Mitsubishi Outlander PHEV Forum

It is currently Sat Nov 17, 2018 9:57 pm

All times are UTC - 8 hours [ DST ]




Post new topic Reply to topic  [ 95 posts ]  Go to page Previous  1 ... 4, 5, 6, 7, 8, 9, 10  Next
Author Message
 Post subject: Re: Drive battery degradation and the out of whack IMO BMU.
PostPosted: Tue Sep 11, 2018 1:11 pm 
Offline

Joined: Mon Dec 01, 2014 11:30 am
Posts: 3188
Location: Netherlands, Utrecht area
So, tried again. After she arrived home, unfortunately it took about 10 minutes before I could read the data from the car. At that moment it showed 27.9% / 7.3 Ah. I started preheating until the reading was 20.2% / 5.3 Ah. Then I turned off the heater. About three hours later, I checked again. The reading was the same 20.2% / 5.3 Ah.

Is that meaningful data?


Top
 Profile  
 
 Post subject: Re: Drive battery degradation and the out of whack IMO BMU.
PostPosted: Tue Sep 11, 2018 10:46 pm 
Offline

Joined: Mon Sep 26, 2016 11:18 pm
Posts: 909
Location: Poland
anko wrote:
So, tried again. After she arrived home, unfortunately it took about 10 minutes before I could read the data from the car. At that moment it showed 27.9% / 7.3 Ah. I started preheating until the reading was 20.2% / 5.3 Ah. Then I turned off the heater. About three hours later, I checked again. The reading was the same 20.2% / 5.3 Ah.

Is that meaningful data?


Interesting

So apparently your BMU has a good "guess" about the real SOH and capacity of your battery.

Yesterday I did check twice my car while resting .. after ~2.5h and ~1.5h later on ... the battery was 14.1Ah after the trip .. and while resting it was stated at 14.2Ah after 2.5h ... and then 14.3Ah later on ... I never seen the battery going up twice while resting.

It would be looking good ... winning 0.2Ah while resting .. except for the fact that while parked uncharged the night before the battery was going down 2.5Ah from 19Ah down to 16.5Ah (from 16.5Ah down to 14.1Ah was due to a short drive)

In my case the car had from fully charge 2 trips the day before, and 3 small drive yesterday ... but I did not monitor the first trip, so I can't say if in total I lost Ah while parked or not (monitored is -2.5 + 0.2 .. but I bet I must win 1Ah while parked between the 1st and 2nd trip .. still, possibly, as total I lost over 1Ah .. that means my BMU is optimistic about my battery SOH)

Maybe on the weekend I will try to make a proper 40km experiment ... from fully charge to 0EV range .. and check what my BMU will report after rest ... I bet ... my 34Ah declared SOH, is 1Ah above reality ... so my car has just 33Ah capacity at the moment .. that for an almost 5y old battery it is not too bad.

PS: Why did you use pre-heat at the end of a trip ? Bring the battery down from 27.9% down to 20.2% does not sounds a healthy practice ... but ... maybe I can guess why ... still it is a risk on your side


Top
 Profile  
 
 Post subject: Re: Drive battery degradation and the out of whack IMO BMU.
PostPosted: Wed Sep 12, 2018 8:29 am 
Offline

Joined: Mon Dec 01, 2014 11:30 am
Posts: 3188
Location: Netherlands, Utrecht area
elm70 wrote:
PS: Why did you use pre-heat at the end of a trip ? Bring the battery down from 27.9% down to 20.2% does not sounds a healthy practice ... but ... maybe I can guess why ... still it is a risk on your side
As I allowed the battery to cool down for some time, I decided to give it a little load again, before taking first measurement :mrgreen: Don't know if it is a big risk. Seen much lower SOCs while driving. Discharge rate in this case was very modest (4 kW). And if the car was not happy with it, it should not allow it ;)


Top
 Profile  
 
 Post subject: Re: Drive battery degradation and the out of whack IMO BMU.
PostPosted: Wed Sep 12, 2018 10:44 pm 
Offline

Joined: Mon Sep 26, 2016 11:18 pm
Posts: 909
Location: Poland
Some data from my side:

Trip 1: 33.5Ah down to 27.2Ah (0.5Ah lost (??) compared to fully charge which was finish 1h30min before start the trip)
Trip 2: 28.4Ah down to 22.3Ah (1.2Ah win while parked for 8h)
Trip 3: 22.3Ah down to 20.8Ah (0 change, but was 10min after 2nd trip end)

