Aftermarket iMiEV battery upgrade project

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jonescg
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Re: Aftermarket iMiEV battery upgrade project

Post by jonescg »

It might suggest you have a single cell which is bombing out under heavy load, yeah.
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Re: Aftermarket iMiEV battery upgrade project

Post by nuggetgalore »

jonescg wrote: Tue, 28 Jul 2020, 11:44 It might suggest you have a single cell which is bombing out under heavy load, yeah.
In the pursuit to better understand how the iMiEV limits the low depletion of the pack, I made a series of screen shots of the state of the battery with EvBatMon.

I tried to get a shot with about 100 A but my wife took the foot of the pedal too quickly. Nevertheless it shows the pack volt has not totally
collapsed although the low cell is considerably below the top cell


```` about 1km left on GoM ``Average cell volt 3.35 ``````` ```````` turtle has just stuck his neck out``` Average cell volt 3.42

Note that the low volt cell No 19 all the way and the high volt cell No 43 stayed on from about 2 km RR.
At higher SoC resp cell voltage the numbers jump all over the place because many cells have voltage very closely matched.
To find out at what low cell voltage the BMS will call it quits one would need to do these tests with a battery in a worse condition.
What is the opinion of the brains trust
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Re: Aftermarket iMiEV battery upgrade project

Post by nuggetgalore »

jonescg wrote: Tue, 28 Jul 2020, 11:44 It might suggest you have a single cell which is bombing out under heavy load, yeah.
Part two.
Some screen shots of charging a (down in capacity) iMiEV battery from turtle to full.

straight after running her to turtle I put her on the charger.
Charging at 8 amps all appears to be normal ,the high and low cells still the same as when running it flat.



This time it appears it takes a very long to fill to the ~98 % it usually charges to.
I cannot recall if I ever saw it reach 100% SoC .


Edit: some Qs re the EvBatMon App and CanIon App : quite number of Gauges do not work, but I'm not too concerned about that. I wished though that it would have a gauge showing the odometer, would make it easier to sort the images from different iMiEVs. I can get that on the CanIon app, but it does not give the detailed battery info as does EvBatMon. For some unknown reason it does not display the cell volt chart if I looked at the temp chart during the session, only if I go there first after shut down.
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Re: Aftermarket iMiEV battery upgrade project

Post by richi »

It won't surprise you to hear that you have a bad cell (possibly more than one).
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Re: Aftermarket iMiEV battery upgrade project

Post by nuggetgalore »

richi wrote: Sun, 09 Aug 2020, 16:09 It won't surprise you to hear that you have a bad cell (possibly more than one).
I agree, that is why I try to replace the cells.
Not sure if it was a smart move, but the 60 Ah cells have arrived from Perth and maybe I can complete the project Chris has started.
It will be a slow process, a lot of unknows to be researched. The Corona restrictions make certain things more difficult as well.

But in the mean time I endevour to gather as much information re the cells in my iMiEV as possible.
I checked with the icarsoft-i909 the voltage of each cell after a nearly full charge (rested several hours after charge) and recorded it on a spreadsheet (42 of the cells are (were) 4.10 V, and 46 were 4.09 V with no exception). As I am locked down and hardly drive, it may be some time until the battery charge is low(er) when I will check and record the cell volts again. This information may or may not be useful at a later stage. I will post the result if anybody is interested.

So at the moment I will parallel all the 60Ah cells and hopefully in a few weeks they should be at an equal voltage before assembling into the
12 modules.
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Re: Aftermarket iMiEV battery upgrade project

Post by stealthhack »

suziauto wrote: Mon, 06 Jul 2020, 07:48 Hi Everyone,

I purposely don't say much whilst I am still working on the project as I get so many messages and I prefer to announce the results when finished. Anyways, we have installed the cells and removed them a few times. The first install included the modifications to the cell boxes, the design and fabrication of BMS connection tags ( now have 500 in stock ) . The first install was the cells as they arrived with 30% SOC, the logic was the cars BMU would charge and balance these cells. What happened was some cells were too low and the error state prevented charging. Out they came and we have 10 small single cell chargers so we charged all 88. Upon installing we had some cells too high prompting another error code and no charging. So using the scan tool we identified the 2 overcharged cells and got the pack apart and discharged those 2 cells. This time we had charging, 30% on the fuel gauge and 56Km on range guess o meter. A few driving cycles but the best we can achieve is 56 km and 30%. The issue being the %SOC difference between the low and the high cells. Effectively so wide a gap that the BMU could not manage the balancing. So today the cells are all coming out and we will assemble them as 1 large 4v cell to self-balance with a small charger on the end of the string to keep some input going in (4v 8200Ah battery lol ). Some might say a no brainer and after all this, I agree we probably should have done this from day 1.

Other things we have learnt is how to reset BMU cell values, cell softening ( a low-level balance ) and how to get the car to calculate the cells SOC.

Based on what range was shown at 30% SOC .. it looks promising.

So when we are finally happy with this modification and worked out the procedures to get this done efficiently, we will post the results here and start promoting the Mod as a supply and fit to start and hopefully as a kit one day for DIY.

Cheers Graeme
Graeme, is there any progress on the new battery pack for I-Miev?
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Re: Aftermarket iMiEV battery upgrade project

Post by suziauto »

well they are working well , still locked in at 49Ah so we are getting standard range. Trying to work out how to release the other 45Ah but we are hopeful some software being written.. hopefully soon.
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Re: Aftermarket iMiEV battery upgrade project

Post by richi »

Do you mean that, after the two resets and a DBCAM, the SoH estimate reads 49 Ah? I think that's to be expected. The question really is: How far can you drive before seeing the turtle?
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Re: Aftermarket iMiEV battery upgrade project

Post by stealthhack »

the Turtle is based on voltage? I think that Graeme should make a video while driving the I-MIEV until 3,5-3,4V per cell.
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Re: Aftermarket iMiEV battery upgrade project

Post by brendon_m »

The software in the imiev can understand up to 60Ah so I'd expect that to be the max the SoH can be set to but what the actual range ends up being is the real question. Who cares what the SoH reads if the range checks out.

A brute force way around software limits would be to put a bypass link around the current sensor in the pack so that it only reads half the current in and out.
I don't know how the car would respond but similar things have be done on a leaf with success
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Re: Aftermarket iMiEV battery upgrade project

Post by mikedufty »

Also similar to the results with a doubled up battery (repeat post I made earlier)Post below from the guy who did it, which suggests you could get the extra range.
(from http://myimiev.com/forum/viewtopic.php?t=2793#p23784 ,there is more discussion there )
His setup had the extra battery connected in after the current monitoring which I guess would have a similar effect to the sensorr bypass suggested by Brendon.
___________________________________________________________________________

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Re: Additional pack

Fri Sep 11, 2015 7:02 am
I never ran it for a long time but adding an additional pack will work. The range meter starts out with a normal range (like 70 miles) regardless of how many packs are connected. The segments on the meter start to drop at a slower rate with two packs and the available range drops very slowly. Although the car reads current through the original pack, it doesn't read the current of the additional pack. Therefore, the car thinks it is using less energy (like driving down a mountain) because only 1/2 of the energy to run the car comes through the original pack and it's hall effect transducer. I didn't drive it to low battery cutoff or anything near to it because there was no monitoring on the external pack. However, the range looked like it would be nearly doubled. The additional pack (which was a standard I-MiEV pack with the steel bottom mounts removed) actually fit in the back of the car with the seats folded down. The rear weight bias and the higher CG with the pack in the back made the handling a little dicey. Plus it looked a little silly with a couple of large orange power cables going out the passenger side rear window and going into what looked like the gas tank door to other drivers.
