Loosing main battery charge during parking

[Bert]

Hi folks,

I've got a weird problem with my 2014 PHEV, 57000km, SOH on 82.6%/31.4Ah:

Every morning I drive 15km to work and park the car over there at the same location. For about 2-3 months now, I've noticed that the capacity of the main battery has dropped one click while parking when checking the battery capacity after a few hours. The GOM also shows between 3-10km less range. Before that (so a few months back) the battery level was always the same and the GOM even showed 1-3km more due to the ambient temperature rising during the morning.
I need to flag that this car has NO Wifi, so the aux battery does not get the top up at 2pm

I've hooked up an OBD Bluetooth device and connect the PHEV WatchDog to it (see the Dog's Facebook group for more info). It's a similar app as the EVBatmon, just... better, I guess?

So, the results showing that I'm loosing between 0.9-2.4Ah in a very short period of time just by leaving the car on the same spot as the last 2 years before. I've parked the car at 8am and checked afterwards at different times. The ambient temperature is around 18deg C in the morning and 24-28deg C at midday. When arriving at the car park, none of the battery modules have a higher temperature than 23degC, all seems to be fine.
Below are the results from the last three days showing the actual capacity of the main battery at that point of time:

Tuesday
8am: 20.7Ah
10am: 19.6Ah
1pm: 19.6Ah
5pm: 19.6Ah

Wednesday
7:50am: 21.5Ah
8am: 21.5Ah
8:30am: 21.5Ah
9:15am: 21.5Ah
10am: 21.5Ah
12pm: 20.6Ah
5pm: 20.6Ah

Thursday
7:55am: 20.4Ah
9:40am: 19.3Ah
10:30am: 19.3Ah

The only load using the main battery is the aircon, heater, aux charger and the inverters for the motors. None of that is active while car is turned off though.

Question is where does this significant amount of energy go to during the park session?

Thanks for your thoughts guys.

Cheers from Down Under.

 

[elm70]

Interesting

I guess you are not having any programmed time for air-con or heating on your MMCS, but anyhow it is good to double check this setting

Capacity in Ah left on the battery it is an artificial number .. so I would not use as main source of analysis.

You should check the Min and Max volt in your battery at the time you leave, and the time you come back after hours.

Personally I did notice that the voltage normally it does increase while the car is left unplugged after being driven in similar condition as you. Still not sure in the hot day of summer this also happen or if not even reversed. The reason of voltage increase .. is a normal Lithium battery behaviour, very visible especially for old battery or battery with high internal resistance ... once the battery has no more load (driving can cause a load up to 5 time the capacity of the battery), the battery need some time to go back to its natural voltage (voltage is always depressed under load), this time can be even "hours" in some cases ... or minutes in fresh lithium battery with high discharge capacity ....

Anyhow .. assuming your MMCS has no program for activate climate on your car ... the only thing connected to the main battery while it is off ... it is the BMS ... maybe it is working "hard" for re-balance your pack while it is not used ... or .. maybe it did develop a power leak (but it is unlikely)

 

[greendwarf]

Is it sitting in the sun? If so then the car will be hotter than ambient and the aircon is supposed to run independently to keep the batteries cool. :idea: ?

 

[elm70]

Is it sitting in the sun? If so then the car will be hotter than ambient and the aircon is supposed to run independently to keep the batteries cool. :idea: ?

If the battery exceed some temperature , I think there is some protection with the ac inside the battery

I think the level is 35deg

What I notice is that leaving the car in the sun, the cabin temperature is quite high. but the battery are under the car in the shadow, so it is "hard" to bring them above 35deg, unless it is a very hot day

 

[tweedie]

have you by any chance left the OBD Bluetooth on and you started to get this weird problem? I am sure I read somewhere on this forum recently that drained its battery as he/she left their odb device plugged in.

 

[Bert]

I guess you are not having any programmed time for air-con or heating on your MMCS, but anyhow it is good to double check this setting

No, as said, the car has no Wifi feature, therefore no programmable AC or heater function. And the power leak occurs at different times ONLY in the morning!

