Drive battery degradation and the out of whack IMO BMU.

[anko]

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.

I thought we had been there. This would not be a result of driving in Safe mode but a result of driving faster than 125 km/h most of the time. When driving between 65 and 125 km/h in Save mode you will see pretty much the same (dis)charge pattern as you see when driving in Normal mode with a depleted battery.

 

[STS134]

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:

Where do you get the idea that I use the ICE "most of the time" and rarely ever use the batteries? I go to the gas station about once every 600-800 miles in the PHEV, and in my older ICE only car, I had to do it about once every 350-450 miles. So I've roughly doubled the amount of distance I can go without going to fill up. It should be noted that the PHEV has about the same size gas tank, but gets only 25 mpg in ICE mode (as opposed to about 32 mpg combined in my ICE car). So the battery is actually being used what, about 40-60% of the time? I just refuse to use it on the freeway. Yesterday though, I did quite a bit of driving on surface streets and actually hit empty on the battery gauge. Took probably 60-90 minutes of driving to get it that far down, which is much less a 1C average discharge rate. This, despite the fact that I used Save mode on the freeway anyway earlier in the drive. Better to drain the batteries on the surface streets at a low C rate than on the freeway at a high C rate. This also helps save the ICE, which doesn't have to cycle on and off as much but can just run continuously for a time and then shut off. If my trip doesn't actually end up consuming all of the battery because it's short and/or a lot of it is on the freeway, then it's okay to arrive with half of your battery charge still left. In fact, this actually lowers your average DoD which is good for the battery as well. That's another thing that people seem to forget.

I thought we had been there. This would not be a result of driving in Safe mode but a result of driving faster than 125 km/h most of the time. When driving between 65 and 125 km/h in Save mode you will see pretty much the same (dis)charge pattern as you see when driving in Normal mode with a depleted battery.

Sure. But if the battery isn't actually depleted, it'll consume the battery in short order at those speeds, which is what's bad for the battery. Hence my saying that they dropped the ball. Between 50 mph and 78 mph, it'll consume the battery quickly and for no good reason other than it hasn't been programmed well. It really shouldn't do that unless the user selects EV priority mode. And, like a Tesla will do if you tell it to charge the battery to 100%, it should warn the driver that doing this frequently will kill your battery faster.

 

[greendwarf]

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:

Where do you get the idea that I use the ICE "most of the time" and rarely ever use the batteries?

I didn't - I merely pointed out that the reverse of your "complaint" is equally true. There are many PHEV drivers, especially business users, who were attracted by the financial incentives but never charge the batteries. :roll:

 

[jaapv]

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.

I thought we had been there. This would not be a result of driving in Safe mode but a result of driving faster than 125 km/h most of the time. When driving between 65 and 125 km/h in Save mode you will see pretty much the same (dis)charge pattern as you see when driving in Normal mode with a depleted battery.

Agree. I bought this car to use, not to press buttons. A piano is more suitable for that.
So one might, possibly, reduce the wear of the battery marginally by applying all kinds of theories. It is like saying: buy a Porsche, but never negotiate a bend faster than 15 MPH, to make sure that the tyres and suspension don't wear. :roll:

 

[Woodman411]

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.

I thought we had been there. This would not be a result of driving in Safe mode but a result of driving faster than 125 km/h most of the time. When driving between 65 and 125 km/h in Save mode you will see pretty much the same (dis)charge pattern as you see when driving in Normal mode with a depleted battery.

Agree. I bought this car to use, not to press buttons. A piano is more suitable for that.
So one might, possibly, reduce the wear of the battery marginally by applying all kinds of theories. It is like saying: buy a Porsche, but never negotiate a bend faster that 15 MPH, to make sure that the tyres and suspension don't wear. :roll:

Nice illustration, as long as the Porsche driver understands that by burning rubber and taking high speed turns, that $4,000 tire set will not last long. Somehow though I don't think Porsche drivers will be confused/angry that their tires didn't last as long as the tire warranty.