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Re: Aftermarket iMiEV battery upgrade project

Post by nuggetgalore »

suziauto wrote: Fri, 14 Aug 2020, 15:42 well they are working well , still locked in at 49Ah so we are getting standard range. Trying to work out how to release the other 45Ah but we are hopeful some software being written.. hopefully soon.
Is the limit because of charging not enough or is the car limiting the outgoing Ahs?
stealthhack wrote: Fri, 14 Aug 2020, 17:29 the Turtle is based on voltage? I think that Graeme should make a video while driving the I-MIEV until 3,5-3,4V per cell.
Volts may be one of probably several conditions the BMS/EV-ECU calculates turtle, yes would be great to know how it all works and possibly to change the appropriate parameters.

I have paralleled about half the 60Ah cells into groups of 8 and 20 so far, I am surprised how quickly the volts evened out to within less than 5 mV. No idea if that is good news or not and also what will happen when I connect the groups. Some are now
about 3.54 V , others 3.72. The individual cells volt range was 3.1 to 4.05 (just a couple), the bulk of the cells range 4.43 to 3.63V
I intended to retap the M4 with M5 or M6 but have changed my mind now that I saw how the cell is made. It appears that the contact plate is very thin glued to an insulating layer on top of the positive volt frame of the cell .The thread is formed into a relatively small diameter plug that is peened to the contact plate. The pilot hole for the thread forming is generally just deep enough for the thread to be 5.5 mm deep. The poor quality of the thread is partly because the top few threads are loose/sloppy and swarf or debris at the bottom of the hole preventing the bolt to go to that depth (required if using an 8mm bolt fixing a 2 mm bus bar with 0.7 mm washer).
So far on about 7 of 10 holes I cleaned out the debris and finished the thread with a bottom tap, checking with a bus bar and feeler gauge that when fixing the bus bar the bolt is not bottoming. So I hope that engaging the better part of the female thread deeper down with an added 2 mm (ie 3 more turns) is good enough.
Last edited by nuggetgalore on Tue, 18 Aug 2020, 11:51, edited 1 time in total.
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Re: Aftermarket iMiEV battery upgrade project

Post by nuggetgalore »

richi wrote: Sun, 09 Aug 2020, 16:09 It won't surprise you to hear that you have a bad cell (possibly more than one).
Ok, with nothing better to do (no thanks to you,covid-19), I did some more data mining on my battery.

2010 model iMiEV battery data

EvBatMon battery data: 98.5% charged 360.2 V (31.7 Ah of 32.1 Ah capacity)
battery condition 66.88% 05/08/20 10:30:00 62,146 km


iScanner i909 data 05/08/20 10:30:00

cell A cell B cell C cell D cell E cell F cell G cell H CMU
4.09 V 4.10 V 4.09 V 4.09 V 4.09 V 4.09 V 4.09 V 4.09 V ID01
4.09 V 4.09 V 4.09 V 4.09 V 4.09 V 4.09 V 4.09 V 4.09 V ID02
4.10 V 4.09 V 4.09 V 4.10 V 4.09 V 4.09 V 4.09 V 4.09 V ID03
4.09 V 4.09 V 4.10 V 4.09 V 4.10 V 4.10 V 4.10 V 4.10 V ID04 4 cell module
4.10 V 4.10 V 4.10 V 4.10 V 4.10 V 4.10 V 4.10 V 4.10 V ID05
4.10 V 4.10 V 4.10 V 4.10 V ID06
4.09 V 4.09 V 4.09 V 4.09 V 4.09 V 4.09 V 4.09 V 4.09 V ID07
4.10 V 4.10 V 4.09 V 4.10 V 4.09 V 4.09 V 4.10 V 4.10 V ID08
4.10 V 4.10 V 4.10 V 4.09 V 4.10 V 4.09 V 4.09 V 4.10 V ID09
