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Set to delayed charge by rate and departure - but sometimes starts immediately?

6K views 15 replies 10 participants last post by  volt3939 
#1 ·
2013 Volt

I’ve tried searching through the older threads for this topic, as I have to assume others have noticed the software bug related to using delayed charging by rate and departure. It’s a bit difficult to explain, but I’ve tested it several times so I'm pretty sure I am describing the details accurately.

The summary is that it seems the algorithm behind the charging based on rate and departure time is somehow based on how much charge you can get in 3 consecutive sessions.

I typically only charge a few hours at home (on a 120V) .. just enough to make it to ~18 miles to work [where I can use their 240v chargers and charge completely]. So I often set my ‘off peak’ time to be defined as only 1am – 3am on the weekdays. (And only allow charging during off-peak). Now I do have the weekends set with off-peak from 1am to 5pm - pretty all day so I can be sure to have a full charge and/or can recharge during the day.

So here’s the scenario.
Let's say I have 10miles of charge left, so I only want to charge 2 hours (~4miles/hr charging) from 1am - 3am. If it’s Sunday, Monday, or Tuesday night.. the delayed charge will not work as expected .. and will ‘overlook’ my settings and start charging immediately. If it’s a Wed or Thur night, then a 2 hour charge from 1am to 3am the next morning works fine.

I think I’ve figured out why this is.. there seems to be some logic decision that if 3 sessions of the scheduled charge will NOT fully charge the car, then the charge will begin immediately. So on Sunday night – it looks at the Monday am 2 hrs, Tues am 2 hrs, Wed am 2hrs and decides that 6 hrs is not enough time to fully charge the car. So it starts immediately. Now if it’s Wednesday night – it looks at the Thurs am 2 hrs, Fri am 2hrs, and Sat am 17hrs. So it’s happy that the car will be fully charged, and will start at 1am as I had planned.

Tricky, huh.. I played around with this in various ways, and I’m positive this is the issue.
If in the above scenario I have 18 miles of charge left, a 2 hr charge works fine on any day (and I’m assuming that’s because 3 sessions of 2 hr charging will give me the necessary 24miles to fully charge the car).

So has anyone else noticed this? Could it be user error? I believe I have all my departure times set to 7am or 8am.. but don’t think that figures into the logic?

I don’t understand why they don’t just charge based on rate (or for that matter – based on times you select). If I say I only want to charge from 1am-3am, then just start charging at 1am.. if it’s fully charged before 3am, so be it. If it’s not done charging at 3am, stop anyway.
 
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#3 ·
When using delayed rate and time of departure the Volt will delay charging to the off peak times only if there is sufficient time for a full charge in the off peak period(s) prior to the time of departure, otherwise charging starts upon plug in (its explained in the manual). Volts top priority is to get a full charge. So this explains the days your volt starts chaging immediately. The Volt does not look ahead multiple days, it only looks at the time period between the sime of departure and the the time when you plug in. As for the days when charging is delayed either there is sufficient time and you are getting a full charge before the departure, or there is likely an error in the way you have it programmed. I know the programming is less than intuitive, so maybe something is not set correctly. Possibly posting some pics of the programming display, along with the amount of charge used (not miles) will help the forum to analyze the issue. We would also need to know if you are charging with an L1 or L2 EVSE.
 
#5 · (Edited)
From the manual:

Delayed Rate and Departure Time:
The vehicle estimates the charging start time based on the utility rate schedule, utility rate preference, and the programmed departure time for the current day of the week. The vehicle will charge during the least expensive rate periods to achieve a full battery charge by the departure time. Electrical rate information from the utility company for the charging location is required for this mode.

Also, if the selected electric rate settings result in a very long charge completion time, the vehicle will start charging immediately upon plug-in. For example, if the electric rate table is set up with all “Peak” rates and the rate preference is to charge during “Off-Peak” rates only, then the vehicle will start charging immediately upon plug-in.
The example given is an extreme one, so it's not 100% clear how this would extrapolate to your specific example of 2 off-peak hours.
 
#7 ·
Hi there, Thanks for the questions. I use a standard 120V house outlet at home when I'm having this issue. I did just look to see when my departure times were set for, and they are all set to 7am. But I'm not sure how this plays into anything.

I don't know how to see 'amount of charge used'. I only use the car displays to set my times, not an app. So I am using the Battery icon in the display in front of the steering wheel to tell me roughly how many miles I have left on a charge. I know that's not exact [depends on AC/heat/speed], but it's a good enough rough estimate for me. Also, I live in CA, so no cold temperature issues at play either.

