miggols99
Posts: 18
Joined: Tue Feb 01, 2022 3:27 am
Location: Japan

Losing Charge When Parked Up

So I don't know if this is just a side effect of my very tired battery (24 Ah, or around 50% SoH), but I've found my SoC to be very unstable above 70%. Here's what I'm seeing recently:

- Charge to 100% on level 2 (RR @ 80~90km depending on the driving style)
- Drive around 10km back home from a charging station, RR @ 70km, 90% SoC (I rent, so charging at home involves running a cable out the window...)
- Come back to the car after a couple of hours to find the RR has gone down around 6-7km, with the battery gauge also losing a bar - I can literally see the bar disappear right before my eyes! SoC has also dropped 7-8%. This happens even after just 5~10 mins parked up, so it doesn't seem to be parasitic drain.

Going below 70% the battery gauge/RR behaves as expected.

Has anyone else experienced anything like this?
I have charged to 100% then driven longer distances (30~40km), but when I do that the meter doesn't seem to drop as quickly for some reason.

This in addition to the battery degradation gives me a real-world range of maybe 60km which means charging at any possible chance...
I do a lot of short trips so if not for this it would be perfect for my needs, but at this rate I may have to say goodbye to this one and look for another with a healthier battery :(
EV: 2009 Mitsubishi i-MiEV
ICE: 2019 Suzuki Wagon R
dopey
Posts: 23
Joined: Mon Jul 11, 2022 3:23 am

Re: Losing Charge When Parked Up

If I am not mistaken the traction battery is physically disconnected when the car is parked, making any sort of actual consumption 'impossible'. -- one reason heater, etc does not work until the car is in 'Ready'.

The range gauge is some sort of estimate based off consumption+previous driving.

Any chance when you first get in the car, something like A/C or heat is coming on that you had switched off when you parked? Sitting in the car and toggling these things you can see an immediate change to the range estimate on the car.

50% SoH is quite low though -- and quite shocked you get 80-90km RR out of that. If you are able to check your SoH, can you check your cell voltages? Just speculating, but perhaps if you have cell(s) which are way below others that it causes some funkiness and effectively triggers the car to reduce it's Ah after sitting?


My 63% SoH range display varies wildly, some full charges i'll be at 109km other's at 80. Real world anywhere from 45-80km depending on speeds we drive..


(Very new myself to this car, so may be waaay off but have not personally noticed such reduction other than 'estimate' range due to A/C or heat being on vs off).
JoeS
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Re: Losing Charge When Parked Up

@miggols99, when the aircon is activated, the RR (Range Remaining) drops by ~10%. When the heater is activated, the RR drops by ~20%. Perhaps this is a reason for your 'inconsistent' RR drop?
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miggols99
Posts: 18
Joined: Tue Feb 01, 2022 3:27 am
Location: Japan

Re: Losing Charge When Parked Up

Thanks for the replies. The weather has been quite mild recently, so no aircon/heater. I'll have to see if I can just sit in the car for a bit and see what exactly is going on using OBDZero when the SoC drops...
EV: 2009 Mitsubishi i-MiEV
ICE: 2019 Suzuki Wagon R
PV1
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Re: Losing Charge When Parked Up

Given that you have a very early i-MiEV (2009), it may not behave like most of our cars.

The drop in SoC wouldn't be caused by heat or A/C. My guess is that the instrumentation isn't calibrated to the actual capacity of the battery. The car is expecting less voltage sag (from assuming more capacity than actual), but after sitting, it reads the cell voltages and adjusts down to match the actual charge of the battery. My one car, Koorz, exhibits behavior like this from time to time, but the opposite. It will gain 4-5% charge if parked after a short drive (5 miles or less). I have decent capacity, but higher internal resistance in that pack.

To fix this, it might take a dealer calibration. Newer i-MiEVs like many here on the forum can do this on their own, but older ones need the diagnostic tool to perform capacity calibration.
"Bear" - 2012 Diamond White Pearl ES with QC
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miggols99
Posts: 18
Joined: Tue Feb 01, 2022 3:27 am
Location: Japan

Re: Losing Charge When Parked Up

So funnily enough, after getting in the car this morning I found I had recovered a bar since the day before, from 7 bars, 1 below half, to 8.
Since my SoH is so low, perhaps the battery management system is just not able to keep up?