4.09 V 4.10 V 4.09 V 4.09 V 4.09 V 4.09 V 4.09 V 4.09 V ID10 4 cell module
4.09 V 4.09 V 4.09 V 4.10 V 4.10 V 4.10 V 4.10 V 4.10 V ID11
4.10 V 4.10 V 4.10 V 4.10 V ID12


EvBatMon battery data : Bat SoC 15.50% 327.1 V (5Ah of 32 Ah)
battery condition 66.67% 62,210km 1 Bar flashing 6 km RR

iScanner i909 data 17/08/20 14:30:00 capacity 32 Ah (corresponds with EvBatmon
but voltages not really)

cell A cell B cell C cell D cell E cell F cell G cell H CMU
3.74 V 3.77 V 3.75 V 3.74 V 3.74 V 3.75 V 3.75 V 3.75 V ID01 29.97 / 29.96
3.74 V 3.73 V 3.74 V 3.74 V 3.73 V 3.74 V 3.74 V 3.74 V ID02 29.87 / 29.83
3.75 V 3.73 V 3.72V 3.74 V 3.73 V 3.74 V 3.75 V 3.74 V ID03 29.91 / 29.87
3.73 V 3.74 V 3.76 V 3.74 V 3.76 V 3.74 V 3.76 V 3.75 V ID04 29.96 / 29.94
3.77 V 3.78 V 3.77 V 3.77 V 3.76 V 3.77 V 3.76 V 3.77 V ID05 30.11 / 30.10
3.77 V 3.77 V 3.77 V 3.77 V - - - - ID06 15.07 / 15.06 4 cell module
3.75 V 3.75 V 3.75 V 3.75 V 3.74 V 3.75 V 3.75 V 3.75 V ID07 29.97 / 29.97
3.76 V 3.77 V 3.75 V 3.76 V 3.74 V 3.74 V 3.76 V 3.76 V ID08 30.03 / 30.02
3.76 V 3.76 V 3.75 V 3.74 V 3.77 V 3.76 V 3.76 V 3.76 V ID09 30.05 / 30.03
3.75 V 3.76 V 3.74 V 3.74 V 3.74 V 3.74 V 3.74 V 3.75 V ID10 29.96 / 29.94
3.75 V 3.74 V 3.73 V 3.77 V 3.77 V 3.76 V 3.77 V 3.77 V ID11 30.04 / 30.02
3.77 V 3.77 V 3.77 V 3.77 V - - - - ID12 15.07 / 15.05 4 cell module
Lowest cells are 3.72 (1) and 3.73 (5)
Highest cells are 3.78 (1) and 3.77 (20) including all 8 cells in the two 4 cell modules.
Data collected about half an hour to one hour after stopped driving before putting it on charger.

At the early stages of charging I observed that the cell balance drives turn on and off on cells that are in the high range and on the lower range cells are off.

The i909 is quite clumsy to read data. It also jams itself when scrolling down deep into the BMU at cell balance drive CMU ID09 cell H. Fortunately the voltages can be read from two different menus.

Sorry about the jumbled data table.
Somehow the formatting on draft page does not translate to a nice table format on the submitted page, time to learn more about posting spreadsheets and such.

Re the 60Ah cells, was quick to get them to within 300 or so mA , but took much more time to get to within 200 and now waiting longer again for less than 100 mA.
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Re: Aftermarket iMiEV battery upgrade project

Post by richi »

I'd be also looking at the cell Voltages at low SoC (at, say, two blobs). If possible, monitor cell Voltages under load, too.
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Re: Aftermarket iMiEV battery upgrade project

Post by nuggetgalore »

richi wrote: Tue, 18 Aug 2020, 15:15 I'd be also looking at the cell Voltages at low SoC (at, say, two blobs). If possible, monitor cell Voltages under load, too.
Table one is at nearly full charge ,
table two shows the cell volts at only 1 bar shortly before turtle would come on with the low cells highlighted in red.

Pretty much as low as I dare to go if you look at the screenshots a few posts ago : at 88 amps not far from empty EvBatMon thinks the low cell is at 3.38 V but a few kms later at turtle and only drawing 5 Amps it is down to 3.18 V. That was only the third time I took the battery down to turtle, just to check whats happening and always put it on the charger straight after.
