Lastmanagenemt: unnötig erhöhte LL-Drehzahl? | Posts 16+

Hi,

"Immediately after starting the engine, I see 14.6 volts on the display (with the lights and afterglow on), which then drops to 13.6 volts when I turn on the two seat heaters. However, this is because the meter is still getting its power through the same connection as the seat heaters, which is connected to the thin cable of the cigarette lighter socket (rated for 10 amps, the seat heaters draw 7.5 amps), which explains the voltage drop through the cable."

I'll definitely install a separate measurement line for that.

Best regards,

Jan.

Julian wrote:

During a proper cold start, the generator's load was never above 45%, which would be approximately 63A. And I have more consumers "in the system" than you do... fascinating!

It's important to remember that the rated power of a LiMa (e.g., 90 A x 14 Volt = 1.26 kW) is only achieved at high rotational speeds.

At idle speed, each alternator only produces a fraction of its maximum output (approximately 1/3, according to an old book on automotive electrical systems) and therefore needs to be operated with a significantly higher regulator duty cycle to achieve the same current output as at its rated speed.

Therefore, a 45% load at idle for a 140 A LiMa is likely not 63 A, but perhaps around 20 A.

My 90A lithium battery would therefore provide even less power, or conversely, would already be operating at its maximum capacity regulated by the controller.

In addition, the alternator's power output drops off very sharply at lower engine speeds. That is to say, a 7% reduction in the LL (low-speed) motor speed (like the 840 rpm I have instead of 903 rpm) could potentially result in a 25% reduction in electricity costs (this is just an estimate).

Quote:

What is the capacity of your battery?

70 Ah.

(approximately 1/3 according to an old book about automotive electrical systems) and therefore, to provide the same amount of current, it must be powered with a significantly higher regulator duty cycle than at its rated speed.

Therefore, a 45% load at idle for a 140 A LiMa is likely not 63 A, but perhaps around 20 A.


Maybe? Your book must be old or compiled by the ADAC.

To verify the utilization rate (I had previously discussed this with Gremlin without success), I installed an ammeter on the generator at the company yesterday. At 35% utilization (in the MSG), I measured 50A, while the theoretical value would be 49A.
Then I connected some consumers and increased the load on the LL to 50%, measuring 71A at 50% load.

I honestly don't know how the % is measured, but I believe I have verified the MWB with that method.

Hi Ulf,

Have you already read this? /viewtopic.php?t=6826

The number of consumers is likely to be quite low for your Polo, but perhaps the issue of short trips is relevant.

Marco wrote:

The number of consumers is likely to be quite low for your Polo, but perhaps the issue of short trips applies.

Yes, short-distance travel could be included.

As a compensation for the few consumers, I probably only received a 90A alternator, while our ALH Ibiza has the 120A one (like my ex-Basis-G3 did).
Or, one might believe that one can save money on the LiMa (lithium-ion battery management system) because the load manager is monitoring it .
Well, my personal consolation is: Weaker LiMas are slightly lighter than powerhouses (and also cheaper to replace later).

@Julian:
Your measurements and calculations naturally confirm your assumption.

This morning, I experienced the same issue I've seen before: a very slow increase in the onboard voltage after startup, during the afterglow period.
I gently touched the accelerator pedal, and sure enough: I could increase the voltage by pressing the gas, which was noticeable on the display and in the brightness of the parking light.

-> Another "proof" that my engine was running at full throttle, i.e., (still) unregulated, and also that the "problems" would be significantly less severe at the factory-specified idle speed (903 rpm according to VAGCOM).

I'll connect the diagnostic tool (Lappi) in the next few days and log the alternator load.

ulf wrote:

Well, my personal consolation is: Weaker LiMas are slightly lighter than powerhouses (and also cheaper to replace later).

You have to give it to Ulf, he always finds a solution!

Our Passat also has a higher idle speed when cold (after adaptation, approximately 950-970 RPM when cold). However, this is a constant issue. Around 70° Celsius, the display shows a reading, but the RPM drops to 880.

However, he already exhibited this behavior before the adaptation (although within the range of 800-880 revolutions).

The old 1Z model didn't have that feature; it always ran within the same range (although, if it was really cold, it might sometimes run a little higher, but I didn't notice it).

Best regards, WarLord.

WarLord wrote:

Our Passat also has a higher idle speed when cold (after adaptation, approximately 950-970 RPM cold). However, this is a constant issue. Around 70° Celsius, the display shows a reading, but the RPM drops to 880. He had exhibited this behavior even before adapting (only within the range of 800-880 revolutions).

What engine do you have in the Passat?

Is the 115 hp PD engine compatible with the KB ATJ transmission?

This morning, it even started up with over 1,000 revolutions per minute (but it was also very cold, and the car hadn't been running for quite a while, about a week).

Best regards, WarLord.

Okay, here's another update:

At approximately 840 rpm and with a warm engine, running the low beam headlights, rear window defroster, heater on full blast, and the radiator fan on setting 1 (next to the engine and priming pump) is enough to overload the alternator: the onboard voltage drops to approximately 13 volts.

