Drive battery degradation . Houston, do we have a problem?

[jaapv]

It should make about 5% difference.

 

[AutoE]

Following up on an earlier post... I've a 2.5yo PHEV with battery capacity rated at 76% and range rarely indicated above 22-24km. We had an exceptionally hot couple of days in the summer 2015 and saw a huge drop in estimated range from low-40km to high-20km. We spoke with the dealer and was told its the A/C but if we wanted to have evaluated it would take a few days or more. We passed as we were told its really just the system overestimating A/C consumption. I didn't exactly believe and though range eventually bounced back above 30km it was never 40km again. We have a garage but during the day the car is often in the sun. No where are we told you must park in the shade... We've never fast charged, such doesn't exist here and 95% of the charging is at night.

What's the dealer procedure for evaluating battery condition? Few hours, day, days?

 

[anko]

When the battery is fully charge each cell sit at 4.1v, and this means 328v .. considering 330v so you add ~1% bonus on a wrong maths too.

I didn't say "330 volt", I said "330-ish volt". But even if I had used 330 volt in my calculation, it would not have made a difference, as:

328 v * 29.5 Ah = 9.676 kWh
330 v * 29.5 Ah = 9.735 kWh

You presented your results earlier as 6.5 kWh and not 6.50 kWh of 6.500 kW. So, I presented the outcome of my calculation also with a precision of one decimal. And guess what, doing so using 328 volt and 330 volt both lead to an outcome of 9.7 kWh. So, no. I have not been adding any bonus.

Normally energy in a given battery is reported by nominal voltage x capacity ... in this case nominal voltage is 3.7v pre cell ... so conventional maths should use 296v * 29.5Ah = 8.73kwh .. 1kwh difference is not a little thing .. over 10% error

You know very well that while discharging the voltage of the battery drop from 4.1v down to 3.7v (@ ~30% SOC) .. fully discharge the lithium cell means to discharge it down to 3.0 or even 2.75v .. only going down to such voltage the total capacity is measured .. that in theory should be 29.5Ah (a value that can't be measure in the PHEV)

What you are saying is that the Ah number reported by the PHEV cannot be the 'normally reported nominal capacity'. And I can understand why you would say so. But if you do not trust the 29.5 Ah number to be the nominal capacity, how can you know that I am wrong with my "sits at 29.5 Ah * 330-ish volt"? I cannot proof I am right either (don't even want to). Just saying I do not believe that I can drive 45 or even more km from just 6.5 kWh (144 Wh / km). Also, I have a hard time believing I am loosing 1.5 out of 8 kWh while charging.

Under load .. so when using over 30kw power form battery, that means 100A current, for a 40Ah cells is 2.5C discharge rate .. but it is even more evident at max power from battery, that is around 5C or 200A ... the voltage per cell drop significantly between 0.1 to 0.2v per cell .. (voltage drop is a waste energy that goes on increasing the battery temperature) .. so ... the 8,73kwh is already an optimistic energy level.

That you waste energy by draining the battery fast makes sense. But this doesn't mean that the wasted energy was not present in the battery when it was still full.

 

[elm70]

didn't say "330 volt", I said "330-ish volt". But even if I had used 330 volt in my calculation, it would not have made a difference, as:

328 v * 29.5 Ah = 9.676 kWh
330 v * 29.5 Ah = 9.735 kWh

...

Normally energy in a given battery is reported by nominal voltage x capacity ... in this case nominal voltage is 3.7v pre cell ... so conventional maths should use 296v * 29.5Ah = 8.73kwh .. 1kwh difference is not a little thing .. over 10% error

You know very well that while discharging the voltage of the battery drop from 4.1v down to 3.7v (@ ~30% SOC) .. fully discharge the lithium cell means to discharge it down to 3.0 or even 2.75v .. only going down to such voltage the total capacity is measured .. that in theory should be 29.5Ah (a value that can't be measure in the PHEV)

What you are saying is that the Ah number reported by the PHEV cannot be the 'normally reported nominal capacity'. And I can understand why you would say so. But if you do not trust the 29.5 Ah number to be the nominal capacity, how can you know that I am wrong with my "sits at 29.5 Ah * 330-ish volt"? I cannot proof I am right either (don't even want to). Just saying I do not believe that I can drive 45 or even more km from just 6.5 kWh (144 Wh / km). Also, I have a hard time believing I am loosing 1.5 out of 8 kWh while charging.