A perk of owning an i-MiEV here in Japan is that Mitsubishi's charging card gives you a free dealer battery calibration every year. I talked about this in my other thread, but I actually had this done around 4-5 months ago, so I would assume the battery is calibrated as well as it can be. I do probably use DC charging a lot more than is good for the battery though, mostly due to not being able to charge at home..
EV: 2009 Mitsubishi i-MiEV
ICE: 2019 Suzuki Wagon R
miggols99
Posts: 18
Joined: Tue Feb 01, 2022 3:27 am
Location: Japan

Re: Losing Charge When Parked Up

So I was able to capture this loss of range using OBDZero.
Before turning the car on, the SoC and range remaining show the same as when I parked up.

However, after putting the car into "Ready", I can see the SoC drop from 90.5% down to 83.5%, with a consequent drop of 6km of estimated range!

Image
Image

I wonder what could cause around 0.5kWh to disappear into thin air?
Or is this simply the car's way of recalculating the true SoC?
EV: 2009 Mitsubishi i-MiEV
ICE: 2019 Suzuki Wagon R
CZeroOwner
Gold Member
Posts: 66
Joined: Mon Jan 15, 2018 1:47 am
Location: Denmark

Re: Losing Charge When Parked Up

Hi Miggols99

There are a number of curious things about the two screenshots. Look at the last line that shows the capacity and the Ah remaining. The car computes the SoC by dividing the Ah remaining by the capacity and multiplying by 100. To find the Ah remaining the car sets the Ah remaining to the capacity when the car it is charged to 100%. After that it keeps an account of the Ah removed from the battery using the amps measurement. This is called coulomb counting. OBDZero also keeps an account of the Ah removed from the battery starting with the capacity at 100% charge. I have not found a direct read out of the cars Ah account but computing backwards from the capacity and the SoC the car's account is 21,27 Ah in the first shot and 19,62 in the second shot. On the other hand OBDZero's Ah account is much lower 15,02 in the first shot and 14,56 in the second. OBDZero believes that almost 9 Ah have been used since the car was charged to 100% while the car "believes" there has only been 2 to 4 Ah used. In my cars the computed car Ah account and OBDZero Ah are always very close to each other but they are not here. So something is not right. Could you please send me the data collected by OBDZero. Thats the text files in the OBDZero folder. I may be able to answer your questions after I have seen the data.

Cheers
David
miggols99
Posts: 18
Joined: Tue Feb 01, 2022 3:27 am
Location: Japan

Re: Losing Charge When Parked Up

@CZeroOwner: Sorry for the late reply - I was away travelling. I'll send over the text files in a PM in a bit.

Perhaps unrelated to this problem, I took the car in to a dealer as I have been having problems using certain public chargers.
This owner of a 2010 i-MiEV goes into the details in their blog post below:

https://ameblo-jp.translate.goog/studio ... r_pto=wapp

(my car shows the exact same symptoms...i.e. a dying OBC)

They told me that error codes P1A2F and P1A4B (Malfunction of the BMU traction battery cell system) are showing up, and I would have to pay over 1 million yen ($7,000 USD at the current rate) to replace the traction battery, which is obviously unrealistic for a car I bought at more than half of that :roll:

If the OBC fails completely, it would qualify for a service campaign they say...


I have been getting "cell voltages difference too large" errors as shown in Hobdrive, so I may need to do a few "calibration" charges.
The charging stand I use most frequently has an unusual charging curve, as it doesn't seem to taper off much at all when reaching a higher SOC, so I am not sure cell balancing is taking place.
EV: 2009 Mitsubishi i-MiEV
ICE: 2019 Suzuki Wagon R
CZeroOwner
Gold Member
Posts: 66
Joined: Mon Jan 15, 2018 1:47 am
Location: Denmark

Re: Losing Charge When Parked Up

miggols99 wrote: Mon Sep 19, 2022 9:08 pm I would have to pay over 1 million yen ($7,000 USD at the current rate) to replace the traction battery.
I was quoted twice that by the local Citroen dealership. I'm wondering how much it would cost to ship a battery from Japan to Denmark. However I only payed the Japanese price for a new battery, for my car. So I'm just curious.

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