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Old 02-06-2022, 01:33 PM   #1 (permalink)
JSH
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Bought a 2017 Bolt EV

As some of you know from posts in other threads - I bought a 2017 Chevy Bolt EV back in November. Paid $24K out the door for a fully loaded Bolt with 32K miles. Not a bad price in the current market but 2 years ago I could have got a new Bolt for that.

This will be a thread for any modifications, general observations, and dealing with the battery recall.

So far I've really liked the Bolt. It is a bigger and quicker version of my old Spark EV with better tech.

Modifications:
To date just snow wheels and tires + scrounging a spare tire. The Bolt is based the Gamma II platform so the GM parts bin is pretty deep.

Snow Tires / Wheels:
I bought 15" aluminum wheels off a 2013 Chevy Sonic. I mounted my old Blizzak 15" snow tires from my old Prius. (I sold them to a co-worker after I sold the Prius, he never mounted them, I bought them back for $100)

Spare Tire:
The Bolt doesn't come with a spare. It has room for a spare under the floor in the hatch but GM was too cheap to provide one on a $43,000 car. I sourced a compact spare from a Cruze, bought a 19mm deep socket online, and a cheap breaker bar from Harbor Freight. For a jack I just put my compact Craftsman floor jack in the back for now. I may get a bottle jack sometime but I had the floor jack already.


Battery Recall:
As most people know - Chevy is replacing the battery in every Bolt made due to a manufacturing defect in the LG cells. (LG is footing the bill) Until the replacement is complete GM recommends charging outside and only using from 30% SOC to 90% SOC. Then in December they released a software update that they claimed would allow normal use, charging inside, and just cap charging at 80%. I got that recall at the end of December and it took 2 hours.

I WOULD NOT recommend anyone get the recall. Prior to the software update I was getting 200 miles of range per charge. After the recall the range dropped to 130 miles and has slowly crept up to 160 miles. There is no way 80% of the battery is still available after the recall. With my current miles / kWh I should be getting about 175 miles per charge if 80% of the battery is available. What's done is done, all I can do now is is get the battery replaced to lift the 80% cap.

Last week I got a notification that my car is eligible for a battery replacement. I called my local dealer that works on EVs (not all Chevy dealers do) and they said they would order the battery. Once it was in shipment to their dealership they would call me to set up an appointment. Their estimate was that it would be 4 to 6 weeks from now. When I was in for the software update they had 9 batteries stacked up so they are doing a bunch of recalls.

Charging:
As with the Spark, I can charge for free at work although I don't go into the office every day anymore. However, with the much larger battery I can go longer without charging so there is no real need to charge at home if I don't want to. I could have just used the 120V EVSE that came with the Bolt but I bought a Wallbox Pulsar Plus Level 2 charger with the car for $500. It is pretty nice, easy to install, and allows charging from 1 amp to 40 amps. Sends notifications and charging stats to my phone via Wifi or Bluetooth.

I did some experiments last week and found charge efficiency varies wildly based on state of discharge. All charging sessions were done at 45F and charged to the 80% limit.
  1. When I charged after using 31.4 kWh charging to 80% required 33.4 kWh at the charger. 6% charging loss
  2. When charging after using 13.9 kWh charging to 80% required 15 kWh at the charger. 8% charging loss
  3. When charging after using only 2.4 kWh charging back to 80% required 3.4 kWh at the charger. That is a HUGE 42% charging loss.

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Old 02-11-2022, 12:33 PM   #2 (permalink)
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I decided to run the Bolt down to near 0% SOC to see how much battery capacity is left after the software recall. It is most definitely not 80% as claimed by Chevy in the recall notice. I suspected they may have capped the top level at 80% but also took some capacity from the bottom. Testing confirmed my suspicion.

This week I topped off to 80% and then started driving for a couple days to drain it to near 0% SOC.

Observations:
At 10% SOC the battery level gauge went orange, I got a warning that power was reduced, and I should charge. I laughed because I still had almost 30 miles of range left which was about 1/3 of the total rated range in my Spark EV.

At about 5% the car stopped showing estimated miles remaining and just said LOW. I found this REALLY annoying because the time you really want to know your remaining range is when the battery is almost dead. (The MyChevy app still showed estimated range and even added tenths of a miles)

Capacity:
In the end I drained the battery from 80% SOC to 4% SOC. The app showed 8.7 miles remaining. I drove 160.1 miles, used 40.1 kWh of electricity, and efficiency showed 4.0 mi/kWh. So that math checks out.

The capacity doesn't check out though. According to the SOC meter I used 76% of the battery capacity. However, 40.1 kWh = 67% of the rated usable capacity. So Chevy is holding back 9% SOC at the bottom - or my battery has massive capacity loss in only 35k miles of driving.

Looking at it in miles: 80% of the battery is 48 kWh. At my 4.0 mi / kWh I should be able to go 192 miles on a charge. So Chevy is holding back 23 miles of driving range.