 

[user 1877]

A few years ago I was lucky enough to have a Porsche Boxster as a company car including private mileage fuel. Now I am retired I am delighted to own an Outlander PHEV. Guess what, I drive the cars somewhat differently :lol:

 

[STS134]

I think something is wrong with my BMU. In about 2.5 months of owning this car, I've seen the SoH go from 99.2% to 96.1%. Despite the fact that my typical usage pattern is to charge the batteries to 12/16 bars on the gauge (around 4.03-4.05V/cell) and then discharge them only to 8/16 bars on the gauge, before charging them back up again, so only a 20% DoD and max charge level of around 75-80%. There's no way the batteries should be degrading this quickly. More than 1% a month?!? It's currently on track to be at around 65% SoH in around 3 years. If that actually happens that I'm getting a free replacement under warranty.

 

[anko]

By not (never) charging your batteries to full, you deny the BMU the chance to keep track of the actual capacity of your battery. It must then fall back to preprogrammed degradation trend lines, that include time and distance based degradation.

BTW: I lost 8.7% in the first 9 months. According to the BMU. Mitsu says, degradation is most when the car is new and settles down over time. Not sure that I agree.

 

[greendwarf]

I think something is wrong with my BMU. In about 2.5 months of owning this car, I've seen the SoH go from 99.2% to 96.1%. Despite the fact that my typical usage pattern is to charge the batteries to 12/16 bars on the gauge (around 4.03-4.05V/cell) and then discharge them only to 8/16 bars on the gauge, before charging them back up again, so only a 20% DoD and max charge level of around 75-80%. There's no way the batteries should be degrading this quickly. More than 1% a month?!? It's currently on track to be at around 65% SoH in around 3 years. If that actually happens that I'm getting a free replacement under warranty.

So only driving on EV most of time (similar to me) but what about longer journeys where you empty the battery. Are you getting less range? After 4 years and 30,000 miles I'm still getting around the 25 miles per full charge that I had when new. Of course, I haven't a clue what the BMU or SoH are up to either. :lol:

 

[elm70]

I think something is wrong with my BMU. In about 2.5 months of owning this car, I've seen the SoH go from 99.2% to 96.1%. Despite the fact that my typical usage pattern is to charge the batteries to 12/16 bars on the gauge (around 4.03-4.05V/cell) and then discharge them only to 8/16 bars on the gauge, before charging them back up again, so only a 20% DoD and max charge level of around 75-80%. There's no way the batteries should be degrading this quickly. More than 1% a month?!? It's currently on track to be at around 65% SoH in around 3 years. If that actually happens that I'm getting a free replacement under warranty.

It sounds the BMU software is not getting better in our Mitsubishi ...

It is also possible that your battery did not born with 100% capacity, and the BMU is quickly adapting to this.
Normally the change done by the BMU is just 0.1Ah difference every month

Anyhow ... a way to know how good is the battery is following:

-Fully charge the car.
- Drive in pure EV mode up to 0km ev range left, avoid start ICE .. else the calculation is more complex and there could be more errors
- Check on PHEVwatchDog the SOC .. it should be around 30% SOC -> 0% EV range .. around 10Ah left
- Let the car rest for 2 hours, without charge it
- Check again with the PHEVwatchDog ... is the car believe there is more then 10Ah left, it means the BMU was underestimating the battery capacity .. if there is less then 10Ah ... bad news ... your battery is worst then what BMU did estimate

 

[elm70]

So only driving on EV most of time (similar to me) but what about longer journeys where you empty the battery. Are you getting less range? After 4 years and 30,000 miles I'm still getting around the 25 miles per full charge that I had when new. Of course, I haven't a clue what the BMU or SoH are up to either. :lol:

Possibly you adopted to a more "soft" driving style

I can do almost the same EV km as when I got my car, even if I lost 8% capacity in these 2 years ... but I'm driving way more soft then at the beginning ... I was used to floor the gas pedal on my previous car very often ... on the PHEV the right foot need to be gentile else it will kick in ICE which is "annoying"

Compared to 2y ago ... now very often when I left unused the car for some hours, when I come back I lose often around 5km of range .. sign that the battery is even worst then what the BMU believe it is ...

