Canion Battery Readings

[siai47]

I don't mean to step in here and stir things up, but you cannot get 16 KWH out of a I-MiEV pack the way it is configured in the vehicle. I have had the battery apart and the 8 cell modules are rated at 1440 KWH and the 4 cell modules are rated at 720 KWH. There are 10 8 cell modules and 2 4 cell modules in the pack for a total of 15,840 KWH available when new (with some disclaimers). To get this output, the battery cells (according to the LEV-50 data sheet) must be charged to 4.2 volts and discharged to 2.75 volts. Neither voltage is reached in the I-MiEV. To increase the life of the battery pack the charge voltage is limited to 4.105 volts per cell as a upper limit by the BMU. On the discharge side, the lower limit (on a new pack) is well over 3 volts when shutdown occurs. Therefore, no where near 16 KWH is actually available for use. I have mentioned in another thread, I think the BMU allows the lower limit to drop as the battery ages allowing the masking of actual pack degradation until the 2.75 volt threshold is reached on the weakest cell in the 88 cell string. After this point is reached, the first significant loss in range will be noticed by the vehicle operator. There are a number of ways to determine the health of the pack but none are easy to do with accuracy without placing a device called an electronic load on the individual cells so you discharge at a constant current that will not impacted by the change in cell voltage as it decreases. The current has to be as specified by the manufacturer of the cell ("C" rate) to really see what's going on. Each cell in the string needs to be monitored as the pack is only as good as the capacity of the weakest cell. With the CANION you need to see what the cell voltages and balance are looking like when the pack is close to or at vehicle shutdown. If those voltages are near 3.25 volts you are in decent shape, if approaching 2.75 volts, you've got some serious degradation starting. If you use other methods you will be able to monitor the percentage and rate of capacity loss in you pack but not really be able to see the actual KWH number of the pack

 

[offgridQLD]

Small correction, 15,840whr not 15,840kwh. That would be bigger than a submarine traction pack

Kurt

 

[siai47]

my bad (about the KWH vs. WH) . But just think how many miles the range would be!

 

[PV1]

my bad (about the KWH vs. WH) . But just think how many miles the range would be!

[sarcasm]
I can't buy the i-MiEV. It only goes 61,380 miles on a charge. I can't drive back and forth to work and take road trips. I'll run out of charge while driving down the road. Besides, it can't recharge in 2 minutes, so that just proves it won't work for me.
[/sarcasm]

:lol: :mrgreen:

I saw the next gen Yuasa batteries will be 150 Ah instead of 50 Ah. How does a 186 mile range sound?

When I did my range/health check a while back by driving down to 9%, my cells ranged from 3.675 volts (cell 88) to 3.650 (cell 9) at rest.

https://www.dropbox.com/sh/fojjfy7lpig0k0h/AAD7hHIcyVIBMa7QkjzpZiNLa?dl=0

 

[bobakka]

This is where my coefficient come from, 13.44 x 1.2 = 16 kw-h

A ratio of 60/50 or a coefficient of 1.2 is the best match for my iOn electric car which have a 16kWh battery capacity. In other words, this coefficient seems to give a proper result, but for my car only...

Now I understand where you get 60/50 or 1.2 from. But that is based on your assumption that your car has a 16 kw-h battery capacity. But that is not achievable.. How old is your imiev? and with how many km? Maybe you only have 15 kw-h..?

While driving, I get a higher slope, 0.1527 kWh per % SoC, but this number is also too low because those kW-h are a mixture of Wh-out when I press the accelerator and Wh Reg when I slow down.

But you do not know if this slope is too low or too high. If Wh-out is correct and Wh-reg is too low, this slope will actually be too high..

No matter about no coefficients, your equation will give a number, if by the time your battery capacity decreases, this number will also decrease.....

I have done some testing today and yesterday. I find slope to be 11,64 and 11,60 for charging. Correcting with your factor 1.2 that is 13.97 and 13.92. I find slope to be 12,43, 12,32 and 13,27 when driving. Assuming that SoC is correct, the the formula for my car Wh-out/Wh-reg is between 1,07 and 1,14.

I see a difference between Wh-reg and Wh-out that is unexplainable by physical processes (i.e. it is not possible to drain more energy than is supplied to the battery) and it must be due to measurement or computing problems.
I will do more testing to find how consistent the numbers are on my imiev.
I today drove the car as low as a SoC of 17.0 in the morning and in the afternoon the slope increased by almost 7% for the same drive the day before.

I think that my car assumed that battery capacity increased because I emptied the battery more than I have done for a week or two..

