Project OBD2 - Mobile App v1.2.1 and later

[JodyS21]

Interesting. Is there a direct correlation between battery voltage and soc that could be plotted? This would mean that a user could find % soc by viewing the voltage. Not sure how useful that would be but I know some ZS owners have asked for the reundant battery button to show %soc.

Yes there will be exactly that I believe.
It is kinda the only way they can really calculate the SoC.
Somewhere there will be a discharge graph for the battery cells being used, this will be used (algorithm) to calculate the SoC based on the Voltage.

 

[JodyS21]

So can we rely on what the app is telling us?

I'm discussing it with the Thai app developer right now via FB (Captain DIY)...

 

[JodyS21]

Just a thought - is battery soh also directly linked to voltage? As our cars grow older and the batteries degrade will we still achieve for example 450v in a fully balanced HV battery pack or will this naturally reduce over time as the pack degrades?

That is a VERY good question....

If it is the top voltage that a cell can store that is affected by battery degradation, then that it how the SoH could be "easily" calculated.
Plus it would allow the SoC to still use the same voltage discharge algorithm.

If with battery degradation, the max/min voltage stays the same, but the rate of discharge just increases, then it would need to somehow constantly adjust the cell discharge graph algorithm in order to provide an accurate SoC.

 

[JodyS21]

Can some of you guys get the SoC / Volts / min&max cell V from the App when your car is definitely fully charged, plus what the Voltage on the dash is.
-I've done mine at 449V, really want to see what a 455V BMS person gets.

 

[Septian]

Can some of you guys get the SoC / Volts / min&max cell V from the App when your car is definitely fully charged, plus what the Voltage on the dash is.
-I've done mine at 449V, really want to see what a 455V BMS person gets.

I'm due to charge the car either tomorrow or Sunday, I'll do a reading once the balance finishes (Which takes a few hours due to that BMS Variant)

 

[Tango130]

Can some of you guys get the SoC / Volts / min&max cell V from the App when your car is definitely fully charged, plus what the Voltage on the dash is.
-I've done mine at 449V, really want to see what a 455V BMS person gets.

SoC - 96.1%
Volts - General tab 454.5v, Battery tab 452v, DC2DC tab 454v
Dash Volts - 454v
Vmin - 4.192v
Vmax - 4.207
BMS - 0603610R28, updated on 20th October(not 24th I'd mentioned earlier)

 

[JodyS21]

SoC - 96.1%
Volts - General tab 454.5v, Battery tab 452v, DC2DC tab 454v
Dash Volts - 454v
Vmin - 4.192v
Vmax - 4.207
BMS - 0603610R28, updated on 20th October(not 24th I'd mentioned earlier)

I'm tring to figure out how yours and my voltages/SOC are related.
I don't think its straightforward / linear, as I think it's using the discharge profile to calculate the SoC from the Voltage...

Do you think you could see what the SoC is (from app) when your voltage is a nicely settled 449.75V. Im guessing it'll match mine.

449.75v / 93.2% = 482.56v @100%
454.5v / 96.1% = 472.94v @ 100%

454.5-449.75 is 4.75v / 96.1-93.2% is 2.9%
So 4.75V = 2.9%

 

[mystreet]

Is the app developer stating that the ful SOC is 455v? Therefore anyone not achieving this the calculation is therefore not 100%.

Ignore all the above, just looked at my readings and at 454.75v Soc is at 95.9% ?

 

[Garyhfly]

Another one for the spreadsheet, (thankyou JodyS21for your work) - imported and delivered Sep 2020, has not been back to dealer since, no graphics, can charge locked or unlocked.

App continually crashed on my Android10 phone but was stable on an Android9 tablet.

 

[KasEV]

I'm tring to figure out how yours and my voltages/SOC are related.
I don't think its straightforward / linear, as I think it's using the discharge profile to calculate the SoC from the Voltage...

Do you think you could see what the SoC is (from app) when your voltage is a nicely settled 449.75V. Im guessing it'll match mine.

449.75v / 93.2% = 482.56v @100%
454.5v / 96.1% = 472.94v @ 100%

454.5-449.75 is 4.75v / 96.1-93.2% is 2.9%
So 4.75V = 2.9%

@JodyS21
Looks a bit out on a limb.... The calculations on linear proportion...... our batteries don't behave that way????????.
Anyway I am a bit at a loss.
If you had charged and balanced your car before taking the reading then, I would expect SOH = SOC = 100% since your car is relatively new.
Not sure why yours was showing 93%
Has your battery degraded by 7% already?

 

[macd2401]

The voltage discharge curve on a lipo battery is relatively flat for most of the central part. The extreme ends of the curve are more like sheer drops.

My last charge was on a rapid charge, and it reported 100% on the dash, 97% on the app. I would be ok with that slight mismatch because the battery is effectively 100% for our use. Think the difference may be because it was a rapid charge.

