anko
Well-known member
Maybe, because of a pessimistic BMU, 30% SOC reported by MBU was in fact more than 30% actual SOC, before the procedure?Bert said:
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Drive battery degradation and the out of whack IMO BMU.
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Trex said:This is from the same website as above but from their Technical information manual.
Please note the Calculating total amount of battery (including capacity adjustment) using History of battery usage and History of discharge and charge
on the bottom left of the BMU.
Thanks for the picture Trex
This is exactly what I did observed
There are only 2 way for calculate the capacity into a Lithium battery:
1) - By known the capacity at state A, and knowing how much current have been extracted (oor added) from the battery in the time between state A and B .. so the capacity of the state B can be computed = Capacity B = Capacity A - Consumed Current
2) - Having a table between Voltage and Capacity, knowing the voltage level of the Lithium battery allow to know the capacity ... if the battery is left unused for at least 2 hours for get stabilized from eventual voltage drop from the "heavy" usage
So .. this is what our PHEV is doing.
- Our PHEV believes it has a SOH set to value X .. from factory is 38Ah (let assume this value for clarify the scenario)
- Let assume the battery is fully charged ...then the PHEV know there are 38Ah usable from the battery -> 38Ah = SOC
- While the PHEV is under usage, the PHEV ECU (or BMU ecu) monitor all the time the current in and out (this monitoring can have computations and measuring errors, but that's a "detail" for now)
- Let assume 10Ah as been consumed in the trip, and then the car is parked unused for 3h. End voltage let say is 3.80v per cell.
- Just after the trip the car believe it has 28Ah capacity left, only based on the original capacity - consumed current .. voltage is not relevant when car is used, since is much lower then expected due to the "stress" of usage.
- After 3h we switch on the car .. the Voltage per cell is now up to 3.90V
- Now the ECU will compute and correct the SOC ... SOC is now based on the Voltage .. let say 3.90V per the ECU PHEV table is equal to 70% SOC ... so the ECU will consider as new SOC Capacity = % * SOH -> 70% * 38Ah = 26.6Ah
- 26.6Ah is now consider as base for EV range estimation (together with the last trip consumption history)
- The PHEV notice and register a "missing" capacity ... 26.6Ah vs 28Ah ... so 1.4Ah deficit .. this is consider as error
- The PHEV store all the errors and on monthly (or every X days) base or based on error level threshold (which will arrive first) .. all the error are added together .. and if the ECU detect that in average the error was negative for X Ah ... it will change the Ah SOH accordingly .. it can be reduced by 0.5 if the error accumulated is high .. or only 0.1Ah if the error was low ... but as well SOH .. can be increase if the PHEV detect the error was "positive"
This explain why somebody notice the missing capacity in the PHEv after 2h or more of resting
This explain how the SOH is changing in our PHEV
Assuming the monitor of the current is correct .. and assuming the voltage-capacity in % mapping table .. it is correct .. the system above is perfectly fine for monitoring the degradation of the battery without the need to fully charge and discharge the battery, something that is is not really possible and as well it will age faster the battery too
With the MUT / or wrong Smoothing procedure people can reset to 38Ah the SOH ... but the system in place slowly will detect the error of the assumed SOH and it will be "corrected" automatically by the car ... still .. while the correction is happening, people can enjoy longer EV range, since simply the battery can be discharged more then what Mitsubishi did originally design
Bert
Well-known member
anko said:
So you think the SoC was 35% but the BMS showed only 30% via the CAN BUS? If we assume we have at least another 5% missing at the top (100% SoC is in reality 95%), this would mean only 60% usable battery capacity = 7.2kWh. The charger pushed almost 10kWh into the car though and I don't believe we have only a 50% charger efficiency...
Bert
Well-known member
elm70 said:
That's what I experience, the cell voltage rises over time while parking but the available Ah and EV km drop at the same time. Is this enough out of whack?
