Vampire Drain

[Bobby]

I will unplug after a charging session, garage is also about 82-84. No BMS fans are running. Car is at 80%. Then 3-4 hours later when I go to drive, the car is at 77%

Possible dumb question, but why unplug?

 

[Sandvinsd]

Possible dumb question, but why unplug?

Convince for when I want to leave later primarily. No other reason. I’ll unplug if I go to the garage for something and the charging is done. But doesn’t matter for this point. Car is at 76-77% charge whether car remains plugged or is unplugged.

What matters more is having the car plugged while waiting for a charge after midnight. BMS will run off and on for hours to keep the battery at the optimal expecting a charge. Lucid needs to have a timer function so that the car only runs the precondition fans just before initiating the charge.

 

[hydbob]

Convince for when I want to leave later primarily. No other reason. I’ll unplug if I go to the garage for something and the charging is done. But doesn’t matter for this point. Car is at 76-77% charge whether car remains plugged or is unplugged.

What matters more is having the car plugged while waiting for a charge after midnight. BMS will run off and on for hours to keep the battery at the optimal expecting a charge. Lucid needs to have a timer function so that the car only runs the precondition fans just before initiating the charge.

2 hours after I unplugged this morning, the SOC dropped 1%. Will check 4 hours after unplug

 

[Sandvinsd]

Where does the energy go? 77-82% goes to move the car.

 

[hydbob]

Where does the energy go? 77-82% goes to move the car.

4 hours later, 91 degrees, 1% loss

 

[dawktah LucidGT]

4 hours later, 91 degrees, 1% loss

I wish we could get participation of some of the engineers at Lucid. I don't understand why a car sitting idle needs to cool the batteries?

 

[Adnillien]

Maybe, just maybe its not real. Whatever method the car's software is using to calculate the SoC isn't accurate? I'm not an engineer, how do you calculate how much a battery is charged?

This is a question that I have asked customer care a couple of times. Both times I was told that the question was sent to engineering and both times I did not get a response. I would love to hear an answer from Lucid.

To my simple way of thinking there are two ways to estimate SOC.

One way is to use the temperature corrected voltage of the cells in the battery pack. Then translate that voltage to SOC by knowing the cell voltage versus SOC curve that is a function of battery chemistry. Even though the curve is known for the cell chemistry, there may be slight differences between battery packs and this will also change over time as the battery ages. Several of us have been told by Lucid to run the charge down to below 20%. I believe this is helps each car's calibration of its specific SOC versus voltage curve. Additional errors come into this method anytime there is current into or out of the battery because and internal resistance appears as a voltage when current is flowing. The temperature correction may be difficult to measure since all cells in the module may not be at the same temperature. It appears that the BMS components that measure the temperature corrected voltage are are the module level.

Another method to determine SOC is to measure current into and out of the battery since batteries are nearly 100% efficient with respect to electrons in and electrons out. Measuring current is not that easy. One way is to use a very precise low resistance shunt and measure the voltage across it. This works but the shunt resistance needs to be very well calibrated over temperature and the sampling frequency needs to be fast to capture quick changes in current. It is also creates resistive loss. There are multiple outputs from the the high voltage battery, traction inverter, medium power inverter, low voltage that all have to be accounted for.

I am guessing that Lucid is using the temperature corrected voltage method. It is an estimate and that explains some of what we are seeing with changing SOC. Some is real loss from the battery cooling/heating and the communications modules waking up. Several people on the forum have been told by Lucid that there are errors in the efficiency shown mi/kWhr calculation. Some of those errors my be in the SOC estimation itself.

 

[hydbob]

I wish we could get participation of some of the engineers at Lucid. I don't understand why a car sitting idle needs to cool the batteries?

To keep them within a certain temperature range to reduce degradation of the cells would be my guess.

 

[hydbob]

6 hrs later, 92 degrees in garage, still 1% loss

 

[Sandvinsd]

6 hrs later, 92 degrees in garage, still 1% loss

You are seeing what I will see if the car is parked without charging. I only get about a 3-5 mile loss (or <= 1%) in about 16 hours if I am not charging. I see a 3-4% loss in the morning if I have charged. My garage is in the 70’s usually, rising to the low to mid-80’s at the high after a charging session.

