Battery SoC Indicator

So yesterday I went on my first long ride after purchase… A total of 81km non-stop.


I kept a constant tab on the battery percentage and noticed something unusual.
The flight was charged to a 100%, after 0.5km the battery dipped by 2%…
Then upon reaching 90%, after 0.5km again, dipped by 2%. This case kept happening Everytime at 80,70,60 Upto 10% as well…
I noticed that I was doing 1.2 ish km for each battery % and hence this drop of 2% within 0.5km was just baffling.
In the end I expected to do 100km atleast but due to this battery loss almost 20% (2%*10)(20km) in total was lost.
Would like to know the reason behind this or if it’s a glitch on my flight…
P.s., As I stay near hennur, the distance to Nandi hills was 54km one way. I expected to complete this trip but had to turn back…

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Observed the same. I have only noticed 100% to 98% drop after 0.5KM. Will keep an eye at 90, 80…

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I had already raised a ticket with Ather, but response was it depends on driving style. I was bit confused with response since how would my driving style be consistently different when it is multiple of 10.
I have already driven my flight for 5000+ km. and my predicted range is 93 in Sports Mode.
I have requested someone from Ather to drive my flight and confirm it is not a problem with the vehicle. Will keep you all posted about the progress.

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I was riding on the airport road at almost constant acceleration… I noticed this happening at every multiples of 10 only… so definitely does not depend on riding style. Would like @AtherTeam to look into this or provide a suitable explanation…

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Today observed 2% at 100, 90 and 80 consistently. Rode the vehicle slower than usual, the 2% drop happens always.

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I guess this is the trouble with showing a charge remaining percentage. My guess is that the resolution at which the BMS reads the state of the battery is not 1% – They might not be able to track for every 1%, but maybe 2-5%?

I remember the same issue with Macbook Pros a couple of years back, where it used to show wildly varying time remaining notifications, because of a resolution issue. They fixed this by removing the predicted battery remaining.

Your reading should obviously get better if you track in larger intervals than watching the percentage drop.

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So far I have noticed this drop only on 100. I always doubted this on how the system calculates the battery%

Recently @Shreyas has explained few of the possible reasons…

I never noticed it on 90, 80. Probably because my ride is less than 10 kms…

Today, I checked and I could see a drop from 70-68. :slight_smile:

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Your statement might be true if we observe erratic changes in charge remaining % be it at multiples of 10 or anywhere in-between. But i observed getting 1% per KM consistently today and on a downhill with very less acceleration saw battery % drop from 90% to 88%
This does not occur at any other % of battery but at multiple 10 only.

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Even I noticed the same, dropped from 100% to 98% for less than 1 km. I rarely charge 100% and noticed it dropped to 98% very quickly or less than 1 km.

Yesterday, I checked whether 2% drop happens at 10%. I had observed the below behavior.

Started the vehicle at 40% charge and within 500 metres, went to 38%. I shut down the vehicle at 30%.

Again in the evening, started the vehicle at 30% and in no time it went to 28%.

When about to reach home with 300 metres left for the destination, it was 20% and suddenly it became 18%.

I kept it for full charge. Morning took the vehicle at 100% and within 300 metres, it became 98%.

I think either ‘9’ never showed up or for very few seconds because, in these 4 instances I could not see the dashboard saying 39 or 29 or 19 or 99.

At 30% and 20% it stayed little longer than usual… So probably it’s correcting that by moving to ‘8’ skipping ‘9’

It’s nothing to do with acceleration or trickle discharge as might be possible at 100%, it should be either calibration or calculation issue…

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Not sure if anyone noticed, the battery percentage always reduces by 2 units from multiple of 10. Eg from 100% it will become 98%. 90% will become 88%

Not actually!!

Just got reply from Ather team that they are aware of this trend in the discharge of the battery in the vehicles. This is being monitored by the team. They should be able to come with a resolution for this in the future over the air update.

Great :slight_smile:

Now that we have @Shreyas attention, asking one of the questions I had asked few times but yet to get an answer :slight_smile:

I have consistently tried and confirmed that the battery % is wrong after full charge.

Charge to 100% and drive for 500 metres and the SOC drops to 97%. Drive for few more kms e.g 5 kms at 7%. Now, dashboard shows 90%. Shutdown the vehicle and turn the vehicle ON after few hours. The battery % will be 93%. I believe that the increase is because of the initial drop which was wrong.

I have verified this quite a few times and can be reproduced every single time.

Now the question:
Why does it happen and can this be fixed?

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Off the top of my head there are 2-3 things that can cause this:

1. Measurement and calibration of voltage vs SoC.

2. Voltage ‘Bounce back’,
A commonly used term that is used for a phenomenon for Li-ion cells. During high current draws, the voltage across terminals drops lower than the open circuit voltage, or the voltage for lower current draws.

This happens on account of internal vs external resistance changing constantly.

This graph kind of shows that effect. (Source)

Which means it is extremely difficult to measure the instantaneous SoC and you cannot rely on the voltage alone. Based on the average current drawn, the value of the displayed SoC has to be fine tuned.

3. Sudden drop in voltage for the initial draw.
This again can be one of the factors that you see because of which the SoC suddenly drops for the initial few kms. Especially if the acceleration is high as soon as the vehicle starts.

18650chargeDischarge-powercell-web

4. The last thing that may be happening can be
Once the vehicle gets fully charged, the charging point cuts off power and the battery goes into the idle state. After which the charge goes down by a certain value. After a while it restarts charging back to 100, and the cycle continues. It may so happen that you remove the charger during the idle stage when the battery is discharged by a small amount and as soon as you start moving the SoC drops.

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Hi @Shreyas In 3rd Owners meet, I heard this will be fixed (2 percent down at every 10%).

I missed to hear the reason behind. Can someone share what was the issue here?

This question was answered by Chaitanya. He said it was due to some software algorithm mismatch due to which it was jumping by 2%. He also said it will be fixed in the next OTA update.

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Reason I am asking is with what happened today:
Today, I forgot to charge and noticed SOC was 18%. I waited until it reaches 40% and started the vehicle within a minute of removing the charger. Now, I drove for max 200 metres and SoC was back to 38%. No way, it was because of acceleration or discharge.

So, one learning. Once it reaches 28%, 38%, 48%, no use in waiting until it reaches 30%, 40% or 50%, because the wait is not worth as its going to go down anyway within 200 metres.

Thanks Rajesh… So, actually the charge is not dropping. Only the numbers are dropping because of a glitch.

There are multiple things which might happen if you start driving immediately after charging as the SoC in 450 is measured using voltage method. This is true after Shutdown and restart too. Sometime back, Shreyas was narrating about voltage bounce back phenomenon. It is bit technical and variation is bound to happen. Suggest you/we to use battery% on dashboard as a guide.