EVBatMon Readings

[PV1]

Did a 143 mile trip yesterday. Drove 10 miles, topped off on level 1, then all highway driving with AC into the pack the rest of the day. Did two quick charges, first to 92% and second to 98% (QC bottomed out at 5 amps then shut down). Two cells peaked at 106 F briefly.

What does this have to do with EVBatMon? I got home with two bars and did a full recharge. I now have 45.1 Ah of capacity! This is up from 44.4 Ah. I drove 6.9 miles before losing the top bar (a record for the particular route I drove to work this morning).

So, it pays to do a calibration charge a couple of times between winter and summer.

 

[mdbuilder]

Calibration charge for me as well last night. Went from 39.6 or .4, I forget, to 40.1 Feels better being over 40 ah for some reason

 

[tinoale]

Just got my first reading :
2012 C-zero (16kWh version), 55k km, 37.1Ah left, 77.29 PMC

Considering how little range I have actually lost, I cannot believe it was 48Ah when I got it new, no way.
Without the data points, I'll never know.
I an wondering though if the car doesn't store some kind of history somewhere in it's memory. Would be awesome to be able to pull it out.

 

[Lic]

EVBAtMon shows 37.4Ah for my 2012 i-miev (51k km)

36.9Ah (54k km) right now.

 

[Malm]

Just got my first reading :
2012 C-zero (16kWh version), 55k km, 37.1Ah left, 77.29 PMC

Considering how little range I have actually lost, I cannot believe it was 48Ah when I got it new, no way.
Without the data points, I'll never know.
I an wondering though if the car doesn't store some kind of history somewhere in it's memory. Would be awesome to be able to pull it out.

You don't fill it lost all that capacity because when new the car doesn't use all its capacity (car stops with 0, 0 % Soc but with high voltage in the cell, surelly over 3,6 V). Maybe it works in the first two years as if it only has 42 Ah instead of 48. That's why we don't fill loss of capacity in the two/three first years.
In the beginning of juillet mine was at 33.2 Ah. Then, one day went to 34.2 Ah, and in 6 of August was down to 34.1 Ah. 93.000 Km in 5 years and 4 months.

 

[bobakka]

You don't fill it lost all that capacity because when new the car doesn't use all its capacity (car stops with 0, 0 % Soc but with high voltage in the cell, surelly over 3,6 V).

Malm, you think this is the way that iMiev hides capacity in the first years?
If you are right then the CellVoltage as a function of a fixed %SoC should be an indication of real iMiev battery capacity?
For example for 17% SoC (1 bar) the CellVoltage should drop from something like 3,7V when the car is new and hiding capacity to 3,5 V when the car has shown all its capacity.
My iMiev with now 111k km show around 3,6V CellVoltage for a 17% SoC reading.

 

[PV1]

I've seen my battery as high as 45.1 Ah. This is for a year old, LEV50n (improved cells) pack with average daytime high temperature of 90 F. The calculated capacity continually drops in .1 Ah increments, at what I believe to be each week. The car will do a re-calculation when charged to full from 2 bars or less. When I first started using EVBatMon, my Ah capacity was lower, but two calibration charges in hotter weather increased the value.

I think a new battery value of 48 Ah is a bit high. Realistically, 46 Ah should probably be considered 100% (unless someone's seen a higher value). Remember, our cars stop charge at 4.1 volts instead of 4.2, plus the margin at the bottom (which steadily decreases as the car ages).

 

[Malm]

"Malm, you think this is the way that iMiev hides capacity in the first years?
If you are right then the CellVoltage as a function of a fixed %SoC should be an indication of real iMiev battery capacity?"
YES.

 

[Malm]

My car show regularly a decrease of 0,1 Ah each 20 days.
With the higher temperatures it did a recalibration last month. Hot weather this summer, maybe the hottest one ever. Portugal is now with a significant part of its forests on fire. So, only if I had a big fridge to stop it inside I could escape to this higher temperstures. I do some refrigeration when driving, what keeps it under 40°C.

Still, after a very bad first 3 years, now with my methods os keeping the batteries at lower temperatures my degradation rates are one of the slowest of all.

 

[Malm]

34 Ah is the current capacity. It assumes that, from information obtained with time. But it is only a guess, as I show.

 

[Malm]

No one more saw SoC over 100%?

 

[Phximiev]

That is a good point and the answer is?

