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

[maby]

...
My battery sits at 29.5 Ah. And yet, I still manage 45 km (real km, not just predicted range) every now and then. With the current temperatures, I can achieve my daily commute of 2 x 40.5 km on electricity without to much trouble, unless I have a very strong head wind. This does surprise me, I must say.
....

It surprises me too! The absolute best EV range I ever got out of ours was 48km and that was driving very gently when the car was a couple of weeks old!

 

[GreyBigFoot]

Maybe, the low SOC buffer is related to the currently available capacity, not the original capacity.

That would make perfect sense... Managing the low buffer as the battery capacity is reducing...

Or else we'll never have the opportunity to use those last 30% of SOC...
And let's not forget this is a hybrid car, as long as there is petrol in the gas tank it will keep on running.

I can generally see about 10Ah reported when Hybrid mode starts to kick-in which is about 28% of SOC.

 

[HHL]

My car shows just under 90% with EVBATMON, it is 3 years old and has 27,000km on it. I charge it just about every day, but it is not always down to where the engine starts. My friend's car which is the same built date, has over 50,000km on it, he does a daily commute of about 100km with daily charging only at home, EVBATMON reports 95%. Had my car for about 18 months and initially it showed just under 92%, so it really hasn't changed much but was surprised that his is holding up so well as the battery cycled much more.

 

[Grigou]

...

Maybe, the low SOC buffer is related to the currently available capacity, not the original capacity.

Very likely I think. At least in percentage, not in absolute value.

So it doesn't change the % of degradation, and if you've lost 20 % of capacity you should have lost 20 % of range.

My battery condition is 85 % and I can confirm that I've lost about 15 % of range I think.

 

[anko]

...

Maybe, the low SOC buffer is related to the currently available capacity, not the original capacity.

Very likely I think. At least in percentage, not in absolute value.

So it doesn't change the % of degradation, and if you've lost 20 % of capacity you should have lost 20 % of range.

My battery condition is 85 % and I can confirm that I've lost about 15 % of range I think.

Yeah, that was a stupid remark of mine, I guess. Altogether, I know for a fact that the engine starts at the same SOC percentages (depending on speed, of course) as it did before.

If the buffer had been fixed in terms of Ah, going down from 37.4 Ah to 29.5 Ah (like mine did) would have meant a reduction in usable capacity of 28% instead of 21%.

 

[zzcoopej]

My battery sits at 29.5 Ah. And yet, I still manage 45 km

Correct me if I'm wrong -
29.5Ah x 300V = 8850 Wh.
8850/45km = 197 Wh/km

This is pretty close to the figure I use for the PHEV of 190Wh/km and agrees with others findings eg http://www.aevasa.kestar.com.au/docs/2014_Mitsubishi_Outlander_PHEV.pdf

However its nowhere near the sticker values of 134Wh/Km and 52Km range, but then we already know no-one drives the PHEV like they do in the tests.

Working on "new" values - 40Ah x 300V / 52Km = 231 Wh/km, so its easy to conclude that the PHEV is hiding a lot of capacity (134 vs 231 is a big gap!).
I've actually long held a hunch that the PHEV might even have the same 50Ah cells as the iMiEV just stamped as 40Ah to allow them to degrade with no real loss of range. 40Ah/50Ah magically = 80% .... remember the Mitsubishi claim of "80% capacity after 10 years"?

 

[elm70]

My car shows just under 90% with EVBATMON, it is 3 years old and has 27,000km on it. I charge it just about every day, but it is not always down to where the engine starts. My friend's car which is the same built date, has over 50,000km on it, he does a daily commute of about 100km with daily charging only at home, EVBATMON reports 95%. Had my car for about 18 months and initially it showed just under 92%, so it really hasn't changed much but was surprised that his is holding up so well as the battery cycled much more.

This sort of confirm my "theory"

Your friend car does stay short time fully charged .... every morning his battery got "fully" discharged ... and I expect it get top up only in the night .. so .. possibly it is fully charged for 3/4h a day .. and in ideal discharged state for over 15h a day.

I guess your PHEV does stay longer at fully charge status and not so often down to the ideal "discharged" status

PS: The PHEV while using ICE/Hybrid mode does cycle the battery in the most battery friendly voltage range

 

[elm70]

My battery sits at 29.5 Ah. And yet, I still manage 45 km

Correct me if I'm wrong -
29.5Ah x 300V = 8850 Wh.
8850/45km = 197 Wh/km

This is pretty close to the figure I use for the PHEV of 190Wh/km and agrees with others findings eg http://www.aevasa.kestar.com.au/docs/2014_Mitsubishi_Outlander_PHEV.pdf

However its nowhere near the sticker values of 134Wh/Km and 52Km range, but then we already know no-one drives the PHEV like they do in the tests.