I hear what you are saying about the Volt wanting to be fully charged, but I almost never charge it fully at home during the week. And it's only during the early portions of the week that are a problem. [Hence my thought process of the three day logic]. I have played around with this a fair bit (I'm an engineer and do root cause analysis all the time ;-) )
In the situation I describe above, with having ~10miles left of charge.. if I set the off peak time to 3hrs [1am to 4am], it is not day dependent. Meaning on Monday am, the car only charges 3 hrs even though it will only be a ~22miles of charge when I leave for the day [which is not until ~7am]

Anyway, I know it's a weird one, and obviously I work around it, or charge an hour more than needed. Just finally decided to see if anyone else had seen this/heard of it, or knew that a fix was going in.
 
#8 · (Edited)
"Also, if the selected electric rate settings result in a very long charge completion time, the vehicle will start charging immediately upon plug-in."

That would be the exact reason. I hadn't seen that before. I think I figured out that 'a very long charge completion time' is three days ;-)

Thanks all for your information.
 
#9 ·
Hi Debbie!

I know this sort of skirts an answer to the issue you were describing (think you did get an answer though), but have you considered opening up your charging windows to be beyond the 1am-3am timeframe? In asking my question, I'm assuming that the off peak rates you're looking for have a larger spread than that, unless they don't?
 
#10 ·
Hi ClarksonCote:

Yes, that's what I do when I hit that particular situation.. just open the window for another hour or two.. whatever it takes to switch over to delayed charge instead of immediate. Not a big deal. Just saw it as a 'bug' but it seems it is actually expected behavior given the 'if it's going to take too long to fully charge' criteria.
And if I really wanted to be overly-frugal with my charging at home, I could set off-peak to 5am - 9am and just know I'll be leaving at 7am anyway. ;-)
 
#11 ·
There has got to be a good Dilbert comic in this somewhere. :D

I'm a software developer, so I can recognize the attention to tiny details here. Only an engineer who looks at the most precise details would take the initiative to save a few pennies on the electric bill by splitting charging times like that.

Debbie, I am sure you are outstanding at your job! :)
 
#12 ·
Ha SteveC. You are so right.. Dilbert for sure.

And ironic that I started this thread the same day I spent the whole afternoon making sure 'selecting or un-selecting button X' does all the things I think it should. [ie. software user logic] ... which is probably why I got so curious about the volt charging logic.. it's in the blood.

As for the splitting charging.. I'm assuming you are talking about the charging 5a-9a while leaving at 7am comment? I only thought of that as I was trying to describe the odd scenario on this thread. Haven't done it yet ;-)
 
#13 ·
The Volt's charging algorithm is one of those overly complicated pieces of engineering that you see on a Mercedes-Benz, the clear leader in over-complicating things to the point they get in the way and annoy you to no end. Nissan did it the right way in the Leaf. You set a start time and an end time with the option of having different windows on different days. If you plug in during that time period the car starts charging. If it's outside the window it doesn't.

Works every time. No muss. No fuss. Having the charging window operate automatically based on the car's estimate of how long charging will take was just dumb. Hopefully they just deep six it in the next generation.
 
#14 ·
Having the charging window operate automatically based on the car's estimate of how long charging will take was just dumb.
DonC, I particularly liked that feature. It optimized charging through the night, and sucked more juice during the shoulder rate times only when necessary. It saved me money.

...but after I got the L2 chargers installed, it didn't matter, since I always get a full charge during the off-peak rate period.

Debbie: I meant splitting charging between home and work. :) But I think the "charging 5a-9a while leaving at 7am" idea really should work.
 
#16 · (Edited)
I think tying in the GPS would work better. That way, you could say, at home never charge during the peak times set up in the rate schedule, for other locations, charge immediately.

...Nissan did it the right way in the Leaf. You set a start time and an end time with the option of having different windows on different days. If you plug in during that time period the car starts charging. If it's outside the window it doesn't.

Works every time. No muss. No fuss. Having the charging window operate automatically based on the car's estimate of how long charging will take was just dumb. Hopefully they just deep six it in the next generation.
That also results in charges that finish in the dead of night, rather than minutes before departure, resulting in a cool off period after the charge stops. In winter you want the heat from charging to still be in the battery when you start out, rather than having to use power to condition the battery...
 
#15 ·
Would love to have different settings for charging day or night.
I'm able to plug in at work so would love to have a setting to charge immediately upon plug in 8-5, at night delayed for TOU and rate.
have to remember to double plug in the morning to get the charging to start immediately when I get to work.
 
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