 

[anko]

Anyhow ... a way to know how good is the battery is following:

-Fully charge the car.
- Drive in pure EV mode up to 0km ev range left, avoid start ICE .. else the calculation is more complex and there could be more errors
- Check on PHEVwatchDog the SOC .. it should be around 30% SOC -> 0% EV range .. around 10Ah left
- Let the car rest for 2 hours, without charge it
- Check again with the PHEVwatchDog ... is the car believe there is more then 10Ah left, it means the BMU was underestimating the battery capacity .. if there is less then 10Ah ... bad news ... your battery is worst then what BMU did estimate

My BMU believes my battery is at about 67% (26.2 Ah). When drained to 30%, there is about 7.8 Ah left. Not likely that number goes up to above 10 Ah after two hours of rest. According to the above, that would automatically mean my BMU is overestimating my battery capacity.

Should it no be something like: check if the Ah number has gone up or down after two hours of rest?

 

[elm70]

Anyhow ... a way to know how good is the battery is following:

-Fully charge the car.
- Drive in pure EV mode up to 0km ev range left, avoid start ICE .. else the calculation is more complex and there could be more errors
- Check on PHEVwatchDog the SOC .. it should be around 30% SOC -> 0% EV range .. around 10Ah left
- Let the car rest for 2 hours, without charge it
- Check again with the PHEVwatchDog ... is the car believe there is more then 10Ah left, it means the BMU was underestimating the battery capacity .. if there is less then 10Ah ... bad news ... your battery is worst then what BMU did estimate

My BMU believes my battery is at about 67% (26.2 Ah). When drained to 30%, there is about 7.8 Ah left. Not likely that number goes up to above 10 Ah after two hours of rest. According to the above, that would automatically mean my BMU is overestimating my battery capacity.

Should it no be something like: check if the Ah number has gone up or down after two hours of rest?

10Ah at 30% is for battery with high SOH:
With 100% SOH, 30% is 11.4Ah
With 95% SOH .. 30% is 10.8Ah ...

What I mean with 10Ah .. was an example ... what is important is to write down the SOC and Ah after a trip in EV mode from full to "0km EV range" ... let the car rest for 2h unused and uncharged .. and then check again the SOC and Ah ...

If Ah goes up while resting .. it means real SOH is bigger then the BMU believe it is
If Ah goes down .. SOH is less then what BMU report/believe

As we know .. SOH is an heuristic implementation from Mitsubishi ... which may not support all possible driving habit ...

 

[anko]

Should it no be something like: check if the Ah number has gone up or down after two hours of rest?

10Ah at 30% is for battery with high SOH:
With 100% SOH, 30% is 11.4Ah
With 95% SOH .. 30% is 10.8Ah ...

What I mean with 10Ah .. was an example ... what is important is to write down the SOC and Ah after a trip in EV mode from full to "0km EV range" ... let the car rest for 2h unused and uncharged .. and then check again the SOC and Ah ...

If Ah goes up while resting .. it means real SOH is bigger then the BMU believe it is
If Ah goes down .. SOH is less then what BMU report/believe

As we know .. SOH is an heuristic implementation from Mitsubishi ... which may not support all possible driving habit ...

So ... yes

 

[STS134]

By not (never) charging your batteries to full, you deny the BMU the chance to keep track of the actual capacity of your battery. It must then fall back to preprogrammed degradation trend lines, that include time and distance based degradation.

BTW: I lost 8.7% in the first 9 months. According to the BMU. Mitsu says, degradation is most when the car is new and settles down over time. Not sure that I agree.

Well I do charge the batteries up to full, at least once every 2 weeks or so. And I try to drain them all the way to the point where the ICE turns on as well, at least once every 2 weeks. Usually if this hasn't happened for 2 weeks, I'll intentionally run the battery all the way down and then charge it all the way back up.

 

[STS134]

Anyhow ... a way to know how good is the battery is following:

-Fully charge the car.
- Drive in pure EV mode up to 0km ev range left, avoid start ICE .. else the calculation is more complex and there could be more errors
- Check on PHEVwatchDog the SOC .. it should be around 30% SOC -> 0% EV range .. around 10Ah left
- Let the car rest for 2 hours, without charge it
- Check again with the PHEVwatchDog ... is the car believe there is more then 10Ah left, it means the BMU was underestimating the battery capacity .. if there is less then 10Ah ... bad news ... your battery is worst then what BMU did estimate

My BMU believes my battery is at about 67% (26.2 Ah). When drained to 30%, there is about 7.8 Ah left. Not likely that number goes up to above 10 Ah after two hours of rest. According to the above, that would automatically mean my BMU is overestimating my battery capacity.

Should it no be something like: check if the Ah number has gone up or down after two hours of rest?

