Power Needs of Battery Management System?

[NORTON]

bro,
Your car has a problem.
You need to keep shaking their cages at corporate. Call again and don't talk to the same advisor. Is there a way to email all your evidence?
640 Watts continuously would eventually have the battery freezing cold. It is in an insulated container.

I just got mine off a public Chargepoint networked L2. When I tapped the display it showed the kWh used and "Not Charging". I have seen it with the 'Green Light' flashing and drawing 0.6kW if I unplug it right after getting the Onstar txt.
I got the Onstar txt stating: "OnStar: Your 2014 Spark has completed charging. For help, call 888-466-7827. Text STOP to cancel."
And then 17 minutes later got the Chargepoint txt stating "ChargePoint: Your vehicle plugged into XXXX is drawing very little power and may be fully charged.".
That 17 minutes is when TMS is continuing to cool the pack, I suspect, then there is no more current flow.
IF it was left connected in 100° heat TMS may cycle on and off as the day goes on.

640 watts continuous can't be right. Even a big black Tesla sitting in the sun wouldn't need that much power continuously for TMS.

I installed this kWh meter in my home L2/L1 EMW Juicebox: http://smile.amazon.com/bayite-BAYITE-PZEM-061-Multimeter-Voltmeter-Transformer/dp/B00YY1KOHA?ie=UTF8&psc=1&redirect=true&ref_=oh_aui_detailpage_o05_s00

I haven't charged at home in a long time, but for you bro, I will spend a few cents this evening to try see how mine behaves before and after I get the Onstar txt.!!!
It's 86° now and cooling to 79° by 8:00 PM, so similar temps, no?

Anything for a Spark EV Bro!!!!

 

[brothergrimm]

Appreciate it, Norton! I may not have any further updates for a week, but I will follow up on this.

 

[SparkevBlogspot]

Since power went down to 100W without sounds, it does point to temp related parts activating (pump, etc).

Since your mi/kWh is not much off, it's probably something normal during operation. 55 MPH=10.7kW (5.1 mi/kWh), 700 W represents 6.5%. If it's something outside of normal operation, you'd see less than 5 mi/kWh (like 4.8).

One thing that I don't know about is delayed charging. If it's truly faulty temp issue, delayed charging would also cause noise and lots of power use. If it doesn't make noise in delayed charging, it's something other than faulty temp issue.

Another question. When the car is "on", does it make whirring noises even after 5 minutes of not moving while in "P"? Since the car has fake noise maker, you have to make sure you're in "P" to test. Mine becomes silent after 30 seconds, even at 85F ambient.

So try delayed charging at night at under 70F. If it still makes noise when it shouldn't be charging, you can contact them again and tell them the car is making noise all the time even when it should be quiet and show them at the dealer with delay charging enabled when it's cool. Since drive to the dealer would consume power, delayed charging is the only way to show them the power draw / noise when it should be silent.

Finally, don't forget to turn off delay charging!!! I forgot once, and had to take the gas car.

 

[NORTON]

...One thing that I don't know about is delayed charging. If it's truly faulty temp issue, delayed charging would also cause noise and lots of power use. If it doesn't make noise in delayed charging, it's something other than faulty temp issue....

I don't know exactly how 'Delayed Charging' works with TMS. (It's a question that I lost my window of testing until next winter gets here.)
I would like TMS to use some power to keep the battery temp happy, but not actually charge at home, before my departure time.

Do we know how this works, for sure?

So, for our bro, I plugged in at home !
The distance does not include a ~5 mile lunch run and I saw 91° during most of my drive home.
I used my 'country' drive home. 50-45 MPH posted, or less. driven at +5 the posted. AC set to 75°, recirc.



Dang, I need to detail my displays... Hay fever season,, yuck, sorry...


Disregard exact numbers. I know they are incorrect. I need to measure current with a certified clamp-on ammeter and then create a correction factor. Or figure out a resistor value to put in series with the current sensor. The current number is higher than it should be, which makes the kW and kWh numbers to high also.


So, in a half an hour I can start monitoring TMS and it's behavior.

