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

[robdickinson]

Some of us are outside the manufacturers warranty situation also :/

 

[elm70]

Some of us are outside the manufacturers warranty situation also :/

Unless somebody stop regular servicing ...
Isn't 8 years warranty over a battery failure ?

So all the PHEV should be cover by a "disaster" event (till 2021) .. but possibly not by massive battery degradation

 

[anko]

Some of us are outside the manufacturers warranty situation also :/

Unless somebody stop regular servicing ...
Isn't 8 years warranty over a battery failure ?

So all the PHEV should be cover by a "disaster" event (till 2021) .. but possibly not by massive battery degradation

I think it is the other way around. In NL, early PHEVs had 2 (or 3) year overall warranty and 5 year against failure of components related to the EV drive train. Later they issues a statement where they guarantee 67% SOH for 160.000 km / 8 years for early PHEVs.

So, what if it fails in the 6th or 7th year? :mrgreen:

 

[elm70]

Interesting

Where I can find this statement about 67% of guarantee for 8y or 160k km ?
If it is valid for early PHEV in NL .. maybe it is also valid for NL PHEV exported inside EU ... who knows :mrgreen:

So ... it sounds your PHEV can qualify for this guarantee "soon", since your PHEV is not far from 67% SOH.

 

[anko]

You did not use lot of power from your car ... I think weak cell can be better seen at high current .. so when you are as close as possible to the 60kw power limit ...

Indeed, I didn't. More or less purposely. As because of the low SOC (and the bad state of my battery) the engine would come on and provide power. And battery discharge would be even lower (if I would not change into charge). I'll give it another shot some time. Maybe I can do this tomorrow. Will try to monitor full daily commute (my wife needs the full EV tomorrow, so I will be driving the plug in :mrgreen: )

Did a new test.

First coloured column shows power demand (more red is higher, more green is lower or even regen)
Second coloured column is diff between highest and lowest cell (more red is bigger diff, more green is lower diff)



Full spreadsheet: https://www.dropbox.com/s/qukw38muaskgil0/cell%20stuff%20high%20power.xlsx?dl=0

 

[robdickinson]

Some of us are outside the manufacturers warranty situation also :/

Unless somebody stop regular servicing ...
Isn't 8 years warranty over a battery failure ?

So all the PHEV should be cover by a "disaster" event (till 2021) .. but possibly not by massive battery degradation

My car is a Japanese import into New Zealand, not sure how Mitsubishi NZ would view that for big jobs like battery replacements etc?

I know other brands are having dodgy air bags replaced, and nissan is looking at the 30kwh battery issue on imports here.

 

[maby]

...

I think it is the other way around. In NL, early PHEVs had 2 (or 3) year overall warranty and 5 year against failure of components related to the EV drive train. Later they issues a statement where they guarantee 67% SOH for 160.000 km / 8 years for early PHEVs.

....

Are you sure about that? I thought that someone here had discussed this with Mitsubishi and they claimed that the original comment about extending the battery SOH warranty to early cars was an error. Mine is a late 64 car and I don't think we have any SOH warranty - just the relatively useless total battery failure warranty.

 

[anko]

Yes, I am.

 

[jaapv]

So am I.

 

[elm70]

You did not use lot of power from your car ... I think weak cell can be better seen at high current .. so when you are as close as possible to the 60kw power limit ...

Indeed, I didn't. More or less purposely. As because of the low SOC (and the bad state of my battery) the engine would come on and provide power. And battery discharge would be even lower (if I would not change into charge). I'll give it another shot some time. Maybe I can do this tomorrow. Will try to monitor full daily commute (my wife needs the full EV tomorrow, so I will be driving the plug in :mrgreen: )

Did a new test.

First coloured column shows power demand (more red is higher, more green is lower or even regen)
Second coloured column is diff between highest and lowest cell (more red is bigger diff, more green is lower diff)



Full spreadsheet: https://www.dropbox.com/s/qukw38muaskgil0/cell%20stuff%20high%20power.xlsx?dl=0

The spreadsheet is "encrypted" and the picture except for the colors can't be read.

Based on color code apparently on higher power there is higher cells voltage unbalance , so apparently some cells has much higher IR then other

 

[Harald]

The spreadsheet is "encrypted" and the picture except for the colors can't be read.

I just opened the Dropbox Link?

Full spreadsheet: https://www.dropbox.com/s/qukw38muaskgil0/cell%20stuff%20high%20power.xlsx?dl=0

Might be that the numbers in the XLSX are shown as Hexadecimal values?

 

[anko]

Need to download the XLS. Not show in Browser window.

A few of the first columns are indeed the raw hexadecimal data from the OBD port. But starting from column H, you get the good stuff.

BTW: I appreciate you guys making an effort :!:

 

[elm70]

Battery isn't perfectly balance at the begin of XLS, but it is almost the same unbalance at the end. So ... none of the cell is looking weaker then other

It is "strange" to see that at apparently 97.98% SOC, voltage per cell is only 4.03 ... it should be 4.08 at least

Apparently your PHEV can go down to 24.7% SOC ... mine has ICE kick in at 30% and never goes below 30% ... unless I drive ultra slow and with very little power request (your PHEV did pulse even 55kw power while at very low SOC)

The cell on column BI .. has an IR higher then other .. since it jump from highest voltage to lowest voltage based on the load

Max delta voltage is 0.039 which in theory is very bad ... but in practice it is only due to different IR inside the battery pack ... so you pack still have similar capacity inside cells but this cells has significant difference in IR (was this only now or was this cell with high IR also when "new" ?)

