Aftermarket iMiEV battery upgrade project

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Re: Aftermarket iMiEV battery upgrade project

Post by nuggetgalore »

coulomb wrote: Sat, 26 Sep 2020, 10:21 Another update on the Minicab MiEV with the 94 Ah cells. This week I started with a baseline range test, getting the Range Remaining meter down to 1 km before the turtle......
Interesting report, thanks.

Once the battery is down to turtle, how much energy can you charge back into the pack?
Do the cells reach 4.xx V?
Another interesting bit of info would be good to know if after driving about 80 km to turtle, when charging to full,
does the charging take a balancing rest of several minutes? I assume the cells are being balanced all the time (I observed with the i909 the balance drivers are switching on and off all the way from empty to full). A second assumption is that if during charging the balancing falls behind schedule, this pause in charging allows the balancing to catch up. I have yet to catch the moment when it pauses to see what the drivers do.
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Re: Aftermarket iMiEV battery upgrade project

Post by coulomb »

nuggetgalore wrote: Sat, 26 Sep 2020, 12:41 Once the battery is down to turtle, how much energy can you charge back into the pack?
Good question. It would have been on the EVSE's screen too, but they had to move the car before I got there. I'll try to measure it next time. However, according to the BMS via the G-Scan tool, the battery was at 44.5 Ah. The battery was down to 4.5 Ah after the turtle appeared. So according to the BMU, 40 Ah was used. This was before the gadget was connected, so that is presumably reasonably accurate; Ah don't depend on chemistry or cell voltage.
Do the cells reach 4.xx V?
Yes. At the start of the big range test, the lowest cell voltage was 4.075 V, so the highest cell voltage would have been around 4.100 V. I believe that the OBC always charges to 4.10 V. It may be possible to get a little more range from NMC cells by increasing the OBC finishing voltage, to perhaps 4.15 V (perhaps with a switch, so for normal use you'd still charge to 4.10 V).
Another interesting bit of info would be good to know if after driving about 80 km to turtle, when charging to full, does the charging take a balancing rest of several minutes?
Ah, the infamous pause that tricks some EVSEs into forcing a reduced charge rate (if interested, see about this post). I don't see why this would change with the different size/chemistry battery, though it may happen more or less frequently I suppose. I prefer not to wait around for a charge, since the MiEV has a small OBC, so a "full" charge takes some 5 hours (with only ≈40 Ah unlocked). I don't have any remote reporting set up. A fast charge is a possibility, though none are nearby (yet; one is coming ≈3 km from the workshop). [ Edit: and fast charging has to be checked carefully; it's likely controlled by the BMU and so it could charge too fast for the new cells. The new cells seem to recommend 1C as the "rapid charge" rate; that's only 94 A. I believe that the factory cells can be charged at higher than that. At least the BMU should limit every cell voltage to about 4.1 V, and hopefully the new cells' temperature is monitored just as well as the old. ]
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Re: Aftermarket iMiEV battery upgrade project

Post by Riore »

wovenrovings wrote: Wed, 16 Sep 2020, 16:47 There is another guy in brisbane, Daniel Rykiert, that has put a second 150AH pack in the back of his Minicab. Not sure if he is an AEVA member.
I just lurk TBH.
Anyway he has it spliced into the wires to DC wires to the motor controller.
I added the main positive and negative of the add-on pack to the positive and negative contactor in the original battery. No cutting of anything, undid the bolt in the contactors and placed the additonal crimped wires and tightened the bolt again.
He has reported seeing over 200km on the GOM and fast charging of 47kW. This experience may lend hope to the idea that tricking the current meter from the battery might work.
I have done some testing;
- I used the 50kW and 350kW fast chargers to test the QC capabilities and they seem to cap at 47kW for our voltage batteries or (125Amps) the main pack was pulling about 10kW and the additional pack was pulling about 35kW.
- Due to the discharge chemistry voltage differences between the two packs behave oddly.
-82% to 15% gave me around 3km per loss of 1km on the GoM
-I drove 170km on the highway. At the 15% SoC on the main BMS the secondary pack starts feeding heavily into the main pack under light load and idle. I drove a further 50km around town until the turtle came up at 10.5%. Drove a further 10km home with still 10.5% remaining.
-Charged the car with my AC charger 14amp (3300watt), secondary pack said it had only depleted 70Ah. 13 hours 2 minutes and 6 seconds later it was at 100% SoC again. Pulled 42.9kWh from the wall.
-The GoM hasn't gone above 144km surprisingly.
-There is no issue with QC it just plugs in and goes and so does AC. Some people with Nissan Leaf reported having to disconnect the secondary pack and start the charge and plug the second pack in while charging.

