Prius C software bug, critical battery design issue akin to Boeing MAX MCAS flaws

it is not a design flaw, because you're the only one having this problem.

1) how long (time/miles) have you owned her?

2) any history we should know about?

3) when did it start doing this?

4) have you tested/charged/replaced the 12v?

5) it is possible you have a parasitic drain, this can be tested

 

c three and four have those weirdo proximity key/pushbutton start thingies. Those are known for (sometimes) having issues with battery drain depending on local radio conditions and the overnight storage of your keys.

Try storing your key in a metal box (cookie tin, refrigerator etc) for a few nights, see if it acts up on any of those nights.

No, that's not a suggested cure, it's just a test to see if that's what is really going on. People are reporting similar symptoms on lots of different cars with similar key/pushbutton-start features.

Enough with the fearmongering, get your stuff together and get your car fixed.

 

Having separate auxiliary (12-volt) and hybrid vehicle batteries, with the high voltage supply from the latter disconnected by relays or contactors when the vehicle is not operating, is a standard feature of hybrid vehicle designs, not only Toyota’s but also those of GM, Hyundai, and many other automakers.

If the auxiliary battery isn’t available to power the electronic control units that provide for control and electrical protection of the hybrid system, the high-voltage battery remains safely isolated, by design.

That’s far more likely, or perhaps—as others have kindly suggested—there is a problem with parasitic load.

The usual cause is explained in the Owner’s Manual (PDF) on page 8: “Approximately five hours after the hybrid system is turned off, you may hear sound coming from under the vehicle for several minutes. This is the sound of a fuel evaporation leakage check and, it does not indicate a malfunction.”

 

This seems a bit over-exaggerated and almost like one of those posts people make when they are car bashing...
Hopefully that's not the case and he isn't a one and done for search results.

That being said, there are many threads about the 12v battery preventing the car from starting. The normal recommendation on this thread seems to be to replace it after about 3 years. But since you're using your dash cam (while the car is off), this can certainly be prematurely draining the 12v battery. It doesn't get recharged by the car when it's off.

This isn't any different than any other car with a bad 12v, it just doesn't seem as obvious because you don't get the normal starter click noises and dimming headlights when you try to turn the ignition. A Corvette will leave you stranded if you have a bad 12v battery too.

Now... if the car dies WHILE driving it... that would be a cause for alarm. I recommend that you spend the $200, change your 12v battery yourself and keep keeping on.

 

From the headline alone.... I mean honestly, comparing a car with an inconvenient no-start problem to a mass fatality air crash that hasn't even been fully investigated yet?

It helps no-one and is disrespectful to many.

 

Maybe it is his camera that is draining the battery.
It is also known that the ODBII port is hot all the time and anything plugged in there will run it down.
Could be that his battery is just worn out.

Out of the millions of C's on the road, ONE with an unusual problem does ***NOT*** indicate a "design defect".
Anyway, posting crap like this is NOT the way to get anything fixed.

 

we need @JackTheNarrator to start a class action

 

The Prius will wake up all the time and do all sorts of stuff. This is normal behaviour. And once your aux battery dies, it is DEAD. These aux batteries are like golf-cart sized and since they have such an easy life, they have almost no capacity. When you kill an SLA, it will never be healthy again. And in a Prius, that can be the difference between working and not working. Especially if your trips are short, as it will never charge up fully. Replace that aux battery. If it has been jumped once, think of replacing it. If it has been jumped twice, REPLACE IT NOW.

You jump a Prius via the "jump terminals" under the hood... So yes, you open the hood open the plastic cover and jump from there. If your average drive is a mile, it is very likely that the battery is just never able to charge.

Yes, that's how it works. Want a problem to accidentally send 200VDC onto the body or random metal part or arc-weld something? Probably not. Some newer cars now have a 12v maintainer feature built in which is nice. It will wake up in the middle of the night and actually charge the 12v from the high voltage pack for a short time and then turn off again. But no Toyota does this yet.