Very interesting theory, elm70. This would explain the miscalculation the BMU makes and the dropping SoH as well. It would also explain why the SoH is going down faster when on long journeys with tons of little charges and discharges of the battery. The error threshold is been reached much earlier and it moves the SoH level down to protect the battery. The BMU is not sure about the true SoH any more.
If this is real, what a piece of crap this software is!
Bert said:
Voltage rise after usage, it is normal ... I see this happening since almost 20y on Lithium battery which I use since ages from RC Model Hobby (in the old day I was trying (and succeeding, flying on RC airplane using 18650 battery from a laptop ... that was a high capacity battery but with low power ... vs hobby battery that normally have high power and low capacity)
Especially old Lithium battery, or more in general high resistance battery ... do get visible voltage depressed under usage (heavy usage) , and need hours for jump back to the "correct" voltage based on charging level.
In my case I can see that sometime my SOC after parking goes up, and sometime goes down ... normally on short journey after fully charged, I can experience a gain in SOC .. but after adding a 2nd traveling lag without recharge .. I can see SOC going down .. and the other way around ... so ... possibly the win and the loss get compensate on my PHEV .. still not fully compensated, since I'm dropping 0.1Ah a month
My theory here is that the mapping between voltage and SOC in % .. is not always accurate for every voltage .. but I think even if this mapping has some error, it should be compensate by the "main logic" described above
About the software quality ... I think software wise it make lot of sense ... since it is not possible nor wanted to fully discharge the battery for check the battery condition.
What we experience ... I believe is mainly a "natural" battery degradation .. for some is more and for some is less .. but is due to weather condition, and charging-discharging behavior
But it is possible that there is some error on the current flow measured while the car is moving ... still ... it should be self compensated :
If the PHEV believe more current is consumed then what it is in reality .. then it may believe that the SOH is higher then the real SOH .. but due to higher monitored battery consumption the EV range will be reduced .. similar if the measured current is less then what happen .. the PHEV may believe that SOH is lower then the real SOH, but again this get compensated in EV range
So ... all in all ... I think this design is totally fine ... and I can't think any other way for measure SOC and SOH without a deep battery cycle
anko
Well-known member
Before or after the procedure?Bert said:
Commonly accepted is 70% usable capacity * 12 kWh = 8.4 kWh after losses.
What if, before the procedure, your BMU thought you had lost 1/7th of your capacity. So, only 7.2 kWh available. So, after discharging 7.2 kWh after a full charge, the BMU would assume it was at 30% SOC, where in fact it was at 40% SOC. Effectively 10% or 1.2 kWh would not be used.
anko said:
Driving slowly the last km in EV mode it allows to discharge the battery down to almost 25%
Considering 90% charging efficiency ... we have 12kwh * 75% / 90% = 10kwh
Anyhow ... these battery are 40Ah when new, but Mitsubishi decided to don't use the last 2Ah or the last 5% .. so .. normally the battery are discharge to 35% or 3.81v per cell .. or in case of slow driving down to 30% real SOC
Assuming the real SOH is 80% .. but after fake battery smoothing, so after resetting the BMU, these are assumed as 100% SOH .. what will happen is that the PHEV will allow to discharge the PHEV from 100% down to 15% or 10% (in case of slow driving at the end of trip) .. charging will be still the magical 10kwh (this case is from 10% to 100%, instead of 30% to 100%) .. this means due to the buffer used by Mitsubishi, after a fake smoothing it will look like the battery is as good as new .. except that when monitoring the car after a long EV trip without charging and after over 2h of rest, the car will realize that the battery SOC is way lower then predicted and it will start to update the error management and redefine the SOH .. as well ... if the car is not connected to a charger, it will kick in the ICE as soon as the car is "started"
I guess this "buffer" on the BMU is for a reason ... so I expect that a fake battery smoothing will only cause to degradate faster a battery that is already more degradated then "normal"
Bert
Well-known member
10kWh after the procedure...anko said:
That's what I was saying in a couple of my videos: the software loses track of the real capacity over time and goes down to protect it, makes rather conservative assumptions than going to high. What you're saying above is exactly correct and the real battery capacity has not changed. The BMU reset has brought it back to 100% capacity and also the range was there, so this proves the battery must be still at ~100%SoH.anko said:
Again it's the crappy software which makes us believe the battery shows degradation. I now call it 'software degradation' in my videos because the battery is totally fine and lives a happy life under the blanket of this algorithm...