Capacity in Ah left on the battery it is an artificial number .. so I would not use as main source of analysis.

I think Ah is the ONLY true way to measure the capacity as it shows the usable SOH/SOC of the whole pack. I will check on the cell voltage as well for these times and post some figures later.

Anyhow .. assuming your MMCS has no program for activate climate on your car ... the only thing connected to the main battery while it is off ... it is the BMS ... maybe it is working "hard" for re-balance your pack while it is not used ... or .. maybe it did develop a power leak (but it is unlikely)

The balancing does only take place while the battery is charging as far as I know. You normally can see the intake power dropping after 30-45min of charging (from an empty battery) to around 1kW for around 15min before it slowly climbs up again to the full charge power. As far as my research went, the BMS is only active when the car is active and while charging.
Correct me if I'm wrong here...

have you by any chance left the OBD Bluetooth on and you started to get this weird problem? I am sure I read somewhere on this forum recently that drained its battery as he/she left their odb device plugged in.

Well, to be honest, I have had this problem for a few months now and bought the OBD to get my head around it just two weeks ago. Also, yes, I leave it on all the time but it would only discharge the aux battery, not the main battery. If it would it takes a constant amount of power rather than a huge amount once and then nothing any more for the rest of the day.

Is it sitting in the sun? If so then the car will be hotter than ambient and the aircon is supposed to run independently to keep the batteries cool. :idea: ?

The cooling system does not turn on while the car is OFF. Last summer we had over 45degC and it did turn on. It activates straight away though when the car is in Ready mode or while it charges during these temperatures but not while OFF...


I forgot to mention that I measured the aux battery voltage in the morning and before I used car again after 9h and it was almost the same voltage. I wanted to make sure it does not get topped up from the main, even the car has not Wifi and hence no auto top up at 2pm.
The amount of energy which is leaking is around 0.9-2.4Ah, so up to 10% of the usable capacity. That is quite a lot and need to go somewhere... I really get the suspicion the BMS is somehow faulty.

 

[elm70]

No, as said, the car has no Wifi feature, therefore no programmable AC or heater function. And the power leak occurs at different times ONLY in the morning!

Programming AC or heater can be done over MMCS there is no WiFI need for it as far as I know.

I think Ah is the ONLY true way to measure the capacity as it shows the usable SOH/SOC of the whole pack. I will check on the cell voltage as well for these times and post some figures later.

Measure Ah in a battery it is not possible, the only way to know how much Ah are left in a battery is to fully discharge the battery, so when it is 0, you know how much was before ... so .. there is no way to have an accurate reading of it, and each BMS has its own way to "guess" the battery capacity at any given state

So, use a post processed , with a fuzzy logic, information for extract any "real fact" .. in my book it is a wrong starting point.

You should monitor the total voltage, possibly all the cell voltage, but at least the min and max voltage and as well, recording which cell was the weakest ,.. monitor the temperature is also not a bad idea but temperature is the BMS module, not per cell.

The balancing does only take place while the battery is charging as far as I know. You normally can see the intake power dropping after 30-45min of charging (from an empty battery) to around 1kW for around 15min before it slowly climbs up again to the full charge power. As far as my research went, the BMS is only active when the car is active and while charging.
Correct me if I'm wrong here...

BMS is definitely connected all the time to the main battery pack, it is also the only thing connected to the main battery when the car is off ... so it is the only source of leak of power except for a battery that does leak internally

Is the BMS active only when the car is charging ... I don't know ... maybe ... but if they made a very advanced BMS it can take car to take juice from the strongest cells and put on the weak cells (simple BMS just discharge the cells which have too high voltage) .. and this process need to be done all the time for be efficient

Anyhow , since BMS act on each single cell and not at total voltage or total capacity of the pack ... just checking Ah that is a guessed number ... at is an index for the entire main battery ... you will never be able to see if the issue is due to a single weak cells , which the BMS need to re-balance, or due to a single leak at the BMS level ...

 

[Bert]

OK, so the car has definitely no AC/heater pre-programming feature in the MMCS. The menu button is just not there...