BI cells .. has an estimated IR of 1.7mOhm ... vs 1.5mOhm IR from AX and AY cells

In my view .. there is nothing abnormal ... just "normal" battery degradation

 

[anko]

Many thanks for elaborate analysis!

Apparently your PHEV can go down to 24.7% SOC ... mine has ICE kick in at 30% and never goes below 30% ... unless I drive ultra slow and with very little power request (your PHEV did pulse even 55kw power while at very low SOC)

I can go to 55 kW (and a bit beyond) on very low SOC (even far below 24.7%). This is the ongoing discussion between Maby and myself. I think this data 'proves' that you do not need to maintain high SOC to get full power from the battery But it doesn't mean the engine didn't kick in. It did. As a matter of fact, part of the power spike is probably caused from driving the generator to crank up the ICE.

It is "strange" to see that at apparently 97.98% SOC, voltage per cell is only 4.03 ... it should be 4.08 at least

Could this be a result of the BMU underestimating capacity / SoH?

Max delta voltage is 0.039 which in theory is very bad ... but in practice it is only due to different IR inside the battery pack ... so you pack still have similar capacity inside cells but this cells has significant difference in IR (was this only now or was this cell with high IR also when "new" ?)

So, if it does not affect capacity, what does it affect?

 

[elm70]

It is "strange" to see that at apparently 97.98% SOC, voltage per cell is only 4.03 ... it should be 4.08 at least

Could this be a result of the BMU underestimating capacity / SoH?

If the BMU or charger can't charge up to ~4.09v per cell .. yes, the battery capacity (SOH) will be reduced by the BMU logic

Did you check which voltage you have immediately after full charge ... and , maybe after 1h / 2h or more from charging is completed and car left unused ?

Max delta voltage is 0.039 which in theory is very bad ... but in practice it is only due to different IR inside the battery pack ... so you pack still have similar capacity inside cells but this cells has significant difference in IR (was this only now or was this cell with high IR also when "new" ?)

So, if it does not affect capacity, what does it affect?

It does not affect capacity in the pure sense of capacity in Ah
A high IR, it implies that under heavy load the capacity in kWh will be reduced .. and potentially the cell with high IR can get more "hot"
IR is only impacting the efficiency ..

Note: Capacity should be always referred in Ah ... kwh of capacity it is tricky .. since any non ideal battery will have lower kwh capacity with high load compared to a low load ... actually due to voltage depression in lithium cell, even the capacity in Ah is reduced under heavy load .. but if the capacity is measure after a rest period ... this has almost no impact ... but looking how manufacture expose their datasheet ... each battery is declared to have a specific capacity in Ah based on a defined load ... since in this datasheet only continuous discharged is consider as benchmark

 

[anko]

Thanks again!

 

[anko]

It is "strange" to see that at apparently 97.98% SOC, voltage per cell is only 4.03 ... it should be 4.08 at least

Was 4.095 @ 99% this morning (about 5 hours after completing full charge)

 

[elm70]

It is "strange" to see that at apparently 97.98% SOC, voltage per cell is only 4.03 ... it should be 4.08 at least

Was 4.095 @ 99% this morning (about 5 hours after completing full charge)

OK ... then it is looking 100% normal .. even better then my PHEV

From your attached XLS this is in the first line
34,5 -22,47 322,4 -7,244328 97,98 4,023 4,033 0,010 4,027 4,027 4,027

Definitely in this case short after starting your PHEV the battery was seen at almost 98% but with only 4.03v per cell ... which is very strange
My PHEV after 10km trip and a 8h rest has 4.03v per cell

PS: I see up to 36kw power back on regen braking ... so you still must like to use B5
PPS: I have just seen a video about the usage of super capacitor in conjunction of lithium battery for EV ... the producer of super capacitor stated that the peak on regen braking does short the life of a lithium battery by a factor of 2 ... yes, not an impartial option ... but this has been always in line with my understanding of lithium battery "care" ... what he did not state was the huge cost of super capacitor, the issue to deal with capacitor with just 2.85v max each .. and the extra complexity for manage super caps in conjunctions with lithium in a car

 

[anko]

PS: I see up to 36kw power back on regen braking ... so you still must like to use B5

I do. But I think we can also get that using B0 + brake pedal? I am close to having a valid claim. For this capacity must be below 26 Ah before performing a recalibration procedure and must stay or drop below 26 Ah after the procedure. Procedure was performed at 25.9. Ah went up to 28. Now back at 27.4. It is a matter of time and distance. But I am running out of distance (still 3 years but only about 15.000 km before warranty expires), so I don't think this is the right time to start nursing my battery ;-)

PPS: I have just seen a video about the usage of super capacitor in conjunction of lithium battery for EV ... the producer of super capacitor stated that the peak on regen braking does short the life of a lithium battery by a factor of 2 ... yes, not an impartial option ... but this has been always in line with my understanding of lithium battery "care" ... what he did not state was the huge cost of super capacitor, the issue to deal with capacitor with just 2.85v max each .. and the extra complexity for manage super caps in conjunctions with lithium in a car

Interesting stuff indeed.

 

[elm70]

PS: I see up to 36kw power back on regen braking ... so you still must like to use B5

I do. But I think we can also get that using B0 + brake pedal? I am close to having a valid claim. For this capacity must be below 26 Ah before performing a recalibration procedure and must stay or drop below 26 Ah after the procedure. Procedure was performed at 25.9. Ah went up to 28. Now back at 27.4. It is a matter of time and distance. But I am running out of distance (still 3 years but only about 15.000 km before warranty expires), so I don't think this is the right time to start nursing my battery ;-)

Understood ...

Yes ... B5 is your friend now