[Jeffrey204]

Within the last couple weeks, the "Cord" (120v) charge complete time for my 2016 Volt has become way off, estimating several hours longer than actual. I charge at 12 amps and the charge takes about 12.5 hours from empty to full like it should, but the estimate (whether at home or away) will estimate upwards of 17 hours. The estimate used to be within 30 minutes of actual. This messes with the delayed charging feature I use to charge during low cost time of use periods on my electric rate plan by making it start charging earlier to try and meet my departure time.

My 2016 will show the estimate in the charging screen on the center stack before being plugged in. It'll give the estimate based on immediate charging until I'm close enough to trigger the "home" location-based charging, which factors in my TOU rates and calculates when to start charging based on rate preference and departure time. After plugging in and it checks the power supply, the estimate is the same as before plugging in, overestimating by several hours. Only once it begins to charge does the estimate start to drop as charging completes.

For example, last night I'm at 20% battery and set to 12 amp charging. I have mid peak from 9-11pm and then off peak 11pm-7am. The estimated completion is 11am (14 hours of charging), and since I have my departure time set to 7am it started charging in mid peak since it thinks it won't be done before departure. I get a text alert when charging is complete so I know charging completed at 7:15am (10 hours of charging). The power coming in is good, I've checked with a kill-a-watt and the empty to full charge time is about 12.5 hours as it should be.

I checked over the course of the night to see that 11am estimate drop. At 10:30pm after an hour and a half of charging the estimate dropped to 10:45am, and probably at some point in the early morning as the charge reached 100% the estimated time dropped to the current time. But it doesn't explain why it's overestimating by several hours at the start.

Has anyone seen this or have more info? The only thing I can think of is I can check charging history on the Myvolt site. During a three week vacation last month, sometimes I'd come home before peak TOU would start and plug it in. The car is set to charge mid and off peak only, so it would start charging, stop during peak, then continue after. On Myvolt in charging history it shows the charging duration for those days as including the peak hours if it started before and finished after. For example, it'll say 14 kWs charged, duration 18 hours, even though 7 of those hours were paused for peak TOU. If the estimate takes into account charging history data, it may overestimate the time until that data becomes stale.

Thanks in advance.

 

[quirkySquirt]

Hmmm, charging actually completes in expected ~13hrs @12A, but OnStar estimate is way off? How are you reading your estimated charge completion times? MyChevy or RemoteLink (OnStar) or directly off the the Volt's center console? Do all three agree (they should)?

That does suck since charging based on a preset completion time is nice to have.

As a workaround, if the charge time is predictably always 13hrs (from empty), perhaps you can use the TOU charging feature? In the manual, it's called "Delayed (Electric Rate and Departure Time)". I haven't used it but from the manual it appears you can set the TOU to bracket your expected charge time to force the Volt to always charge 13 hrs before your departure time. You'd accomplish this by setting the 13hrs preceeding departure as "cheap".

 

[Jeffrey204]

Hmmm, charging actually completes in expected ~13hrs @12A, but OnStar estimate is way off? How are you reading your estimated charge completion times? MyChevy or RemoteLink (OnStar) or directly off the the Volt's center console? Do all three agree (they should)?

All three sources (center console, OnStar app, MyChevy) report the same inaccurate charge complete time.

As a workaround, if the charge time is predictably always 13hrs (from empty), perhaps you can use the TOU charging feature? In the manual, it's called "Delayed (Electric Rate and Departure Time)". I haven't used it but from the manual it appears you can set the TOU to bracket your expected charge time to force the Volt to always charge 13 hrs before your departure time. You'd accomplish this by setting the 13hrs preceeding departure as "cheap".

I have that feature enabled, so it'll charge when power is cheapest. The biggest issue is I set it to dip into more expensive TOU periods if needed to have the charge complete by my departure time, but since the estimate is so far off it thinks it needs to do that even though charging could be done completely during only the cheap times.

 

[jtechau]

My 2017 has done this most of the time I've owned it. I've had a couple software updates during that time, and the charge complete time worked fine after the update - for a week or two - then started slowly increasing. Charging takes the normal 12+ hours; just the complete time is wrong. Which, as you say, sucks for those of us on a TOU rate plan.

 

[MP81]

Mine has just recently begun to do this - but we're talking about double the time it should take.

I had one bar left last week, and it told me it would take 27 hours to charge (on 12 amps).

Granted, I don't believe my area actually has off-peak hours (at least, when I checked I couldn't find anything saying we did - nor does my bill specify that), but I like the charge to be done as late as possible in the morning, so there is some remnant of battery conditioning prior to me pre-conditioning a few minutes before leaving.

 

[etz]

Mine too....discussed in other thread
http://gm-volt.com/forum/showthread.php?281393-Innaccurate-Charge-Time-Estimate

 

[MP81]

Mine too....discussed in other thread
http://gm-volt.com/forum/showthread.php?281393-Innaccurate-Charge-Time-Estimate

That's a link to this same thread...

 

[etz]

That's a link to this same thread...