10Ah at 30% is for battery with high SOH:
With 100% SOH, 30% is 11.4Ah
With 95% SOH .. 30% is 10.8Ah ...

What I mean with 10Ah .. was an example ... what is important is to write down the SOC and Ah after a trip in EV mode from full to "0km EV range" ... let the car rest for 2h unused and uncharged .. and then check again the SOC and Ah ...

If Ah goes up while resting .. it means real SOH is bigger then the BMU believe it is
If Ah goes down .. SOH is less then what BMU report/believe

As we know .. SOH is an heuristic implementation from Mitsubishi ... which may not support all possible driving habit ...

Hmm...I have my PHEV Watchdog set to display kWh so I don't know what those numbers mean. I never liked the Ah measurement because to convert to energy, you have to know voltage, and voltage is not constant throughout the full SoC range of the battery, varying from around 3.75-3.80V/cell up to around 4.10V/cell.

 

[anko]

Hmm...I have my PHEV Watchdog set to display kWh so I don't know what those numbers mean. I never liked the Ah measurement because to convert to energy, you have to know voltage, and voltage is not constant throughout the full SoC range of the battery, varying from around 3.75-3.80V/cell up to around 4.10V/cell.

How do you think PHEVWatchDog calculates kWh?

Shouldn't be to difficult to temporarily change display settings for the app? Anyway, mine currently sits at 7.9 Ah (while charging) which is translated by the Dog to 2.4 kWh. Total capacity sits at 26.2 Ah, which the Dog translates to 7.9 kWh. Current voltage is 309 volt. Must remember to check again when (near) full, to see what 26.2 translates to then.

EDIT - Now, at 322,1 total pack volt, remaining capacity of 26.2 Ah still translates to 7.9 kWh (which suggests approx. 330 volt is used in calculation). And current capacity of 16.9 Ah translates to 5.4 kWh (which suggests approx. 310 volt is used). Earlier current capacity of 7.9 Ah translated to 2.4 kWh (which suggested approx 330 volt was used).

 

[anko]

What I mean with 10Ah .. was an example ... what is important is to write down the SOC and Ah after a trip in EV mode from full to "0km EV range" ... let the car rest for 2h unused and uncharged .. and then check again the SOC and Ah ...

If Ah goes up while resting .. it means real SOH is bigger then the BMU believe it is
If Ah goes down .. SOH is less then what BMU report/believe

Mine when sown from 98.9% (25.9 Ah) immediately after a full charge to 98.5% (25.8 Ah) after 8 hours (rather than 2 as I had to go to sleep at some time ;-) ) Not a huge difference, but certainly not up.

 

[elm70]

What I mean with 10Ah .. was an example ... what is important is to write down the SOC and Ah after a trip in EV mode from full to "0km EV range" ... let the car rest for 2h unused and uncharged .. and then check again the SOC and Ah ...

If Ah goes up while resting .. it means real SOH is bigger then the BMU believe it is
If Ah goes down .. SOH is less then what BMU report/believe

Mine when sown from 98.9% (25.9 Ah) immediately after a full charge to 98.5% (25.8 Ah) after 8 hours (rather than 2 as I had to go to sleep at some time ;-) ) Not a huge difference, but certainly not up.

It is relevant if SOC go up or down while resting ... only after a trip (battery discharge) ... the more is discharged, the better ... ideally without ever using ICE, from a full charge status start

How the SOC change after a full charge I guess it is not much relevant ...

This is because the BMU assume the car has XX Ah .. it will monitor the current flow ... and when this accumulated flow cause to get only 30% of capacity left ... it will want to start ICE .. before starting ICE .. if the car get stopped and 2h of rest ... then the BMU assumed capacity , it will be compared to the voltage of the battery after rest, which indicate the SOC ... so if the voltage will be too low and the SOC in AH will be reduced .. then the assumed value of the SOC at the beginning of the trip was too optimistic

At the end ... nothing is a precise calculation .. the current flow sensor can have an error, and this will impact on the real SOC ... but as well, if the sensor is detecting less current then real, SOH may be lower then real, but estimated EV range will not be impacted ...

 

[anko]

I see, I messed up completely . Too much coffee. Not enough coffee. I don't know. Next attempt tonight.

Thanks for enlightening me.