12V battery

Current status on the "overvoltage problem": I have an open ticket with
HUSA customer-care, I took the 100% useless trip to a dealership that
they forced me to do, the tech heard my explanation of the generic problem
and looked at the little voltmeter sitting in my "bridge" and basically went
"shrug" ... now HUSA is escalating to "national agents". Why they couldn't
have just done that last Wednesday, I can't imagine. Anyway, still working it.

A 13.6V *average* would probably be okay, but I'm not even seeing those
lower-voltage events here. I did in warmer weather, perhaps charge/float
algorithms take ambient temp into account. 14.8 - 15 still seems wrong.

_H*

 

That discussion has been moved to its own thread, Tracking the 12v Battery with OBD2, to separate it from a more general discussion of Torque Pro and other OBD2 readers.

 

With apologies for returning to the OT :

It was my turn in the barrel today. Tried to turn on my one month old car and - stone cold dead, with the 12v. battery measuring 2.8v. And 64 kWh in the main battery, but not a drop to drink. What's wrong with this picture? Oh, yes, the Aux Battery Saver was enabled. Fat lot of good that did.

Hyundai Roadside Assistance promptly sent the AAA, who "jump started" the car with a portable pack. My first drive was to buy one of those suckers for myself. Never again.

When the car came back on, the climate system started running. I wonder if I inadvertently started it up when I was testing the Bluelink app to see if I had the problem everyone else is complaining about. I don't think I turned climate on, but that app has a mindless of its own. Could that have kept running until it drained the battery? The car was sitting for three days, plugged into an EVSE that's enabled from 11 pm to 10 am.

Should I replace the 12v battery, since it was completely drained?

 

Its probably fine being discharged so briefly. If you have a charger and load tester I would slow charge it up and give it go with the load tester. Or just bring it to your dealer and let them test it.

 

A lot of auto parts stores will load test for free as well.

 

I doubt the AC was running draining the battery. That's only possible I'd you left it on when getting out. The bluelink climate control always use the high voltage battery! That's why the yellow light in the front grill logo turns on when you do that.

 

This is the latest that I've gotten back from Hyundai USA. It's a total
fail, where they've basically blown me off and refused to escalate the
problem back to Korea to see what could be done about it.

"Disagreement", my butt. They refuse to acknowledge that there's any
issue, rather than googling "agm" and "float voltage" and finding the
numerous references that show their engineers in the wrong.

Expect your 12V to die in 2 or 3 years, or sooner if you've had any of
the well-documented episodes with "battery care" being anything but.
I told them in reply, if a TSB or campaign ever gets issued on this that
I want to be among the first to know. Like they'll give one wet fart
about that...

_H*

 

Can someone tell me whether these readings indicate a 12v problem? I'm taking it into a dealer tomorrow and could use as much info as possible (in addition to the 12v battery going dead once).

In the past four days, the battery has lost between 2% and 11% SOC (per Torque Pro) when parked overnight unplugged. It's been between 70% and 80% the past couple of days, with just a few miles of driving. Right now it's at 70% and 12.36v.

Are they powering the 12v functions off the high voltage battery, and relying on the LDC and Aux Battery Saver+ function to keep the 12v battery charged?

<rant>IMO this vehicle's software and electronics have been over-thought and under-tested.</rant>

 

But how certain are we that TP's idea of SoC(aux) is at all meaningful? Personally, I would not front up to the dealer or manufacturer with data I was not 100% sure I knew was accurate and relevant.

My voltage logging tests (posted above) have not shown any obvious problem on my own car, but of course I haven't had a battery issue. It might be a good idea to purchase a standalone battery logger so you can track voltage when the car is inactive, because that seems to be when the failure happens. I have this one on order but it's on a very slow boat from China and so I can't provide a review yet.

As to how it all works, my best guess so far is that the LDC uses the current shunt on the battery negative terminal to manage current in and out of the aux battery by setting its own voltage, which is also the 12V 'system' voltage. The car's 12V systems don't care about running on an exact voltage. The LDC does this to first charge the aux battery on entry into any of these modes: 'Run', Battery Saver (I think based on a time trigger), or when initiating charging. After several minutes of charging it drops voltage and ensures nearly zero average current is drawn until the mode is exited.
The mode where the battery is under moderate discharge is when the car is 'on' but not in run mode. When the car is sitting unused, it's lightly loaded, the current depending on the time sitting and if the 'welcome mirrors' mode is active. Those details were documented by a UK owner on the SpeakEV forum, which is worth joining as a few others have had ongoing 12V battery problems.

 

I'm not going to risk my credibility with the service advisor by showing them TP until I know them a lot better. But how hard I push on this will depend somewhat on my confidence that there's an ongoing issue, and some of you are better equipped to evaluate that than I am.

But I should have been tracking voltage (more credible with the service advisor and confirmable with my VOM) in addition to SOC (more meaningful to me). This morning, TP said 12.3v and my VOM said 12.36.

I see a logging graph while driving, but my concern is voltage loss while powered off. Have I missed something?

My 12v battery does add SOC when I drive.

 

No, TP doesn't draw data when the car is not in run, charge or battery saver modes, that's why I've purchased a logger ... which I notice has arrived in the country today. There were some thoughts that the battery was being overcharged or damaged from over-voltage, so I wanted to check up on that. I'm fairly confident that it's not happening on my car, at least while driving. TP aux voltage matches my VOM to an impressive 0.01V.
SoC on the traction battery is complicated to calculate (as I described elsewhere) and TP only has to read registers that the car populates. I'm unsure what the situation is with the aux battery but I'll be impressed and surprised if it uses the same technology.
Interestingly, if you visit i3 forums they talk about 'registering' a new 12V battery. That may be required to establish the initial SoC with the monitoring system so that it can track battery status after that and determine when a charge is needed.