 

[bobakka]

Therefore, no where near 16 KWH is actually available for use.
If you use other methods you will be able to monitor the percentage and rate of capacity loss in you pack but not really be able to see the actual KWH number of the pack

My question is how I can monitor the capacity loss?

I have owned my imiev for almost 4 years and been driving 77777 km. My 80% capacity guarantee expires in 14 months or 22222 km. I am positive that I have a range decrease, but it is very difficult to calculate how much. So how do I open a guarantee case against Mitsubishi if I need to?

I think the Canion app is a large leap forward, but it has also large limitations as it is based on Can Bus information.

 

[BlueLightning]

It's a 16 kw-h battery because there is 88 cells, the LEV50's start with 50Ah x 3.7V x 88 cells = 16.28kWh, and it is well documented that the on board computer will not allow to use more than 90% or 95% of the 16 kw-h of the battery, Blue Lightning was built on march the 11th 2011 and is on the road since august the 27th 2012, I have been driving only 24 000 km. I charge the battery with a kill a watt at the wall since the begining and till now this battery is still able to pump from the wall the same amount of electricity. Thanks to Malm, we know that with a lost of capacity, charge is a faster process and that less electricity is loaded.

When I use the heater alone the slope is of 16 kW-h per 100% SoC. Wh out which is a negative value and Wh-Reg which is a positive value while driving are too complicate to handle for me, I do not deal with Wh out and Wh reg for capacity measurement.

I have done some testing today and yesterday. I find slope to be 11,64 and 11,60 for charging. Correcting with your factor 1.2 that is 13.97 and 13.92.

(13.92-16.28)/16.28 = 14% lost of capacity, is it bad for 77777 km and 4 years? from now you have these numbers as reference to see the evolution, I advise you to do more measurements to get an average and then to wait a bit. The lost of capacity might be slowing down.

My question is how I can monitor the capacity loss?

I trust and use this equation with the help of a kill a Watt on the wall

Capacity = 100 x Charge efficiency x "Wall kW-h" / (SoC final - SoC initial)

Charge efficiency for a 10 Amperes charge is 88.0 %, for my 16A charge, 81.2%

Mesure de charge à la prise

 

[offgridQLD]

have owned my imiev for almost 4 years and been driving 77777 km. My 80% capacity guarantee expires in 14 months or 22222 km. I am positive that I have a range decrease, but it is very difficult to calculate how much. So how do I open a guarantee case against Mitsubishi if I need to?

I'm just trying to relate this to a conventional ICE car.

Complaint...
I have driven 100,000km over 5 year and my engine seems to have a little less compression and doesn't get as good fuel economy as it did when it was new.

Response...
Sure I can sell you a new car.


We all don't want battery capacity decline but hey it's a battery they all wear out. Unless the capacity loss es excessive then I don't think its a issue. My view is Mitsubishi would replace or repair batterys based on there discretion and tests not the data that the customer provides.

Kurt

 

[siai47]

The nominal voltage of the I-MiEV battery is 3.6 volts not 3.7 which gives you 50 amps X 3.6 volts X 88 cells or 15,840 watt hours (got that right this time). This is from the spec sheet for the LEV-50 cell and is actually marked on the 8 cell battery modules. In addition, I had my car's battery capacity checked for reference when it had 30 miles on it by the dealer with the M.U.T III and it had a capacity of 49.5 amp hours. The dealer said he had never seen one with the full 50 amp hour rated capacity. If you are worried about your pack degradation and think it is below the limits specified in the Mitsubishi battery warranty then the dealer is going to have to test it anyway. When I get my recalls done, I am going to have the capacity of the pack measured and find out where I stand after almost 2 years. I have a known starting point (If you ask your dealer everyone might have this starting point as my dealer said that Mitsubishi required them to check the capacity prior to delivery) so I can easily find the amp hour loss since I received the car. That loss, not watt hours is what Mitsubishi is going to use to determine if your pack falls below the warranty threshold. Amp hours available is the only thing the M.U.T III checks for.

 

[bobakka]

In addition, I had my car's battery capacity checked for reference when it had 30 miles on it by the dealer with the M.U.T III and it had a capacity of 49.5 amp hours.

How does M.U.T. III work? Does it measure available capacity or total capacity??

When my car was testet a year ago at 60000 km it had a capacity of 39.6 amp hours. My dealer did not mention anything about a start point. If my start point was 49.5 amp hours then I already had a capacity loss of 20% last year. But I am pretty sure my available capacity has not been reduced by 20% as I did not see a 20% range reduction (I believe).

