Main Traction Battery Upgrade i-MiEV

[MickeyS70]

Did you start at 100% SOC @ 45Ah capacity? Can you confirm the tortoise appeared around 10% SOC, power loss 1-2%?
Did you try a BMS reset at this stage to access some of the remaining NMC capacity?

 

[kiev]

I did a range test today.

That's why i was confused, what does 8 miles after turtle have to do with range? How far did it go before the Turtle would tell me something about Range.

What was the Pack voltage at Turtle would tell something about remaining energy.

Started at 16 bars on fuel gauge, then drove it down to 1 or 2 bars flashing? Turtle at 0 bars?

 

[kiev]

@MickeyS70

Concerning temperature sensors: Paul has added small metal plates to attach the CMU to the cell terminals, so there is a direct thermal path similar to the OEM thermal path. There is one junction on each CMU that is done using a wire with a ring terminal, so the thermal path is thru the wire which is still better than an air ball.

The little sensor boards (to monitor cell temperature and voltage) mounted with the white flex bubble are really a nice compact solution designed around the LEV cell--some of that mitsubishi innovation hidden in the details. Nobody else does this, e.g. Tesla and BMW use a bunch of wires.

 

[stoatwblr]

Since there is no real thermal control for the Pack (just blow some air around inside), it is a question of how effective or important are the temperature measurements?

Given the thermal sensitivity of the cells, it's critically important

Both charge and discharge currents are limited if the cells are too hot or too cool, plus the pack temperature controls the use of both the blower and the chiller

Thermal runaway is a very real risk once the cells go over 40C, whilst excess charge current when too cold will cause permanent damage

It's a pity Kolyandrex has disappeared - but on the other hand if someone else was to take on the task of reverse engineering the BMU programming it may be possible to publish what they find (kolyandrex kept the details close to his chest)

The ECU repurposed for BMU function is the same one used on late 1990s/early 2000s Mitsubishi EVOs and I'd imagine widely used on Mitsubishis of the era. Opening the spec means that third parties could become involved

 

[stoatwblr]

The ECU repurposed for BMU function is the same one used on late 1990s/early 2000s Mitsubishi EVOs and I'd imagine widely used on Mitsubishis of the era. Opening the spec means that third parties could become involved

I think this document will help a lot, along with IDA-Pro (https://hex-rays.com/ida-pro/ )

 

[coulomb]

I think this document will help a lot

Lots of good clues, for sure. Thanks!

Alas, some critical files are missing, and there is:
"It [ the pdf document ] assumes you know how to dump your ROM to a hex file using ECUFlash."

I think I looked at ECUFlash some time ago, and decided it didn't do anything I wanted at the time. But it could certainly be worth another look. Unfortunately, it looks like the last change was 15 years ago in 2009. And it looks like it's no longer open source, per this post, which isn't supposed to be possible.

[ Edit: At least, it looks like it will be possible to extract Mitsubishi firmware without extreme hacking skills. Even if reassembling isn't practical, patching is a possibility. ]

When I get some time...

 

[piev]

Hey Guys,

I didn't take that good of notes during the experiment but I recorded the data if anyone wants to slug through it. I will but it may be a few days.

Not sure your questions are relevant to what I was trying to prove to myself. My goal was to see if the vehicle would drive after empty. I pretty much proved it won't. The OBDZero is very accurate on mimicking the MiEV capacity calculations from what I can see. It reported the Capacity, the capacity used and the remaining capacity. I started at BMUCapAh 44.7 Ah or maybe BattCapAh 43 it depends on which value you use because there is a 2 in OBDZero. When the remaining capacity reached 0.3Ah there was a reduction of power but not at 10% which would have been around 4.5Ah. It didn't stop until 0.1Ah. so I suppose the Car won't let you use 100% to start with since it only charges to 4.1V. Not sure if that is why to 50Ah is only 45Ah in the MUT3 or if they also give margin at the bottom. It obviously is not looking at cell voltage at all to know when the battery is depleted.

