EUC World: Increasing battery resistance

[Aztek]

I see increasing battery resistance reading with each charging cycle.

In the beginning it was 0.29 ohms, after 2 charges became 0.30 ohms. Now, after no more than 10 chargings is 0.32 ohms.

Do any of you, technically competent people, know what and why is going on?

Seems like it is not a good thing.

Edited August 15, 2021 by Chriull

[Chriull]

Hi @Aztek- i split your post off. I see no relation to "battery not charging to 100%"!? As new, interesting topic this deserves an own thread.

47 minutes ago, Aztek said:

n the beginning it was 0.29 ohms, after 2 charges became 0.30 ohms. Now, after no more than 10 chargings is 0.32 ohms.

That's changes in a low percentage range.

How do you measure the resistance?

Which accuracy has your measurement? (Absolut and relatively comparing consecutive measurements?)

How were battery conditions (temperature, resting time, state of charge, ..) at the different measurements?

I'd guess nothing grave happening here? But would be interesting if you report follow up measurements - if there are definit trends to be seen or just scatterings by innacuracies?

Maybe estimated/calculated/derived values like EUC Worlds battery resistance value can be used as "battery state monitor"?!

These values are from the ks16xs from your profile? Still with 20sp3 LG MJ1 as stated in

 

With 3x10 A max (continous) discharge current they should about take the burden? If not riding the ks16xs too extreme?

Edited August 15, 2021 by Chriull

[Aztek]

8 minutes ago, Chriull said:

split your post off. I see no relation to "battery not charging to 100%"!? As new, interesting topic this deserves an own thread

Yes, thank you!

 

8 minutes ago, Chriull said:

How do you measure the resistance?

That's EUC World reports. i don't use any other means of measuring it.

 

9 minutes ago, Chriull said:

How were battery conditions (temperature, resting time, state of charge, ..) at the different measurements?

Well, this is a hard one. Externally, the conditions are similar - 50-60 % charge in battery pack, environmental temperature - summer (25-27 degrees Celsius), charging about 30 minutes after a ride.

Unfortunately the internal temperature sensors of the wheel cannot be used, as they are faulty (showing around 0 - 15 degrees Celsius) and KS does not care repairing it.

12 minutes ago, Chriull said:

But would be interesting if you report follow up measurements

Yes, I will report here next charging cycles.

 

13 minutes ago, Chriull said:

ks16xs

Yes, it is still this wheel (I made only about 250 kilometres on it as i got it new few months ago) and nothing has been changed inside.

[Chriull]

1 hour ago, Aztek said:

That's EUC World reports. i don't use any other means of measuring it.

So it's derived from some numbers reported from the wheel and not too much accuracy to be expected. Maybe somewhat increased by averaging of many samples?

So although absolute values could be not too accurate consecutive measurements could show even small trends?

1 hour ago, Aztek said:

Well, this is a hard one. Externally, the conditions are similar - 50-60 % charge in battery pack, environmental temperature - summer (25-27 degrees Celsius), charging about 30 minutes after a ride.

Temperature and charge state have very strong impact on the battery resistance.

Afai think/heard a bit the battery resistance is derived while normal operation (to show more accurate state of charge?). So your seen changes should be more dependend on your driving behaviour and ambient conditions than on the charge cycles?

Maybe @Seba has time and pleasure to tell a bit about the resistance value? As he knows where this number comes from and what one can expect/deduct from it!

[Seba]

2 minutes ago, Chriull said:

Maybe @Seba has time and pleasure to tell a bit about the resistance value? As he knows where this number comes from and what one can expect/deduct from it!

EUC World measure battery circuit resistance and in King Song it works very good and gives reliable values. It not only include internal resistance of battery cells, but also include BMS and wiring resistance.

3 hours ago, Aztek said:

In the beginning it was 0.29 ohms, after 2 charges became 0.30 ohms. Now, after no more than 10 chargings is 0.32 ohms.

It's absolutely normal for XS battery, as it's just a single, 20S2P 777 Wh pack. And as @Chriull mentioned, battery state of charge and temperature has significant impact on battery circuit resistance.

[Chriull]

@Aztek- sorry, i just moved your topic again and put "euc world" in the title so others noticing this value can find this discussion more easily.

[Aztek]

30 minutes ago, Seba said:

absolutely normal for XS battery, as it's just a single, 20S2P 777 Wh pack

So I should expect resistance increase with 0.01 ohms every 3 charging cycle to some terminal value when the battery pack would be as good as rubbish?

How long with this speed?

400 cycles? Seems unlikely...

