Ah Rate And Full Charge

[macarose]

I just measured the Ah rate on my I-MiEV with a full charge and 19,000 miles.

It came out as 38.3. Would this be indicative of losing roughly 24% of my battery capacity? When I fully charge it goes up to 84 miles on the meaningless range indicator and I noticed that the car simply doesn't provide a true 62 miles when it's at full charge if I use the A/C and drive normally.

Any insights on how to use Canion to determine battery loss would be helpful if I'm not doing it right. Thanks for all you do.

 

[Don]

You never had the use of the claimed 50 Ah, so no, you haven't 'lost' 24% of your battery capacity. 35 to 38 Ah as reported by Canion is very typical for cars with 20 or 30K on them. Lower 40's is common for a new pack

I wouldn't call the RR display 'meaningless' as it is reporting on how you're using the car, which can be very helpful for you to get the most out of it. If you're recharging to 84, but can't actually drive 62, then that probably means that your 15 mile trip home just prior to recharging is very different than your trip away from home the next morning - Are you coming more downhill going home and more uphill leaving home? That would be my guess as to a part of your discrepancy

While Canion can be helpful for some issues, it's also a bit like a new parent with a digital thermometer - "Why is my kid running a temperature 3 days out of 10 . . . . and should I be worried?" :lol:

Don

 

[DBMandrake]

Not sure what you mean by "Ah rate" - the Ah figure shown on the first screen is the battery management system's estimation of the usable Ah capacity of the battery. This figure doesn't depend on the current state of charge, but is an estimate of the usable full charge capacity.

As for what represents a 100% state of health - nobody is really sure. The cells are rated at a nominal capacity of 50Ah when new, however the car does not charge the cells to the full 4.2 volts, only about 4.1 volts, which is equivalent to about 90% of the usable capacity, so 0.9x50=45. One guy on here got a reading of 45.4Ah after his battery was replaced under warranty and there is some evidence to suggest that the factory new usable capacity charged to 4.1 volts per cell was probably 46Ah, so that is the figure I have decided to use for lack of more concrete information.

So that means your 38.3Ah figure is a SoH of 83%, which is still good.

You might find my Ah figures measured over the last year of interest:

http://myimiev.com/forum/viewtopic.php?f=23&t=4014&start=20#p35790

I thought my battery was starting to die since January this year however it's looking a bit like the car was just over estimating the available capacity remaining and that after a calibration it realised that it was lower than it thought it could be. So the Ah figure should always be taken with a grain of salt - the figure on mine has actually gone up by 1Ah recently...

 

[kiev]

What does Canion report for the pack voltage and for the difference between the max and min cell voltage? If you have a low cell or unbalanced pack, then the Ah capacity data will be affected, as will the State of Charge %. Temperature is a big factor also that affects the measurement. It is a dynamic variable.

If you are getting RR of 84, then without A/C and driving eco you could likely get 62 miles on a full tank.

We really don't know how the car calculates Ah capacity, nor what it really means with respect to the specs on the Yuasa datasheet.

 

[DBMandrake]

I wouldn't call the RR display 'meaningless' as it is reporting on how you're using the car, which can be very helpful for you to get the most out of it. If you're recharging to 84, but can't actually drive 62, then that probably means that your 15 mile trip home just prior to recharging is very different than your trip away from home the next morning - Are you coming more downhill going home and more uphill leaving home? That would be my guess as to a part of your discrepancy

Or, the GOM just has a mind of its own... Seriously though, there is something fishy about the full charge range estimate on these, I get these kind of nonsense estimates all the time on mine, so I pay no attention to the full charge estimate.

I do a very regular daily commute and my RR after a full charge the following morning can be anywhere from about 54 miles to 83 miles for the same driving style and conditions. I kid you not.

Yet I always get pretty consistently about 60-63 miles of usable range with no heater in warm weather. So when the estimate starts off pessimistic the RR actually goes up for the first 10 miles of driving, and if it was very optimistic it goes down rapidly for the first 10 miles!

By the time it is down to about 70% the RR figure becomes quite accurate if you drive consistently, but my advice would be to ignore the 100% charged range remaining figure and don't worry about it. It's just nonsense...

 

[DBMandrake]

What does Canion report for the pack voltage and for the difference between the max and min cell voltage?