I think it does not sound right if M.U.T III measure available capacity and it measures almost 50 amp hours when the LEV-50 battery pack is spec'ed to 50 amp hours as the total capacity and at the same time we know that Mitsubishi is conservative with regards to available capacity. This does not add up.

 

[bobakka]

I have done som more test.
Yesterday I started with 99,5 SoC and drove until 12.0, charged up to 96,5, drove down to 13 and charged back up to 99,5
The resulting Canion screenshot is below.

https://www.dropbox.com/s/u30w12uocdc8ni3/pict_2014-12-06_22-41-40.png?dl=0

The result is that WhOut is almost 10% higher that WhReg.
WhOut should have been some % lower that WhReg due to internal losses in battery (and electronics?).

That means that the CanBus values Canion reads is not accurate - at least not with respect to Wh.
I assume from the discussion on this forum that we trust WhOut values, but not WhReg values.

 

[bobakka]

Charge efficiency for a 10 Amperes charge is 88.0 %, for my 16A charge, 81.2%

Hi BlueLightning
Is the 16A charger less efficient than the 10A charger? I thought it was the other way around.
And how do you calculate charge efficiency?

I find that WhReg is around 77% of what you call "Wall Kw-h" measured with external kWh-meter.
Given that WhOut is around 10% higher that WhReg (shown in my previous reply) and that WhOut is "correct",
I find that my 16A charger has a charge efficiency of 85%.

 

[siai47]

In answer to bobakka's 20% loss post, I would go back to the point that the BMU "masks" the battery degradation by limiting how low the cell voltages go until a minimum is reached and then the true capacity loss starts to be noticed. New I-MiEV's don't use all the available capacity of the pack until this point therefore the range doesn't change and no perception of loss is noticed by the driver. I think there are so many variables to determine an actual capacity number for the pack that Mitsubishi uses the amp hour storage of the pack as a reference. Amp hour capacity of the pack can determine the percentage of degradation without doing the complex calculations of the continuous voltage drop during discharge to come up with a KWH value which (if done) leads to the same conclusion. The hall effect transducer in our pack just measures the number of amps passing through it over time. This number, not range, AC watts going in to charge, trying to calculate charger losses, balancing losses, vehicle loads during charge, cutoff points, etc. just complicates what needs to be known. If you start with a known pack voltage (in our case 4.105 per cell) and discharge it to a known cutoff point (the lowest point the weakest cell can be safely taken to) and measure the amount of amps that were delivered from the pack of 50 amp hour cells---then you have the answer. Our cells are rated by Yuasa at 50 amp hours with a nominal voltage of 3.6 volts. Multiply 50 X 3.6 and you have 180 WH per cell. 88 cells X 180 WH equals 15,840 watt hours or 15.84 KWH which is the actual rating of a new I-MiEV pack. So, for example, if you found during the M.U.T. III test that your pack had 39 amp hours capacity, you would know that 39 X 3.6 X 88 = 12,355 watt hours or 12.355 KWH of capacity is available. Dividing it out you've lost around 22% of the original possible capacity. Going back to the first sentence of the post, the pack capacity was always falling but not noticed because of the BMU. Li-Ion batteries tend to fall off in capacity quickly at first and then start to level off. The BMU hides this by giving the driver a constant usable capacity even though the actual capacity is dropping.

 

[bobakka]

Mitsubishi uses the amp hour storage of the pack as a reference.

I support your view there. Amp hour is easy to measure and calculate.

Our cells are rated by Yuasa at 50 amp hours with a nominal voltage of 3.6 volts.
.. if you found during the M.U.T. III test that your pack had 39 amp hours capacity,
.. you've lost around 22% of the original possible capacity.

I support your view here also.

One question is however what the M.U.T. III measure when capacity is hidden from the user.
Does it measure available or total capacity?

The other question is when the warranty kicks in?
Given 39 amp hours capacity and 22% degradation, is this above or below the 20% guarantee?

 

[siai47]

I don't know what they measure (total or available capacity) when they are doing the capacity test. However, it seems like it must be a total capacity test. The car never charges to the full 4.2 volts that the LEV-50 cell is capable reaching nor does it normally drop to the lower limit of 2.75 volts. The cell needs to be cycled fully to reach 50 amp hours, therefore to get near that number when the car was new, at a minimum they must be going down to the 2.75 volt threshold with the M.U.T. III. I assume the scan tool could force the BMU to adjust both the maximum and minimum voltages the pack could see if Mitsubishi wanted to do that. As far as capacity loss for warranty purposes is concerned, I have never read the warranty policy (I voided mine right off the bat anyway). Again, I am pretty sure that Mitsubishi knows exactly what the amp hour capacity of each pack was when the car was delivered. My dealer stated that a capacity test was required on each car prior to delivery. In my opinion, that would be the starting point. In my example I used 39 KWH (which is a little lower then bobakka's actual) but if you knew what Mitsubishi recorded at delivery and what was recorded at the last test and that calculation exceeded 20% then I would think you met the requirements for a failed battery if 20% is the threshold.