 

[MickeyS70]

When the remaining capacity reached 0.3Ah there was a reduction of power but not at 10% which would have been around 4.5Ah. It didn't stop until 0.1Ah. so I suppose the Car won't let you use 100% to start with since it only charges to 4.1V. Not sure if that is why to 50Ah is only 45Ah in the MUT3 or if they also give margin at the bottom. It obviously is not looking at cell voltage at all to know when the battery is depleted.

You’re correct, during discharge the remaining capacity value (max 45Ah) is used for all calculations. [EDIT] Later models seem to have a safety function where low cell voltages trigger power reduction and ultimately complete shutdown. The tortoise coming on around 10% SOC is therefore just a warning of worse to come if ignored, e.g power reduction around 1-2% and complete shutdown close to 0%

What you might not be aware of is that you can tap into the remaining NMC capacity after the car shut down as the BMU stores the values in a volatile memory.

If you disconnect the 12V Aux these settings are erased and when powered up again the BMU sets a new SOC based on cell voltage only. Due to different chemistry you won’t get close to 100% but the car will happily drive another few miles until the scenario repeats itself. It’s been proved that with multiple resets the majority of the 93Ah capacity is actually accessible.

Not very elegant, but it works, see below (follow contributions from Ionysos, from Feb 24 onwards)

https://www.goingelectric.de/forum/viewtopic.php?t=82690&start=50

 

[piev]

Looked at data. Started at 140261 Km. Drove to 140327 Km. That’s 41 miles or 66km. The BMURemAh was 25.2 and SoC1 and 2 were 56.6%. Range shown was 33 Miles. Ending BMURemAh 0.2, SoC1 and 2 were 0.5%. Voltage was 347.9 at start and 324.9 at end. Minimum cell 3.95 start and 3.695 v end.

41-33 = 8 miles past empty

That would be around 72 miles if full.

 

[MickeyS70]

Voltage was 347.9 at start and 324.9 at end. Minimum cell 3.95 start and 3.695 v end.

Usually a full battery should show around 360V (4.1V/cell)?

If you do a BMU reset @ 3.7V your SOC should jump up to around 20%…

 

[kiev]

@piev said,

My goal was to see if the vehicle would drive after empty. I pretty much proved it won't.

oh okay now i understand what you were testing.

That "45Ah" setting in the BMU memory is a hard limit for now until someone figures out how to change it.

 

[stoatwblr]

I think I looked at ECUFlash some time ago, and decided it didn't do anything I wanted at the time.

Kolyandex made claims that the firmware is readable/writeable with his mmc tool and a MUT3 interface: https://forum.kolyandex.su/

 

[MickeyS70]

Kolyandex made claims that the firmware is readable/writeable with his mmc tool and a MUT3 interface: https://forum.kolyandex.su/

Unfortunately he seems to have gone AWOL but there is some encouraging movement regarding CAN-hack alternatives (very long but highly informative):

https://forums.aeva.asn.au/viewtopic.php?t=5515&start=825

 

[phebbler]

Hello everyone, I am new to posting this forum and interested in doing this cell swap.

Over the winter of 2022-2023 I mated a 1984 TVR 280i body onto a 2012 i-Miev Chassis. The i-Miev at the time only had about a 60km displayed range, about 52km actual for me.

In the summer of 2023 I dropped the battery pack and replaced the 12 weakest cells with used pulled LEV cells from a seller on eBay and am now able to drive about 72km actual with 80km showing when fully charged. Since I have to drive 40km of highway round trip just to get to the edge of Saskatoon I would like to do this swap to hopefully get back to around 100km range.

Hello piev, I was wondering if you installed the cells as charged from the supplier or did you have to manipulate the voltage of each cell prior to assembling them into the pack? After reinstalling the pack and placing the car on the charger for the first time were you able to change all the cells up to 4.1V or did it require any special process?

I don't have access to a mut-3 so I was planning on just letting the BMS adjust over time like I did with the cell swap which only took a few trips. I would definitely like to purchase one if anyone can suggest an aftermarket mut-3 system that is known to work and be compatible. I have found various systems out there but because of the cost versus the questionable compatibility and vendors I have been hesitant to purchase one.