While resting in the evening car lost 2.3Ah .. down to 18.5Ah
After the night car lost other 0.3Ah ... down to 18.2Ah

So ... in total +1.2Ah - 2.6Ah ... so car lost 1.4Ah ... while using 13.9Ah

I bet on my next few short trip I need today I will gain 0.1 or 0.2Ah .. so ... ending with ~1.2Ah "lost" ... so ... my battery that is 34Ah per the BMU .. is possibly just 32.7Ah .. with the handicap that I can't use the top 0.5Ah .. since the charging process end too fast, (or immediately after charge car lose 0.5Ah) .... so .... it is more like a 32.2Ah ... that is just 85% SOH real :oops:

Next day ... after Trip 4 and rest ... down to 15.4Ah ... so further 0.4Ah lost :cry:

So .. initial win 1.2Ah
Later ... Total lost : 3Ah
Balance : Lost 1.8Ah .. used ... 16.3Ah ... over 10% waste while "parked"

EDIT update:
Trip 1: 33.5Ah down to 27.2Ah (0.5Ah lost (??) compared to fully charge which was finish 1h30min before start the trip)
Trip 2: 28.4Ah down to 22.3Ah (1.2Ah win while parked for 8h)
Trip 3: 22.3Ah down to 20.8Ah (0 change, but was 10min after 2nd trip end)
Next Day:
Trip 4: 18.2Ah down to 15.8Ah (2.6Ah lost overnight)


Last edited by elm70 on Thu Sep 13, 2018 3:11 am, edited 1 time in total.

Top
 Profile  
 
 Post subject: Re: Drive battery degradation and the out of whack IMO BMU.
PostPosted: Thu Sep 13, 2018 2:30 am 
Offline

Joined: Mon Dec 01, 2014 11:30 am
Posts: 3188
Location: Netherlands, Utrecht area
I read somewhere (Andy related discussion?) that it could have to do with voltage? IIRC, something in the line of:

After a trip, voltage slowly goes up. As kWh cannot change, Ah must come down.
After a rest, voltage slowly goes up. As kWh cannot change, Ah must go up.

No idea whether this makes sense :oops:


Top
 Profile  
 
 Post subject: Re: Drive battery degradation and the out of whack IMO BMU.
PostPosted: Thu Sep 13, 2018 2:57 am 
Offline

Joined: Mon Sep 26, 2016 11:18 pm
Posts: 909
Location: Poland
anko wrote:
I read somewhere (Andy related discussion?) that it could have to do with voltage? IIRC, something in the line of:

After a trip, voltage slowly goes up. As kWh cannot change, Ah must come down.
After a rest, voltage slowly goes up. As kWh cannot change, Ah must go up.

No idea whether this makes sense :oops:


No ... kwh is not equal to a simple Ah x voltage ... since voltage is function of the discharge level ... I don't think car care of kwh ... I'm quite sure it does care only of Ah ... only current can be monitored ... also battery discharge diagram always show how many Ah can be consumed .. but never show how many kwh could be extracted from a battery

Yes ... while driving ... SOC is based on initial SOC minus monitored consumption (or flow, since it can have regen and ICE charge too)

While resting ... after enough rest ... the SOC is adapted based on Voltage

This is the tricky part, since the PHEV/BMU must have a mapping table which map voltage to SOC in % ... absolute SOC based on voltage is due to SOH too ... so ... 3.95v should be 66% of SOH ... so .. assuming 34Ah SOH .. 3.95 should be 22.4Ah (on a 30Ah SOH ... it would be 19.8Ah) .. but this apply if there is a linear relation between 3.8v 30% to 4.1v 100% ... but I believe there is a map in the car in charge for this ... possibly this map get updated while battery smoothing is executed

Definitely the mapping between SOC and voltage ... it is off in my PHEV .. since at some voltage the SOC is over estimated , and at other levels it is underestimated

Error/corrections of 1Ah and 2.6Ah ... are quite massive in my view ... and this can cause big confusion on the EV range shown on the dash

PS: I'm partially surprise to have lost 0.3Ah over night, after a lost of 2.3Ah after many hours of car at rest ... maybe the battery was a bit colder in the morning ... or ... there must be some leak in the BMU ... as well ... was also strange to see at some point over 0.02v of unbalance between cells in the back ... which later on at lower voltage and after rest ... got below 0.005v ... something that I may justify by active balancing while driving and maybe while parking too ...