[ Edited Coulomb: corrected units. ]
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Re: Aftermarket iMiEV battery upgrade project

Post by coulomb »

Riore wrote: Sat, 26 Sep 2020, 14:43 I just lurk TBH.
Thanks for posting now. So your secondary pack is 3x the capacity (150 Ah vs 50 Ah) of the original? Wow. What BMS (if any) do you have with the second pack?
- I used the 50kW and 350kW fast chargers to test the QC capabilities and they seem to cap at 47kW for our voltage batteries or (125Amps) the main pack was pulling about 10kW and the additional pack was pulling about 35kW.
Interesting. To provide 350 kW, you need 400 A at over 800 V. 400 A at 350 V is still 140 kW.

The only 350 kW chargers I know of near Brisbane are the ones at Coochin Creek (Glasshouse Mountains), and they're CCS type 2. I assume you are using CHAdeMO; there are also 2 CHAdeMO stations listed in Plugshare (I've not been there as yet). These are listed as 100 kW.
- Due to the discharge chemistry voltage differences between the two packs behave oddly.
-82% to 15% gave me around 3km per loss of 1km on the GoM
So this difference is presumably why you see ≈3x the range as opposed to ≈4x on paper. Though perhaps your original pack is considerably depleted in capacity?
-I drove 170km on the highway. At the 15% SoC on the main BMS the secondary pack starts feeding heavily into the main pack under light load and idle.
What sort of current transfers between the packs?
How are you measuring this?
How are you measuring figures such as 15% SOC above? Canion?
I drove a further 50km around town until the turtle came up at 10.5%. Drove a further 10km home with still 10.5% remaining.
You drove 10 km with the turtle showing? Are you able to generally keep up with traffic?
So that's a total of about 170 + 50 + 10 = 230 km. What's the Minicab range when new?
-The GoM hasn't gone above 144km surprisingly.
Those Mitsubishi designers had such limited vision, not anticipating this sort of thing! ;)
-There is no issue with QC it just plugs in and goes and so does AC.
Great to hear.

Is your connection to the secondary pack before or after the current sensor? Based on the GOM behaviour, I'd guess it's after [ edit: was before ], so the BMS doesn't see the current from the other battery. [ Edit: But the current sensor would see the transfer current from secondary to main pack. ] At times, there would be very significant differences between the current measured by the main battery current sensor, and power drawn by the motor controller. The fact that this doesn't cause trouble codes is encouraging for the current sensor modifying gizmo.
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Re: Aftermarket iMiEV battery upgrade project

Post by coulomb »

@Riore,

sorry to pepper you with questions, but now I'm curious as to how you physically built the secondary pack. You mention contactors for the secondary pack; were these from another Minicab or iMiEV pack? I assume that 150 Ah cells would not fit 48 mm apart, so you would not have been able to use the original CMUs, correct? In any case, I don't see how you could connect the CMUs to anything.

Is this where you paralleled the contactors?

Where to parallel secondary pack.jpg
Where to parallel secondary pack.jpg (113.36 KiB) Viewed 1214 times
Or perhaps further down, on the other side of the current sensor?

[ Edit: had pack+ and pack- in the wrong place. ]
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Re: Aftermarket iMiEV battery upgrade project

Post by nuggetgalore »

Riore wrote: Sat, 26 Sep 2020, 14:43
wovenrovings wrote: Wed, 16 Sep 2020, 16:47 There is another guy in brisbane, Daniel Rykiert, that has put a second 150AH pack in the back of his Minicab. Not sure if he is an AEVA member.
I just lurk TBH.
Anyway he has it spliced into the wires to DC wires to the motor controller.
I added the main positive and negative of the add-on pack to the positive and negative contactor in the original battery. No cutting of anything, undid the bolt in the contactors and placed the additonal crimped wires and tightened the bolt again.
Now that is rather interesting,thanks for posting.

So if the two packs are both connected to the contactors, and the service plug is pulled, there is still full 340 -360 V DC at the contactors ?
I suppose there are additional fuses and switches or contactors to disconnect the additional pack from the original pack. 175 anderson's I think have been used in a similar additional pack set up, but I think he connected it to the inverter with a contactor linked to the main plus contactor (last up / first down in the power up /power down sequence.

Edit.: I drafted this before I saw coulombs post (got called to watch Endevour and Paradise, got to comfort Mrs nugget with all those murders....)
Yes that is how I interpreted where the connection is where you point to on the picture of the contactor array.
Edit 2.:
I think where you marked pack- and pack +, that goes to the inverter, pack are the two lower terminals of the QC contactors and the upper three terminals of the minus & plus and the precharge contactors. I hope I don't make a fool of myself here.
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Re: Aftermarket iMiEV battery upgrade project

Post by Riore »

coulomb wrote: Sat, 26 Sep 2020, 20:10 Thanks for posting now. So your secondary pack is 3x the capacity (150 Ah vs 50 Ah) of the original? Wow. What BMS (if any) do you have with the second pack?
The secondary pack is 90x 150AH 3.7v NMC. I bought 88 Cells but they sent 90 so I just threw them in as the configuration had two spots left anyway 15cells (left to right) x 6cells (rear to front) box that fit perfectly behind the rear seats. I bought a BMS from China but wasn't happy with its construction so I'll need to modify it but at the moment the pack is BMS-less but I manually monitor the cells periodically. I use a columb counter shunt that shows me the Voltage, AH, temperature, charge and discharge current of the secondary pack, it also controls the contacts manually and allows for setting Over voltage, Over current, Under voltage.
Interesting. To provide 350 kW, you need 400 A at over 800 V. 400 A at 350 V is still 140 kW.

The only 350 kW chargers I know of near Brisbane are the ones at Coochin Creek (Glasshouse Mountains), and they're CCS type 2. I assume you are using CHAdeMO; there are also 2 CHAdeMO stations listed in Plugshare (I've not been there as yet). These are listed as 100 kW.
I used the Coochin Creek CHAdeMO charger which is a Tritium PK350, these support upto 920V 200A over CHAdeMO according to the spec sheet.
So this difference is presumably why you see ≈3x the range as opposed to ≈4x on paper. Though perhaps your original pack is considerably depleted in capacity?
My original pack is at 36.5AH acccording to Canion.
What sort of current transfers between the packs?
How are you measuring this?
How are you measuring figures such as 15% SOC above? Canion?
Most I have seen feeding between the packs is around 2kWh but I haven't tested this at a wide range of SoC. When I throttle 100% the secondary pack pulls around 20kWh and the main pack pulls 10kWh, dropping it into neutral and the secondary pack is feeding back into the main pack to stabilize voltages.
Canion reports the SoC from the cars BMS.
You drove 10 km with the turtle showing?
Yes
Are you able to generally keep up with traffic?
It was still happily pulling the 32kWh limit, I reached 70kph with turtle on.
So that's a total of about 170 + 50 + 10 = 230 km. What's the Minicab range when new?
Not sure of the range new but without the secondary pack I was only getting 70KM on the highway (100%-20%) and 100KM around town (100%-20%)
Is your connection to the secondary pack before or after the current sensor? Based on the GOM behavior, I'd guess it's after [ edit: was before ], so the BMS doesn't see the current from the other battery. [ Edit: But the current sensor would see the transfer current from secondary to main pack. ] At times, there would be very significant differences between the current measured by the main battery current sensor, and power drawn by the motor controller. The fact that this doesn't cause trouble codes is encouraging for the current sensor modifying gizmo.
The connection is after the sensor which was a lucky fluke as there is no easy read arrow showing the current flow on it like the Nissan Leaf videos I watched. It took many hours for me to drop the battery and pull it by hand from under the jacked vehicle and put it back. So much relief that it was correct the first try.
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Re: Aftermarket iMiEV battery upgrade project

Post by Riore »

coulomb wrote: Sat, 26 Sep 2020, 20:35 @Riore,

sorry to pepper you with questions, but now I'm curious as to how you physically built the secondary pack. You mention contactors for the secondary pack; were these from another Minicab or iMiEV pack?
I bought them from China. TE Conectivity EV200AANA. It just to connect and disconnect the packs if I needed to because in some viedos I saw some issues arose with Nissan Leafs having issues with charging refusing to initiate with two packs active the bypass was to start the charge on the main pack and connect the second pack after but this hasn't been a problem for me with my Minicab.
I assume that 150 Ah cells would not fit 48 mm apart, so you would not have been able to use the original CMUs, correct? In any case, I don't see how you could connect the CMUs to anything.
This isn't a something I have looked into for my design.
Is this where you paralleled the contactors?
Yeah, I connected it to his side of the contactors the positive right is the precharge positive contactor apparently so I selected the middle contactor. The negative on the left is where I put my negative cable. [/quote]
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Re: Aftermarket iMiEV battery upgrade project

Post by Riore »

nuggetgalore wrote: Sat, 26 Sep 2020, 22:14 So if the two packs are both connected to the contactors, and the service plug is pulled, there is still full 340 -360 V DC at the contactors ?
If I pulled the service plug the main pack connection I made from the main pack to the secondary pack would read 0v, I would open the contactors before I did this as a safe caution anyway to cut the connection from the secondary pack but I don't think it would be necessary.
I think where you marked pack- and pack +, that goes to the inverter, pack are the two lower terminals of the QC contactors and the upper three terminals of the minus & plus and the precharge contactors. I hope I don't make a fool of myself here.
Correct the bottom posts on the bottom 3 contactors go to the cars different inverters.
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Re: Aftermarket iMiEV battery upgrade project

Post by nuggetgalore »

Riore wrote: Sun, 27 Sep 2020, 05:24 I use a columb counter shunt that shows me the Voltage, AH, temperature, charge and discharge current of the secondary pack, it also controls the contacts manually and allows for setting Over voltage, Over current, Under voltage.
Did you build that coulomb counter combo yourself or could you buy it of the shelf?
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Re: Aftermarket iMiEV battery upgrade project

Post by Riore »

nuggetgalore wrote: Sun, 27 Sep 2020, 09:15 Did you build that coulomb counter combo yourself or could you buy it of the shelf?
Its called a JUNTEK VAT4300 400V 300A.
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Re: Aftermarket iMiEV battery upgrade project

Post by coulomb »

I corresponded with Weber about recent progress on the 94 Ah battery upgrade range restoration project. His correspondence is greatly appreciated; thanks, Weber!

He found a great name for what I'm attempting at present: current spoofing. We're substituting adjusted (spoofed) current reading values instead of actual current readings. If a digital box is added to correct these current readings, that would be un-spoofing (perhaps de-spoofing). Naming a thing is an important step towards understanding that thing.

But he made a great point: current spoofing has limitations. [ Edit: In fact, @Richi pointed this out two weeks ago, but I wasn't listening. Sigh. ] When the minimum cell voltage falls below a certain point, regardless of the amp·hour counter, the BMS is still going to bring on the turtle. I wasn't paying much attention to the voltage, as it looked to me that the main limitation was the amp·hour reaching a certain level. He figured that if the turtle is presently arriving at say 50% SOC of the new cells, but that voltage corresponds to say 20% SOC of the old cells, then the BMS isn't going to allow much further driving no matter what the amp·hour counter value is.

So I've redrawn the overlaid LMO and NMC graphs far more carefully, and this is the result:

LEV50 vs NMC 2.png
LEV50 vs NMC 2.png (66.88 KiB) Viewed 1186 times
I've drawn two lines at 3.75 V and 3.65 V, corresponding roughly with the lowest cell voltages of two measurements. The first was with the Range Remaining meter at 21 km; state of charge was 25% (and "display" SOC 29.5%; I don't understand what the latter is about). The lowest cell voltage was 3.785 V. The second measurement was at turtle, 1 km on the Range Remaining meter, 10% SOC (and also 10% displayed SOC). Lowest cell voltage was 3.655 V (rested, taking measurements). The reported SOC are far from those on the graph; I assume that's because the above graph at 1C contains significant internal resistance adjustments. So really I should be measuring at around the 50 A mark; perhaps I'll figure out a safe way of doing that.

However, it's clear that Weber has a very valid point. Taking the 3.65 V line (the lower of the two horizontal thin blue lines), the NMC cell is indeed at 49% SOC, while the corresponding SOC for the old cells (what the BMS will be believing is the true SOC) is 27% SOC. That's not going to allow for much extra driving, regardless of the extent of current spoofing. [ Edit: this result is unlikely to change in our favour when internal resistance and different C rates are taken into consideration. ]

So what might work better is what Weber calls cell voltage spoofing. With voltage spoofing, a small computer can look up the differences in the graphs, and tell the BMU "what it wants to hear" to get the SOC of the new battery roughly correct. Obviously, analog spoofing of 88 cells all at once is totally impractical, but it could be done at the CAN bus level, by a man-in-the-middle CAN filter between the CMUs and the BMU. This is a private CAN bus, unfortunately not the same bus as would need to be intercepted for unspoofing. But perhaps one box near the BMU could do spoofing and unspoofing, and fix the Range Remaining and power meters at the same time. It would need 4 (!) CAN bus interfaces. It happens that the CMUs to BMU CAN bus is on the same connector (C-26) as the current sensor signals that I've been working with.

It happens that the format of the CAN bus packets between the CMUs and the BMU is fairly well known; I managed to work it out myself studying the CMU firmware. It has been validated by other parties. So that does sound moderately doable.

So I have lots to think about.

[ Edit: added sentence starting "With voltage spoofing... ". ]
[ Edit: NMO → LMO. Dislexia, sigh. ]
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Re: Aftermarket iMiEV battery upgrade project

Post by antiscab »

possibly more work, though I wonder if the CMUs firmware could be reprogrammed to such that the cell voltages reported to the are scaled such that 4.1v = 4.1v actual, 3.65v = 3.45v actual (meaning 0v = 1.7v actual)
Without the original source code it would mean writing firmware from scratch, though if the CMUs just report voltages and do balancing, that might not be too bad.
does anyone know what micro is used?
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Re: Aftermarket iMiEV battery upgrade project

Post by coulomb »

antiscab wrote: Mon, 28 Sep 2020, 00:03 possibly more work, though I wonder if the CMUs firmware could be reprogrammed to such that the cell voltages reported to the are scaled such that 4.1v = 4.1v actual, 3.65v = 3.45v actual (meaning 0v = 1.7v actual)
I'm not following your mapping, but I think I get the idea. I do have a binary image of a CMU, so patching is possible. I haven't looked into how to program [ i.e. reflash ] them however.
Without the original source code it would mean writing firmware from scratch, though if the CMUs just report voltages and do balancing, that might not be too bad.
There is a hell of a lot of code in there for just reporting volts, temps, and doing balancing. I have to admit to understanding only maybe 20% of it so far, after months of reading it on and off.
does anyone know what micro is used?
It's an NEC V850 ES, or at least that works with Ida Pro. NEC bought out by Renesas ten years ago. It's 32-bit, 32 registers, a little quirky but OK to work with. [ Edit: some details in this MyIMiev topic. ]

Reflashing the CMUs is scary, and may not be able to read original code to put it back. Also, de-spoofing (so you can read real cell voltages with Canion etc) can't be done that way (still need a separate box for that). One CAN filter near the BMU could spoof and unspoof to the exact original readings. Of course, if the CMU mappings are simple enoughm they could possibly be undone accurately enough by a separate box.

Thanks for the thoughts.
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Re: Aftermarket iMiEV battery upgrade project

Post by nuggetgalore »

coulomb wrote: Sun, 27 Sep 2020, 21:28 I corresponded with Weber about recent progress on the 94 Ah battery upgrade range restoration project. His correspondence is greatly appreciated; thanks, Weber!



So I've redrawn the overlaid LMO and NMC graphs far more carefully, and this is the result:


LEV50 vs NMC 2.png
When Chris posted the graph for the 60Ah cells I did plot some of the pertinent points on the LEV50 graph and saw the same thing, but of course with lesser accuracy.
It nearly stopped me from buying the cells because it appears that in the V range the car uses the LEV50 should have about 45Ah, the LiYuan 60 Ah less than 40 Ah . The graph on the cell spec sheet is much flatter than Chris's graph (would be, they want to sell the product).
3.6V60Ah-NMC.pdf
(190.09 KiB) Downloaded 51 times
The big worry is still what happens at 2C or more.
The fact that my recording of low cell voltages under load indicates that the car quite happy accepts cell voltage down to or very near to 3.1 V, I took the punt. If I ever get to load the cells to approx 120 A* for a short burst, I find out if my horse ran last.

* CanIon max display I ever observed is about 180 A,with gear shift in Eco,it appears to top at about 122 A. I mostly drive in Eco anyway, so I might have to block the D and B slots.
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Re: Aftermarket iMiEV battery upgrade project

Post by coulomb »

nuggetgalore wrote: Mon, 28 Sep 2020, 17:49 CanIon max display I ever observed is about 180 A,with gear shift in Eco,it appears to top at about 122 A. I mostly drive in Eco anyway, so I might have to block the D and B slots.
? The data sheet says maximum continuous discharge is 3C. That's 180 A. So you'll rarely hit that 3C, and even then only briefly (?), when they are rated at 3C continuous. Of course, that might be if they're infinitely heat sunk to 25°C. But I suspect you'll be fine.
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Re: Aftermarket iMiEV battery upgrade project

Post by tonyw »

Don't know whether this information is useful to the discussion or not, so take it or leave it...

The other day we ran out of juice on the way home from a shopping trip. Fortunately we were able to pull into the car parking area outside an office, where the nice people let us plug into their GPO for 45 minutes while we went and had lunch.

That was the second occasion I've run it down to a stop: the previous time I managed to limp into the carport at home, but having to switch off for a minute and try again, to get the last few metres. The last hundred metres or so were driven at a crawl.

On both occasions, we were down to a single flashing bar on the display, and no tortoise (I refuse to call it a turtle, which is a marine animal with flippers, while a tortoise is a land animal and the star of the original fable). GOM indication was about 9 km remaining IIRC.

I have never observed the tortoise light (except every time I turn on the power switch). If the tortoise light is supposed to be lit by <the lowest cell going below a threshold>, then the <give up, don't go any further> threshold must be above that, else we would see the light come on first.
cheers

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Re: Aftermarket iMiEV battery upgrade project

Post by bladecar »

I'm pretty sure the only time I've seen the tortoise symbol was when my bms was faulty.
In the past I followed general advice and occasionally ran it down til the battery indicator was flashing and there was 5 or so range left.
I haven't done that lately.
So my car just runs way down but I know what it's at when I leave home because on those occasions, I left home for that very purpose.
My car has a good life, mostly.
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Re: Aftermarket iMiEV battery upgrade project

Post by wovenrovings »

I have had the tortoise a couple of times. First time I was able to drive at least a kilometer in tortoise mode before reaching a charger. The second it went to 0 range then tortoise then stopped in about 100m. That was on hill. Just other day it went to 0 range about 1 km from home with my wife driving. Reached home no problems. Looked at it with canion and it said 7% left. So the GOM is exactly that.
If I can help let me know. I would really like to be able to do more than 100km.
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Re: Aftermarket iMiEV battery upgrade project

Post by coulomb »

wovenrovings wrote: Thu, 01 Oct 2020, 19:14 I have had the tortoise a couple of times.
Thanks. I have only about 150m of tortoise experience, and none in my Leaf.
I would really like to be able to do more than 100km.
That's certainly achievable now.

Here is a week late update. Since the original base range test of about 80 km, with the current spoofer installed, it now managed 110 and 130 km on two range tests, on both of which I ran out of time and didn't get to the tortoise. Since then, Joe (the owner) drove it this past long weekend (Queen's birthday public holiday last Monday) and had charges end with the Range Remaining meter (RR, aka GOM) read 165 km twice, and 155 km twice. One charge was a fast charge. He didn't allow the RR to drop below 35 km, since my tests didn't get it below 54 km (and I have the advantage of seeing the lowest cell voltage). In hindsight, I should have urged Joe to set up Canion or similar last week, for extra peace of mind.

On my last range test, RR was decreased 114 km over 130.2 km of driving (with more air conditioning this time). So that's about 0.876 km lost for 1 km gained, i.e. the RR meter was usable and actually slightly pessimistic. That's for the RR without air conditioning engaged; when the air conditioner is engaged, it displays a different RR figure. Taking only the "with air con on" figures, the RR meter lost 83 km for that 130.2 km of driving, or a very pessimistic 0.637 km/km. But when the air conditioning was off, the RR meter lost quite close to 1 km for every km driven. I'd say that's pretty good, and I'm surprised that the BMS "learned" the new conditions so quickly.

The BMS is still "learning" a lower capacity for the NMC pack. It's dropped from 45.8 Ah estimated to 43.3 Ah, a drop of almost 5.5% in 2-3 weeks. My guess is that it will continue dropping its estimated capacity for weeks or months, hopefully slowing down soon. I assume that this will make the RR figures a little more pessimistic. It could take some time to find the ideal current spoofing multiplier.

The current spoofer was designed to multiply the current readings by 0.64. I suspect that it's actually closer to 0.53 - 0.59; I can't be certain since we changed EVSEs part way, and I can't recall the exact charge currents with the two EVSEs before the spoofing. For pure amp·hour correction, the ideal multiplier would presumably be the ratio of the pack capacities, i.e. 50 / 94 (or is it 93? I can never remember) ≅ 0.53.

I hope to record the new (with spoofing) tortoise conditions today, to find out what range can be expected from current spoofing alone. It's looking good for just current spoofing; it seems that voltage spoofing won't be needed.

For giggles, here is the prototype current spoofer. Note the second PCB at the left, with the rail-to-rail buffer op-amp. Hopefully the final product will be much smaller and simpler.

Proto current spoofer internal sm.JPG
Proto current spoofer internal sm.JPG (184.66 KiB) Viewed 683 times
Note the automotive style, waterproof connectors.

Proto current spoofer external sm.jpg
Proto current spoofer external sm.jpg (148.74 KiB) Viewed 683 times
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Re: Aftermarket iMiEV battery upgrade project

Post by weber »

That's great news. Am I correct in saying that you've shown you can access 80% of the capacity of the new battery? What was the lowest cell voltage it got down to?

Do you have any hypotheses as to why you don't need (a) current unspoofing or (b) cell voltage spoofing?

Surely that horrendous circuit (4 multi-turn trimmers!) and 6 V battery can be replaced with a few 0.1% resistors (at most 6). You just have to correctly characterise the source and load, as to voltage and resistance, with some well-chosen measurements.
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Re: Aftermarket iMiEV battery upgrade project

Post by nuggetgalore »

coulomb wrote: Fri, 09 Oct 2020, 08:42

In hindsight, I should have urged Joe to set up Canion or similar last week, for extra peace of mind.
To watch amps , low and high cell voltage or whatever one might be interested in ,
I use EvBatMon. Just select the Gauge of interest and place it where it suits, the numbers are nice and big and visible without having to risk taking the eyes of the traffic.
An added bonus is you can capture the moment by just touching the camera icon, taking screen shots with CanIon is a pain and impossible while driving (with my smartphone anyway).
Plus we ought to support apps made by Aussies.....
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Re: Aftermarket iMiEV battery upgrade project