Oh yea, huh. Computers are hard..... lemme try this one
http://gm-volt.com/forum/showthread.php?280665-Charging-completion-estimate-way-off-Cold-weather

 

[MP81]

It seems to be drifting farther and farther.

I think right now it is estimating that at 12 amps, on a >50% charge (I only use 4-5 bars of range right now with the warmer weather), it will take over 24 hours to complete, so it starts charging immediately.

I'm going to look through the TSBs today and see if I can find anything...right now it's not so big of an issue, since we don't seem to have off-peak rates at all, but in the winter, I like it to finish as close as possible to me leaving, so the batteries will be that much more warmed up when I pre-condition.

 

[MP81]

An update:

I found that running my 30 gallon air compressor while charging at 12 Amps will most certainly pop a breaker. When I reset the breaker and came back outside, the charger had the red light illuminated, so I unplugged the car from it, and it (the extension cord) from the wall, since it stayed red until after I did that. Plugged the car back in and it continued charging (still under the impression that it takes a couple decades to charge a half-depleted battery).

When I came outside to the car in the morning (which I had pre-conditioning for about 3 minutes, since it's in the 50s), I noticed the cluster said "--:--" for the charge estimate (since it usually says something other than "Fully Charged" while pre-conditioning, until I unplug it). It said "Fully Charged" as normal after unplugging.

When I went to plug in last night, I noticed the location-based charging had been turned off (on it's own) and it was set at 8 Amps, but the estimate of completion was accurate. After going through the settings and turning that back on, then back to 12 Amps, and deferred charging, it said it'd be done on time, and not have to start until about 11:30PM.

So it seems to have "reset" itself (whether coincidental, or due to the breaker tripping), though this morning I still got the "--:--" completion time on the cluster - and the charge/drive stats are showing about 130 miles since last full charge, despite it fully charging every night (and 130 miles would indicate it started that prior to the breaker tripping)...

 

[Jeffrey204]

An update for all who are still following this thread, I went to the dealer yesterday for an unrelated issue. I was getting the occasional "Battery Saver Active" message while driving, and I suspected a loose connection to the 12v battery. They checked the connections, which were fine, but did report that the 12v battery was lower than it should have been. My understanding is that the 12v should be charged off the high voltage battery while the car is on, and while it seems to have been doing that I'm not sure why it wasn't able to keep the 12v fully charged (maybe a bad 12v battery).

Anyway, they fully charged the 12v and that seems to have reset the charge time estimates as they are back to being accurate now. I can't know for sure whether disconnecting the 12v while they hooked it up to a battery tender reset the system, or if a weak 12v causes issues with the charge time estimates (possible, since the 12v seems to be a source of many strange issues in other threads).

Those still seeing inaccurate charge time estimates should check the status of their 12v to make sure it's fully charged, or try disconnecting the 12v to trigger a reset.

 

[jtechau]

Those still seeing inaccurate charge time estimates should check the status of their 12v to make sure it's fully charged, or try disconnecting the 12v to trigger a reset.

If all else fails - reboot.

 

[snic]

Hmm. I seem to be having the same problem lately. Charge times have been wildly overestimated both by the reading on the console and in the MyChevrolet app. I guess I'll try disconnecting and reconnecting the 12V battery to see if that helps. If it does, I will become very suspicious that Microsoft had something to do with writing the Volt's software .

The only other weirdness that I've noticed lately is that the OnStar app no longer works to check the car's status. It gives an error (although the keyfob functions work fine). The MyCheverolet app works, but I had been using the OnStar version before. Not sure if they're related, but we'll see if disconnecting the 12V battery help.

(By the way, I found another thread with a few other people reporting the same problem last year, 2016. Unfortunately no one reported a solution. It did seem to be an issue only with 120 V charging, though, not 240 V.)

 

[snic]

I guess I'll try disconnecting and reconnecting the 12V battery to see if that helps.

I tried this and it worked. Before I did it, I noted that it told me that charging would start at 10:45 and end at 7:15 (8.5 hours) to charge from 53% to full at 12 amps. Afterwards, it tells me that it will start at 1:30 and end at 7:15 (5.75 hours). I calculate the charge time to be 6.1 hours (based on 13 hours for a full charge x 47%). So it is now much more accurate.

Now the question is, why did this happen, how often will it happen, and does Chevy know about this? I really don't want to disconnect my 12 V battery every couple of weeks.

 

[VoltenRock]

Great tips on this thread. This just started happening to me -- estimating 24 hours (huh?) to do a full charge on the Level 1 charger--wildly overestimating. It seems to be about 7 hours off on 8 amps and 4 hours off on 12 amp.

I noticed it slowly getting more and more "off" with increasing temperatures. My suspicion is that the Volt thinks it will need energy for TMS, which could add up given that the level 1 charger takes forever to top off energy lost from TMS.

It could be reading this data based on the number of times the TMS runs during the day and the current ambient temperature. Where this algorithm fails, though, is that it doesn't consider nighttime temperatures and that my car charges in the shade. Maybe it is only using recent driving operation data for this number, not historical data from TMS operation during charging. Software update required.

