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 Post subject: Loosing main battery charge during parking
PostPosted: Wed Sep 13, 2017 5:37 pm 
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Joined: Tue Dec 08, 2015 1:59 pm
Posts: 12
Location: Lockyer Valley, QLD, Australia
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.


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 Post subject: Re: Loosing main battery charge during parking
PostPosted: Wed Sep 13, 2017 10:40 pm 
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Joined: Mon Sep 26, 2016 11:18 pm
Posts: 516
Location: Poland
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)


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 Post subject: Re: Loosing main battery charge during parking
PostPosted: Thu Sep 14, 2017 1:34 am 
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Joined: Tue Aug 05, 2014 1:32 pm
Posts: 1340
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: ?


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 Post subject: Re: Loosing main battery charge during parking
PostPosted: Thu Sep 14, 2017 1:39 am 
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Joined: Mon Sep 26, 2016 11:18 pm
Posts: 516
Location: Poland
greendwarf wrote:
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


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 Post subject: Re: Loosing main battery charge during parking
PostPosted: Thu Sep 14, 2017 1:48 am 
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Joined: Tue Apr 25, 2017 2:42 am
Posts: 22
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.


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 Post subject: Re: Loosing main battery charge during parking
PostPosted: Thu Sep 14, 2017 4:45 am 
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Joined: Tue Dec 08, 2015 1:59 pm
Posts: 12
Location: Lockyer Valley, QLD, Australia
elm70 wrote:
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!

elm70 wrote:
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.

elm70 wrote:
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...

tweedie wrote:
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.

greendwarf wrote:
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.


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 Post subject: Re: Loosing main battery charge during parking
PostPosted: Thu Sep 14, 2017 10:35 pm 
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Joined: Mon Sep 26, 2016 11:18 pm
Posts: 516
Location: Poland
Quote:
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.

Quote:
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.

Quote:
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 ...


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 Post subject: Re: Loosing main battery charge during parking
PostPosted: Sun Sep 17, 2017 5:06 pm 
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Joined: Tue Dec 08, 2015 1:59 pm
Posts: 12
Location: Lockyer Valley, QLD, Australia
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.


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 Post subject: Re: Loosing main battery charge during parking
PostPosted: Sun Sep 17, 2017 11:44 pm 
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Joined: Mon Sep 26, 2016 11:18 pm
Posts: 516
Location: Poland
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


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