OBDII data for HVB

I don't trust the ETE estimate, however in my case it overstates the battery capacity compared to an actual test.

I would suggest you both do a full-blast-heater rundown test, and then let is know the measured battery capacity and the reported ETE when fully charged.

Hybridbear: my guess is that your reported ETE is a little higher than what a test would measure
Breeves: my guess is that your reported ETE is lower than what a test would measure...16.4 kWh battery capacity at 17K miles doesn't seem right.

I'll do this tonight. Wish I wouldn't have charged up at work. Going to have to drive extra fast on the way home with the heater blasting so it doesn't take an hour to run down

You need to do this test starting with a fully charged battery. Zero the trip meter and then start running it down. You can use driving as part of the drawdown, but for consistency I'd do the whole thing with the heater. That way it's more repeatable.

When I get home I"ll run the test. Thanks.

Did the test last night:

-Fully charged, started test ~30 mins after full charge
-Unplugged car
-Started car and reset trip meter
-Turned heater on hi until battery hit 0% and the "battery depleted" message appeared
-Trip displayed 17.2kWh consumed.

17.2kWh seems in range but still low. I should have checked battery temperature before the test. It likely had cooled down some after charging.

Thoughts?

Yes, please re-run the test with battery temp at the 98F setpoint.

Did you notice what the ETE showed at the beginning of the test? I'm interested to find out how closely your ETE matches your test result. My ETE is significantly more than my measured capacity.

That said.....

My experience was that I lost about 4 kWh (19.5 assumed original, about 15.5 now) over 48K miles, call it 1 kWh/12K miles.

If that holds for you, my guess would be that you are at about 18 kWh now. However, there are other factors...

1. There is mileage related fade, and there is time related fade. I've gone through two summers (bought car in Sept 13). If you've also gone through two summers, that will hurt you. (two summers per 48K miles vs two summers per 17K miles). How many summers for you?

2. I tried to be gentle on the battery, practicing just in time charging when practical. Don't know what your practices have been.

On the other hand, my profile provides fairly deep discharges. I'm now reaching work with only about 3 kWh remaining. So every charge cycle is deep. If you didn't need to push your car so hard, that would help you.

But all things considered, my best guess is your number around 18. That's less than 10% loss in 17K miles, pretty good. It will be interesting to see what your re-test shows.

I guess it's pretty cold in St Louis right now, so you may need to wait for a warmer day to do this.

I can force the batter to get pretty warm with FORScan but it would be better to do it on a warmer day.

In the cold I always plug in L2 when the car isn't in use. With heater i have been using 50-60% battery to get to work. I charge L2 there. I'm probably decently hard on the battery...

That's about the same as I was when the battery was still fresh, used maybe 55-60% to get to work, less to get home (downhill). Now I need 80% to get to work. So I'm taking the Volt and my wife is driving the Focus until the weather warms up.

How many summers?

I bought the car this summer. I'm assuming its been through two but it came from California. It just sat this summer unfortunately waiting to be sold...

In the summer I only used about 40% to get to work... maybe 45% with AC and fast driving.

My ETE consistently reports about 18.7-19.05 kWh at a full charge. This has decreased over time. I have not done a full discharge cycle with heat to test what the trip meter shows. I will try to do one soon. Our FFE is up to 24k miles now. The lease allows for a maximum of about 30,500 miles, but I doubt I'll even hit 27k miles when I turn it in this August.

I tend to do a deep discharge (to under 10% displayed SOC remaining) once a week or more during winter. During the summer it's rare that the displayed SOC goes below 30%. I have been continuing to track my data at a full charge each time I leave with a full charge & I'll try to update my graphs soon. There seems to be a pretty clear linear decrease in estimated ETE at 100% based on the ETE & abs SOC reported at a full charge.

My FFE was built December 2, 2012. It was originally leased out on Long Island in August 2013. We got it from the original lessee in July 2014 and are finishing out their 2 year lease. It sat at the dealer on Long Island from December 2012 until August 2013.