[Seba]

2 minutes ago, Aztek said:

So I should expect resistance increase with 0.01 ohms every 3 charging cycle to some terminal value when the battery pack would be as good as rubbish?

How long with this speed?

400 cycles? Seems unlikely...

No, you should expect that battery circuit resistance (BCR) will fluctuate in 0.30 - 0.40 ohm range. If it will go above 0.50 ohm, you should start to worry. But not earlier. Just monitor BCR.

[Aztek]

54 minutes ago, Seba said:

If it will go above 0.50 ohm, you should start to worry.

Thanks! This is the value I missed.

So, over 0.5 ohm, change of wheel or battery pack should be planned?

[Chriull]

11 minutes ago, Aztek said:

Thanks! This is the value I missed.

So, over 0.5 ohm, change of wheel or battery pack should be planned?

As long as batteries charge to full voltage (no imbalance) and have enough capacity (reachable range) and are able to deliver enough current for your burdens (acceleration, incline, ...) there is no reason to change.

But over time battery will get worse and not fullfill your requests anymore. Or just be misbalanced and get potentially dangerous.

You'll notice this by driving/charging behaviour and can "double check" it with looking at changed resistance value. 

Inbetween beeing "not as good as new anymore" is no problem or danger.

But this battery resistance value can maybe be used to compare how batteries degrade under different charging strategies, etc..

[Aztek]

To complicate the things, yesterday's charging reported 0.25 ohms resistance

I made a full charge till the amperage went to zero and the plug reported only 10 watts of power consumed i.e. some 30-40 minutes after the charger turned green.

After I had some of the mysterious beeps coming from a wheel switched off...

[KØBG]

I'm confused. The internal resistance of a battery, known as ESR, which stands for Equivalent Series Resistance, can't be measured with a simple ohmmeter or voltmeter. And it isn't a direct measure of SoC (State of Charge), nor is it a direct measure of DoC (Depth of Charge) . 

In ICE vehicles which use BMS, Battery Mounting Systems, use a Hall device to count coulombs. It is my understanding, that the Hall devices in a brushless, three-phase are used to determine the position of the rotor, and are not measuring coulombs.

So where is this measurement coming from exactly?

Alan

[Chriull]

4 minutes ago, KØBG said:

The internal resistance of a battery, known as ESR, which stands for Equivalent Series Resistance, can't be measured with a simple ohmmeter or voltmeter.

This is a value newly shown by EUC World. Should be somehow calculated/derived from battery voltage (sags) and battery current while riding.

4 minutes ago, KØBG said:

And it isn't a direct measure of SoC (State of Charge), nor is it a direct measure of DoC (Depth of Charge) . 

Exactly.

There is just a strongly increasing resistance at lower soc, but imho not really usefull as reverse relation.

Afai understand these posts @Aztek follows the reported resistance changes over charge cycles...

 

[Aztek]

13 minutes ago, Chriull said:

resistance changes over charge cycles

Yes, as reported by EUC world, although, I think, the ks apps report these too.

Not sure if it is useful as a measure after all. I'll just keep an eye on it.

[Seba]

17 hours ago, Aztek said:

Yes, as reported by EUC world, although, I think, the ks apps report these too.

Battery circuit resistance measurement is a unique feature of EUC World. You won't find it in KS app.

17 hours ago, Aztek said:

Not sure if it is useful as a measure after all. I'll just keep an eye on it.

It's very useful, because it may give you an early warning of failing battery circuit. For example, problem with battery connector (contact oxidation, connector overheating) inside the wheel may be visible as a sharp rise in BCR value. Same applies to BMS circuitry. Battery imbalance or cell degradation will be indicated as constantly rising BCR value.

[Miko.cz]

I like this idea, maybe we should also collect some samples? (my findings here are poor)
My KS-16S 680Wh (6850km, 16 months old):

• Resistance by EUCWorld is 0.14 - 0.19 Ohm (around 0.17 now in Winter at the end of charging - balancing/gLED, by default charger 67.6V, room temp 21°C)
• Batt new Voltage was up to 67.8V (now Im able to reach max. 67.7V).

[ffontana]

Ks s18 with 4.800km: 0,23ohms

Ks s18 with 1.000km: 0,19ohms

 

Great if we all report readings.

[Boogieman]

Interesting topic.

Is this available only on KS wheels and if Yes, all of them or just specific ones?

If on other wheels, which ones? (haven't seen that option on my Sherman, gonna check for update in play store)

[Chriull]

11 minutes ago, Boogieman said:

Is this available only on KS wheels and if Yes, all of them or just specific ones?

It should be available for all wheels measuring and reporting battery current, like KS and Inmotion.

Begode and Leaperkim do only motor current measurement.