I did some more testing over the weekend and left the car sitting with almost 80% SoC and after 2h it leaked only 0.3Ah and nothing else any more for the next 16h. So obviously some power is leaking over the first few hours and nothing afterwards any more and it is depended on the SoC.
This morning after driving to work I lost 1.1Ah,7km or one click on the battery gauge while parking between 8-9:30am. I'm sure there is nothing further leaking until I leave at 5pm... this was with 60%SoC.

Strangely this is only happening for the last 3 months and never happened before. I usually had 2-3km more when parking from 8am-5pm as the outside temperature raises during the morning.

I blame the battery as it is already down to 82% health after 3.5years and 57000km. I'll log a fault with MMAU and see what they are saying... That's definitely not normal and nobody else with the PHEV is apparently experience this loss of charge while parking.

 

[elm70]

Ideally ... you should check Min , Max and Total Voltage .. both when you left the car and when you are back.

I have seen multiple time that my range got increased after 11km drive when I take my car 8h later .. but ... I think sometime I also notice that I have less range .. especially if I left the car with less then 15km range left .. it can tell me at restart I have even less then it .. but I never put much attention on it, since EV range is a fuzzy number ... so is the Ah capacity left on the main battery .. plus ... I don't bother to connect my EvBatMon or other diagnostic every time I use my car .. normally I do once in a while

What I did check was the route of the increase of range .. and I did notice that the voltage did increase while my car has been left off .. but this is a normal on Lithium battery ... and does not really have much to do with temperate ... it is not because in the morning is colder then in the afternoon.

If you are now experiencing regularly lost of range and capacity .... my bet is that one of your cell is weaker and does get some balancing while the car is idle .. or the weak cell does impact more on the EV range after you restart the car .... check the Min and Max voltage .. and you may find a route cause

Knowing if a cell is weak ... is quite important .. since a single bad cell can ruin the total batter capacity

 

[Bert]

Ideally ... you should check Min , Max and Total Voltage .. both when you left the car and when you are back.

OK, so, I've done that:

While driving to work I had a min of 3.742V and max of 4.072. Left the car there at 8am. When I cam back at 1:30pm to check it had 14km less on the GOM and -2.8Ah. The min was 3.945V and max 3.948V.

That does not seem to say anything though...

Thanks

 

[elm70]

Ideally ... you should check Min , Max and Total Voltage .. both when you left the car and when you are back.

OK, so, I've done that:

While driving to work I had a min of 3.742V and max of 4.072. Left the car there at 8am. When I cam back at 1:30pm to check it had 14km less on the GOM and -2.8Ah. The min was 3.945V and max 3.948V.

That does not seem to say anything though...

Thanks

I guess Min and Max (3.742V & 4.072) .. are not for an "instant" but during the trip ... since it is looking you started with 4.072 and due to acceleration the lowest voltage was 3.742 .. yes this Min Max .. don't bring much value.

So .. Min Max .. is important when taken in the same time/condition for the entire battery pack, for spot if there is any weak cell in the pack.

So ... a simple way would be to check just after arrive at destination and just before you restart after have left the car parked for a while. Possibly also take a reference of the total battery voltage in both situations

What is interesting is (The min was 3.945V and max 3.948V.) .. that means the battery pack is looking well balanced when you are restarting the car.

Ideally .. I would take the following measure (it is just a screen shot on EvBatMon .. not sure how to do on PHEV Watchdog):
Before start the trip ... Screen shot the Total Battery voltage (should be around 328V), and Min Max voltage (should be very close to 4.10v both for Min and Max) ... once arrived ... just before switch off the car .. take the same snapshot .. and then .. just before restart ... take again the snapshot

PS: I have to say .. that also in my case .. sometime I believe I get less range after leaving the car in some special condition ... normally after the first trip from fully charged, once I restart I get more range .. but in the rare case I do make an extra trip without recharge, I believe I lose few km .. so normally when range left is below 15km after 2nd trip .. at next restart I can get even less.