It's important for this test to have any validity that the car is first charged to 100% and left to fully balance the cells (wait until it switches the charger off) and then discharge it to a known, low state of charge of say 30% reported on Canion. Then the maximum imbalance between cells should be checked.

Checking it at a high state of charge is relatively meaningless if the battery has been recently balanced.

Here is an example from my car after discharging from 100% to 33%:

Cells 25 and 70 are consistently slightly weaker than the rest but not by enough to worry about.

 

[JoeS]

DBMandrake, without becoming obsessive about it I would keep an eye on Cell #70...

...I do a very regular daily commute and my RR after a full charge the following morning can be anywhere from about 54 miles to 83 miles for the same driving style and conditions. I kid you not.

Put on at least 10,000 miles in all sorts of temperature and rain and wind conditions, and let's see if you still hold that view. :roll: It's my opinion that, due to its simple algorithm, our RR is 'better' than the Leaf's GOM, and over the years I've learned to rely on it without reservation - but also with the understanding of the environment I'm driving in.

 

[DBMandrake]

DBMandrake, without becoming obsessive about it I would keep an eye on Cell #70...

Both cells 25 and 70 are slightly weak by about the same amount - the screenshot just didn't catch them at a moment when they were both the same.

Yes I am keeping a close watch on them - as I have only had Canion for a short time I don't have any historical cell balance records from before my Ah figure started dropping more steeply.

...I do a very regular daily commute and my RR after a full charge the following morning can be anywhere from about 54 miles to 83 miles for the same driving style and conditions. I kid you not.

Put on at least 10,000 miles in all sorts of temperature and rain and wind conditions, and let's see if you still hold that view. :roll:

As a matter of fact I have already done 13,000 miles in just over a year in all sorts of temperature rain and wind conditions from -10C to over 20C.

I'm not sure I understand your response though - my point was that on the same commute, in the same temperature and traffic conditions during a single week, the full charge range reported can vary anywhere from 54 miles to 83 miles with no explanation why.

This morning it said 71 miles, two days ago it said 57 miles - driving conditions were almost identical! This is why I said I don't trust the full charge estimate. I just ignore it.

While driving the car it uses the last 15 miles of average consumption to calculate it, however it does not use just the last 15 miles driven when showing the full charge estimate. Some other calculation method is used there. I've proven this to my satisfaction by carefully keeping a log of driving conditions and especially the last 15 miles before stopping to charge and they do not correlate with the reading after a full charge.

It's my opinion that, due to its simple algorithm, our RR is 'better' than the Leaf's GOM, and over the years I've learned to rely on it without reservation - but also with the understanding of the environment I'm driving in.

The Leaf GOM is really inaccurate in general but is worst when the battery is getting low where it consistently reports more range than is possible. (Lots of people complaining about this)

After doing 13,000 miles its my opinion that the full charge range estimate in the Ion cannot be trusted, however once the battery is down to about 80% the range remaining from that point is quite accurate, and especially the last 10 miles or so are very accurate.

 

[Don]

While driving the car it uses the last 15 miles of average consumption to calculate it, however it does not use just the last 15 miles driven when showing the full charge estimate. Some other calculation method is used there. I've proven this to my satisfaction by carefully keeping a log of driving conditions and especially the last 15 miles before stopping to charge and they do not correlate with the reading after a full charge.

We'll have to agree to disagree there - I can usually 'guess' within 2 or 3 miles what my full charge RR will show before I start the car, based entirely on how and where I drove the last 15 miles

If you believe this isn't the way it's calculated, how do you think it is done?

Don

 

[DBMandrake]

While driving the car it uses the last 15 miles of average consumption to calculate it, however it does not use just the last 15 miles driven when showing the full charge estimate. Some other calculation method is used there. I've proven this to my satisfaction by carefully keeping a log of driving conditions and especially the last 15 miles before stopping to charge and they do not correlate with the reading after a full charge.

We'll have to agree to disagree there - I can usually 'guess' within 2 or 3 miles what my full charge RR will show before I start the car, based entirely on how and where I drove the last 15 miles

Remember that there may be significant differences between the USA and EU versions of the car, or that our cars could be on different firmware versions that behave differently. So because it doesn't happen to you doesn't mean it doesn't happen to anyone.