Post by coulomb »

weber wrote: Fri, 09 Oct 2020, 12:33 Am I correct in saying that you've shown you can access 80% of the capacity of the new battery?
I think we can access up to about 99% of the capacity this way, the last ≈1% being lost by not charging to 4.2 VPC.
What was the lowest cell voltage it got down to?
Today I got it down to 3.200 V (lowest cell), and the last 150 m to the workshop took it down to 3.175 V. It seems to be well and truly "over the cliff" by that point.
Do you have any hypotheses as to why you don't need (a) current unspoofing ...
It seems that the current sensor inside the battery is only used for a very limited number of purposes, perhaps two: for the power meter, and possibly for fast charging. It would be a "nice to have" to unspoof the current readings so that the power meter regained its full range, but I think most users would agree it's not essential. I've just had an evil thought: that power meter is probably one of those current driven things that could be unspoofed by an analogue amplifier somewhere between some computer and the dash. So no CAN bus filtering would be needed. But alas, it seems that the energy meter is driven by yet another "CPU" inside the dash. The "combination meter" has its own connection to the main CAN bus.

Energy usage indicator inside combination meter.png
Energy usage indicator inside combination meter.png (20.74 KiB) Viewed 642 times
As for DC fast charging, my guess is that a suitable current (likely 125 A) is requested, and if it only appears that ≈55% of that current is supplied, it just shrugs and assumes it's a lower power fast charger. When a cell voltage approaches too high a voltage (these are pretty similar for LMO and NMC), it will increase and decrease the requested power until the cell is near but below the voltage limit. It doesn't care what absolute value of charge current is required to keep the cell safe.

Finally, there is the motor controller. Since power seems unaffected by the current spoofing, it seems that the motor controller has its own current sensors. Obviously at least 2 phase current sensors are needed, and perhaps it doesn't care what battery current is required to sustain a given phase current, or if it does, it has its own current sensor.
Do you have any hypotheses as to why you don't need (b) cell voltage spoofing?
This surprised me. I guess that the tortoise is largely or solely determined by estimated battery capacity, and the "go no further" limit hasn't been hit yet. The graphs for NMO and NMC effectively align in the low SOC "cliff", so the existing protection should serve for NMC about as well as for NMO cells.
Surely that horrendous circuit ... can be replaced with a few 0.1% resistors (at most 6). You just have to correctly characterise the source and load, as to voltage and resistance, with some well-chosen measurements.
The prototype served its purpose well, I feel, but yes, I suppose I should have done some judicious measurements first. In fact, I should do that before the next prototype.

[ Edit: added sentence re combination meter having its own connection to the main CAN bus. ]
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Re: Aftermarket iMiEV battery upgrade project

Post by nuggetgalore »

coulomb wrote: Fri, 09 Oct 2020, 18:44


As for DC fast charging, my guess is that a suitable current (likely 125 A) is requested, and if it only appears that ≈55% of that current is supplied, it just shrugs and assumes it's a lower power fast charger. When a cell voltage approaches too high a voltage (these are pretty similar for LMO and NMC), it will increase and decrease the requested power until the cell is near but below the voltage limit. It doesn't care what absolute value of charge current is required to keep the cell safe.
Watching the on/off dance of the balance drivers during charging I made an assumption that the BMS
calculates a voltage based on min max and total pack volt ( referred as the target voltage,an item that can be read by the i909). This target voltage is then used to turn on or off the individual shunts or whatever is there to correct voltage differences between cells.
I have no proof other than that the balance drivers operate from the very start of charging to the very end, no matter if at the start of charging the SoC is high or low.
I think,not 100% sure, that during the rest period the drivers are off, I was thinking it may continue to actively balance, but maybe not.
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Re: Aftermarket iMiEV battery upgrade project

Post by dracekvo »

Whot you mean about battery Molicel INR-21700-P42A?
Maximum charge is 8.4A. With use 15pcs. We have max charge 126A. This is enought for DC-DC charging (max. 125A)

https://www.imrbatteries.com/content/molicel_p42a.pdf

In europe cost 1pcs 4.3€. One LEV50 = 65€. All pack 5720€.
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