 

[zzcoopej]

No one more saw SoC over 100%?

I'm not quite sure what you mean, are you questioning a SoC reading of over 100%? If so, I think the reason Mitsubishi sometimes report 102% etc is so their calculations still start from around 100% a few hours after charging has finished. SoC can drop 3-4% in the first 24 hours.

 

[Malm]

Real SoC is over 100%. That doesn´t make any sense. Neither going there because after a few hours it will go lower. If that was the case, why not doing it all the time?

This is what I think is the answer. The car estimates a number for its current battery capacity. My i-MiEV established that the actual capacity is 34 Ah. So, for my car, 34 Ah is 100% SoC. But the current battery capacity is not a stable number (depends on temperature, maybe with other things), and not decreases always at the same rate, so it can be a little (sometimes not so little) wrong in this difficult task of evaluating battery capacity. In the day that I took that EVBatMon screenshot, the real current battery capacity was 34,6 Ah (and not the 34 Ah that it assumed to be 100% SoC capacity). When it was charging, voltages where not at maximum when it reached the 34 Ah (and so the 100% SoC), so it charged more, until cells went to values near de 4,105 V (the maximum voltage that the i-MiEV allows in its cells when charging). When the charge ended, the energy in the battery was 34,6 Ah. If 34 is 100%, then 34,6 is... 101,7%.

So, the 102% results of an incorrect judgement of its real current battery capacity, when the car is working with a value that is under the real one. Sometimes, the car makes a correction of its current battery capacity, maybe my car should make one, geting close do 34,6 Ah.

 

[PV1]

I returned from my Ohio trip and did a full charge from 2 bars. Battery capacity is now 45.4 Ah (was 45.1 Ah at the last calibration charge). That ought to make the 7 Springs trip easier.

 

[JoeS]

I returned from my Ohio trip and did a full charge from 2 bars. Battery capacity is now 45.7 Ah (was 45.1 Ah at the last calibration charge). That ought to make the 7 Springs trip easier.

Dang, it just keeps getting better with age! PV1, do you have a chronological list of the readings you obtained - perhaps temperature is a significant variable?

 

[PV1]

I've been using this thread as a record. Going back through, here's what I have:

April 8, 2016       43.2 Ah   First started using EVBatMon
April 9, 2016       43.1 Ah
April 14, 2016      43.1 Ah   Calibration charge, remained 43.1 Ah
May 21, 2016        42.8 Ah   Steady drop to 42.8 Ah
May 25, 2016        43.7 Ah   3 bars to full
June 22, 2016       44.4 Ah   Calibration charge
July 13, 2016       45.1 Ah   Calibration charge (I remember that day, it was hot)
September 23, 2016  45.4 Ah   Calibration charge

There may be some temperature correlation, but most of these readings were taken in similar environments. Last night's calibration charge may have had battery temperatures up a bit, but nothing crazy (ambient temps topped out at 84 F, battery is currently 78 F).

***EDIT*** I goofed. It says 45.4 Ah capacity, not 45.7 Ah. Sorry for the excitement. Posts have been updated.

 

[mdbuilder]

I saw your report yesterday so I figured I'd do the same. I had a fairly intensive driving day with a trip for breakfast, one for a medical appoint with my son in the morning then to work and back in the afternoon. Still had 7 bars left so when I went out foe takeout for dinner I drove really fast and ran the A/C on max even though it wasn't needed .

Still, there were 4 bars so after dinner I hit the gas station (needed to hit the atm!) and ran the HEAT. Once in the garage still at 3 bars another 15 minutes or so with max heated defrost took it down to 2 bars .

This morning I checked Evbatmon and it shows 40.6Ah which is 1.0 Ah higher than when I bought the car at the end of May for a 2.5% gain in capacity, I've now added 3,300 miles to the 11,244 it had at purchase FWIW...

 

[PV1]

Might have been my car's deep sleep, but it now reports 46.1 Ah!

The deep sleep I'm referring to is that Bear totally drained the 12 volt battery (3.8 volts per my meter) over the weekend. I just revived it.

 

[mdbuilder]

Sounds good, how many actual miles do you get with the 45+ ah?

Mine has dropped .1 to 40.5. I am up to just under 5k miles since the end of May. Last weekend my son and I did 62 miles of mostly 50-55 mph highway driving, range meter flashing @4 pulling into the drive way.