Bert
Well-known member
elm70 said:
The BMU reset did not change any cell voltage ranges though. I checked this several times. I cannot support your assumption the PHEV is using battery capacity from 100% down to 15 or even 10% SoC. If this is true I would have seen far lower voltages at the end of a journey and also at the end of charging (4.1V is not 100% SoC). You're right in saying the BMU will see the battery as new or replaced battery.
Interestingly, we have now several cars here in Australia which had this been done and I know of one car acting very different to mine, even it was down to ~80% SoH before the procedure as well. The fact though that this car is been driven in far slower traffic then mine makes me thinking that the battery consumption calculation has a big influence on the overall result of the BMU and also must have a relatively high error factor. Usage, charge and recharge habits must play a big role in guessing the SoH.
Bert said:
I can't agree with your view
As well, your videos about he PHEV did show multiple times that your EV range and SOC was going down while your car was parked for over 2 hours.
Couple of times you did report that after a trip in 100% EV mode, you did report that the ICE did kick in as soon your restarted the car after over 2h parking ... once was also documented in a video, showing the battery voltage at around 3.76v per cell (even down to 26% SOC the voltage per cell should be never below 3.80v)
These for me these are clear signs that the assumed SOH is above the real SOH .. or at least the SOH is to high for the measured current flow monitored during your car usage
Every time the SOC goes down while parked , it means that the SOH is bigger then what it is in reality (or at least the reality that the PHEV can sense via voltage monitor after over 2h rest and current flow integration and monitoring)
Every time this happen, in my view the PHEV record this error , between the Ah SOC before and after the parking rest .. and based on the history or the accumulation of these error over days, the PHEV may decide to reduce the SOH (but if may even decide to increase the SOH if the car detect that after parking there is more capacity then what predicted)
The tricky part of my "assumption" .. is about:
A - How the PHEV will update the SOH if the car is never charged and used all the time in ICE mode ...
B - How the PHEV will update the SOH if the car is immediately charge after every EV usage, without any "rest" time for check the voltage level
About A ... I guess the PHEV may not bother to update the SOH .. as long the car is used in pure hybrid mode.. the real SOH is not relevant ...
About B ... maybe the PHEV has some tricky way to allow the battery to rest for check the real SOH/SOC before starting the charging process
Anyhow .. I can't say the software is garbage in the PHEV ... I also don't see how SOH and SOC can be monitor in EV without ever allowing fully discharge the battery ... I believe the 90.5% SOH in my PHEV is about correct ... the only way to prove it would be to take out one cell from the battery and bench test the real capacity .. and then adding the 5% buffer that Mitsubishi decided to have for "safety" ... I guess this it may be happening soon in some of our PHEV .. since possibly once "retired" these battery could be used as power walls .. and somebody will monitor it ... assuming he will be able to check over the "Dog" before the battery get removed from the car.
What they should have done better .. maybe it is to measure the IR of the battery .. this at least is looking does not get updated, or maybe it is just not properly recognized by EvBatMon and the WatchDog .. the IR of the battery is a clear indication of ageing and battery degradation
Bert
Well-known member
elm70 said:
Well, before the software update during the recall last year, the algorithm never seemed to downgrade the EV range while parking. In Winter it kept the the same range or a small gain and in summer it bumped it up to 2-5km. Unfortunately I did not have the Dog at this time so could not really see what was going on. I only could monitor the EV km on the GOM which was.. well it's a GOM. Now with the Dog we can see what is happening and be more precise in our assumptions.
Again, after the reset why did the car have so much pure Ev range without changing the voltage range at all. It can be only related to the software which was protecting the real SoH before that. Otherwise the capacity would not have come back.