I think the pack suffered from fast charging too often by the previous owner, I only did it once in the 3 1/2 years since I bought it.
Anecdotally to me it indicates that the discharge curve is relatively flat down to about two bars, then falls of a steep cliff as all lithium cell curves do. I also feel that Mitsubishi built in a hefty safety margin in deciding at what point the low battery warning (turtle) comes on, 3.1 Volts is still a fair bit above the 2.75 low limit as per specs of the LEV50s. Better safe than sorry.
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Re: Aftermarket iMiEV battery upgrade project

Post by richi »

Sorry, I'm a moron: I misread the thing on a tiny phone screen, before my second coffee.

Know that the difference in actual charge between a Voc of 3.1V and 2.75V is … well, I believe the technical term is "not a lot."
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Re: Aftermarket iMiEV battery upgrade project

Post by nuggetgalore »

richi wrote: Tue, 18 Aug 2020, 20:59

Know that the difference in actual charge between a Voc of 3.1V and 2.75V is … well, I believe the technical term is "not a lot."
Yes ,judging from the graph(s) of the LEV50 and LiYuan 60 Ah cells, at around 3.5V they go down very sharply.
Which temps me to ask a hypothetical question for the brains trust.
As all the iMiEVs and especially the 2010 models that do not have the LEV50N cells would have a bunch of cells worse than the rest (see chart of mine at 1 bar GoM and Bat SoC 15.50% 327.1 V (5Ah of 32 Ah) and also the low volt cell(s) under load (screen shots of BatEvMon app).
How much might be gained by replacing the worst dozen or so cell with the better ones out of a similar aged car, assuming either one of the cars is damaged or otherwise poor or gets a refit of new cells?
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Re: Aftermarket iMiEV battery upgrade project

Post by brendon_m »

Prius packs get rebuilt all the time by combining the best cells of multiple packs. There's no reason that it won't work in an imiev but sadly the gains are probably not worth the labour involved.

On your chart you have the top cell at 3.78V and the bottom cell at 3.72V. If you were to keep going until the top cell also reached 3.72V (and presumably the bottom cells drop much lower) how much further down the road do you think you'll get because that would be the best case scenario of what you stand to gain by replacing only the especially crook cells
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Re: Aftermarket iMiEV battery upgrade project

Post by nuggetgalore »

brendon_m wrote: Thu, 20 Aug 2020, 19:46 Prius packs get rebuilt all the time by combining the best cells of multiple packs. There's no reason that it won't work in an imiev but sadly the gains are probably not worth the labour involved.

On your chart you have the top cell at 3.78V and the bottom cell at 3.72V. If you were to keep going until the top cell also reached 3.72V (and presumably the bottom cells drop much lower) how much further down the road do you think you'll get because that would be the best case scenario of what you stand to gain by replacing only the especially crook cells
Yes that is the 6000 dollar question.
I will play with the i909 again at various SoC and check if the low cells are changing.It is of course impractical (impossible even) to check cell volts with the i909 under load , so what ever I read is at rest. EvBatMon does indicate top and bottom cell(s) under load, the cell numbers change all the time but the volt reading not ( meaning several cells have the same volt). Exception is (was) cell 19 (cell C in module 3 I guess) appears to be a lot sicker and that in the module with the lowest total voltage (stressed because of the bad cells???).
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Re: Aftermarket iMiEV battery upgrade project

Post by richi »

Yeah, on the one hand, replacing it appears to give you little gain. But on the other hand, the bad cell is probably going to continue to degrade much more quickly than the others.

The SoC and SoH estimates are based on the Voc of the lowest cell (modulo some fiddle factors). So before too long, you'll end up with a pack that gives you 30 miles range instead of 60. However, if by some fluke the bad cell stabilizes and doesn't continue to degrade, then you've saved yourself a job by watching and waiting.