Top
 Profile  
 
 Post subject: Re: Drive battery degradation and the out of whack IMO BMU.
PostPosted: Thu Sep 13, 2018 6:35 am 
Offline

Joined: Mon Dec 01, 2014 11:30 am
Posts: 3188
Location: Netherlands, Utrecht area
I understand I think. Maybe kWh is not the right approach. But altogether, there is a certain amount of energie stored in the battery. How many Ah that translates to depends on voltage, right? And for sure, voltage will drop during the discharge. But does starting voltage not have an effect? First (part of an) Ah discharged contains a lot of energy ...?


Top
 Profile  
 
 Post subject: Re: Drive battery degradation and the out of whack IMO BMU.
PostPosted: Thu Sep 13, 2018 12:27 pm 
Offline

Joined: Mon Sep 26, 2016 11:18 pm
Posts: 909
Location: Poland
Trip 1: 33.5Ah down to 27.2Ah (0.5Ah lost (??) compared to fully charge which was finish 1h30min before start the trip)
Trip 2: 28.4Ah down to 22.3Ah (1.2Ah win while parked for 8h)
Trip 3: 22.3Ah down to 20.8Ah (0 change, but was 10min after 2nd trip end)
Next Day:
Trip 4: 18.2Ah down to 15.8Ah (2.6Ah lost overnight)
Trip 5: 15.6Ah down to 14.3Ah (0.2Ah lost while parked)
Trip 6: 14.3Ah down to 13.0Ah
Trip 7: 12.9Ah down to 11.8Ah (0.1Ah lost while parked, this was even less then 2h rest)
Trip 8: 11.8Ah down to 10.7Ah
After 3h rest ... capacity is neither going up or down .. is still reported to be 10.7Ah .. 10.7Ah equal to 1km EV range left

So, in total I did 21km + 12km .. so only 33km ... quite a poor result, since I have only used AC on trip 2 and trip 3 only
Total capacity consumed was 13.9Ah + 7.2Ah
Total capacity lost while parked was: 1.7Ah (2.2Ah including the 0.5Ah missing after a full charge)

Anyhow ... possibly the best test would be to fully charge the car .. and consume all the battery in 1 trip .. and then check SOC after 2 or 3h rest ...


EDIT ... after further rest ... I made last check for the day .... battery jump up from 10.7Ah to 10.9Ah (still only 1km EV range left) ... so total battery lost while parked is 1.5Ah instead of 1.7Ah


Last edited by elm70 on Thu Sep 13, 2018 12:46 pm, edited 1 time in total.

Top
 Profile  
 
 Post subject: Re: Drive battery degradation and the out of whack IMO BMU.
PostPosted: Thu Sep 13, 2018 12:34 pm 
Offline

Joined: Mon Sep 26, 2016 11:18 pm
Posts: 909
Location: Poland
anko wrote:
I understand I think. Maybe kWh is not the right approach. But altogether, there is a certain amount of energie stored in the battery. How many Ah that translates to depends on voltage, right? And for sure, voltage will drop during the discharge. But does starting voltage not have an effect? First (part of an) Ah discharged contains a lot of energy ...?


Battery capacity is always in Ah ... just look at the following graph, which can be found in many datasheet for lithium battery

Image

Test is done with different load, which cause a different voltage .. higher the load, is lower the voltage but the Ah is constant (more or less) .. so for higher load the energy extract from the battery is less .. so speaking of kwh is "wrong" ... since we should refer to ideal energy in kwh with the lowest load .. while speaking of battery capacity in Ah .. it is quite accurate independetly by the "load"

PS: this graph is relaive atipical ... normally with higher load (so more current) the capacity in Ah is partially reduced (so not only less kwh (actually much less), but even less Ah)


Top
 Profile  
 
 Post subject: Re: Drive battery degradation and the out of whack IMO BMU.
PostPosted: Sat Sep 15, 2018 11:11 am 
Offline

Joined: Mon Dec 01, 2014 11:30 am
Posts: 3188
Location: Netherlands, Utrecht area
That is deep. Really need some time to digest ;-)


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 95 posts ]  Go to page Previous  1 ... 4, 5, 6, 7, 8, 9, 10  Next

All times are UTC - 8 hours [ DST ]


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
© Mitsubishi Outlander PHEV Forum - part of the MyElectricCarForums.com Group