Of course the true and real capacity can only be determined by fully discharging+charging the battery and storing these information in the BMS. This will never happen in the PHEV though for known reasons. The software should therefore be capable of calculating the SoH itself and not providing us with false information. Not any other EV/PHEV I've ever heard of has 20% loss of capacity due to degradation within the first 50.000km or almost 30% at 80000km as seen by others. That would be the worst battery ever, not suitable for any EV! If other EVs suffering from such a degradation it would have been made public you think already?
You can only measure two things on a cell directly, the voltage and the temperature. For everything else there is already a calculation necessary which may or may not be accurate. And I still think the current software is not good enough to do that job. I also doubt Mitsubishi will ever update this software on the older models as from an economical perspective, selling new cars is far more profitable than keeping existing ones alive.
For me it is very logical and quite correct on Mitsubishi side
As far as I know also the Nissan Leaf especially the 1st generation did/does suffer from battery degradation .. but since Nissan did guarantee some % of SOH inside X years and Y miles ... degradated battery from the Leaf get substituted once they get too bad.
Anyhow ... the battery stress in our PHEV is bigger then in normal EV ... our PHEV is requested to be discharged up to 60kw and charged up to 35kw .. and for a 12kwh battery these are big number ... especially normal driving require often burst over 40kw , and regen brake over 15kw ... so in normal usage the battery get get a high stress ... think of a tesla with a 100kwh pack ... in normal driving hardly is needed more then 70kw. and regen does not need to be more then 50kw ... for a 100kwh battery these number are so low that the voltage of the pack does possibly never get depressed like our PHEV (I have notice up to 3.3v per cell, in our PHEV which bounce back to 3.80 at rest ... a sign of a huge stress for the battery .. something I believe can't happen on big tesla)
For example the Lead had 80kw power, and 24kwh battery ... so worst scenario is a power usage 3.3:1 vs 5:1 .. and normal usage in Leaf possibly is around 30kw power burst ... so almost 1:1 vs 3:1 ... so ... you can see how much more stress the PHEV battery get compared to other EV
I think that our PHEV battery does degrade relative fast ... and it is not a software error .. the only "responsibility" of the software is to have the "dirty task" to calculate and show the battery degradation.
It would have been interesting to know what would be the result after a proper battery smoothing in your PHEV, unfortunately the dealers in Australia are doing this procedure in the wrong way .. instead of doing the smoothing they just reset some BMU parameters ... causing even more problems .. even if for a short time this look like that the battery in the PHEV is again as good as new
PS: A very significant case .. is in one of your video .. you did show that after having used the car in EV mode .. after 2h or more of rest ... voltage per cell was 3.75v and the ICE did kick in as soon as you switch on the car ... this is a clear sign that the PHEV did allow to overdischarge the battery ... and this is due to the fact that in your PHEV at the time the SOH was bigger then what was in reality .. so .. if the SOH is bigger then the real SOH .. it is normal that the software does reduce SOH and reduce EV range after usage and rest without charging.
As far as I know also the Nissan Leaf especially the 1st generation did/does suffer from battery degradation .. but since Nissan did guarantee some % of SOH inside X years and Y miles ... degradated battery from the Leaf get substituted once they get too bad.
Anyhow ... the battery stress in our PHEV is bigger then in normal EV ... our PHEV is requested to be discharged up to 60kw and charged up to 35kw .. and for a 12kwh battery these are big number ... especially normal driving require often burst over 40kw , and regen brake over 15kw ... so in normal usage the battery get get a high stress ... think of a tesla with a 100kwh pack ... in normal driving hardly is needed more then 70kw. and regen does not need to be more then 50kw ... for a 100kwh battery these number are so low that the voltage of the pack does possibly never get depressed like our PHEV (I have notice up to 3.3v per cell, in our PHEV which bounce back to 3.80 at rest ... a sign of a huge stress for the battery .. something I believe can't happen on big tesla)
For example the Lead had 80kw power, and 24kwh battery ... so worst scenario is a power usage 3.3:1 vs 5:1 .. and normal usage in Leaf possibly is around 30kw power burst ... so almost 1:1 vs 3:1 ... so ... you can see how much more stress the PHEV battery get compared to other EV
I think that our PHEV battery does degrade relative fast ... and it is not a software error .. the only "responsibility" of the software is to have the "dirty task" to calculate and show the battery degradation.