If this theory is correct, resetting the 12V might make it "forget" this recent TMS data thereby defaulting to the standard more accurate charging times, not accounting for TMS operation.

EDIT: just noticed in the other thread the discussion on battery issues as possible culprit. Will have the dealer check it next week when I bring it in for the backfire fix.

 

[snic]

Do let us know what the dealer says. Two local dealers completely blew me off, as I documented in what ended up being a very lengthy thread on the topic. That thread unfortunately got deleted during the forum's move to new servers.

Anyway, although there's a fair amount of speculation that "12 V battery issues" impact the charge time overestimation problem, so far no one has come out and said (a) they have this problem, and (b) replacing the 12V battery (or repairing some component related to it) fixed the problem.

Finally, in the earlier mega-thread, there was some suspicion voiced that location-based charging has something to do with it. I initially tested that idea by turning off location-based charging. I noticed that the charge time estimates gradually became less bad, but then stabilized at some inaccurate value rather than completely normalizing.

I am now in the middle of a somewhat better test: first, I disconnected and re-connected the 12V battery. This resets the charge time estimate to something fairly accurate, as noted upthread. I've done this several times previously, and every time, the charge time estimate gradually increases over the next several days or weeks. However, this time, I also turned off location-based charging. Instead, I just set the car to charge at 12 amps whenever I return home. All other settings are the same (i.e., I use rate-based charging to maximize charging from midnight to 8 am). I did this about 10 days ago, and so far the charge time estimates have not increased. (That is, they are slightly higher than the real charge time, but that's the case even right after I do the battery disconnect/reconnect procedure, and the estimates have not increased substantially since I did that.)

So, my fingers are crossed that I've finally found a workaround: first disconnect/reconnect the 12 V battery, then turn off location-based charging.

 

[VoltenRock]

So, my fingers are crossed that I've finally found a workaround: first disconnect/reconnect the 12 V battery, then turn off location-based charging.

We have one possible workaround, which I may be trying soon. However, I'm also going to the dealer to get my squeaky door panels fixed along with the afterfire/backfire update. Anyone else tried to get the dealer to fix this? I use delayed charging and now this is getting ridiculous because I want to charge overnight, but the wildly inaccurate times (getting worse in the colder weather), means I have to bump my departure time by 3-4 hours on 12 amps to get it right.

 

[snic]

We have one possible workaround, which I may be trying soon. However, I'm also going to the dealer to get my squeaky door panels fixed along with the afterfire/backfire update. Anyone else tried to get the dealer to fix this? I use delayed charging and now this is getting ridiculous because I want to charge overnight, but the wildly inaccurate times (getting worse in the colder weather), means I have to bump my departure time by 3-4 hours on 12 amps to get it right.

My workaround doesn't work, at least not 100%.

I think there are two things going on: gradual changes in charge time estimate (almost always in the "longer" direction), and sudden large shifts. My impression so far is that nothing prevents the gradual changes. However, the sudden shifts do not happen often, and I *think* the frequency is reduced by turning off location-based charging. I also have the clock set to manual rather than automatic (i.e., I instructed it not to automatically sync with the cell phone signal) because I had a suspicion that the sudden large shifts had something to do with an error while the clock was synching.

If you disconnect/reconnect your 12 V battery, you will definitely see an immediate re-set to the original estimate (~12.5 hours for a full charge). Over the next few days to weeks, it will gradually shift. For instance, the last time I disconnected it was Oct 11, and now I have the departure time set at 8:45 am in order to have the car finish charging at 7:15 am. A week or so ago, it was set to 8:15 am. If you pay attention, it's possible to keep up with the car's gradual shifts. The sudden shifts are impossible to predict, however.

 

[jcanoe]

I have never set location based charging on my 2017 Volt as far as I can recall. Lately the estimated charge completion time has been longer than expected. Over the summer I had been using a public level 2 charging station and not always completely recharging the Volt's battery while using this station. I'm not sure if this is related. I rarely need to charge more than 2 hours at a time to completely recharge. I will continue to monitor my recharge time now that the weather is turning colder and I will be using more of the battery each day including some electric heat.

 

[Andy00778]

I also have this problem and it seems to be worse lately. The error was not that bad initially, but now it shows like 13 hours to charge at 12A when there is already 35% charged. Time estimates are closer when it’s only down a couple of bars but anything past halfway gives ridiculous estimates. Actual charge times corresponds to what it should be. I use a simple calc. to adjust a temp departure time to “fool” the system so that I capture charging times from midnight to 6 am when the rate is 2 cents/kWhr

I take % of charge needed x 1.1 (losses) x 14.2 (battery size) / 1.4 ( 12 A charge rate kW) = hours needed


One trick I tried ( only once so far) seemed to help. I toggled the charge from departure time to departure & rate time, which gave a completely different completion time estimate since I have it set to charge in the super off peak rate period (12 am-6am), then toggled it back to departure time. Time estimate then seemed to go to something more reasonable. Maybe someone else can try this to see if it works for them.

Can’t try this again for a while, heading to Florida tomorrow and only charge L2 there.