Working on "new" values - 40Ah x 300V / 52Km = 231 Wh/km, so its easy to conclude that the PHEV is hiding a lot of capacity (134 vs 231 is a big gap!).
I've actually long held a hunch that the PHEV might even have the same 50Ah cells as the iMiEV just stamped as 40Ah to allow them to degrade with no real loss of range. 40Ah/50Ah magically = 80% .... remember the Mitsubishi claim of "80% capacity after 10 years"?

29.5Ah is battery "estimated" capacity (it is not a measured value, since it would need a full charge and discharge cycle, something that never happen in the PHEV)

PHEV is designed to leave 26% (more or less) capacity in the battery before kick in the ICE .. so from 29.5Ah only 21.8Ah are available

Calculate the KWh is a bit tricky .. since fully charge the battery should be 328V .. and at 26% should be around 296 ... but yes let's consider 300v as average voltage (under load the voltage of the main battery can go down to around 288v and even less)

21.8Ah x 300w is just 6.5KWh

Making 45km with it, implies using 145Wh per km .. that is quite "impressive" ... my PHEV on the dash does show "random" number about the EV consumption in KWh / 100km .... but normally it is anywhere from 26KWh to 13Kwh ... (at 120km/h I'm quite sure I see around 50kw power used .. and this implies around 400wh per km .. that's explain why on the motorway my PHEV run out of EV only after around 18km)

If I remember well Tesla S are reported to use at "best/with care" 300Wh per miles .. so 187wh per km .. so .. I'm impress that Anko PHEV can do much better then a Tesla S

 

[anko]

I'm impress that Anko PHEV can do much better then a Tesla S

Maybe the Tesla guys are better at math :mrgreen:

From empty (as empty as it gets) to full, my car accepts about 8 kWh. This does include losses in the charger and wires from the main switchboard to where my car is, but at the end it should be a bit more than the 6.5 kWh you calculate. So, my PHEV is not doing that good. And otherwise, indeed my car must be doing better than a Tesla S, as it is what it is

 

[elm70]

I'm impress that Anko PHEV can do much better then a Tesla S

Maybe the Tesla guys are better at math :mrgreen:

From empty (as empty as it gets) to full, my car accepts about 8 kWh. This does include losses in the charger and wires from the main switchboard to where my car is, but at the end it should be a bit more than the 6.5 kWh you calculate. So, my PHEV is not doing that good. And otherwise, indeed my car must be doing better than a Tesla S, as it is what it is

:shock:

From 8kwh to 6.5kw .. is 18.7% loss .. it sounds realistic to me ... what does says MMCS about your charge I doubt that MMCS seen this as 8kwh charge in the charging cost page.

Is your EvBatMon reporting 29.5Ah ?

Can we agree that this is 29.5Ah * 300v -> 8.8kwh ?

That means your car instead of 12kwh as from factory has only 8.8kwh capacity .. both new and old .. 74% is usable and 26% is kept "unused" for avoid faster battery degradation

So .. 8.8kwh x 74% = 6.5kwh

What can be wrong with my maths ? :evil:

Anyhow ... I don't doubt your words .. I'm sure you can do 45km .. it is how slow you drive these 45km the question to me ... I'm sure I can do 70km with my PHEV .. but I know it will take me over 2h drive to prove it :mrgreen:

 

[anko]

:shock:

You present calculations that lead to the conclusion that my PHEV is more efficient than a Model S. If the last bit is not true (and I cannot imagine it is), than the first bit must be wrong. Why are you shocked? ;-)

From 8kwh to 6.5kw .. is 18.7% loss .. it sounds realistic to me ...

I think / hope losses in the charging process are far less than 18.7%.

Is your EvBatMon reporting 29.5Ah ?

No, my own tool is. But deep down, EvBatMon was based on my own tool, so I am pretty sure EvBatMon will report the same. And so does the dealer.

Can we agree that this is 29.5Ah * 300v -> 8.8kwh ?

That means your car instead of 12kwh as from factory has only 8.8kwh capacity .. both new and old .. 74% is usable and 26% is kept "unused" for avoid faster battery degradation

So .. 8.8kwh x 74% = 6.5kwh

What can be wrong with my maths ? :evil:

What happens to the voltage under load does not appear all that relevant to me.
The question is: what does "26% buffer" mean? Is it 26% of max kWh? Or 26% of max Ah?

When fully charged, the battery sits at 29.5 Ah at 330-ish volt. This is 9.7 kW.