 

[MickeyS70]

Hello piev, I was wondering if you installed the cells as charged from the supplier or did you have to manipulate the voltage of each cell prior to assembling them into the pack? After reinstalling the pack and placing the car on the charger for the first time were you able to change all the cells up to 4.1V or did it require any special process?

I don't have access to a mut-3 so I was planning on just letting the BMS adjust over time like I did with the cell swap which only took a few trips. I would definitely like to purchase one if anyone can suggest an aftermarket mut-3 system that is known to work and be compatible. I have found various systems out there but because of the cost versus the questionable compatibility and vendors I have been hesitant to purchase one.

Hello and welcome to the forum:
Easiest way to ‘bench balancing’ cells is to connect them in parallel and let them equalise over a few days before putting them in the car. Charging will end once a cell reaches 4.1V, therefore balancing beforehand is essential.

Due to different cell chemistry the BMU will have great difficulty adjusting the capacity (if at all) easier and quicker to tell the car that a new battery has been installed. Instead of a MUT3 you can use a Lexia/Diagbox clone to perform this task, see discussion below.
https://myimiev.com/threads/i-miev-and-lexia-3-and-diagbox.4042/
Nice car btw..

Mickey

 

[phebbler]

Hello and welcome to the forum:
Easiest way to ‘bench balancing’ cells is to connect them in parallel and let them equalise over a few days before putting them in the car. Charging will end once a cell reaches 4.1V, therefore balancing beforehand is essential.

Due to different cell chemistry the BMU will have great difficulty adjusting the capacity (if at all) easier and quicker to tell the car that a new battery has been installed. Instead of a MUT3 you can use a Lexia/Diagbox clone to perform this task, see discussion below.
https://myimiev.com/threads/i-miev-and-lexia-3-and-diagbox.4042/
Nice car btw..

Mickey

Thank you for the reply. I will check out the link.

 

[piev]

Hello phebbler,

The cells I purchased came balanced. In fact, everytime I bought cells from China they came balanced. Around 50% SOC. 3.6 or 3.7 I can remember now but they didn’t vary even by a millivolt.

I just installed them and the car charged them all to 4.1v and does still charge them to 4.1. They don’t vary much and it balances at the end.

Oh, I downloaded the MUT3 SE software off of a Russian site and bought the windows driver from them. It works with Tactrix 2.0 OBD device.

https://forum.kolyandex.su/viewtopic.php?f=6&t=82

 

[phebbler]

Hello phebbler,

The cells I purchased came balanced. In fact, everytime I bought cells from China they came balanced. Around 50% SOC. 3.6 or 3.7 I can remember now but they didn’t vary even by a millivolt.

I just installed them and the car charged them all to 4.1v and does still charge them to 4.1. They don’t vary much and it balances at the end.

Oh, I downloaded the MUT3 SE software off of a Russian site and bought the windows driver from them. It works with Tactrix 2.0 OBD device.

https://forum.kolyandex.su/viewtopic.php?f=6&t=82

That sounds good. I have sent a request for quote from the vendor you posted the contact info for. It seems like it should be a fairly straight forward battery upgrade. I also appreciate the link for the software and the suggested device. I appreciate everyone's help.

 

[piev]

I installed the can bridge between the ev ECU and the BMU. The car will go to ready and I drove it… now it’s charging. Weird thing is I’m getting BMU CAN bus errors. The MUT won’t talk to the BMU I just get errors. I tried several different configurations with the terminating resistors. I drove it with a terminator going to the BMU and no terminator going to the EV ECU. Not sure why I’m getting the error. Any ideas?

 

[MickeyS70]

CAN bus is terminated at both ends, putting a bridge in the middle shouldn’t require any additional resistors unless the signals are completely isolated. Maybe not all required messages make it through or at least not fast enough, I remember OZ Auto had to upgrade their bridge’s processor power to make it work?

Is your CAN bridge operating bi-directional?