My Prius is not well :( Check Hybrid System Msg

If it is of any comfort, my parents today turned on the Insight after a 2 day stop and did not start! The 12V battery was dead. The Honda assistance was baffled as well - it is not excluded that a light (maybe the dome light) might have been indadvertedly left on. And I do hope so.
But who knows? It is annoying nevertheless...

 

If the 12V battery is low on voltage, down to a critical level, it might be that the system starts to fail due to software/hardware malfunctions - a bit like a computer that has defective RAM - you start seeing all sorts of weird errors and behaviours.
The ECUs will issue warnings and failures. The fact that the ICE starts, is a good sign. The ECU has seen a 12V low, and since the HV is high enough it used MG1 to start the ICE to charge everything up. It also means that all other systems are OK, including the inverter, otherwise it would not have started the ICE.

But it is also not good that a 2 year old 12V battery starts to fail...
(my parent's Insight 12V battery failed them yesterday after 2 days of not driving it - apparently they did not leave anything turned on...)

What's wrong with these 12V batteries?!?!?

 

I think both your theories are spot on for the info given. I would go to the dealer and have them print off all codes. Having them test the battery is fine, but unless it is way dead, then it will be useless. Buy a $10 (or in your case 10GBP ) multimeter and test the battery from the terminals themselves. Car off, car in acc, and car in ready. That should give an easy look at if the inverters low voltage output is ok and if the battery is ok. The dealer's 12v test is usually just the onscreen diagnostic and not very accurate. With an SLA battery a couple hundred millivolts is a big difference.

Do you have the same law of no idling allowed while parked? Since you are a cabbie, I would guess you sit idle alot. if you are no in READY mode, then are you in acc mode to run the radio and such?

 

If 12V power drops too low the battery ECU will lose it's record of the HV batteries SOC. When 12V is fully restored (car enters Ready) the battery ECU will make an estimate of the SOC based on temperature and voltage. It won't necessarily be correct, and would need to go quite low and then quite high again to be really accurate again. I guess what i'm saying is, that sounds normal if 12V has is weak.

As per 2k1Toaster, whack a multimeter on it.

 

I wonder if your despatch computer/radio/meter has a continuous parasitic drain even when Ready/ignition is off?

When my 12V fails i'm not going to replace it with the same one, i'll put in a more normal sized battery, there's plenty of space.

 

Yes. The Prius battery is not designed for use while "off" at all. It is a holdover from a Japanese philosophy. They do not sit and wait in their cars with everything on. You will not see a large battery factory installed from Japan. When Japanese vehicles are shipped to Europe or the USDM, a much much larger 12v is fitted. However, not so with the Prius. Hence it is considered "dinky" and small here, whereas it is really just a normal size and us westerners are just used to gigantic batteries to play our tunes for an hour with the car off.

If this is normal for you, I highly suggest getting a deep cycle battery (gel/marine like an optima). Normal SLAs cannot take discharging. Once they do they are never the same. Gels/Marines can be killed and brought back to almost full health many times over. They are made for your situation, and there even exists an adapter pack to put an optima in the Prius 12v space.

This is another sign of all the regen power going to the 12v system instead of the HV system.

All of the above. The symptoms can point to all 3 of the problems. However, if the 12v doesn't work, then you can assume it is the HV pack or the inverter. I would then suspect the inverter since the HV pack would not fault the car until it is very very dead.

 

Does it contain a clock or any sort of memory? Like your cab ID number or anything? If so, then it is always powered. The power drain is probably small, but present. A small drain on a small battery is equivalent to a larger drain on a larger battery.

With all this extra info I would highly suggest buying a multimeter and measuring the 12v SLA directly.

 

So your window test tells you:

Your 12V battery level was quite low.

After entering Ready the 12V bus went normal - this means your DC converter (which supplies 12V, the car has no alternator) is working. You were able to enter Ready (and drive), this means your inverter is working.

That's pretty good evidence your 12V battery is going bad, and i do suspect your cab equipment has helped it on it's way (both parasitic load while parked and shut down, and any time you're spending in Accessory mode)

If the dealer replace it, expect to have to replace it yourself in another 18 months. If they won't, I'd try and get a higher capacity one in there, or be very careful to never use accessory mode.

 

To me it is sounds more and more a close to end of life 12V battery. All the extra accessories are running from it and the Prius battery is not designed to sustain all that. Plus 72.000km - it is equivalent to a 5 year life of a "normal" 15k EU driver...
The fact also that the windows are moving slowly is also a sign. All runs off the 12V battery...
And if you change it, I would, if possible, have Toyota put at least a standard sized one - point them out that you have a *lot* of accessories on top of the standard set, that run off of it.

 

Take into account though, that the 12V battery in the Gen3 Prius is not a regular one, rather smallish, and you are "overloading" it with extra accessories that normally people don't have in their cars. So installing, in case this is broken and they refuse to pay it under warranty, a normal sized one.

 

My thoughts as well. After the warranty work there's probably a good chance the 12 volt battery will soon need to be replaced. Hopefully not, but I would have to have eliminated that myself before any technician put their hands on my car. A positive is your getting a new HV battery. :rockon: