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McRat 02-17-2019 02:23 PM

When you run the car down to 0%, 0 miles -
I should have taken a notepad with me, but this is going off memory, it was 43-49F in the morning:

At 9% I got my first Low Battery warning which you clear by pushing the left thumb roller bar. AFAIK, full power was available.
At 4% I floored it, and found it would only produce about ~67% power? then the bar graph stops moving. This is enough for freeway use.
It stayed at 4% and 4 miles for a very long time. I was worried it was frozen.
At ~3% a blue line appears on the power bar graph which is your peak power, which is now about 50%. As you keep the pedal floored, the blue line lowers it's limit. Still adequate power.
At 1% another warning, you cannot adjust cabin temp upwards, mine was stuck at 76F. Power was about 40% peak.
At 0% and 0 mi, "Very Low Power" "Battery Saver Mode On", turns off climate, and blacks out center display. If you touch it, it will light back up. Blue line still exists at 40% of travel. So I believe there is power left, how much I do not know. TOPIx says the ECM reads 2% power when dash says 0%.

Now I will try to map out how linear the power % gauge is by monitoring each hour. Wish it was a warmer day. On a Chevrolet Volt (LG Chem cells like I-Pace), this JuiceBoxPro 32a loses 13% between the wall and the battery. It takes 16.1 kWh to fill a 14.1 kWh SOC window (0-100% charge on dash) on a 2019 Volt which has the same size onboard charger as the I-Pace, so that's the number I will use.

Hour 1 the EVSE pulled 7.14 kWh the car reads 7% but only 11 miles. I'm thinking the bottom is deliberately skewed on miles because I also saw it freeze at 4mi and 4% for a few miles.

I'll graph it out for a 100% charge. But it's not an optimum day. It should give us an idea of how accurate the dash % SOC meter is. How linear it is.

But I was mostly curious what happens when you hit 0%. I did not drive after 0% though.

PGhiron 02-17-2019 02:29 PM

@McRat A Brave soul you are. What is back-up plan during your testing if the car just quits?

Dantrium 02-17-2019 02:44 PM

I hit 0% twice on my trip home from picking the car up from the dealer. Of course I didn’t know enough about BEV’s to understand the significance, I just assumed it was like my fuel gauge in any other car and reaching zero generally means you have about a gallon or so left. I was within a mile or so of the chargers both times, so it wasn’t a problem

McRat 02-17-2019 02:45 PM


Originally Posted by PGhiron (Post 27561)
@McRat A Brave soul you are. What is back-up plan during your testing if the car just quits?

The last 1% I stayed very close to home. The neighbors probably thought I was nuts.

There is also a tow hook that comes with the car. If it would roll, I could tow it home slowly.

sciencegeek 02-17-2019 03:33 PM

Very informative story, thanks McRat!

I will also start recording the kWh input and SoC from now on more systematically. A single charging test I did yesterday from 30% to 70% SoC implies a lower buffer (i.e., "going into negative displayed SoC") of ~4.7 kWh. But I need to get better data to do more definitive results.

Ps.: that doesn't imply that you can use those 4.7kWh ... because they surely have a death buffer

Time2Roll 02-17-2019 07:15 PM

I am curious how shifting goes at 0% or lower. My Rav-4 would eventually turn off the motive power but you could coast or push the vehicle. Once in Park that was it until the battery was back to 5%. I believe there was a manual procedure (pitn) to get it back into neutral to push or roll up on a tow truck. I believe the LEAF did something similar and you basically needed to stay in neutral if you expect to push or tow the vehicle.

McRat 02-18-2019 02:24 AM

Well... It took 12h45m to fully charge from 0% to 100%. (Says 99% but car reports charged full, and stops charging).

It is not linear.

To climb from 0% to 50% requires 40.3 kWh from the wall.
To climb from 50% to 100% requires 51.6 kWh from the wall.
Total drawn power 91.9 kWh. Assuming 87.6% efficiency based on a different car with 32a L2 charging, that means 80.48 kWh made it into the battery. However the air temp at the car was 49-58F during the charging with intermittent rain. And 0% is not really 0%, there is still room down there but I won't deliberately run a battery to true zero. It would suck if it did what some lithium batteries do, that is, not accept a charge when the voltage hits bottom.

Now the efficiency could be higher or lower. The JuiceBoxPro 32 could have some error, and the bottom buffer size is unknown. But that's the best I can do to estimate true battery capacity.

The important takeaway is that the the top 50% is actually 56% of your range, and the bottom 50% is 44% of your range.

McRat 02-18-2019 02:18 PM

The battery might not have been warm enough for a maximum charge. This AM it was in the 40's and has risen to 52F, but at 88% charge, I still do not have full regen, the Green Line is still showing. Normally, the green line disappears between 95% to 91% depending on temp.
Just a theory.
I think Spring and Summer are going to change a lot of what we hear reported with range and charging behavior. This is a universal trait for EVs, with all having differences.

sciencegeek 02-23-2019 06:10 PM


Originally Posted by McRat (Post 27557)
But I was mostly curious what happens when you hit 0%. I did not drive after 0% though.

Well today I did. Everything went as you described, until 0% 0 miles. At that point I was 3 miles from home. After another mile it told me to pull over in a safe spot because it was powering down. The pleasant warning bell did nothing to allay my panic. Well, it let me creep home at 20mph (I think the max would have been 25). So now I know that I have at least three miles after it hits 0 (at 56F and no hills) though I wouldn't want to push it any further.

sciencegeek 02-24-2019 12:31 AM

By the way ... I ran six stop signs and was lucky to have had a green light on a right turn >:)

Mister Dave 02-25-2019 08:30 PM

Where's the "You're friggin' crazy" forum button?

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