Range/Capacity Test

[sefs]

Yesterday, I took the wife on a range test up a US highway until the range remaining equaled the trip traveled. I learned some interesting things in my 2012 FFE.

The day was partly cloudy, about 80F. The trip was started on 100% SOC, tire pressure checked, and of course, climate control off. My odometer was 14,529 miles at the end of the journey.

We ended up traveling 93.1 miles (my personal best), with 192 wh/mi, and 17.9 kWh consumed. We stopped at 2% SOC. When I saw this, I thought, "I can only do about 18 kWh after 2 years?? 8% capacity loss?", and with no further investigation I would have thought this was true.

However, today, I decided to run the battery down to open contactor at the end of my work commute. This wasn't easy, so I commuted home with the windows open and the defroster set to max. FYI, the defrost setting will consume the max power. You must have the defrost vent exclusively selected. The heat will be on max, and the A/C will be on max (A/C to dehumidify the air). Anyway, I ended up getting 19.4 kWh before the contactor opened. This means that I have 1.5 kWh left in that 2%. Interestingly enough, the 18 kWh is what my BECM predicted when I queried it with IDS. So, I think I might recalibrate the SOC and see if the car gets a more accurate kWh remaining prediction.

Long story short, at worst I've lost 0.5% capacity and I'm going to recalibrate the SOC.

 

[michael]

So here's what I saw yesterday...


Fully charged at home, ETE showed 18.2 kWH. I drove a few miles and the energy used (dash) was 1 kWH, but the ETE was already down to maybe 16.3 kWh. In other words, the ETE had dropped almost a full kWh more than the consumed energy would imply. This is something we all have seen...the % falls more than expected in the very beginning.

I drove about 35 miles an stopped for a few hours. I then noted that the sum of ete and energy used had increased back up to 18.2. It was as if the thing recalibrated itself.

Arriving home, I had gone 70 miles. ETE was 2.5 kWH and energy used was 15.7...again the sum was still 18.2.

Why is this? What does it mean? I don't know but it's clear we can't depend entirely on either the dash energy consumed readout or the ETE shown with an OBD scanner. The numbers are reasonably close but not exact.

Incidentally, if I apply my consumption rate 225 Wh/mile to the remaining charge, it would extrapolate to right around 80 miles range, 90% freeway at 60-65 mph with air conditioner running.

Questions for Sefs:

how would you recalibrate SOC? And why do you think 17.9 kWh is 92% of original? This implies original usable at 19.5. Best I can tell, max usable is (90%- 8%) x 23 =82% x 23 = 18.8. When I fully charge, my displayed ETE is inconsistent but usually between 18.8 and 18.2 (but sometimes higher or lower!?!)

 

[GladeStorm]

I'm going to recalibrate the SOC

-I assume that's a service function within the IDS (?).
I've also seen discrepancies: The last time that I ran to "Stop Safely Now", I found that it occurred precisely when BATT_TO_EMPTY_ESTIM hit zero-- but the displayed SOC still read 4%.

 

[sefs]

So here's what I saw yesterday...


Fully charged at home, ETE showed 18.2 kWH. I drove a few miles and the energy used (dash) was 1 kWH, but the ETE was already down to maybe 16.3 kWh. In other words, the ETE had dropped almost a full kWh more than the consumed energy would imply. This is something we all have seen...the % falls more than expected in the very beginning.

I drove about 35 miles an stopped for a few hours. I then noted that the sum of ete and energy used had increased back up to 18.2. It was as if the thing recalibrated itself.

Arriving home, I had gone 70 miles. ETE was 2.5 kWH and energy used was 15.7...again the sum was still 18.2.

Why is this? What does it mean? I don't know but it's clear we can't depend entirely on either the dash energy consumed readout or the ETE shown with an OBD scanner. The numbers are reasonably close but not exact.

Incidentally, if I apply my consumption rate 225 Wh/mile to the remaining charge, it would extrapolate to right around 80 miles range, 90% freeway at 60-65 mph with air conditioner running.

Questions for Sefs:

how would you recalibrate SOC? And why do you think 17.9 kWh is 92% of original? This implies original usable at 19.5. Best I can tell, max usable is (90%- 8%) x 23 =82% x 23 = 18.8. When I fully charge, my displayed ETE is inconsistent but usually between 18.8 and 18.2 (but sometimes higher or lower!?!)

Michael,

I'm getting similar results with the ETE. I'm not sure why, but the definitive test is to fully charge and completely discharge via the HVAC. This is a constant load, and there is no regen charging loss to mess with the estimated net energy consumed. There is a SOC correction service function in the IDS. I'm thinking this may help re calibrate the SOC estimation. Do the capacity test yourself. Charge the battery to 100%, roll the windows down, and use the HVAC to drain the battery until the contactor opens. I believe this is the only definite way to measure the current capacity of the battery. I had always heard 19.5 kWh as the maximum anyone had ever saw.

 

[sefs]

I'm going to recalibrate the SOC

-I assume that's a service function within the IDS (?).
I've also seen discrepancies: The last time that I ran to "Stop Safely Now", I found that it occurred precisely when BATT_TO_EMPTY_ESTIM hit zero-- but the displayed SOC still read 4%.

In my test today, I ended up seeing 0.4 kWh beyond stop safely now. At that point, the ready to drive icon went away, and the HVAC compressor and PTC heater quit.

 

[sefs]

I ran the SOC correction service function and my estimated capacity is back up to 18.8 kWh. This still isn't the full 19.4 kWh I got yesterday, but a lot closer than the 18.2 kWh estimate I got when I charged to full. Interestingly, I arrived at work with 2% greater SOC than normal today. This is just anecdotal, however. My range estimation is pretty screwed up from running the HVAC so much :lol: The estimate was 29 miles after that rundown.