@Mark I , Even the Toyota Prius I bought in 2005 ran the HVAC from the high voltage battery!

 

Yes, I remember having my 2014 MS recalled soon after delivery to replace the 12V battery with a marine battery. Never had any issues with it (before or after tbf).

So back to your point, you are saying the car should keep the battery topped up to 13.6V (min) at all times when the car is active (driving? or any status not in deep sleep?).

Isn't this done anyway? You already mentioned the impact of a long commute - what is is about the 12V charging schema that you think is wrong?

 

So back to your point, you are saying the car should keep the battery topped up to 13.6V (min) at all times when the car is active (driving? or any status not in deep sleep?).

Yes.

Isn't this done anyway? You already mentioned the impact of a long commute - what is is about the 12V charging schema that you think is wrong?

No.

BEVs are being programmed to cut the charging during operation ("to save HV battery, thus help range") and the voltage drops back to 12V, leading to sulphation.

 

@MikeS You have an OBD dongle, are you able to confirm that the 12V battery doesn't get charged during driving?

 

I do not have an OBD. I have a BM2 battery monitor and it most definitely gets charged while driving and normally around 14.7 volts. Lots of info here - https://www.ioniqforum.com/threads/bm2-battery-monitor-info.44343/#post-542367

Personally, I think most of what is being stated about how the 12v is being charged is a red herring as those with 12v problems are a small minority and even smaller when specific failure have been identified.

It seems from all the info I have read about the subject that the primary causes are still as listed in my OP. The one additional cause I would add is still under the excessive loading title. This is owing to dealers not supporting the 12v when working on the car. The recent SW updates for the ICCU issue seems to be a specific cause of recent failures. The techs need top support the 12v when working on the car when the car cannot maintain the 12v battery, such as when the car is not fully on, in utility mode or the boot/bonnet are left open. If it is not supported the 12v battery gets drained and then will struggle to hold a charge thereafter and likely fail within a short time.

 

Given that the 12V battery will gradually wear out, even if looked after perfectly & charged perfectly, you would hope the mfr has thought of this & programmed the Top-up process properly. In the case of Hyundai (& I assume Kia) they haven't. I've analysed this in detail & fed back to a senior H guy who used to be present here, hopefully this is getting back to where it matters.

H's strategy on the original Ioniqs was "Test the 12V once a day, give it a topup if volts <12.7V". That was it. The simplest possible software to write, and a poor design behind it. This is called "polling" and is not the way to respond to a low-voltage situation, as these can happen at any time when you least expect it.

H changed this to "Test the 12V 6 times a day, give it a topup if volts <12.7V" when they had problems with the early Konas, but failed to apply it to the identical-electrics ioniq '38! Dunno about the '28. This new strategy can just-about keep a damaged 12V going (mine, flattened twice, was getting 6 topups every day - I replaced it with new which gets just the one. In both cases the car's idle on driveway, not plugged in, doing nothing for a week).

Correct approach is an event-driven (interrupt based) response, where the instant the 12V drops into danger zone, the car reacts. H simply didn't consider what happens if someone leaves a door open, or radio on, so keeping the car awake & the computer on, drawing 200W continuously for 10-20 minutes. No surprise that anything keeping the car awake when not fully powered-on means the 12V can die well before the next 4-hourly test takes place. Cr*p design is behind a lot of the problems H have had. And they know it now, but certainly won;t admit it!

H have a "Utility Mode" you have to select, which keeps the HV battery connected in so the 12V gets a continuous charge, should you actually want to leave the door open while you pack the car! This reveals what a bodge the "polled" approach is, as if the car had an interrupt-driven (= event-driven) system, it would automatically wake up whenever the 12V needed help, and Utility Mode would not need to exist. The car would just "behave" properly whatever was thrown at the 12V system, like always-on 24/7 dashcams, powerful sub-woofer boom-boxes, ...

Would be interesting to know if the Leafs do an on-demand top-up whenever battery gets low, or what. I rather suspect they coded this bit correctly.

 

Correct approach is an event-driven (interrupt based) response, where the instant the 12V drops into danger zone, the car reacts.

The correct approach is <14V, not <12.7V, then there would be no issues.

 

Going to leave this here about the 12V vs 48V issue:

 

I got to 45 seconds in and for cars with new tech they were wrong already.

The claim that you can use less copper was true for old technology.

It's just not true any more.

Wires need to have a minimum gauge to have the physical strength to be bent and shaped in a loom. That minimum gauge is 'near enough' large enough to cope with all the latest low-power technology around the car (LED lights, etc..).

In any case, should be made from aluminium wire for weight and cost saving, if that was the plan all along.