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Re: Aftermarket iMiEV battery upgrade project

Post by nuggetgalore »

The 60Ah cells are all now at exactly 3.63 V paralleled up. I am still waiting for some material to arrive before I can assemble the modules.
I probably should charge them up to a similar pack voltage as the original pack V is at rest the time I swap them over so the BMS is less likely to get confused. Not that I think 319 V (88x3.63) is any worry for the pack , it is happily running at less than 300 V under load.
Any comments appreciated.
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Re: Aftermarket iMiEV battery upgrade project

Post by nuggetgalore »

jonescg wrote: Sat, 08 Feb 2020, 16:48 new cell layout.jpg

This looks to be the least worst termination arrangement for the 60 Ah prismatic cells. It allows for the modules to be terminated at the forward end, meaning a lot less copper than otherwise. Fly-wired to each cell top will make the BMS happy. The BMS should sit on top with a minimum of fuss too.


The links as supplied between the modules are straight pieces of copper bolted with M8 to the minus and plus bars of the adjoining modules. As the height of the cells are inconsistent by more than 1.5 millimeters, I wonder if that link should be flexible to allow for temperature expansion , height mismatch and vibration? As posted before, a lot of care has to be taken to connect the cells with the rather small threads in the terminals.
Any suggestion for flexible connectors please.
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Re: Aftermarket iMiEV battery upgrade project

Post by jonescg »

Flexible links would be ideal, yes, but they are a custom construction and I hadn't got that far. The solid module-module links would be fine provided the modules themselves were secured well using some bracketry. The slight height difference won't be too big a deal, but it might call for some slight bending and shaping of the links. I presume they are long enough, but it's also possible that they aren't quite long enough, so by the time you get to the fifth module it could be a bit short.
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Re: Aftermarket iMiEV battery upgrade project

Post by nuggetgalore »

jonescg wrote: Wed, 26 Aug 2020, 09:04 Flexible links would be ideal, yes, but they are a custom construction and I hadn't got that far. The solid module-module links would be fine provided the modules themselves were secured well using some bracketry. The slight height difference won't be too big a deal, but it might call for some slight bending and shaping of the links. I presume they are long enough, but it's also possible that they aren't quite long enough, so by the time you get to the fifth module it could be a bit short.
Would these battery cables be OK, 100mm long, 188 amp rating?


https://www.ebay.com.au/itm/Ready-Made- ... ctupt=true

By the way, I ordered 12 mm long set (grub) screws that I will loctite into the better 4mm holes in the cells. I made a M5 drill and tapping jig to fix those that are marginal, mainly those where the modules connect to each other and are more likely to get stressed.
To make the strongest possible connection in this not ideal situation , with studs the maximum thread lengths is used and the loctite filling the thread shape clearance reduces the chance of the soft aluminium thread deforming under stress. An added benefit of loctite may be that it seals the thread clearance and stops any moisture entering acting as an electrolyte causing corrosion between the less noble Al and SS .

Browsing several (iMiEV) blogs about replacing cells and repairing BMS boards I came across a lot of useful formation. One thing that has puzzled me for a while was the physical location of the cells (numbers 1 -88 )referred to in Cani0n and EvBatMon versus the cell allocation according to i909 and MUT3 (CMUxx Cell A-H). Irrespective if the 60Ah upgrade is a success or not, swapping really bad cells is an alternative, therefore one needs to know exactly which cell is the crook one.
This drawing by kiev can be found here :
http://fsamw.myevblog.com/i-miev-techni ... bms-notes/
and here:
http://myimiev.com/forum/viewtopic.php? ... ion#p38832
with a lot of other useful stuff.
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Re: Aftermarket iMiEV battery upgrade project

Post by jonescg »

For the links between the 4s module and the last 8s module that might be OK, but for going between the 8s modules you'll be better off with a short braided link.
http://www.exelinternational.com/flexib ... ctors.html
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