macarose
Posts: 10
Joined: Sun Sep 25, 2016 11:28 am

Ah Rate And Full Charge

Tue May 01, 2018 6:32 am

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
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Re: Ah Rate And Full Charge

Tue May 01, 2018 7:08 am

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
2012 iMiEV SE Premium, White
2012 iMiEV SE, White
2017 Chevy Volt Premier
2014 Ford Transit Connect XLT SWB wagon, 14,000 miles
1979 Honda CBX six into six

DBMandrake
Posts: 53
Joined: Mon Mar 20, 2017 4:57 am
Location: Scotland

Re: Ah Rate And Full Charge

Tue May 01, 2018 7:10 am

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:

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...
- Simon

EV: 2011 Peugeot Ion
ICE: 1997 Citroen Xantia V6

kiev
Posts: 663
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Re: Ah Rate And Full Charge

Tue May 01, 2018 7:14 am

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.
kiev = kenny's innovative electric vehicle

DBMandrake
Posts: 53
Joined: Mon Mar 20, 2017 4:57 am
Location: Scotland

Re: Ah Rate And Full Charge

Tue May 01, 2018 7:19 am

Don wrote: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...
- Simon

EV: 2011 Peugeot Ion
ICE: 1997 Citroen Xantia V6

DBMandrake
Posts: 53
Joined: Mon Mar 20, 2017 4:57 am
Location: Scotland

Re: Ah Rate And Full Charge

Tue May 01, 2018 7:24 am

kiev wrote: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%:

Image

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

EV: 2011 Peugeot Ion
ICE: 1997 Citroen Xantia V6

JoeS
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Re: Ah Rate And Full Charge

Tue May 01, 2018 12:11 pm

DBMandrake, without becoming obsessive about it I would keep an eye on Cell #70... :geek:
DBMandrake wrote:...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.
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

DBMandrake
Posts: 53
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Location: Scotland

Re: Ah Rate And Full Charge

Wed May 02, 2018 5:29 am

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

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.
DBMandrake wrote:...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.
- Simon

EV: 2011 Peugeot Ion
ICE: 1997 Citroen Xantia V6

Don
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Location: Biloxi MS

Re: Ah Rate And Full Charge

Wed May 02, 2018 6:53 am

DBMandrake wrote: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
2012 iMiEV SE Premium, White
2012 iMiEV SE, White
2017 Chevy Volt Premier
2014 Ford Transit Connect XLT SWB wagon, 14,000 miles
1979 Honda CBX six into six

DBMandrake
Posts: 53
Joined: Mon Mar 20, 2017 4:57 am
Location: Scotland

Re: Ah Rate And Full Charge

Wed May 02, 2018 7:30 am

Don wrote:
DBMandrake wrote: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!
- Simon

EV: 2011 Peugeot Ion
ICE: 1997 Citroen Xantia V6

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