I don't understand why you keep using Max Voltage x Capacity ... as formula for battery energy

For be precise the formula is Integral V(t) * I(t) dt ... V(t) is the volt by time .. and I(t) current by time with Integral of I(t) dt the battery capacity... this formula can be simplified assuming a constant discharge .. and then it become a simple formula V_average * Capacity ... I agree that define this average volt can be tricky, but for sure average volt can't be the max volt by definition ...

As stated above normally the Average Volt used in this simplified formula is the Nominal Volt of the battery .. and in the PHEV is 3.7v per cell. I never spoke of Nominal Capacity

Anyhow .. all is very fuzzy ... simply because the real battery capacity is unknown ... these are in theory 40Ah battery used in the PHEV ... but for some strange maths from mitsubishi or other ... it is already declassed to 38Ah when reported in EvBatMon as "new"

The guy who made a video disassembling a PHEV battery pack, and creating out of it a "power wall" ... reported that battery capacity is ~40Ah ... but he did not show how he did measure this

 

[greendwarf]

PS: I'm on winter tyres .. and I plan to keep these rubber for all the year ... not going to spend money on a 2nd set of tyres .. maybe this explain a higher consumption especially at "speed"

Is this really cost effective? I understood that there is a significant drop in performance above 7c (especially when wet) but, also that wear for winter tyres rapidly increases with temperature - and it does get hot in summer in Poland.

 

[elm70]

Following up on an earlier post... I've a 2.5yo PHEV with battery capacity rated at 76% and range rarely indicated above 22-24km. We had an exceptionally hot couple of days in the summer 2015 and saw a huge drop in estimated range from low-40km to high-20km. We spoke with the dealer and was told its the A/C but if we wanted to have evaluated it would take a few days or more. We passed as we were told its really just the system overestimating A/C consumption. I didn't exactly believe and though range eventually bounced back above 30km it was never 40km again. We have a garage but during the day the car is often in the sun. No where are we told you must park in the shade... We've never fast charged, such doesn't exist here and 95% of the charging is at night.

What's the dealer procedure for evaluating battery condition? Few hours, day, days?

I was told by a local dealer that battery evaluation can be done only when the car is fully charged .. and it should take less then 1 hours ... at time this dealer did not even had a charger :shock: ... since my car is an import and here the PHEV are extremely rare

In practice .. EvBatMon can tell you the battery status in few seconds

EV range change a lot by having AC on or not .... my PHEV reduce by ~10km the EV range when I click on AC ... it is very simple to test it ... just start the car after full charge and check the range .. and then click on AC ... and click it off again ...

40km range is what my PHEV report now ... my best value I have seen so far is 41km

Yes battery degradation happen when the lithium cells are stored at above 40deg especially if fully charged ... how much ... I don't know ... I have years of experience on using Lithium battery for RC Hobby cars and aeroplanes/drones .... but I store my battery in fresh environment .. and I avoid to leave them in a car if this is under the sun.
If you have EvBatMon ... you may check what is the temperature of the battery once you come back to the car left under the sun ... I would expect that is way more fresh in the battery compartment then not on the cabin ... get above 40deg ... it sounds very hard in Europe, since battery should not be more hot the normal outside temperature ... they should not get an impact from the heat in the cabin due to the sun exposure

 

[elm70]

PS: I'm on winter tyres .. and I plan to keep these rubber for all the year ... not going to spend money on a 2nd set of tyres .. maybe this explain a higher consumption especially at "speed"

Is this really cost effective? I understood that there is a significant drop in performance above 7c (especially when wet) but, also that wear for winter tyres rapidly increases with temperature - and it does get hot in summer in Poland.

Hot days are few and not so hot in poland ... but yes .. it happen to get over 30deg in summer here

The PHEV want to be driven in "grandpa" style .. for be EV efficient ... so tyre consumption is limited even if it gets accelerated by high temperature.

Once consumed .. I will put in a all seasons rubbers

Cost for new summer rubbers and new rims ... I bet it is in the 1000 Euro zone, if not even more .. plus time and space for store the additional set of tyre .. so I'm quite sure is more money efficient to keep the tyres which my car got sold to me (I got it 2nd hand) .. which look to have still quite some life left, possibly less then 30% consumption ... anyhow .. once consumed .. I will be more happy with a all seasons rubber

 

[jaapv]

The braking distance of winter tyres at higher temperatures (i.e. over 7º) is progressively longer than summer tyres. (up to 30% at 30º ) as is their loss of cornering grip. Do take that into consideration in your driving style!

