My 2008 Prius is sick

ronbet,

It is very likely that you have a bad 12V battery.

Either you or the the techs need to check the voltage of the "12V"
battery after it sits overnight. The voltage needs to be checked at the
charging points under the hood, or at the battery itself under the rear
hatch floor BEFORE the car is put in the Ready mode. (Once you get
the Ready light, the 12V bus is supplied by the High Voltage battery via
the DC-to-DC converter and will read ~13.6V. This is most definitely
NOT THE VOLTAGE OF THE "12V" BATTERY.)

I'll bet the voltage will read ~>12V. This means that the battery has lost
~ half its capacity and needs to be replaced.

Typical service life on the 12V battery is ~4 years. However there are a
number of situations that can significantly reduce that number.

I'm surprised that your dealer techs are calling in the "big guns"
before doing such a simple diagnostic.

 

They might be afraid it will zip off by itself .....

but seriously - with a scangauge - is it possible to read the 12v battery, or will the car always show the DC - DC value if the car is in any way on ? I was hoping scangauge would let me watch for any 12v battery changes.

 

Tom,

The ScanGauge is the perfect way to read the capacity of your "12V"
battery -- when it's in good health it should be reading closer to 13V
than 12 after sitting overnight.

Here's what to do:

Set your SG up so that voltage is one of the displayed gauges.
Let the car sit overnight.
In the morning, don't touch either the brake pedal or the Power switch.
Hit the button on the SG on the lower right. It will power right up.
Read the voltage. If it is below ~12.5 it's time to consider a
replacement. If it reads below 12.2, go get a new battery 'cause
trouble is right around the corner.

 

HV battery failure will produce symptoms like this.

Tom

 

I agree, but consider it unlikely given the car's age and mileage.
(But I've been wrong before. )

We have to dig deeper...

ronbet,

Did the tech(s) say anything about trouble codes being recorded or
"thrown?"

If so, what did they say?

If not, you should ask if any were. If so, post them here and the
techno-gurus can tell you (us) what they mean.

 

Could it also be a recalibration? I seen my battery drain then recharge all the way a few years ago. I only seen it do it once. I just passed it off as a recal. Never had a problem since.

 

I would have tended to agree, but I tried this last night... and the multi-meter and scangauge are fairly off from each other. At the battery terminals, I'm seeing 12.6 (not bad, not great, but not bad). The scangauge is seeing 12.3 (almost at replacement territory). YMMV.

 

I think everyone needs to take a deep breath. The thought of replacing a 12volt battery because a multimeter indicates 12v? Hmm, 6 cells at 2 volts apiece equals 12v. If that were the case we would be replacing battery's daily.Have we load tested the battery? What climate does the battery live in. Cold weather is awful on a battery, they don't like to cooperate until their a little warm. Prius 12v battery's are notoriously delicate and fail often, and after dealing with battery problems myself, replacing it with an optima is well worth it. I think after reading what I have I would be more interested in the HV battery.
The groaning noise you are possibly hearing is the defective break actuator, (TSB BR001-07 Brake Actuator Noise) with the foot on the brake, pushing the power button you will hear a groan or some call it a bark for a couple seconds, this is from the above mentioned brake system, I have two of these cars and they both do it, 07 and 09,.

 

This is splitting hairs, but 2.0 volts per cell is nominal voltage only. Normal "open circuit" voltage for a lead-acid cell is in the 2.10 to 2.13 V range, or 12.6 to 12.8 V for the battery. If the battery's at 12.0 V or below, it's discharged. (This is like expecting to find a 2" or 4" dimension on a 2 by 4.)

 

Get an Optoma yellow top and the installation kit, disconnect the battery for 15 minutes (while you install the yellowtop) reconnect and the problem will be in your rear view mirror.

 

Can you possibly record the groaning sound and put it up for us to hear? For example, if you have an iPhone, it has a voice recorder app now.

It is very easy to run the HV battery down to two purple bars just by letting the card sit in Ready mode (on) stopped or creeping along in a parking lot or bumper to bumper traffic for an extended period of time. There's nothing abnormal about that.

You can test the 12 volt battery voltage via http://priuschat.com/forums/newbie-...g-mpgs-dropping-test-battery.html#post1020264.

Although I've never had a bad HV battery, IIRC, common symptoms are the MFD showing it going from full to empty VERY quickly and vice versa, sluggish acceleration w/the ICE revving at higher RPMs than normal and the HV battery fan (in the back seat area) running on high.

I can't speak to squirrelly display arrows or whatever since we can't see it. If you can put up a video on Youtube or something, we could better help.

For reference, the TSB and some chatter about it are at http://priuschat.com/forums/toyota-.../29211-tsb-br001-07-brake-actuator-noise.html. FWIW, my 06 Prius has the brake "honk"/bark sound occasionally. I don't care as I'm out of warranty now and it looks like a huge job anyways (4.4+ hours) and the TSB says it doesn't braking performance.

 

Although, I don't really suggest you spend money to buy a ScanGauge to diagnose problems, esp. problems covered under warranty, if you had one, you could use XGauges to view the state of charge of the HV battery (Soc), HV battery voltage (btV and variants) and battery amps going to/from the battery (Bta) and compare w/others here, under varying conditions. The HV battery temp readings (buc, buf, blc, blf) might be interesting too.

I personally leave Bta and soc up a lot of the time and have sometimes peeked at the temps and voltage.

Regarding

are you sure about this? I've definitely gotten into states (that aren't abnormal) where the ICE may not fire up to charge the HV battery when it's "low" but only when pushing the go pedal.

What happens if you let it run down further? It will for sure run down further and should eventually cause the ICE to fire up. If you get a red triangle of death or a check engine light, then in the latter case, it will throw a code that your dealer can read or you can w/an OBD II scanner.

 

I'd say that you should just drive the car and not worry about it. If your car has a real problem then a DTC will be eventually logged and warning lights will appear (such as the red triangle warning light and the hybrid vehicle icon on the MFD.) Until your car logs a DTC, the dealer service tech is not going to take any further action.

As your car ages you'll note that the traction battery SOC gauge swings more widely than before. Also, if the weather in your area is warming up and you are using the AC compressor now, that will also drain the traction battery more esp when you are driving at slow speeds or at a standstill.

If you still want to worry, then here's my suggestion: if you have mountainous terrain in your local area, then take the car out for an excursion, going up & down the mountain, driving the car as hard as you can while remaining safe and observing speed limits. That will stress the powertrain and if you've got a latent problem maybe it will manifest itself.

 

Hi Ronbet, is that all the time or just when you're starting your journey? It's actually fairly common for the battery to get used a lot while the engine is warming up, and it can definitely cause the HV battery to drop a few bars in the first few minutes after cold start.

I'm not even sure what that means?