It would have been interesting to know what would be the result after a proper battery smoothing in your PHEV, unfortunately the dealers in Australia are doing this procedure in the wrong way .. instead of doing the smoothing they just reset some BMU parameters ... causing even more problems .. even if for a short time this look like that the battery in the PHEV is again as good as new
PS: A very significant case .. is in one of your video .. you did show that after having used the car in EV mode .. after 2h or more of rest ... voltage per cell was 3.75v and the ICE did kick in as soon as you switch on the car ... this is a clear sign that the PHEV did allow to overdischarge the battery ... and this is due to the fact that in your PHEV at the time the SOH was bigger then what was in reality .. so .. if the SOH is bigger then the real SOH .. it is normal that the software does reduce SOH and reduce EV range after usage and rest without charging.
AndyH
Well-known member
My 2018 North American model updates with a higher SOC more days than not after sitting. Let me know how many kWH you're missing and I'll stuff them in a box for the boat ride south. :lol:Bert said:
There are three things that can be measured by a decent BMS - voltage and temperature as you noted, and charge in and out (Coulomb counting). Voltage and temperature measurements should be reasonably accurate and precise, but the error bars expand for energy tracking. The thing that cannot be measured is the actual capacity of a cell for that particular age and temperature. To know the actual cell (and thus battery) capacity, one would have to run a full discharge-charge cycle - and that would increase the rate of battery degradation.
Since we can't know the actual capacity of the battery at any particular time, we can't know the exact state of charge. The problem here isn't the software or the battery, it's the faulty expectation of the operator. This isn't a Mitsubishi problem - this is the reality for all portable devices.
Bert
Well-known member
AndyH said:
I cannot see this as a fault of the operator. Other EVs do not seem to have this problem, I'm sure someone would have noticed and made this public as #parkinggate or something. Furthermore, before the update the BMS has calculated the SoC correctly (in my eyes) and gave me more KM after a rest and temperature rise of the battery during parking. The new version does not do this anymore. I have not changed but the software has...
If they do an update on your 2018 model and it now shows 1Ah less after parking would you say that's OK and think that's better and more accurate than before?
AndyH
Well-known member
With respect, the Outlander PHEV is not an EV. It's a hybrid. The 'problem' here is one of intense observation. Batteries are not static devices - they're electrochemical critters that are in a constant state of change. One might as well be monitoring the volume of blood in their body or complaining when their red blood cell count changes. Normal changes in batteries over time aren't cause for concern with most hybrid owners since most don't know how battery performance changes with use and temperature.Bert said:
I'm driving the car, not using it as an analysis test bed. As I worked with lithium cells for about 10 years hand-building batteries, I understand how they change and I don't get my panties in a knot when the numbers shift around during the day. If my car's reflashed and now it shows a 1 Ah drop when parking, all I can say is that I don't have enough information to know if it's more or less accurate. There are so many variables that even repeated 'test drives' aren't very useful in deciding how the battery's doing. There's a lot of noise in the data - best to focus on the long-term trend.Bert said:
ETA... I had a smart EV for three years. It has an analogue battery charge gauge and a guess-o-meter. There are no monitoring programs available (like the watchdog) that provide cell-level information. I had absolutely no stress about how much the thermal management system took from the battery, and had no stress about the way the state of charge changes through the day because the data weren't available. After a few months, I learned that I needed about 20% of charge to make a 18-20 mile drive - that was all the information I needed in order to use the car to it's max capability.