Winter tyres are environmentally undesirable in summer as they produce considerably more fine (rubber) dust than summer tyres.

 

[elm70]

And then there is the "EV average" meter. Not very useful, as it jumps all over the place, but in my car the most seen values are between 4.5 and 7.0 km/kWh, with the emphasis about 5-6.

I think it update every 1km or even a bit less .. on a short trip (2.3km per google maps) I see this value changing twice, and I guess I was not far away for get a 3rd update

Yesterday I managed to spot a 1kwh/100km ... at 1kwh/100km .. I can drive 600km with my PHEV in EV mode :mrgreen:

1kwh/100km was shown short after I reduce my speed from 100km/h down to 30km/h due to and exit from a fast way to normal urban street

 

[elm70]

The braking distance of winter tyres at higher temperatures (i.e. over 7º) is progressively longer than summer tyres. (up to 30% at 30º ) as is their loss of cornering grip. Do take that into consideration in your driving style!

Winter tyres are environmentally undesirable in summer as they produce considerably more fine (rubber) dust than summer tyres.

I recently seen a video of somebody testing breaking distance from 60mph down to a stop ... using same car .. with summer and winter tyres, in summer conditions .. and difference in breaking space was not that much .. around 5% difference if I recall right.

About "rubber dust" ... I guess it is very very marginal ... else .. I will get my tyres consumed in no time .. instead after 20.000 or more km.

For me ... the main disadvantage is extra rolling noise, and extra rolling resistance

Also .. winter tyres may get worst performance after one summer season usage ... due to extra heat cycles on the rubber ... but ... driving 95% of time in urban environment .. it should not cause the rubber to heat too much either

I'm not say it is common practice .. but it is not exceptional that some cars here keep winter tyres for all the year. Some cheap one do keep even summer tyres all the year, but this is more exceptional and way more "criminal"

Anyhow ... buy a summery tyre set .. is even more expensive then trash my winter tyres and replace with an all seasons one ... so .. once they will get consumed ... I will replace them ... I'm not going back on handling two set of tyres like I had in the previous cars

PS: About driving style .. after over 6 months of PHEV ... I'm almost 100% grandpa style ... this car, if people care to avoid to start ICE .. it does really transform the old driving attitudes

 

[Grigou]

EV range change a lot by having AC on or not .... my PHEV reduce by ~10km the EV range when I click on AC ... it is very simple to test it ... just start the car after full charge and check the range .. and then click on AC ... and click it off again ...

Estimated EV range changes a lot, but real EV range changes only a little bit.
Mitsubishi overestimated the importance of the air-conditioning consumption in the range calculation.
You can confirm that if you look for a long time at the left circular watt meter which shows the aircon consumption, and make your own estimation

 

[anko]

When I checked early may, my Ah number was 29.5. Now, little over one month later, is is 28.9 :shock: :shock: :shock:

 

[elm70]

Also my PHEV is in constant decline ... now I'm down to 35.6 from 35.7 ...

Driving now in B0 all the time .. and rescheduled the charging timer for starting later in the night

Also .. noticed something strange ... at 3.80v per cell .. EvBatMon state I'm only 28.5% real SOC .. and this sound crazy ... it is totally fine to store Lithium cell at 3.75v per cell .. even 3.70 is quite fine ... for the PHEV at 3.80 I'm already below the 0% .. managed to go below 30% SOC only by very low power usage, else ICE would have kick in.

As well .. I know for fact that between 3.80 down to 3.70v there is quite much juice left ..

In my opinion is worst to keep the battery at 4.10v per cell, then not at 3.70v .. yes .. go below 3.70v it is not recommended .. but put this border at 3.8 is "extreme"

Maybe I need a firmware update in my PHEV

 

[anko]

.. but put this border at 3.8 is "extreme"

The border for the battery is not at 26.5 % SOC (and associated cell voltage) but at 14% SOC (and associated cell voltage). Only when SOC reaches 14%, your car will come to a complete stop as the battery cannot deliver anymore power.

 

[elm70]

My issue is the definition of real SOC.

Looking at internet I did find the following table for a Li-Ion cells:
4.2V – 100%
4.1V – 87%
4.0V – 75%
3.9V – 55%
3.8V – 30%
3.5V – 0%

But based on how it is discharged the guy also got :
4.20 volts – 100%
3.97 volts – 80%
3.85 volts – 60%
3.77 volts – 40%
3.72 volts – 20%
3.58 volts – 0%

Somewhere else I find 3.80v being 36% SOC

Does the PHEV is able to count the Ah consumed from a full charge at 4.10v ?