 

[Adnillien]

You are seeing what I will see if the car is parked without charging. I only get about a 3-5 mile loss (or <= 1%) in about 16 hours if I am not charging. I see a 3-4% loss in the morning if I have charged. My garage is in the 70’s usually, rising to the low to mid-80’s at the high after a charging session.

The mid-80's is an ideal temperature for the batteries. They should not require cooling when not being charged.

 

[hydbob]

You are seeing what I will see if the car is parked without charging. I only get about a 3-5 mile loss (or <= 1%) in about 16 hours if I am not charging. I see a 3-4% loss in the morning if I have charged. My garage is in the 70’s usually, rising to the low to mid-80’s at the high after a charging session.

Yea, but this after I charged from 10 hrs on my l2 charger. Just testing loss after unplugging. Data collection mode.

 

[Coltonw011]

I just finished another charging session this morning and after my Homeflex cut off, I went to unplug to reduce the drain, but my fans were not running. Garage was 82 degrees. I have NFI anymore when the BMS fans run or not.

I think a lot of it may be the coolant pump as well. When my charging sessions are complete, whether is l2 or DCFC, there isn’t any obvious BMS fans running. If you listen very closely, you can hear what I can only describe as a whirring sound - this sound continues on for a good 3-4 hours post-charge. I am just guessing the coolant pump is running still. I’ve been logging this ever charge session with a consistent 4-5% loss if the car is parked after charging.

 

[hydbob]

last log for the data, 12 hours post charge, 1% loss on SOC, highest temp the garage got was 93 degrees

 

[dawktah LucidGT]

Are you sitting down? I charged using supplied L2 charger to 100% last night. Completed early this morning. I get to car in garage its DEAD SILENT. Charging light in port is dark. I unplugged and car works perfectly. This phantom issue, well at least the one I'm having leaving it plugged and it losing SoC and having to start charging again seems to be related to the 80% partial battery charge.

 

[dawktah LucidGT]

So did it again before hitting the road. Car finished charging to 100% at 17:15.

Got ready to get in the car to leave around 18:35 this is what it looked like...

Didn't have fob with me during photo to show it's cold and dark.

 

[wdupre1]

I'm wondering if the spurious battery drain is due to key proximity. The layout of my home could cause me, and consequently my key, to come within range of the car causing it to wake up, extend the door handles, start the AC, etc. when I'm walking around my home. I saw that Amazon has a small key pouch, i.e. the "Silent Pocket Signal Blocking Faraday Key Fob Case" for $15.25. I might try it to see if my car will remain asleep. On the other hand, if it works, then I'll have to take the case out of my pocket and remove the key to wake up the Air which rather defeats the convenience of the proximity sensor. Shrug...

 

[WildRide47]

I'm wondering if the spurious battery drain is due to key proximity. The layout of my home could cause me, and consequently my key, to come within range of the car causing it to wake up, extend the door handles, start the AC, etc. when I'm walking around my home. I saw that Amazon has a small key pouch, i.e. the "Silent Pocket Signal Blocking Faraday Key Fob Case" for $15.25. I might try it to see if my car will remain asleep. On the other hand, if it works, then I'll have to take the case out of my pocket and remove the key to wake up the Air which rather defeats the convenience of the proximity sensor. Shrug...

I use a faraday pouch for my key fob.
I put my AGT in my garage at 82%. Key in pouch. Never took the key out.
Next morning percentage was 78%.
Why the drain beats me. Love to hear answers from the forum and whether I should report this to Lucid.

 

[MoniputerLM]

I use a faraday pouch for my key fob.
I put my AGT in my garage at 82%. Key in pouch. Never took the key out.
Next morning percentage was 78%.
Why the drain beats me. Love to hear answers from the forum and whether I should report this to Lucid.

Seems like a large loss, I would call customer support and ask if it's normal

 

[thecodingart]

My car was charged to 90-100%, sat for a week at the retailers and lost 40-50% battery. The drain was … unexpected. After owning a ton of EVs, I wouldn’t call this normal.