Dear all, again I'm contemplating all sources of my issue, I noticed my battery sits at 11.3V when read from the Diagnostics page from the navigation screen with the Power button switched only once. Pushing the Power button again (foot off the brake again), it drops a bit as the system loads it a bit more, but not by much. Obviously when I pit the car into Ready mode, the HV Accumulator holds it up and it will show 14.2V. So I wonder what exactly is the role of the 12V battery to the system as a whole other than obviously to boot up the car by energising the 3 relays to get the HV system ready? Because I keep reading about the importance of the 12V needing to be healthy. Does the whole LV system run off the 12V battery (as opposed to a 14.4V from the DC-DC converter. If it runs of the battery which itself gets propped up by the HV Traction Accumulator then it would of course explain my dire MPG of 42mpg with daily driving. Well it's pretty much always about 42mpg day to day, starting afresh before a long journey, I can squeeze 48mpg. More importantly could my running issue (rattle from transaxle damper), assuming some unacknowledged misfire due to a weak spark across the ignition coil circuit as a whole due to it being supplied directly from the 12V system. Would a bad 12V battery mess with the strength (voltage) of the spark produced from the plugs via the secondary coils, but not enough to throw up a fault? Or any fault at all for that matter. But the voltage will still show 14.2V because the HV battery is supporting it, but in reality the 12V battery is not able to provide enough current to energise the ignition coil in a consistent manner, but it CAN keep lower current drawing things such as ECU's, sensors, etc. Could the12V battery have collapsed cells causing this to happen? If that even happens with AGM batteries. At which point you'd argue that lack of current delivery would show up as a voltage drop or something else would feel that lack of 'power' (shall we say), so that DC-DC converter is working amazingly hard to maintain a steady 14.3V regardless of the load on the battery. I'm going to check the voltage in the morning at the battery with a multimeter, that'll be interesting. I'm probably going to replace the battery anyway, it 'might just' sort the transaxle damper knocking, who knows. As always, I would love to hear your thoughts and experiences.
There's a terminology thing going on here, possibly because you're in UK, where sometimes rechargeable electrochemical storage things are called batteries and sometimes they're called accumulators. It looks like you're calling the 12 volt one a battery and the 202 volt one an accumulator, but we generally just use the term 'battery' for both, and specify which one we mean. (That helps avoid confusion with another part in the car that really is called 'accumulator', but it's a part of the brake system and accumulates pressure.) The car's 12-volt electrical system is just one common bus with both the 12-volt battery and the DC/DC converter output on it. Whenever the DC/DC converter is operating, the bus voltage is the converter output voltage everywhere (leaving aside small voltage drops in current-carrying wires), and that also is the voltage appearing at the 12 volt battery, thereby exceeding the battery's own voltage and charging it. It would be conceivable to have reduced voltage appearing at the igniters, perhaps through some wire harness damage or a flaky fuse or something, but if you suspected that you'd just have to poke the right places with a meter and see. It would not be because of the 12 volt battery, at any time when the DC/DC converter is operating.
Ok that is an answer I like. But I'll replace the battery anyway. It'll kill my HV battery/accumulator eventually. I get your point about the accumulator terminology. And I'll explain why. I work for an University as an electronic tech at an engineering department, and there'a q formula student team, and i'm part of the design team developing an electric racing car at a higher level than the students. So the big battery is technically called an Accumulator since its a collection of batteries which themselves are a collection of 18650 Lipo cells arranged in 6P(200A)x21S ro make to make 5x segments to get to ~440V when charged.
A 12 volt that's a little low will eventually kill your HV 211 v battery I don't really think so The charge circuit that comes off of the inverter which is using the 211 volt HV battery generally when the car is ready that's pushing your 12 volt battery to 14.2 volts which is the charge rate that you usually looking to see or the charge voltage you're looking to see on an alternator type of car wella. The 12 volt battery runs all the computer and all the 12 volt stuff in the car when you turn the car on when the car is ready the complete system is alive and the charge circuit is charging the 12 volt battery that's why you see the 14.2 and then that's what's running all the 12 volt items in the car including the headlights That's why a lot of people have LEDs and what not in places for lights that burn constantly headlights the red tail lights a lot of people leave the turn signals alone so there's no fast flashing. But I don't think my failing 12 volt has hurt my 211 volt HV battery a bit not at all and when I get around to it I just changed the 12 volt for a new one and everything just keeps on going.
I've just checked the battery at the terminals and it's sitting at 12.6V while off, at the first push of Power it drops to 12.5, then 12.3, and 11.4 with the headlights on, in the final ready state it gets 14.8V. I guess it'll do for a little while more.
Ours is just 168 NiMH cells arranged in a single series stack of 28 things, 6 cells each. In Prius jargon, we call the 28 things 'modules', and the whole thing the 'battery'.