AndyH
Well-known member
Here's one example of how state of charge and state of health are estimated:
http://www.analog.com/media/en/tech...nd-State-Health-Estimation-Techniques-....pdf
Note that at best, there's a 2% error - and that rage increases:
http://www.analog.com/media/en/tech...nd-State-Health-Estimation-Techniques-....pdf
Note that at best, there's a 2% error - and that rage increases:
As the battery in our cars is NEVER allowed to fully charge (we never get to 'SOH reevaluation') or discharge, we MUST expect more error over time - because the only thing we've got is 'estimation error increase' due to 'algorithm runtime'. Two percent of our 40Ah battery is 0.8 Ah - that's the best we can expect when the car has zero miles/km/light seconds on the odometer. If the 'battery smoothing' process allows a recalibration, we should be able to expect SOH/SOC numbers to come back to the roughly ±0.4 kWh range before they get back to diverging from reality again. Entropy's the law, especially in non-linear critters like lithium batteries.
Tai626
Well-known member
Is there any chance that Mitsubishi dealer using ultrasound technology to check SoH of our battery pack?
http://www.eenewsautomotive.com/news/measuring-battery-status-ultrasound-cheaper-more-reliable-bms
UPS industry has been using this technology for a while...
Tai
http://www.eenewsautomotive.com/news/measuring-battery-status-ultrasound-cheaper-more-reliable-bms
UPS industry has been using this technology for a while...
Tai
Bert
Well-known member
Tai626 said:
That is very unlikely. The BMU uses coulomb count for keeping track of the SoH and SoC. Obviously not very successful...
STS134
Well-known member
I actually don't think the very brief bursts of power of up to 60 kW in normal driving are what does the damage. For the most part, that's just removing a bit of surface charge (that may have even been put into the battery in the last regen cycle) and in any case, it doesn't tend to last very long. Remember that HEV batteries are charged and discharged at even higher C rates, not because they're demanding much more power, but because their batteries are absolutely tiny (1.5 kWh is a typical HEV battery size). Let's take the 2018 Toyota Camry Hybrid for example. The LE model has a 1 kWh Li-ion pack, while the XLE has a 1.8 kWh NiMH pack. Both of these models have a motor that will do up to 88 kW so...about 88C discharge rate on the LE and 49C on the XLE. Yikes! And the highest our batteries ever see is around 5C. But HEV batteries last a LONG time, don't they? Well that's because the amount of time the battery is actually supplying that amount of current is YERY short.elm70 said:
What does the real damage is the sustained power demand of up to 2-3C (so 24-36 kW) when driving down the freeway. Mitsubishi is managing the battery very poorly in basically programming the car to use the battery as much as it can, until it gets down to 1 bar on the gauge, and only THEN go into hybrid mode. And they also like to brag about how the car can go up to 78 mph/125 km/h in EV mode (but it doesn't mean it's a good idea to actually do it, especially for an extended period of time). That's why I put the car into Save mode whenever I go faster than about 50 mph/80 km/h. This will either use the ICE to drive the wheels directly, or will use the ICE to run the generator, which generates power and immediately consumes it. In any case, it prevents the battery from having to discharge at 2-3C for an extended period of time. And the other thing I do is obviously I don't use the CHAdeMO port much at all.
I think Mitsubishi really dropped the ball in not putting the car into some sort of automatic Save mode whenever the battery would have to discharge at more than 1C for a long time. But then they'd have to deal with a whole bunch of whiners and complainers who bought a PHEV and are trying to never use any gasoline, and really got the wrong tool for the job. The goal of a PHEV is to reduce trips to the gas station, and the goal for a BEV is to eliminate trips to the gas station. Many people choose the former tool to try to achieve the latter goal, and as a result end up destroying their batteries, and to those people I would ask: why are you lugging around a heavy ICE, cooling system/radiator, gas tank, and a bunch of other stuff you almost never use?
greendwarf
Well-known member
STS134 said:
Because I don't want the cost of 2 cars (for which I don't have the space) and to hire an ICE car for the relatively few long distance journeys (e.g. holidays abroad) over the lifetime of my PHEV would cost more than a replacement battery when needed - NB. still getting 25 miles EV per charge after 4 years. :mrgreen:
You might also turn the question around and ask those who spending most of their time using the ICE, why they are carrying the extra weight of the batteries, :lol:
