BEST 0.0% SOC EVER

[Malm]

So, 324 total voltage but 0,0% SoC. Weakest cell at 3,635 V (so far from the lowest limit, 2,75V, but 0,0% SoC).

In my opinion, in the reality, it has more then 10% SoC left (more then 10 km) but don't let me do even one meter.

Why, I told you many times before, my i-MiEV simple fails in getting correctly its SoC sometimes.

This, total voltage of 324 V and 0,0% SoC, only me and my i-MiEV can show. Because it only do this if some conditions happen at the same time (and I know how to gather those conditions). One of them is to have a car that thinks its capacity is 10% lower then it really is.

 

[JoeS]

Nice discussion of this over on the Australian i-MiEV forum:
http://forums.aeva.asn.au/forums/the-best-00-soc-ever_topic4212.html

For myself, while it's of academic interest, I value my pack too much to experiment. I've never taken my pack down to turtle and hopefully never will.

 

[Palm35]

I have done the same test as Malm.
But I haven't took pictures of CanIon.

for me :
SoC 9.0% 317V and then appears the turtle
SoC 0.5% 292V and 11.2km done after seen the turtle
I have a battery pack of 16kWh with 88 cells.
At 0.5% of SoC, the lowest cell was 3.235V

 

[Malm]

Nice discussion of this over on the Australian i-MiEV forum:
http://forums.aeva.asn.au/forums/the-best-00-soc-ever_topic4212.html

For myself, while it's of academic interest, I value my pack too much to experiment. I've never taken my pack down to turtle and hopefully never will.

JoeS, I hope you can see that my 0.0% SoC are not really 0.0%. My car was between 10% to 15% SoC (not 0,0%), as we can see for the voltage. So, at 0,0% I wasn't in turtle.

I hope you can see that ?!?!?!?!?!?!?!?!?!?!?!?!?!?!

My car can´t get his SoC right, but total voltage is always right. I just have to watch the voltage and forget the SoC.

 

[Malm]

I have done the same test as Malm.
But I haven't took pictures of CanIon.

for me :
SoC 9.0% 317V and then appears the turtle
SoC 0.5% 292V and 11.2km done after seen the turtle
I have a battery pack of 16kWh with 88 cells.
At 0.5% of SoC, the lowest cell was 3.235V

OK, If a 5% bar (not a 8 or 7 or 6), If a 5% bar takes approximately 1 kWh from the wall, then you have a 5 stars pack. Like a new one. Congratulations.

I think its the best way to know if our battery is in good condition is to make this test: If it goes to 0,5% and one 5% bar is almost 1 kWh from the wall at 16A L2, the battery is perfect.

I agree with JoeS, we should avoid doing this. So Palm35, I advise you not to do it until two or three years, and just if you are feeling that you need to make the test again. Thank you for the test, it help all of us to know better our cars.

And once again, this time I didn't get it to turtle, PLEASE UNDERSTAND THAT. Otherwise, i´m feeling you are on the beginnings of understanding your cars.

 

[Malm]

Nice discussion of this over on the Australian i-MiEV forum:
http://forums.aeva.asn.au/forums/the-best-00-soc-ever_topic4212.html

For myself, while it's of academic interest, I value my pack too much to experiment. I've never taken my pack down to turtle and hopefully never will.

And let me say, that discussion could be here, if anyone asked me something about that.

 

[JoeS]

Malm, I appreciate that you have experimented and analyzed our battery pack using Canion more than almost anyone on this forum, and I find some of your observations 'interesting' - especially the possibility of an annual 'recalibration' by the onboard computer.

Having murdered FLA, Gel, AGM, LiFePO4, and Li(NMC) battery packs in my various boats and EVs (not to mention countless small NiCd and NiMH), I'm quite content at being overly-conservative with my iMiEV since I bought it and am not leasing it and wish it a long and healthy life.

A brief high-current draw could suck down that Cell#65 below its lower threshold - but the iMiEV will keep us from doing this. My take on all this is that Mitsubishi is being very conservative with how they're treating the pack and are perhaps erring on the 'safe' side. I'm somewhat bemused by the SoC readout by Canion (and recognize the number's seeming inconsistency vs. voltage), but figure it's just another input to digest along with fuel gauge 'bars' and RR to give me a warm fuzzy feeling that I'm not going to get stranded.

Malm, I understand what you're saying and I agree, you are still a significant distance away from the cell's low voltage cutoff point and the pack's true SoC is certainly above zero considering the sum of all the cells shown in your graph. As I said, since I've never fully utilized my pack's capacity, it's of academic interest to me.

Your graph shows a significant disparity amongst cells at this low SoC, whereas after they finish top-balancing they all have identical voltages(?).

Perhaps the only point I'd like to make is that if anyone is running their iMiEV on 'empty' (turtle or close to it), be very easy on the accelerator and don't make any assumptions about how far you can go in that state.

 

[Malm]

Happy to see that you understand that i'm not testing the limits as it seems - Uff....

At least one human being that sees it.

"Your graph shows a significant disparity amongst cells at this low SoC, whereas after they finish top-balancing they all have identical voltages(?)."

At very low SoC 60 mV difference is fantastic. No one will have that difference at 0,0% SoC. Maybe 150 mV in a very good battery, most of the times 200 or 300 (or more). When cells are lower then 3,7 V we begin to see the difference going bigger and bigger.
At 100% SOC - allways less then 0,015 V difference.

That´s what I think. Maybe Palm35 can say to us what was the difference, but I think it was over 100 mV

 

[Malm]

Zelenec had made some interesting tests too. Maybe he can remind us his values.