Okay, the cooler fan (which I can manually control) rarely runs, but its power consumption could probably be replaced by using the high beams and brake lights.

This means that at this load level, there are no reserves left for afterglow or for providing a higher charging current to the battery after a cold start.

Since it seemed a bit weak for a diesel engine, I checked the charging pulses of the alternator using an oscilloscope (voltage drop on the thick cable from the alternator to the battery). If there are faulty diodes (and consequently reduced alternator output), there should be gaps in the pulse sequence.
However, it wasn't the case, meaning my "small" 90A lithium battery seems to be okay and is just a bit overwhelmed by the reduced low-speed setting.

Well, the load manager will take care of things, and besides, I also have the voltage indicator...

Okay, so yesterday I was tinkering with my friend's Golf 4 (1J, ALH engine, 44,000 km, manufactured in 5/00), as he also has a 90A Valeo alternator and a 70Ah battery. (but also manual transmission). Climate control, heated seats, 4-wheel drive, central locking with folding key.

The vehicle is driven exclusively in a short, 3km round trip, mostly by a housewife. When it starts, the interior lights noticeably dim, which suggests that the battery is not in good condition.

The LL (likely referring to a fan or motor) was originally set to 903 RPM at the factory. I lowered it to 840 RPM and then tested it. The supply voltage was 14.36V in the LL (likely referring to a specific electrical context).

When the rear window/mirror heaters, all lights, seat heaters, etc. were turned on, the voltage would briefly drop (to around ~13.1V) and then rise again to 14.36V.

I then adjusted the LL (likely referring to a motor or fan) to a maximum speed of 945 RPM. The same test image was used, but the increase to 14.36V took approximately twice as long as it did at 903 RPM (around 2-3 seconds).

@Ulf:
Are you sure that everything is okay with the energy management system of your 9N? I don't think 13V is high for low-consumption devices; perhaps your limiter regulator is faulty.

Julian wrote:

The LL was factory-set to 903 RPM, I lowered it to 840 RPM and then tested it. The supply voltage was 14.36V in the LL (likely referring to a specific electrical context). When the rear window/mirror heaters, all lights, seat heaters, etc. are turned on, the voltage drops briefly (~13.1V), but then rises again to 14.36V.

In my opinion, that was the sum of all the consumers plus the decreasing charging current from the battery (still from the starting process).
Or did the engine speed automatically increase without any acceleration?

Quote:

Then I adjusted the LL to a maximum of 945 RPM.

Here, the same test image was used, but the increase to 14.36V took about twice as long as at 903 RPM (approximately 2-3 seconds).

Quote:

If that happened without restarting the device, I would suspect a regulator bug. Below the maximum load of the LIM (Load Management), where the excitation current is still pulsed (i.e., < 100%), voltage drops should be corrected much faster than what can be detected with VAGCOM...

Are you sure that everything is okay with the energy management system of your 9Ns? I don't consider 13V to be high for low-consumption devices; perhaps your limiter regulator has a fault.
Perhaps my battery genuinely has a noticeably higher power consumption for short trips, which isn't always compensated for immediately after a cold start?
Our ALH(!)-Ibi immediately revs up to approximately 1100 rpm after every cold start (although there is no voltmeter on board); my Polo apparently only revs above 840 if 13 V are not reached within approximately 5 seconds.

As I mentioned, the oscilloscope showed a completely normal regulator function: below approximately 14.5 volts, a continuous sequence of charging pulses, while above that, a pulsed sequence of charging bursts (I hope that's the correct term).
According to that, the regulator is behaving completely normally.

If the Li-ion battery had increased internal resistance, it should manifest as increased heating... I'll do some temperature tests soon.

Perhaps my car's infotainment system is running at a slower speed than it does in the Golf.

Or did the engine speed automatically increase without any acceleration?


No, the motor speed remained at 903 RPM.


Perhaps my car's translation speed is slower than that of a Golf...


Well, typically, it usually spins twice as fast as the KW.

P.S.: By the way, I was able to verify the Vagcom voltage using a voltmeter at the battery terminals.

Hi,

"However, the behavior with the ALH Ibi is strange. My ASV Ibi, which is quite similar, doesn't do that, even when I turn on both seat heaters, the lights, and the rear window heater shortly after starting the engine." The RPM remains at approximately 920 (I haven't lowered it yet).

Best regards,

Jan.

Jan6K wrote:

The thing about the ALH-Ibi is also strange - something like that doesn't happen with my quite similar ASV-Ibi. The speed remains at approximately 920

.
Hi Jan,

Perhaps it's because you don't have glow plugs?
(-> Battery quickly with max. "Should I increase the voltage to prevent the heating from being shut off again due to the power demand from charging?"

I remember that my AFN (also with glow plug heating) ran a bit higher than usual for a while after a cold start in very cold weather.

Hi Ulf,

That could be it... the GSH (geothermal heat pump) consumes quite a bit of electricity compared to other appliances (if you have one).

Best regards,

Jan.