I've tried to practice just in time charging and be gentle on the HVB. The original lessee charged the car immediately upon being plugged in from what they told me. They also only drove it 4k miles in 11 months, so it wasn't used much. We've averaged almost 1k miles per month.

michael said:

Your biggest problem seems to be that the ETE estimate is particularly inaccurate near exhaustion. I agree that's a problem, but better to have that problem than to have the much greater degree of battery fade that I am observing.

Your chart also supports this. Even with 1.5 kWh reported ETE your cells are balanced to about 10mV. Only in the end stages of discharge do they diverge as the weakest cell falls before the others. I think we have to chalk this up as an example of where the fuel gauging software isn't totally accurate. In reality, battery fuel gauging isn't an easy task, particularly as the cells diverge in capacity.

Click to expand...

I almost got stranded because of this on Sunday. I had a 12.3 mile drive home from my parents house with 19 miles of range remaining when I left. The drive from their house to mine is very efficient since I was forced to take the city route with the freeway closed for construction. I used 1.9 kWh for 12.3 miles according to the trip summary. This is somewhere between 162 & 154 Wh/mi depending on where the acutual kWh used was between 1.90 & 1.99, since either of those values would be displayed as 1.9 on the trip summary & in MFM. The ETE when I left their house was about 3.3 kWh. I figured that I would have no problem getting home. The ambient temp was around 80 F and I had all four windows down with HVAC off. The HVB temp was 81 F, right in its ideal temp range. I hit the battery depleted SSN about 4 blocks from home and hit 0.00 kWh ETE as I turned onto my street. The estimated range in miles didn't go negative until I was within 2 blocks of home, in fact, the car continued to show 1 mile of range even after the SSN appeared! That was very odd! Normally I've seen it say 0 miles before the SSN appears. When I got home I parked & sat in the car for a minute to see what the resting voltage would show. The pack voltage was down to 295 & the cell voltage variation stabilized at 111 mV while at rest. I had the car charge immediately for about 30 minutes when I plugged it in so that the HVB wouldn't sit at such a low SOC for 10+ hours until the normally scheduled charging time in the middle of the night.

I knew that I would be cutting it close since the ETE is not very accurate at such a low SOC, but I wanted to test it out so I didn't charge at all while I was at their house. I didn't think it would be as close as it was, though! The rapid drop in available HVB energy & range decrease at a low SOC has definitely gotten worse over the time I've had the Focus. I'm so glad that I have FORScan at times like these, without it I would be much more worried & stressed about my range than I am.

I just updated my ETE tracking chart with data for the last few months. Surprisingly, the ETE normalized to 100% SOC seems to be going up a bit now...


The ETE by temp seems to be more stable now compared to in the past, the r^2 value is much higher now.


I think that some of the apparent increase in ETE is related to temperature. I looked at some data of the HVB temp at a full charge over different months to see how that might impact it. I don't have a lot of variation because the FFE parks in a heated underground garage at my apartment. In the winter the garage is heated to around 60 F. In the summer it usually isn't much warmer than 70-75F because of being underground.

Here are HVB temps at a full charge, displayed as average, minimum, maximum:
June-August 2015 - 80, 72, 97
September-October 2015 - 79, 73, 95
November 2015-February 2016 - 74, 61, 91
March-April 2016 - 76, 59, 91
May 2016 to-date - 77, 70, 90
Notes: I began tracking data on 5/21/15, so the June-August 2015 includes 6 data points from the last 11 days in May 2015. There is not a lot of variation in the maximum temperature. Usually the only time I see an HVB temp above 85 F when leaving home is if the SOC was really low the night before resulting in a longer charge time & I'm leaving earlier so that the HVB has sat for less time after charging finished. Under normal conditions the HVB temp is almost always 77 or 75 F right now. I have 23 observations so far during this month & the HVB temp was 77 F 10 out of the 23 days. It was 75 F another 5 days. That means that 15 out of 23 days (65%) the HVB temp was either 75 or 77 F. With the current air temps ranging from the mid 60s in the morning to low 80s in the afternoon most days the HVB temp doesn't really change at all. It might increase to from 77 to 79 F if I'm doing a lot of freeway driving, but it usually returns to 77 F while parked. If I take the car to work & leave it parked all day the HVB temp has not been changing at all. This is in stark contrast to winter when the HVB temp would drop from being around 75 F in the morning to under 30 F within a few hours.