If you believe this isn't the way it's calculated, how do you think it is done?

I wish I knew.

I've been trying to figure it out for a year now. All I have determined for sure it that the RR figure reported after a 100% charge is completed is not just a simple calculation based the previous 15 miles of driving before plugging in.

In the US the i-Miev was sold with a 62 mile EPA rating, which is pretty realistic, while in the EU/UK it was sold with a 93 mile NEDC rating, which is a pure fantasy figure.

I have to wonder if the full charge figure is "stretched" towards the NEDC rating to make it appear to line up more with the claimed NEDC figure, and that the figure then morphs down towards reality as you drive the car - something that wouldn't be necessary on a US car which was sold with a claimed range of 62, which it can actually meet.

My battery is currently at 37.1Ah, if we take the 93 mile NEDC figure and multiply it by 37.1/46 we get 75 miles - which is a figure it commonly reports as a full charge RR despite me never getting anywhere near that in actual driveable range.

I find that by the time the battery is down to 80% or so the RR figure has morphed down (or sometimes up) to a sensible figure. Then for the exact same journey the following day it starts off with a ridiculous figure again. It never learns.

BTW if you are skeptical of the morphing from NEDC theory - there is some evidence to suggest that EU/UK Leaf's also highly inflate their 100% charge RR figure regardless of past driving patterns. Again, probably to reduce the discrepancy between the claimed NEDC figure and what the car can actually do, so owners aren't pestering their dealers to find out why the car is reporting 30 miles less range than the claimed range!

 

[JoeS]

DBMandrake, there may well be some merit to your speculation as regards NEDC. For the US market, as a result of numerous consumer and government lawsuits, the carmakers have become quite gunshy.

I rarely fully charge so don't get to see full-charge RR often. Since my previous 15-miles can be anything from a continuous blast at, ahem, 81mph (keeping up with traffic, of course) to a sedate city-street leisurely jaunt, which means, coupled with my eyeballed timer stop-charge setting at around 12 bars, I really never know what to expect. It's only on long trips that I pay attention and compare my Garmin GPS DTG to the car's RR.

On our Maximum Range Remaining competition thread the record is presently at 108 miles, with old-time forum member malm believing that the display upper limit is 109 miles (175km). I believe that the high numbers there were on pre-2012 European models.

Off-topic, around here, the only way to see what can be achieved for a maximum RR is to take the i-MiEV up to Lake Tahoe and come back on Interstate 80 for the 60-mile run down from Donner Summit to Auburn, losing 6000' elevation in the process. :roll:

 

[Jonnoll99]

Apologies if I’m breaking protocol. Beyond frustrated and seeking advice. After painstakingly obtaining a warranty replacement of my traction battery for my 2012 imiev, canion now shows a 25.5ah reading and the corresponding poor range you’d expect, similar to my prior battery. I returned to the dealer to have them reset the computer as I saw others say this would allow the computer to recognize the battery’s actually capacity. However, no luck. Same poor range (40 miles). Any thoughts on what to do, apart from complain to Mitsubishi? They seem a mixture of unhelpful and ill prepared to diagnose the problem.

 

[DBMandrake]

Apologies if I’m breaking protocol. Beyond frustrated and seeking advice. After painstakingly obtaining a warranty replacement of my traction battery for my 2012 imiev, canion now shows a 25.5ah reading and the corresponding poor range you’d expect, similar to my prior battery. I returned to the dealer to have them reset the computer as I saw others say this would allow the computer to recognize the battery’s actually capacity. However, no luck. Same poor range (40 miles). Any thoughts on what to do, apart from complain to Mitsubishi? They seem a mixture of unhelpful and ill prepared to diagnose the problem.

Totally unacceptable.

25.5Ah is only a state of health of 56%!

What was the reading before the swap ?

If it hasn’t changed much they probably haven’t done the battery recalibration process properly or at all.

Take it back and insist they do the job properly.

 

[kiev]

@ Jonnoll99

The factory service manual clearly states that if the capacity doesn't reset, then repeat the procedure until it does.

