HEV 12V Battery investigations

[PhilHornby]

The other morning, I started the car (all normal) and drove to the end of the drive and stopped for traffic. At that point, the car reset. I was actually looking at the dash when it happened.

That would seem to make it unrelated to the 12V battery SoC then. I can't come up with an alternative theory, that would fit that scenario

[Deleted User 1326]

I can't come up with an alternative theory, that would fit that scenario

Sometimes, it can be good for us to adopt the attitude of ‘Oddball’ in 'Kelly’s Heroes’:
https://media.tenor.com/0u6jhAe3f2oAAAA ... e-them.gif

[OzJock]

The other morning, I started the car (all normal) and drove to the end of the drive and stopped for traffic. At that point, the car reset. I was actually looking at the dash when it happened. Never done that before. It was always when I initially started the car.

That’s a variation I don’t think I’ve read in the forum before - has anyone had a similar experience?
G

[Saltcreek]

My climate control settings reset about 1-2 times a week. Nothing else changes so I just accept. I have no clue what is causing it as it is always random.

[OzJock]

Sod's law says it won't happen if you monitor it (a watched kettle and all that...)

There's a photo here: https://www.hyundai-forums.com/attachme ... pg.459525/ of the 12V terminal. Any convenient earth will do for the -ve connection. I expect a voltage of ~13.2V when you start.
I don't know if a) the settings will 'disappear', with the car in the Accessory position and b) even if they do, if the voltage will have dropped significantly by then.

Whatever you see, it's still data to add to the pot.

(My only theory is still that 'something' makes the 12V supply sag for long enough to upset things, but not long enough for the Battery Saver to trigger).

Hi Phil,

Quick bit of data from the day after service, haven’t been able to give this any more time yet

“Tucson
Time Voltage
11:43 12.95
11:49 12.90
11:58 12.91
12:13 12.89
12:40 12.83 >
12:55 12.79 > Trip & aircon reset between 12:40 & 13:21
13:21 12.75 >”

These readings are just taken from the 12v accessory socket in the dash - not sure if it’s regulated.

11:43 to 12:13 were taken with the car just in accessory “On” with the boot open and interior lights off. Interestingly I learned that it doesn’t send any Bluelink notifications. As the voltage was dropping very slowly (and I needed to attend to some work) I then put the car in “On” not “Ready” with the boot open from 12:14, got a series of Bluelink notifications and noticed the voltage dropping. Somewhere between 12:40 & 13:21 the familiar reset happened.

Not as good data as I was hoping to get, how do these voltages compare with your data Phil?

G

[PhilHornby]

Time Voltage
11:43 12.95
11:49 12.90
11:58 12.91
12:13 12.89
12:40 12.83 >
12:55 12.79 > Trip & aircon reset between 12:40 & 13:21
13:21 12.75 >”

These readings are just taken from the 12v accessory socket in the dash - not sure if it’s regulated.

I wouldn't have expected it to be regulated (well if it is, it's not very stable!) ... but it's possible it's connected somewhere in circuit where there is a voltage drop (compared with the main terminal). I'll continue doing my tests from the engine compartment terminal - just for consistency.

Somewhere between 12:40 & 13:21 the familiar reset happened.

Thinking about it, I've never actually observed the Trip Meter etc during a test. Unsurprisingly they have always reset after the Battery Saver has triggered. I'm 'home alone' next week, so I'll try and reproduce this effect. If I can, it will be informative to see if it always happens at a particular voltage ... or if it follows one of the erratic periods in the discharge curve.

I lifted a graph from https://diysolarforum.com (you have to register to see it directly) :-

The voltage you measured (~12.75V) seems a bit early for these modules to be taking any sort of preventative measures - and if they are, they don't seem to be achieving a whole lot by doing it .

To be continued ...

[PhilHornby]

Is it my imagination, or have the reports of flat 12V batteries, with owners locked out and dashboard settings 'reverting to default' ceased

These were very common at one point and now seem non-existent....

It's almost as if the cars have been receiving software updates to modify their behaviour - and yet none have been announced

The last time I updated the 'Maps', I couldn't help but notice how big the update was (compared with, say, my Garmin Zümo maps). I postulate that there were other updates included in that bundle, that have resulted in this change

(The change (possibly) being the introduction of a 'Battery Saver' function, that tops up the 12V battery periodically, from the Traction battery. (Once upon a time, such a mechanism was documented for the PHEV, along with menu entries to control it, though it isn't any more))

[alan sh]

It still happens. We just live with it.

Alan

[pharaoh]

It still happens. We just live with it.

Alan

Same as. Mine happens less frequently now because the car gets used more, plus I switch on the ignition when I'm cleaning the car so that constant door opening doesn't deplete the 12V battery.
I'm pretty sure no updates have been applied to alleviate this problem and if they have, it would have been done by the dealer when the car was in for service rather than via the updates that we can apply ourselves.

[PhilHornby]

It still happens. We just live with it.

I thought there might have been a whole new cohort complaining of these issues - but there doesn't seem to be.

On the other hand, there have been a numbers of reports, from people leaving the car for weeks at a time, with no issue.

Personally, I can't remember the last time the aircon set itself to 22°, which was my main gripe...