 

TP should if anything *increase* your credibility, and it can't hurt
to have a VOM sitting in the passenger seat as well. TP is a
scantool, and so is their GDS that they use to pull codes and
parameters. It's not like TP is doing anything underhanded,
it's just gathering more information.

Techs who are afraid of TP or any similar tool are in the wrong
line of work.

_H*

 

OK, thanks.

So does anyone have any insight as to whether my numbers indicate an issue with the 12v charging system?

 

The service tech said the 12v battery tests fine, and there were no error codes. (Would a dead battery erase them?)

And they didn't even wash the car!

@hobbit, he did seem impressed with Torque Pro, though, FWIW. He said SOC around 70% is normal.

So I guess I wait to see if the battery goes dead again. And then ... ?

 

This is a continuation of some of my observations farther back, when
all I had was a voltmeter to try and observe what was happening with
the 12V system voltage under various operating conditions. Now that
I can observe battery current and DC/DC converter current separately
via OBD2, I have a little more info, as long as OBD2 isn't lying to
me. For reference on monitoring via OBD2, see this thread that got
split off when another thread got too messy; for this post, just
accept it as a black box that the figures can be read.

DC/DC or "LDC" as it's called, i.e. the equivalent of the alternator,
can only produce current one way, or nothing. The 12V battery itself
can have positive and negative currents as it charges and discharges.

I'm still studying this because even though Hyundai USA has basically
blown me off about my "voltage too high for AGM" case, I still want
to understand what's going on and perhaps figure out if there *is*
some weird subtlety in how the LDC running conditions are engineered.
In particular, yesterday was quite warm and I saw a recurrence of
the highly variable conditions I noted upthread here. While it was
cold, though, the rail sat solidly at 14.8V and as high as 15 at
times, possibly in an attempt to match lead-acid charging scenarios
where applied voltage *is* supposed to be slightly higher in cold
weather. But still not that high. I have no idea where the threshold
temperature is for changing behavior yet, of course.

It was a little above 50F yesterday, and I was on a drive long enough
to get the 12V fully charged so it really didn't want any more current
into it. In that state, regardless of rail voltage, that current
measures 0 or maybe -1 amp [charging is negative]. The LDC baseline
powering the car is still 9 - 10 amps, pretty much directly running the
electronics, and never varies much. Here are the voltages I noted:

* 14.8 sitting in Park, 12V battery current still just about 0
* 13.4 sitting in Neutral ; voltage slowly drifts down to that
* 13.4 rolling in Neutral
* 13.4 driving normally, accelerating or steady-state
* 14.8 *any* regen, even the tiny trickle in regen-0 mode
* 14.3 under any of the above, with *certain* large loads turned on

That last entry is the really weird one, not that it isn't all weird in
general. Lighting the headlights makes the LDC drift down to a more
appropriate voltage albeit still a bit high for float, and stay there
REGARDLESS of driving condition. So does turning on the rear defroster,
which is maybe a 200 - 300 watt heater. However, the seat heaters
have no effect, even if they're both turned on high. The fan doesn't
change anything either, even on full blast. It wasn't raining; I didn't
think to try the wipers. What are other typical large 12V loads if
you haven't installed that monster "bassmobile" stereo? Externally
applied loads at the battery, even large ones, don't seem to make
any difference either.

It's not a dependence on what is served through the "intelligent power
switch" module, either. The headlights are, but the rear defrost has
its own relay and comes straight off the "multi-fuse" on a 40A tap.
My guess is that *certain* loads generate traffic on a CANbus to tell
the LDC to move to that intermediate voltage, for some reason, perhaps
an alternate to the 13.8V state to compensate for some high loads that
might stay on for extended times while driving?

When the voltage drifts down, 12V battery current is still 0 and the
LDC output current is about the same. With the current sensor on the
negative side of the battery and the voltage-sense terminal on the
positive, the LDC *must* be fully aware of its condition. The battery
settles back to a reasonable "just freshly charged" resting voltage,
and the LDC follows along but doesn't let it actually supply any of
its own current for running the car. Why being in Park or having regen
going into the main pack matters to this setup, I can't imagine, or
why it wouldn't try to adjust either way if one of those "notable
loads" is on.

If I have one of the still-incandescent visor mirror lights on, I can
see a slow dimming and brightening if I move between D and N while
sitting still. That's an easy "analog" check of what I see on the
little digital voltmeter in the expander box. LED lamps don't really
react to input voltage changes.

I used to observe slightly related behavior in the Prius in warm weather;
its rail voltage would drop ever so slightly going from Park to Drive,
and I could hear a slightly changed note in the inverter coolant pump,
but that's the only change it ever did. All of maybe half a volt, but
apparently by design, still deliberately affected by the driving condition.

I'm firing in all these details mostly to help bootstrap anyone else
who wants to collect more data. I'd love a real answer from Hyundai,
but in the absence of that it would be nice to figure this out from
a "what the F are they thinking" standpoint.

_H*

 

I thought it might be worth searching for patents on the subject to understand the technology. It didn't take long to run into this relevant information at https://patents.google.com/patent/US5783872A/en which is from Northrop Grumman, way back in 1996. There are more modern patents from Ford, LG Electronics and even Hyundai, the latter at https://patents.google.com/patent/US10377237B2/en which specifically refers to "LDC control".

 

This 2012 Hyundai patent is a bit more readable https://patents.google.com/patent/US9413182B2/en
It's no surprise to me that the engineering is very well considered, but also that the company patents every idea they develop.

 

Yeah, it's certainly not a constant 13.8 V system level like it used to be.