Here is a link to a situation just as you have experienced. Print out the procedure and underline the pertinent sentence, then take it when you go back to the dealer. Piev had them try several times before it reset.

http://myimiev.com/forum/viewtopic.php?f=23&t=4182&start=10#p37989

 

[Jonnoll99]

Many thanks for the feedback and encouragement. I've called the dealership and I'll press the issue further. Now that I can see my car's actual AH reading of 25.5 and that the minimum expected value is 45, I have more specifics and context to frame my issue, something they're less likely to dismiss with "well, your range will vary."

 

[Jonnoll99]

In my infinite wisdom, i drove the car until it stopped. I figured, I have AAA and may as well use it. When it stopped due to the computer believing it was at 0% soc, canion shows 337 total volts and 3.875 individual cell volts (no variation in individual cell voltage), and a total wh out of 11126 (which I believe means 11.126 kWh out of the allegedly 16kwh battery). Any thoughts on whether the computer stopped the car because the pack was truly depleted or if these stats suggest I had more juice that the computer was unwilling to use?

 

[DBMandrake]

In my infinite wisdom, i drove the car until it stopped. I figured, I have AAA and may as well use it. When it stopped due to the computer believing it was at 0% soc, canion shows 337 total volts and 3.875 individual cell volts (no variation in individual cell voltage), and a total wh out of 11126 (which I believe means 11.126 kWh out of the allegedly 16kwh battery). Any thoughts on whether the computer stopped the car because the pack was truly depleted or if these stats suggest I had more juice that the computer was unwilling to use?

The car will shut down completely when it believes it has reached 0% SoC - as you have discovered. It doesn't matter if there really is still some capacity left, it will be unwilling to go below a calculated 0% SoC.

3.875v per cell is still quite a high charge - very approximately 30-40% SoC. or about 4-5 bars (16-20 miles range) if your Ah figure in the BMS was correctly calibrated! 0% SoC is normaly about 320 volts or 3.63 volts per cell. At least on my car.

Charge the car fully on AC and check the Ah figure after it's finished. (Completely finished balancing, eg the red charging light has gone out) You might find that it makes an adjustment to the Ah figure, although it's unlikely to go fully to the correct figure in one jump.

It still really needs either the battery reset/replacement procedure, or the battery calibration procedure performing. For a new battery either would do the trick but the former is much faster! The reset procedure just resets it to an assumed 45.8Ah (which only takes a few minutes) and we assume your new battery is near enough to this figure, while the calibration procedure actually measures the capacity but this takes many hours to perform.

 

[Jonnoll99]

Thanks again for all the info. I've created a simple and clear email to the dealership with the salient points you've shared (in particular the service manual and its instructions) plus the readout of my car's AH value of 25.5 from Canion. I'll update the group with the outcome once I hear more from the dealership. Genuinely grateful for the expertise shared in this forum. It's unfortunate a consumer has to become so knowledgeable about his vehicle in order to compel the manufacturer to fix it correctly.

 

[GdB]

Jonnoll99,

I just got my 2012 miev back from a dealer battery check up. I requested a copy of the detailed test results and got back 4 pages, with the first being most useful, and showing "Battery current capacity 26.1 Ah", and "Battery remaining capacity 25.3Ah". Prior to taking it there, the EVBatMon app showed 58%. They don't want to replace the main battery and used the opportunity to try to scam me into buying a $280 dealer 12V battery. Since it was an old, original battery, I did not want to argue it, so I bought a NAPA battery for $98.

How did you get them to replace the original battery? Did it fail to charge to 16 bars? Did it fail completely?

Mine charges to 16 bars. I suspect it should need replacement under warranty before the battery warranty expires in 2.5 years, depending on use.

Many thanks for the feedback and encouragement. I've called the dealership and I'll press the issue further. Now that I can see my car's actual AH reading of 25.5 and that the minimum expected value is 45, I have more specifics and context to frame my issue, something they're less likely to dismiss with "well, your range will vary."

 

[Jonnoll99]

It was a lot of back and forth to get the battery replaced, but ultimately it was the turtle mode kicking in at 8-10 bars remaining that made them take action. The car wouldn’t travel above 35 mph despite showing a 50% remaining charge per the number of bars in the fuel gauge. I expect that had my capacity merely been severely diminished but the car performed as expected, They would have argued non warranty repair eligible normal degradation. My car was charging to 16 bars. And it was somewhere in the 25ah range when the battery was initially replaced.