 

[elm70]

I think I find the reason of this "problem"

Normally Lithium battery after usage, especially if they have high IR, will jump at higher voltage while "sitting" unused.
This explain why EV range may be more after park the car without charging it.

But ... for what I have notice BMU in this PHEV it is always "active" .. and it does always discharge the higher voltage cells if these have a value above some threshold over the lowest or average voltage.

This can cause to lose voltage in the battery pack, especially if some cells have a different IR compared to other and may cause to jump to higher voltage faster or slower compared to others ...

This BMU always active is not really a wise decision from Mitsubishi .. BMU should only balance cells only when these are close to the max designed volt, that is around 4.10v .. unless the BMU can take capacity from the strong cells and give this capacity to the weak cells ... something that does not really exist for now in the EV car batteries .. the normal balancer/BMU .. can only discharge the cells that have a too high voltage, so making the strong cells as weak as the weaker cells in the battery pack.

 

[maby]

...

This BMU always active is not really a wise decision from Mitsubishi .. BMU should only balance cells only when these are close to the max designed volt, that is around 4.10v .. unless the BMU can take capacity from the strong cells and give this capacity to the weak cells ... something that does not really exist for now in the EV car batteries .. the normal balancer/BMU .. can only discharge the cells that have a too high voltage, so making the strong cells as weak as the weaker cells in the battery pack.

Would that strategy not result in the weaker cells being discharged too low when the car is running? It will always draw the same current from every cell so, if one starts at 4.1v and another starts at 3.8, you will be driving the weaker one down to levels where it could be permanently damaged before you get the stronger one down to normal minimum.

 

[elm70]

...

This BMU always active is not really a wise decision from Mitsubishi .. BMU should only balance cells only when these are close to the max designed volt, that is around 4.10v .. unless the BMU can take capacity from the strong cells and give this capacity to the weak cells ... something that does not really exist for now in the EV car batteries .. the normal balancer/BMU .. can only discharge the cells that have a too high voltage, so making the strong cells as weak as the weaker cells in the battery pack.

Would that strategy not result in the weaker cells being discharged too low when the car is running? It will always draw the same current from every cell so, if one starts at 4.1v and another starts at 3.8, you will be driving the weaker one down to levels where it could be permanently damaged before you get the stronger one down to normal minimum.

Yes and no ...

As you know .. Power is Volts * Amps ... so .. having higher voltage means using less Amps (so less discharge) for provide the same required power.

As well .. not every cells may have same discharge path .. some may lose faster voltage at the beginning of discharge and then lose it slower later on. And this is the main problem on losing EV range while parking the car

So .. it is not a good idea for me to balance the cells, unless we are at the end of charging process.

Clearly .. having possible unbalanced cells when close to "real EV zero range" ... (real with real safety buffer) .. it means that the reference to the total battery voltage of the pack is not "usable" .. instead it should consider the weaker cell of the pack as reference for determinate the time to kick in the ICE

Still it is a relative mystery to me what is the reference of our PHEV for kick in the ICE .. since ... the car it is looking to take care not only the battery voltage (which under 10/15min of heavy usage may have still EV range, but the voltage especially in winter is very very low .. and need "hours" of rest .. for bounce back to the expected voltage associated to the left capacity level)

PS: Due to the continuous balancing happening in the car ... it is much more complicated to notice if any of the cell in the pack is much weaker then other ... and this would be a nice information for know if mayor EV range can be regain by just replacing the weak cell(s)

 

[maby]

...

Would that strategy not result in the weaker cells being discharged too low when the car is running? It will always draw the same current from every cell so, if one starts at 4.1v and another starts at 3.8, you will be driving the weaker one down to levels where it could be permanently damaged before you get the stronger one down to normal minimum.

Yes and no ...

As you know .. Power is Volts * Amps ... so .. having higher voltage means using less Amps (so less discharge) for provide the same required power.

...

hmmm, but the cells are all connected in series, aren't they? That would mean that the same discharge current must flow through all of them - one of the laws of electricity (I can't remember the name) is that the sum of all currents flowing into and out of a point must be zero. In order to balance cells during discharge, each would have to have a fairly complex controller built in that is capable of controlling the discharge at high current levels - that is not the case, is it? If I'm drawing 10A of my battery pack, then every cell is supplying 10A...