 

[NORTON]

OK, second try to post this.
After getting the 'bing' from the txt msg from OnStar I immediately went to the EVSE and saw this:

The kWh display is a total of power consumed since I installed this kWh meter in the EVSE late last fall. I spent ~$38 over the winter charging at home.

bro, your car is doing something wrong.
I wish you luck in convincing Chevy and your local dealer that what you are seeing is not normal behavior.

I believe when charging L2, TMS keeps up with battery temp needs. It does not need to keep working after a completed charge in this weather.

I know if I immediately unplug from a DCFC station and start driving I'll still feel cold air from the vents even though I have No Climate Control on. This will last for maybe 5 minutes.
That's the AC compressor running to continue to cool the battery. It's probably not good to unplug from a DCFC and just park the car.

EDIT: Looked at the kWh display before unplugging this morning. No change overnight. Although my kWh meter only has '1kWh' resolution. I can reset it. It displays 99.9 before losing the decimal point.

 

[ZipZap]

I have seen what I'm pretty sure is my Spark doing some active battery cooling when the car is not actively charging but is plugged in. I live in Las Vegas, though, so it's consistently a bit hotter here (we've consistently been over 100F in the past month or so). Here are some different case examples.

Edit: BTW, both of these cases seem perfectly reasonable to me. Just sharing my experience since I suspect I live in a different climate than most of you do.

Case 1 (6/26)- The battery had finished charging the night before (very beginning of the graph). I've noticed short blips like the one at 09:30 many times before (I don't think that one is cooling related), but I'm pretty sure the ones at 13:00, 15:00, and 17:00 are all active cooling. FYI, the ambient temperature was probably about 108F. The rest is normal driving and charging.

Case 2 (6/22 -> 6/23) - I noticed that battery conditioning was starting to show up on my onboard power consumption tracking, so I was playing with delayed charging (so the car charges when it's cooler outside). I set the delayed charge with a finish target time of 06:00 and plugged it in right after my drive at about 19:00. I'm pretty sure that's the cooling system coming on from 19:00 -> 23:00 (ambient temp was still something like 105F -> 97F), but the charge doesn't actually start until about 02:30.

 

[NORTON]

ZipZap,
Thanks for posting that, particularly 'case 2'. That is what I was trying find. I assume it would be similar for very cold weather only a different amount for TMS.
I suppose I should be plugging in at home over night these hot days, and nights....

I would like to gather data the way you did.
How did you get these graphs?

 

[MrDRMorgan]

Does anyone know what the impact outside ambient temperature has on the battery's charged capacity? I am seeing my calculated battery capacity slowly rise as the outside ambient temperature rises.

 

[ZipZap]

I would like to gather data the way you did.
How did you get these graphs?

An OpenEVSE kit with a WiFi kit added. It took a bit of setup, but they guy who makes those kits hosts a webserver that the data gets sent to and I was able to make my own dashboard there.

It's kind of interesting that the car is drawing a lot lower power in Case 2 (and for a longer period). I'm not sure what the difference is there.

 

[SparkevBlogspot]

It's my guess, but #1 at 13, 15, 17 were probably with high ambient temperature, requiring blasting max AC to cool down the pack. #2 at 19 was probably lower ambient temperature that required less blasting and also knew of delayed charging.

Was the battery close to full capacity for #1 while #2 was not? It may be that capacity could also affect things (or not).

 

[NORTON]

ZipZap,

It's weird that it even reports 'Internal charger temp'. This has to be the EVSE itself.
The J1772 connection at the car does not send data out from the actual AC to DC water-cooled HV battery charge within the car, (that I know of).
And the EVSE is just a very small power supply and logic board, a big ass relay and the goes-in and goes-out wires. The relay is either closed or open. The car's OBC controls the current usage.
Who cares what that temp is?

Thanks again for sharing you TMS usage data !

 

[SparkevBlogspot]

EVSE temp gives clues to ambient temperature.

 

[NORTON]

EVSE temp gives clues to ambient temperature.

I doubt it. That plot just followed current flow and when it's hot it's way too hot to be ambient.

Maybe drill some ventilation holes in that home built thing. Maybe a small muffin fan to keep the board happy. Maybe ignore that data.