You seem to be stuck in the 1920's where when you turn the car off, the car was off. That hasn't been true for half a century now. Your key fob requires power when the car is off. Your radio presets, your automatic window adjustments, the fuel gauge, etc. In addition the Prius will wake up and times after the car is powered off and do some maintenance such as priming the brake booster pump and a few other checks. In the newer vehicles the cellular connection will wake the car up to gather data and transmit it back to the mothership.

In your car, the big draw is the brake booster pump. That's about it. Now, when is this activated? It is activated as a feature and for convenience as you approach the vehicle. Not when you're inside, not when it is started, but just when you are near. So first question, where are your keys located when the car is parked? Also keep in mind that everytime a compatible set of keys passes the car, it has to check. Your car is like on those overly excited dogs that sits behind the door eagerly awaiting your return.

Every keyfob that comes in range the car wakes up. "Is this my key? Do you have the matching passcode???? No... Ok" It then powers off some systems and goes back to sleep. If your garage is right off the street for example and people are always walking by or even if you live in an older area where the road may be less than 15ft from your car in the garage, every car that drives by with an SKS fob is waking your car up.

If you couple all of this with a battery that is just old, or was accidentally drained once in its life which happens, then yeah you have a problem. Replace the battery and potentially disable SKS.

Also just so you know it sounds like you don't understand how the Prius "starts". When the car wakes up and matches the key, the brakes are primed drawing about 30A from the 12v aux battery. When you approach the car, the lights the come on. When you get in the car and push the READY button, it draws less than an amp and flicks 3 relays open and closed to connect the HV battery to the inverter. The inverter then bucks down to the 13.8v charge voltage for the battery and now the aux battery is being charged. That's it's whole life. When the engine is to start (either power request or after a few seconds, etc) the car draws power from the HV pack through the inverter to spin MG1 which spins the engine. Fuel is injected, controlled explosions happen, engine now spins MG1 and charges the pack back up. There is no starter. There is no alternator. The aux battery does barely anything.

Tomorrow, before you leave use a digital multimeter and measure the voltage of the 12v battery at the jump point under the hood. Then READY the car and measure again.

 

@2k1Toaster , please correct this if I’m wrong, but monitoring voltage with a Scangauge over the last few months, I have observed two different apparent voltage levels after the HV battery is powered up so that the DC to DC circuit is functioning: one state is 13.6+/-.1 volt that seems to occur when the 12v battery is in a full state of charge and the total 12v demands for lights, fan, and etcetera are quite low. The second state is 14.7+/-.1 volt which seems to occur if either the 12v battery needs charging or if there are moderate to high total 12v demands from all the other 12v peripheral circuits. When my 12v battery was weak a year back, the system never went down to the 13.6+/-.1 volt state, wheras after I installed a new 12 v battery (Toyota brand), it ultimately did. Do I understand this aspect of the electrical system correctly?

 

That matches my understanding. The 12V bus voltage set high for faster recharge when the 12V battery wakes up low, then drops when the battery is 'adequately' recharged. Though 'adequate' may be disputable, as there seems to be a pattern of Prii not keeping these batteries well charged.

 

Yes that's pretty much it. There is another scarier state that I found quite by accident experimenting with much too large loads on the 12v bus backfeeding some server racks, and that's the inverter going into a safety shutdown state ONLY on the 12v rail.

This means it is possible for the car to start via the 12v battery, experience a large load during startup such as a battery with shorted cells or electrical fault. The car will prevent the inverter's 12v rail from powering up but the HV system is already engaged, the car is READY and there is 12v present from the 12v battery itself. Now as you drive around the 12v will get lower and lower, start to throw random faults, and eventually the car will stop and you'll have no charge to reset it assuming the intermittent fault has been cleared.

 

t?

 

Sure looks like a drive-by troll to me.
He hasn't been back since posting his tirade.

Oh.....and we love our C's.....all 3 of them.

 

Prius c sux compared to a b they ruined it

 

what a b?

 

Maybe Toyota is coming out with a Prius D in 2020!!

 

Because everyone wants the D?
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I apologize... I just couldn't stop myself being 12 again.

 

referencing the recent air disaster is pure clickbait and SEO.

 

10 weeks ago the original post. No reply?