I had my PHEV reporting few km EV range left, with voltage per cell at 3.85
And EvBatMon stating 26.5% SOC .. at 3.801V per cell

So ... something is telling me that the maths used in the PHEV is "odd", and as well ... I really doubt that estimated battery capacity and battery condition it is accurate

As result ... I think the PHEV can have a shorter EV range then in ideal mode (considering optimizing battery degradation) .. and does force to keep the battery stored most of the time at high voltage, which is not healthy ...

In my opinion the battery usage should be between 4.05v down to 3.75v .. under 3.72 should start the reduction in power .. and under 3.70v the car should be stopped.

As far as I know ... these different battery level are sort of configurable on the PHEV .. Mr. Vtech .. is able not only to increase the power from battery from 60kw to 110kw, in 10kw steps (or even more precisely) .. but as well if I recall right there are CAM commands capable to change the % for SOC which kick in ICE

Who know .. maybe the car can also change these levels based on battery condition .. like the Ampera is doing that totally hide the battery degradation from the EV range unless the battery degradation is getting very high

 

[HHL]

Since the state of the battery is determined by the chemicals within, it is probably not possible to predict the capacity with 100% accuracy by simply measuring what goes in and out. As the PHEV never allows a full discharge, it would be difficult to accurately recalibrate.
The comments by Anko and Jaap stating that in practice they have not noticed a reduction in EV range commensurate with the reduced capacity shown by the measurement, would bear that out.
My car shows 34Ah and in day to day use the range seems to be just the same as it was when I bought it nearly 2 years ago.
Also, the actual kWh it takes to charge from 1 bar on the meter to full has not changed noticeably, sometimes it takes 8.5kWh, other times more than 9.

 

[elm70]

For me ... for compare apple to apple ...

It would be nice to know what is the "rest" voltage of the battery pack when EV range is zero or low, and as well the EvBatMon real SOC indicated.

Same would be important to know the voltage per cell after the PHEV has been fully charged.

For my understanding if the Lithium battery get degradation it will lose capacity especially in the "high voltage" range.
So for keep the same range with and older battery .... the PHEV should consider 30% a lower voltage

Also it will be interesting to know if the PHEV does charge above 4.10v when the battery is getting older.

Otherwise .. I can also assume that people that get more familiar with the PHEV are abel to drive more "ECO .. so even if there is less battery capacity, by modulating the accelerator is possible to achieve the same range as in the first usage of the PHEV

 

[GreyBigFoot]

Mine's been loosing steadily 0.1Ah every 650kms on the past 10.000kms...

Still I've been managing regularly to get 106% of SOC, measured 30 minutes after full charge.

Today, out of the blue the battery capacity increased 0.5Ah!

Not that I'm very surprised with this... Such has been previously reported by other forum members.

Still, it seems there is some to be understood about how the management unit is handling all those cells :s

 

[Futuresystem]

G'day all from Brisvegas (Brisbane Australia).
Back in March we bought an ex-corporate Mitsubishi PHEV, 16,000 klms on the odo built in Jun 2014, first registration not till Jan 2016, so we are in warranty till Jan 2021. My wife loves it, I love it, so much more pleasant to drive in silent mode much of the time, especially in heavy traffic, (which we all obviously hate).

I decided to lash out on the $47 to buy EvBatMon app, and have hooked it up a couple of times over the last day or two to my iPhone, though often find it doesn't connect properly or give me readings on the first try. Does anybody have any tricks to have it work first time, every time. (I often have to close the app and restart it initially after the OBDII wifi is connected.)

Anyway, we are now at 21,000 klms and showing 35.1 Ah capacity from EvBatMon, which is right in the middle of the graph for that mileage from my understanding- which is good. I was a little bit concerned that the battery might have suffered from long storage, but apparently not, which is good news.

Anyway I'm still learning and the more knowledge the better.
One thing I discovered over the weekend is that you can't do a long steep climb, then expect to regain all that power on the way back down the hill- it obviously protects the battery to keep it from overheating, and not much regenerative braking is available when used like that. I think next time I do that particular drive (it's about 100 klms round trip) I'll press the "save" button on the way up the hill to keep the battery cool, thus letting the ICE do most of the work, then hopefully will gain more regenerative braking on the way down the other side. Has anyone else noticed this?

Thanks in advance

 

[maby]

... it obviously protects the battery to keep it from overheating, ...

It's more a case of protecting the First Law of Thermodynamics, really