 

[ZipZap]

Yeah, I should change the label on that graph to EVSE internal temperature. The unit is in my garage, so the temperature is dampened a bit from ambient, but if you ignore the internal heating spikes when charging, it gives some info about the ambient temperature. The temperatures I mention in the text of my post are noaa data from a nearby airport. That web software (EmonCMS) isn't an EVSE specific thing and will log just about any kind of properly formatted data feed you want to send to it (though the guy who makes the open EVSE kits has made it easier to set up for EVSEs). I hope to soon have another ESP8266 (the wifi part of that expansion kit) board logging ambient temperatures and few more feeding it all kinds of sensor data from my HVAC system.

 

[slackinormackin]

I think i am having the same issues as those mentioned. In May (using a public ChargePoint EVSE), after charging was complete the Spark was pulling no power. Recently, it has switched to drawing a significant amount of power after full which never drops to zero. Attaching two graphs which show my issues....

 

[NORTON]

... after charging was complete the Spark was pulling no power. Recently, it has switched to drawing a significant amount of power after full which never drops to zero. ....

This has to be a battery TMS problem.
If the system is constantly pulling 760 watts, or whatever, eventually you have a battery pack that is ice cold.
Good luck getting Chevy's EV tech support to listen to you , let alone your local dealership.

In this hot weather I get the txt from Onstar that charge has completed. Then ~20 mins later I'll get the txt from Chargepoint that my car is "drawing very little power and is probably done charging".

If I look at the details on the Chargepoint app I see the 20 mins of ~0.8 kW then it drops to zero. That is TMS continuing to cool the pack after the charge has completed.

Side note:
Then on my commute home I don't see any power being used for "Battery conditioning" on the energy usage page. I suspect if you are running cabin AC anyway the TMS uses some of that freon cooling and does not report it as Battery Conditioning.

Again, Good luck guys !! Fight the good fight.

 

[ZipZap]

Recently, it has switched to drawing a significant amount of power after full which never drops to zero. Attaching two graphs which show my issues....

In general, lithium battery packs need to to have the cell voltage balanced every once in a while and I have no idea how the Spark does that. It still seems mysterious to me how a charging cycle could be fixed power (3.3kW) for a certain time and then be fully charged. The cycle I'm familiar with is fixed current until a max voltage is reached followed by a fixed voltage (at the max voltage) until current tails off to almost nothing. Maybe there's some voltage overhead built into the battery pack so that the relatively slow Level 2 charge rate is OK.

I have noticed lower power consumption for a time after charging is complete when the weather is cool (though the time is not as long as indicated in your graphs). I assumed this was the battery management system doing things like balancing the cell voltage.

Here's another example showing some behavior (I presume is normal) from my car a few months ago (Ambient outside temperature over these 3 days was about 45F - 75F, so thermal management for the ambient temperature is unlikely):

 

[NORTON]

...
In general, lithium battery packs need to to have the cell voltage balanced every once in a while and I have no idea how the Spark does that. It still seems mysterious to me how a charging cycle could be fixed power (3.3kW) for a certain time and then be fully charged. The cycle I'm familiar with is fixed current until a max voltage is reached followed by a fixed voltage (at the max voltage) until current tails off to almost nothing. Maybe there's some voltage overhead built into the battery pack so that the relatively slow Level 2 charge rate is OK.....

This is a very good point.
You do see this tapering of current during DCFC. Maybe, as you say, 3.3kW is low enough to keep the peak voltage low enough at the end of charge.
And maybe some of this low power after the 3.3kW is balancing and not TMS.

 

[SparkevBlogspot]

When I took DCFC to 100% long ago, I observed 4 seconds for each 0.01kWh at 99%. That's about 9 kW. Even if it was 5 seconds, it would be 7.2 kW. And yes, no one was waiting or drove by while I was doing this.

I charged it to 100% less than 10 times, and it's been months since doing so. I live on top of a hill (more like a mountain), and 100% would mean wasting lots of friction brakes. I only charge to 80% (1 or 2 bars missing). Still, the battery seems to be doing ok. In theory, cell balancing could also occur during discharge, though I don't know if that happens with SparkEV.

 

[brothergrimm]

Just a follow-up. I haven't gotten a chance to talk to any local dealerships about this phantom power draw. I've witnessed it less while I've...
1) kept the battery between 30-80% charged, and
2) started the charge in cooler weather.

Not sure which one is more helpful.

When/if I talk to a dealer about it, I'll make sure to follow-up on this thread.