 

[Malm]

"especially the possibility of an annual 'recalibration' by the onboard computer"

My weakest theory of all :lol:

 

[me68]

I have a very simple explanation for your battery observations: Some cells are in bad condition - as bad, that the BMS can't calculate a valid SoC value.

0% SoC is basically not bad for cell lifetime, because BMS defines what 0% SoC is. So, if you have a look to the well know technical report of LEV50 cells https://www.gs-yuasa.com/jp/technic/vol5/pdf/05_1_021.pdf, you well see, that GS Yuasa do the lifecycle tests in a range from 4,1V to 2,75V.

The weakest cells in my car has 3,395V at 2% SoC. So far away from 2,75V! So i have no fear running the car down to 2% SoC for battery capacity measurement once a year.

Martin

 

[Malm]

Happy to see that you understand that i'm not testing the limits as it seems - Uff....

At least two human beings that sees it.

As you can see JoeS, not even at 0% and difference more then 100 mV. The me68 car, if it uses 1kWH from the wall, to charge a 5% bar, then it is in excellent condition like the one of palm35. I-MiEVS of me68 and palm35 will do the exactly the same distance as when they where new. Excellent news for all of us.

 

[offgridQLD]

Malm,
Remember you can only do comparisons with cars being charge at the same rate. 240v - 10A charger (mine is roughly 2200w from wall) some US cars run 110v chargers that are perhaps 1100w?) Given it would take double the time to recover 5% into the battery then that is double the time that the (system loads are running) roughly 200w?. So you will always use more power from the wall at a slower charge rate. 3300w charge rate will use even less.

So any comparisons must be with cars being charged at the same rate. Even at the same charge rate there will be some (small) differences if the battery is charged at a different temperature due to pump cycling time. Though I think we can ignore this small pump cycling difference for now.

Kurt

 

[PV1]

Actually, I think the cooling pump (for the electronics and motor, the battery doesn't have water, or even air, cooling while AC charging) runs at set intervals. Within 2 or 3 minutes of plugging in, regardless of temperatures, my coolant pumps kicks in, and runs at set intervals throughout the charge cycle. This doesn't matter what amperage setting or level (1 or 2, from 8 to 13 amps), the intervals seem the same.

 

[Malm]

Malm,
Remember you can only do comparisons with cars being charge at the same rate. 240v - 10A charger (mine is roughly 2200w from wall) some US cars run 110v chargers that are perhaps 1100w?) Given it would take double the time to recover 5% into the battery then that is double the time that the (system loads are running) roughly 200w?. So you will always use more power from the wall at a slower charge rate. 3300w charge rate will use even less.

So any comparisons must be with cars being charged at the same rate. Even at the same charge rate there will be some (small) differences if the battery is charged at a different temperature due to pump cycling time. Though I think we can ignore this small pump cycling difference for now.

Kurt

True. I know that. My numbers are at 16A.

 

[Malm]

Actually, I think the cooling pump (for the electronics and motor, the battery doesn't have water, or even air, cooling while AC charging) runs at set intervals. Within 2 or 3 minutes of plugging in, regardless of temperatures, my coolant pumps kicks in, and runs at set intervals throughout the charge cycle. This doesn't matter what amperage setting or level (1 or 2, from 8 to 13 amps), the intervals seem the same.

And true again. Always with the same intervals no matter what.

 

[Palm35]

I have done the same test as Malm.
But I haven't took pictures of CanIon.

for me :
SoC 9.0% 317V and then appears the turtle
SoC 0.5% 292V and 11.2km done after seen the turtle
I have a battery pack of 16kWh with 88 cells.
At 0.5% of SoC, the lowest cell was 3.235V

I have tried again in august 2014 with CanIon

So:
Soc 18.5% - 116km - 328V -RR 18 km 2 bars
Soc 17.0% - 122km - 327V -RR 12 km 1 bar blink
Soc 12.0% - 128km - 322V -RR 4 km 0 bar
Soc 10.0% - 130km - 316V -RR -- km
Soc 8.5% - 133.7km - 319V - turtle appears at 134.9 km
Soc 0.0% - 146.0 km - 294V lower cell is 3.250V

 

[jsantala]

Lithium cells generally have most of their capacity, let's say 90%, between a very small change in voltage. Therefore, the Ah difference between, say, 2,75 V and 3,2 V, is most likely insignificant. Meaning you could go like a few meters between 2,75V and 3,2V. Whereas you can go miles between 3,2V and 3,65 V. The BMS just probably has some trip value, which if reached while under load will trigger 0% SOC and disable the car until recharged. The trip value being something lower than these, like 2,5 V at a single cell, or something. The numbers here are just guesses, so don't concentrate on the exact values.

 

[Malm]

Lithium cells generally have most of their capacity, let's say 90%, between a very small change in voltage. Therefore, the Ah difference between, say, 2,75 V and 3,2 V, is most likely insignificant. Meaning you could go like a few meters between 2,75V and 3,2V. Whereas you can go miles between 3,2V and 3,65 V. The BMS just probably has some trip value, which if reached while under load will trigger 0% SOC and disable the car until recharged. The trip value being something lower than these, like 2,5 V at a single cell, or something. The numbers here are just guesses, so don't concentrate on the exact values.

I agree. The car is measuring the energy that it uses and with the amount of energy used it gets the SoC. In my car, in the present time, 0-100% energy is about 13,5 kWh. When it measure 13,5 kWh spent then it is at 0% SoC and stops. But I'm sure, if the car have 2,75V in one cell it will stop, no matter what the SoC is. I have seen it in my car, it will stop when one cell goes down to 2,75V, even when it had 14,5% SoC, one bar. So, the exact value is 2,75V, when one cell goes down to that value, then "game over".