 

[Barbagris]

I have done som more test.
Yesterday I started with 99,5 SoC and drove until 12.0, charged up to 96,5, drove down to 13 and charged back up to 99,5
The resulting Canion screenshot is below.

https://www.dropbox.com/s/u30w12uocdc8ni3/pict_2014-12-06_22-41-40.png?dl=0

The result is that WhOut is almost 10% higher that WhReg.
WhOut should have been some % lower that WhReg due to internal losses in battery (and electronics?).

That means that the CanBus values Canion reads is not accurate - at least not with respect to Wh.
I assume from the discussion on this forum that we trust WhOut values, but not WhReg values.

Great job, thanks.

In my hilly conmute I usually see in caniOn 27%-30% of Wh regenerated; I wonder how to use some kind of correction coefficient.

 

[bobakka]

In answer to bobakka's 20% loss post, I would go back to the point that the BMU "masks" the battery degradation by limiting how low the cell voltages go until a minimum is reached and then the true capacity loss starts to be noticed.

If I understand you correct your hypothesis is that the cell voltage for SoC = 0 decreases as the the battery and car gets older?

That is for example when new SoC = 0 is equal to a cell voltage of for example 3.5 V
and when driving 10 000 km SoC = 0 the cell voltage is 3,4 V
and when driving 20 000 km SoC = 0 the cell voltage is 3,3 V - and so on..

I yesterday drove to SoC = 10,5 in minus 6 C (battery voltage above 15 C) with cell voltage from 3,615 down to 3,575.
(I see however in my iMiev that SoC and cell voltage does not have a consistent relationship. I assume that is either due to large fluctuations in SoC calculations, temperature or driving style prior to measurement time)

If your hypothesis is right, Pier with a new battery pack should have with same SoC higher cell voltages than my iMiev.
Agree?

 

[Malm]

"If I understand you correct your hypothesis is that the cell voltage for SoC = 0 decreases as the the battery and car gets older?

That is for example when new SoC = 0 is equal to a cell voltage of for example 3.5 V
and when driving 10 000 km SoC = 0 the cell voltage is 3,4 V
and when driving 20 000 km SoC = 0 the cell voltage is 3,3 V - and so on.."


Yes, I agree with it. So, in first two years, many of the i-MiEV owners don't get any loss in autonomy. The real limit is 2,75V, no matter what the SoC is.

Another thing we always should remember, 100% SoC is not the same amount of energy in every i-MiEV. In my i-MiEV, when it was new, 100% SoC was more or less 16 kWh in the battery. Then after 2 years, my car recalculated the capacity to something like 100% SoC = 17 kWh (that´s why I have the record shared with Mrannen of 175 km mRR).
But after three years, It assumed something like 14 kWh = 100 SoC, and that´s why I can go, after three years to 0.0% SoC with more then 2,75 V in the weakest cell. But I have now less about 18% autonomy compared with when it was new, I think.

 

[jray3]

I have owned my imiev for almost 4 years and been driving 77777 km. My 80% capacity guarantee expires in 14 months or 22222 km. I am positive that I have a range decrease, but it is very difficult to calculate how much. So how do I open a guarantee case against Mitsubishi if I need to?

What 80% capacity guarantee? Is that unique to the Norwegian market, and where else? IIRC, the US-market cars have no capacity guarantee.

Btw, I got the dealer to run a battery capacity test during the rusty bolt recall work, and it came back at 42.6 Ah. That figures 15% below original spec after 30,000 miles (48,280 km), though it's been said (Malm, IIRC) that new cars didn't even hit 50 Ah.
I still have all 16 bars and no change in daily RR estimates (often 81 this summer, typically 56 on freezing mornings).

 

[Malm]

Mine after 3 years and 62000km had 36,4 Ah (something like that). And now, with 3 years and 9 months, almost 75000 km, the same 16 bars, but each one corresponding to 15 to 20% less energy then when it was new. So I do between 15 to 20% less distance with each bar. I think (one more of my special ideas) all i-MiEV recalibrates its capacity after three years. Mine did that, and now I Know that it is not the only one that did such thing. I know another european I-MiEV that has done exactly the same thing.