I'm not a happy customer - but I have no recourse besides getting my battery replaced. (Which is likely Chevy's plan all along)


Charging Efficiency:
My charger showed it took 42.7 kWh to charge back to 80% so that is 6.5% charging losses.
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Old 02-11-2022, 12:52 PM   #3 (permalink)
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Good info...


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Old 02-11-2022, 03:50 PM   #4 (permalink)
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The question could be asked: exactly how far can you go if you can ignore the ever increasing alarms? Also what would be pack voltage there? I have pushed my volt pack to 19 KWH by abusing the cells but I have no way of knowing if that damaged them. Being everything stayed typical, I don't believe I did.
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Old 02-11-2022, 08:50 PM   #5 (permalink)
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Quote:
Originally Posted by Piotrsko View Post
The question could be asked: exactly how far can you go if you can ignore the ever increasing alarms? Also what would be pack voltage there? I have pushed my volt pack to 19 KWH by abusing the cells but I have no way of knowing if that damaged them. Being everything stayed typical, I don't believe I did.
From reading on the Bolt Forum - 0 miles. When the Battery Meter hits zero SOC and range hits 0 miles the car stops and says to shift into park. The battery isn't really at 0% SOC - it is at 5% - but GM has that last 5% locked away to protect the battery.

Cell voltage was was 2.8 to 3.0V for most cells but the total range was 0.4V

This is all before the recall software updates.
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Old 02-12-2022, 09:27 AM   #6 (permalink)
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Hmm so the low cells trigger the bms and you have a wider range of voltage mismatch. Wonder if they are cutting corners on the assemblies. If you turn it off, let it rest, does the SOC recover much?

any given day the maximum difference in my pack is only .2 volt between cells, pretty much the same cell locations charged or discharged. I tried a top balance, and a bottom balance and it didn't make any change worth noticing.
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Old 02-12-2022, 11:12 AM   #7 (permalink)
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Quote:
Originally Posted by Piotrsko View Post
Hmm so the low cells trigger the bms and you have a wider range of voltage mismatch. Wonder if they are cutting corners on the assemblies. If you turn it off, let it rest, does the SOC recover much?

any given day the maximum difference in my pack is only .2 volt between cells, pretty much the same cell locations charged or discharged. I tried a top balance, and a bottom balance and it didn't make any change worth noticing.
That isn't my data it is from ChevyBolt Forum member gallen. His post is the only on I've found were someone has actually driven their Bolt until it stops moving. Unfortunately he did not start this test with a full battery so he didn't have data on starting cell voltage or total kWh used by the vehicle on the run.

When his car stopped moving his readings were:
0% SOC from the app
0.4% User SOC (PID 228334)
4.9% Raw SOC (PID 22432f])

As to cell values he said:
Cell volts spread gets larger as %SOC gets low - up to 0.4 volts range. All cells were +/- 0.01 V when charged, but one cell was much lower than all the others as SOC approached 0, starting at a few % user SOC.


For another look at the Bolt battery there is:
(https://allev.info/2019/02/bolt-battery-buffer/)

He says RAW SOC isn't actually battery SOC and claims there is no buffer in the Bolt battery and GM allows 0% to be used. I don't really follow his logic - it is from a based on a graph from a paper on a different battery - but keys things from the article to me:

He is showing fully charged cell voltage at 4.165 and dead at 2.7 Volts.
When fully charged the Raw SOC is 96.5% when the app shows 100% SOC

Assuming Raw SoC is actual SoC GM is holding back 8.5% of the battery capacity - which what most of the industry was doing 5 years ago.

That is also very close to the 9% I found to be missing on my test. So it looks like the software recall might be holding back another 20% of the battery capacity in addition to the 8.5% that was originally held in reserve.
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Old 02-12-2022, 11:46 AM   #8 (permalink)
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Continuing my charging experiments - last night I charged on the 110V EVSE that came with the car at 8 amps. My wife used 11.9 kWh driving 53 miles to work and back. Per the Kill-a-Watt I checked out from the library the EVSE consumed 14.55 kWh for a charging efficiency of 22.3%. This wasn't directly relatable to the charge on the 220V wallbox because the charge took so long (15 hours) the temperature dropped from 60F at start to 30F at the end.


Here is my spare tire set-up
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Old 02-14-2022, 08:21 AM   #9 (permalink)
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More experiments with charging:

Last night I charged on the 110V EVSE that came with the car at 12 amps. We used 12.4 kWh driving 53.8 miles to a fantastic brewery (Wolves and Peaple). Per the Kill-a-Watt the EVSE consumed 15.35 kWh for a charging efficiency of 22.8%. Charging took 10 hours (per the car's estimate) and temperature dropped from 60F at start to 46F at the end.

So changing the charge setting from 8 amp to 12 amp doesn't seem to have any effect on efficiency and the stock EVSE is MUCH less efficient than the Wallbox I purchased.

I also downloaded the Bolt PIDs and loaded them into Torque Pro so I'll be able to see some more parameters.
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Old 02-14-2022, 09:10 AM   #10 (permalink)
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Any possibility you have PIDS for battery temps? I am curious about the charge rate below 40f since I know it gets reduced below 60 by my chemistry.

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