to check.

Not on the gen3.

For a replacement 12v Battery, you could look at an Optima yellow top and fit it yourself.

http://priuschat.com/forums/gen-iii-2010-prius-care-maintenance-troubleshooting/98415-optima-ds46b24r-prius-specific-12v-battery.html

http://www.optima-batterien.eu/optima-products/yellowtop.html

[kithmo]

Doesn't the MFD have a magic code where it will display various things like battery voltage?

That would only take a few minutes to check.

Not on the gen3.

There is on the T-Spirit:

Put vehicle in Ready or Acc mode (you may press EV to prevent the engine starting and wasting fuel if in Ready mode)

Hold down the "INFO-TEL" button on the NAV

Turn the headlamps on and off 4 times.

The diagnostic screen appears on the NAV.

On the first screen, press; "Function check/Setting"

then on the second: "Vehicle signal"

Battery voltage is the first on the list on the third screen that appears.

This shows the voltage under load in Ready or ACC mode

if you switch various things on/off you can see the voltage vary.

With no load when the Battery had rested for a while mine showed 14.2v in ready mode

Switching the headlamps on it dropped to 10.4v, which shows how weak the Battery capacity is. 10.4v would struggle to turn a starter motor on a conventional car.

[johalareewi]

You learn something every day

[flow]

Exactly the same problem with me! Noticed it on Monday. Went into diagnostics & Battery was reading 8.8V - Still just enough to get the ready light to come on.

It went in on Wednesday to have the centre arm rest replaced (rattle), They checked the Battery out & of course found no fault found. I feel sure its going to happen again & told the service guy to await a phone call from me in the next day or so when it plays up again.

[kithmo]

Doesn't the MFD have a magic code where it will display various things like battery voltage?

That would only take a few minutes to check.

Not on the gen3.

There is on the T-Spirit:

Put vehicle in Ready or Acc mode (you may press EV to prevent the engine starting and wasting fuel if in Ready mode)

Hold down the "INFO-TEL" button on the NAV

Turn the headlamps on and off 4 times.

The diagnostic screen appears on the NAV.

On the first screen, press; "Function check/Setting"

then on the second: "Vehicle signal"

Battery voltage is the first on the list on the third screen that appears.

This shows the voltage under load in Ready or ACC mode

if you switch various things on/off you can see the voltage vary.

With no load when the Battery had rested for a while mine showed 14.2v in ready mode

Switching the headlamps on it dropped to 10.4v, which shows how weak the Battery capacity is. 10.4v would struggle to turn a starter motor on a conventional car.

Further to this, checking the voltage in Ready mode is the charging voltage, i.e. the HV battery is charging the 12v, checking in ACC mode is the battery voltage with no charge going in and with whatever accesories are on.

Apparently 11-12v is ok in ACC mode and 14.x in ready mode with no other loads.