If "26% buffer" means 26% of available kWh, it translates to 9.7 * 0.74 = 7.2 kWh usable.
If it means 26% of max Ah, it translates to 9.7 - (29.5 * 0.26 * 296) = 7.4 kWh usable.

Both numbers make more sense to me than the 6.5 kWh usable you came up with. Both in terms of driving efficiency and in terms of charging efficiency.

 

[jaapv]

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.

 

[anko]

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 have a Wh/km meter on my own dashboard: multiply battery voltage with amperage and divide by speed. Typical value driving 80 km/h is 160 - 190 Wh/km, depending on wind. Obviously, it responds directly to changes in throttle position and wind / road conditions, but otherwise it seems pretty stable / reliable. I don't understand why the EV average meter is so 'wild'.

 

[jaapv]

Indeed. If it really were a decent average, it would be far more stable.

 

[HHL]

Indeed. If it really were a decent average, it would be far more stable.

It seems to recalculate every 5 minutes and therefore only displays the most recent figure. Mine displays kwh/100km, so just move the decimal 2 places and you have wh/km.
I suburban driving it seems to average around 200wh/km.

 

[elm70]

When fully charged, the battery sits at 29.5 Ah at 330-ish volt. This is 9.7 kW.

Maths and physics is not much questionable

What state above is simply wrong

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.

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)

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.

 

[elm70]

Indeed. If it really were a decent average, it would be far more stable.

It seems to recalculate every 5 minutes and therefore only displays the most recent figure. Mine displays kwh/100km, so just move the decimal 2 places and you have wh/km.
I suburban driving it seems to average around 200wh/km.

I'm not sure it does recalculate every 5min or every X meters .. I think it is more up to the distance, since I never seen this value change while I was stopped at a traffic light. .. I think it show a new value every 1km or every 2km.

Definitely every time it shows and update value, it start counting from zero, and this means that ... if it happen the PHEV had a major regen breaking inside this "small" measuring window .. it show up very low consumption .. if it happen that the car did accelerate from 0 to 100km/h .. then it show a huge consumption

I'm using kwh/100km .. and I see value between 5kwh to 40kw/100 , but I'm quite sure I did get even lower and higher values.. so from 50wh to 400wh per km. It would be nice to have a proper average value for the trip .. like the fuel consumption (which in my case is always zero, so not much useful for me) but apparently they implemented some lazy dummy code in this area of the MMCS

 

[HHL]

Indeed. If it really were a decent average, it would be far more stable.

It seems to recalculate every 5 minutes and therefore only displays the most recent figure. Mine displays kwh/100km, so just move the decimal 2 places and you have wh/km.
I suburban driving it seems to average around 200wh/km.

I'm not sure it does recalculate every 5min or every X meters .. I think it is more up to the distance, since I never seen this value change while I was stopped at a traffic light. .. I think it show a new value every 1km or every 2km.

Definitely every time it shows and update value, it start counting from zero, and this means that ... if it happen the PHEV had a major regen breaking inside this "small" measuring window .. it show up very low consumption .. if it happen that the car did accelerate from 0 to 100km/h .. then it show a huge consumption

I'm using kwh/100km .. and I see value between 5kwh to 40kw/100 , but I'm quite sure I did get even lower and higher values.. so from 50wh to 400wh per km. It would be nice to have a proper average value for the trip .. like the fuel consumption (which in my case is always zero, so not much useful for me) but apparently they implemented some lazy dummy code in this area of the MMCS

Well, it is simple enough to work out using the energy taken to recharge, if you do say 40km and then it takes 8kWh to charge it up again, you have 200 Wh.... that figure I found is fairly consistent and compares well with other EV's around, considering it lugs a bit more weight than a pure EV.

 

[jaapv]

Sorry, I should have added that my figures were when attempting to drive at a more or less constant speed, traffic permitting.
The difference between observations in this forum may come from the circumstance that roads over here are mostly completely flat without inclines, not even unnoticeable ones, and the road surface is usually very smooth.

 

[elm70]

Well, it is simple enough to work out using the energy taken to recharge, if you do say 40km and then it takes 8kWh to charge it up again, you have 200 Wh.... that figure I found is fairly consistent and compares well with other EV's around, considering it lugs a bit more weight than a pure EV.

Right ..

My car recharge (now in spring time) around 6/6.5kwh a day, and does 25/30km a day ... but I'm often using preheat in the morning ..

That's lead to average ~200wh per km ...

Anko .... apparently can drive more ECO then me ... also I'm wondering if at 80km/h I can get such low consumption on my PHEV.

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"