 

[KasEV]

The voltage discharge curve on a lipo battery is relatively flat for most of the central part. The extreme ends of the curve are more like sheer drops.

My last charge was on a rapid charge, and it reported 100% on the dash, 97% on the app. I would be ok with that slight mismatch because the battery is effectively 100% for our use. Think the difference may be because it was a rapid charge.

OK, that is understandable.
I guess one may need a regular fast charger rather than a rapid charger for full balancing so sounds OK.

 

[JodyS21]

Is the app developer stating that the ful SOC is 455v? Therefore anyone not achieving this the calculation is therefore not 100%.

Ignore all the above, just looked at my readings and at 454.75v Soc is at 95.9% ?

I believe the data being provided by the ECU is the actual percentage, so it's not being calculated based on a value that is believed to be 100%

The developer Captain DIY, thinks the reason it's not 100% is because of the buffer at the top end of the battery. Which is very plausible of course.

IF the ECU reading is the REAL SoC% of the full 44.5kWh:
100% is 44.5kWh
96.1% is 42.76kWh / 95.9% is 42.68kWh
93.2% is 41.47kWh
Maybe the car's dash/BMS, which is programmed to allow a charge up to 455 or 450V, is also programmed to treat 96% or 93% as the effective (and displayed) 100%.
That would mean that previously (455v) about 42.7kWh was available, now (450v) about 41.5kWh is available as usable capacity.

Need to see what the ECU SOC% is when the cars display SOC% is totally discharged. Unfortunately I didn't have the obd2 dongle when I ran my car totally empty the other day.

 

[JodyS21]

@JodyS21
Looks a bit out on a limb.... The calculations on linear proportion...... our batteries don't behave that way????????.
Anyway I am a bit at a loss.
If you had charged and balanced your car before taking the reading then, I would expect SOH = SOC = 100% since your car is relatively new.
Not sure why yours was showing 93%
Has your battery degraded by 7% already?

That is what I said, I don't think it is linear, (lithium) batteries don't act like that, there is a voltage discharge graph specification.

No ones would appear to show 100% SoC in the ECU data, that's what we're investigating, why it is. Obviously the ECU SoC % in the app is related to the max voltage as can be seen in the data so far.

 

[JodyS21]

The voltage discharge curve on a lipo battery is relatively flat for most of the central part. The extreme ends of the curve are more like sheer drops.

My last charge was on a rapid charge, and it reported 100% on the dash, 97% on the app. I would be ok with that slight mismatch because the battery is effectively 100% for our use. Think the difference may be because it was a rapid charge.

To confirm, you charged to 100% on a rapid charger, then took the reading - 97% on app? Did you get the Voltage and min & max cell voltages (would show if out of balance much/at all).

You have the 455V BMS, like mystreet & Tango130 - they're showing 96% ECU SoC.

 

[Deleted member 2439]

I’ve managed to find an old tablet, but the most recent Android that it will upgrade to is 5.1. Is that sufficient to run the app?

thanks

 

[Davemac278]

I’ve managed to find an old tablet, but the most recent Android that it will upgrade to is 5.1. Is that sufficient to run the app?

thanks

I've tried it on an old Samsung S5 running Android 6. It's worth a try on 5.1

 

[KasEV]

That is what I said, I don't think it is linear, (lithium) batteries don't act like that, there is a voltage discharge graph specification.

No ones would appear to show 100% SoC in the ECU data, that's what we're investigating, why it is. Obviously the ECU SoC % in the app is related to the max voltage as can be seen in the data so far.

OK that is interesting.
But all the same does not read right.
If balancing is working correctly then what ever measurement you use should read soh = soc = 100%
If it doesn't then battery is downgrading or the measurement is wrong or balancing did not work.

 

[JodyS21]

OK that is interesting.
But all the same does not read right.
If balancing is working correctly then what ever measurement you use should read soh = soc = 100%
If it doesn't then battery is downgrading or the measurement is wrong or balancing did not work.

well, I can understand why it says 9x% rather than 100% - as we know we're not allowed to use the full 44.5wKh battery capacity.

This isn't a figure for people to see, so it makes sense that it maybe the real internal SoC of the whole 44.5kWh capacity.

The BMS etc then will determine I'd imagine how much to allow you to charge and discharge to based on this percentage of the actual whole 44.5kWh capacity. Further, based on the amount of the whole 44.5kWh capacity we're allowed to use, they show us the percentage on the dash of the amount we're allowed to use.

E.g. They say we're only allowed to charge and discharge to 95% & 5% of the battery capacity.
So when charging it stops at 95% of 44.5kWh, but they show that as 100% to the user on the dash. When discharging it stop at 5% of 44.5kWh, but they show that as 0% to the user on the dash.

If I were designing the system, that it probably how I'd do it, it is logical.

Re SOH - I have no idea how this is determined, I do not have enough knowledge of how degradation of batteries are measured. Some further night-time reading is needed

 

[Alan5]

Fully charged my car at work today on the granny charger , here's my SOC screenshot.