P.S. its Kirchhoff's current law!

 

[elm70]

hmmm, but the cells are all connected in series, aren't they? That would mean that the same discharge current must flow through all of them - one of the laws of electricity (I can't remember the name) is that the sum of all currents flowing into and out of a point must be zero. In order to balance cells during discharge, each would have to have a fairly complex controller built in that is capable of controlling the discharge at high current levels - that is not the case, is it? If I'm drawing 10A of my battery pack, then every cell is supplying 10A...

P.S. its Kirchhoff's current law!

Sure ... the current that goes from battery pack to the motors (of better the two motors controllers) ... it is same for all the cells which are in series

But ... BMU Discharge is per cell, so in parallel to any of the cell in the pack (all in series) .. there is a resistance that can be activate for discharge individually each cell.

This is very simple ... nothing fancy ... in our PHEV there are possible 10 BMU, one per each module ... the single BMU does check the voltage of each single cell in the module .. if one has been defined to have too much voltage ... then a transistor activate a "short" between the cells, and a "high power" resistor .. forcing to discharge the individual cell with a design decided current .. possibly around 1 or 2 Amp discharge (causing to dissipate max 10w ... so I would guess balancing should never cause to waste more then 200w .. still at this level .. especially in summer it maybe needed to activate some cooling on the BMU )

 

[perfectlifttip]

If all else fail visit some battery dealers and get some professional help...

 

[elm70]

If all else fail visit some battery dealers and get some professional help...

Who are these dealers ?

Considering the 8y warranty .. the only "authorized" people to put the hands on are just "Mitsubishi dealers"

A battery specialist , if any exist , can put its hands on , only after having removed the battery from the bottom of the car
Still it is needed to have decent knowledge on how to disconnect and reconnect the main battery to the Outlander PHEV

I have seen a video of somebody removing / fixing / and reconnecting the battery on the iMEV ... it was not looking something trivial, and it was a team of people inside a well equipped garage

 

[Esparza]

Balancingshould only take place at full charge. If you park the car 1 month it does not discharge as fast as what is described in this post. Is not a energy loose problem, is a energy calculation problem.

 

[elm70]

Balancingshould only take place at full charge. If you park the car 1 month it does not discharge as fast as what is described in this post. Is not a energy loose problem, is a energy calculation problem.

I did monitor with PHEVwatchDog the min and max voltage of each cells in a pack ... after a partial charge (~30/40min after charge finished .. I have a timer over the power source used by the charger) .. and then on the next day after leave parked and unused the car for ~15h

Temperature was almost same in both time of measurement.

What I did notice is that the delta between min and max voltage was lower on second measurement .. but as well, there was a visible reduction in total voltage of the battery pack ... range was also impacted by few km.

Actually here are my data:

12:00 before charging
- 12.0Ah 3.847/3.852 V min/max (temp 1/2 C)

15:20 ... charging stopped at 3pm , 3.6kwh per the MMC:
- 21.9/21.8Ah 3.958/3.966 V min/max (temp 3/6 C)

18:10 .. after 3h rest from charging no usage
- 21.8Ah 3.952/3.958 V (temp 3/4 C)

11:00 .. next day ... no charge ... no usage
- 21.6Ah 3.951/3.957 V (temp 1/2 C)

PS: Interesting to see temperature after charge is the highest with the highest difference ... not sure if this due to battery allocation in the car .. or some cells have higher resistance then other and cause to warm up more then other during the charging process.

PS: If I recall right I also have the battery status of the day before few minutes after the last usage:
15:50 day before
11.4Ah 3.802/3.816v (temp 8/10 C)

After this usage it is visible that battery bounced back from 3.81v to 3.85v .. so did the capacity reported by the apps, from 11.4Ah to 12.0Ah .. still on the MMCS I think was still shown 2km range left in both cases .. delta voltage is looking to have been smooth down all the time the car is left in the "rest" .. from 0.014v gap to 0.005v