What's the power consumption of the UMC not charging?

[neurocutie]

When not charging or not plugged into the car, what does the UMC use?

These days I drive so little, maybe 10mi/week, that I don't see the point of wasting that power if it is appreciable, like even 100 watts.

 

[Entropy512]

Given that it's just enough to keep a microcontroller active along with the losses of the internal DC power supply - I'd guess less than a watt.

My UMC hasn't arrived yet so I can't put it on my power meter.

 

[jdcollins5]

It is so small my power meter does not display it. It displays a really small amp, something like 0.142.

 

[rdskill]

Assuming plugged into 120v circuit = 120v x 0.142 A = 17.04 Watts
If 240v = 240v x 0.142 A = 68.16 Watts

 

[Silicon Desert]

On my panel circuit monitors, mine is showing about 4 Watts, accurate to only plus or minus 10%. So it's very small.

 

[neurocutie]

Thanks, others have also reported a number like 4watts. That's small and not worth worrying about.

So then the only thing remaining is the advice to keep the car plugged in. I think in warm weather, that is probably also okay/good. But in cold weather (still in 30's around here), the energy needed to warm the battery for charging is pure waste, so maybe in winter its better to leave it unplugged if not driving much? A week's gone by and I'm still at 220mi left (from a usual 254mi). Probably actual miles driven less than 15mi.

 

[Entropy512]

I've seen some reports that departure charging without actually leaving (happening a lot due to the current situation) can result in you exceeding your set charge target. But other than that, keeping the car plugged in to keep the battery monitored/conditioned more aggressively is probably beneficial - not just for the main battery, but the 12v aux battery too.

Also, it's definitely warming up here in upstate, it was incredibly warm yesterday when I went into work (employee of an essential business, while we're primarily work-from-home, we have to occasionally go in for on-vehicle testing in the lab)

 

[jerry33]

Thanks, others have also reported a number like 4watts. That's small and not worth worrying about.

So then the only thing remaining is the advice to keep the car plugged in. I think in warm weather, that is probably also okay/good. But in cold weather (still in 30's around here), the energy needed to warm the battery for charging is pure waste, so maybe in winter its better to leave it unplugged if not driving much?

That would be a no. (The Model 3 manual should have approximately the same wording.)

About the Battery

Model X has one of the most sophisticated battery systems in the world. The most important way to preserve the Battery is to LEAVE YOUR VEHICLE PLUGGED IN when you are not using it. This is particularly important if you are not planning to drive Model X for several weeks. When plugged in, Model X wakes up when needed to automatically maintain a charge level that maximizes the lifetime of the Battery.

 

[Rottenapplr]

I’m showing 2.4 watts with the car plugged in and fully charged. I have a meter.

 

[neurocutie]

That would be a no.
Model X has one of the most sophisticated battery systems in the world. The most important way to preserve the Battery is to LEAVE YOUR VEHICLE PLUGGED IN when you are not using it. This is particularly important if you are not planning to drive Model X for several weeks. When plugged in, Model X wakes up when needed to automatically maintain a charge level that maximizes the lifetime of the Battery.

ok, but presumably the idea is simply not to let the battery run down below, say 20%. The language of that statement doesn't entirely make sense: "automatically maintain a charge level that maximizes the lifetime of the Battery". Yet most of us have the charge level set at around 80-90%, not some internal carefully calibrated optimum level. And it is well-documented that the optimum is around 50% (but the curves are gentle).

So does that above advice actually supercede the notion that the battery at 50% forever is a good state to maintain?

 

[Silicon Desert]

So then the only thing remaining is the advice to keep the car plugged in. I think in warm weather, that is probably also okay/good. But in cold weather (still in 30's around here), the energy needed to warm the battery for charging is pure waste, so maybe in winter its better to leave it unplugged if not driving much?

Uh, I don't see what you are talking about. I live up here in Sparks at about 4,000 feet and it gets really cold in the winter. Most nights are below freezing. In 4 years I have NEVER seen the car need to warm the battery while charging at home on the wall charger. That has been the case whether the car is plugged in or not.

 

[Entropy512]

ok, but presumably the idea is simply not to let the battery run down below, say 20%. The language of that statement doesn't entirely make sense: "automatically maintain a charge level that maximizes the lifetime of the Battery". Yet most of us have the charge level set at around 80-90% and it is well-documented that the optimum is around 50% (but the curves are gentle).

So does that above advice actually supercede the notion that the battery at 50% forever is a good state to maintain?

What he's recommending is not fundamentally incompatible with keeping the battery at 50% - drop your charge target if you're expecting it to sit long term.

IIRC, Teslas will check/maintain the 12v aux battery more often when plugged in, for one thing. I could be wrong about that, but better safe than sorry.

 

[jerry33]

ok, but presumably the idea is simply not to let the battery run down below, say 20%. The language of that statement doesn't entirely make sense: "automatically maintain a charge level that maximizes the lifetime of the Battery". Yet most of us have the charge level set at around 80-90%, not some internal carefully calibrated optimum level. And it is well-documented that the optimum is around 50% (but the curves are gentle).

So does that above advice actually supercede the notion that the battery at 50% forever is a good state to maintain?

What it means is that there's little difference. All the 50% tests are about RC cars and off-the-shelf cells rather than Tesla car chemistry. The difference is going to be eaten up by other variables (how you drive, ambient temperature, etc.) There's a case to be made if you leave it for six months (e.g. like a snowbird), but the six to eight weeks you don't drive it for this isn't going to amount to much. And in winter you likely don't want the 12V battery to freeze.

 

[neurocutie]

12V lead/acid chemistry can sit for a month without needing to being topped off. And it is definitely not going to freeze unless we get one of those "polar vortexes".

Setting the charge level to 50% might be a reasonable strategy, but a bit of a nuisance. As long as one sits or moves somewhere within the gentle portions of the optimum curve, I don't see that it should make any appreciable difference.

 

[jerry33]

12V lead/acid chemistry can sit for a month without needing to being topped off. And it is definitely not going to freeze unless we get one of those "polar vortexes".

Setting the charge level to 50% might be a reasonable strategy, but a bit of a nuisance. As long as one sits or moves somewhere within the gentle portions of the optimum curve, I don't see that it should make any appreciable difference.

When I think cold, I think -20 or -30 C. Been there done that too many times.

 

[Entropy512]

12V lead/acid chemistry can sit for a month without needing to being topped off. And it is definitely not going to freeze unless we get one of those "polar vortexes".

Setting the charge level to 50% might be a reasonable strategy, but a bit of a nuisance. As long as one sits or moves somewhere within the gentle portions of the optimum curve, I don't see that it should make any appreciable difference.

With absolutely no parasitic load, sure. But even the background load of a Tesla waking up (cell radio, etc.) will result in the aux battery needing to get topped off from the main battery on a routine basis. Every BEV I know of on the market will monitor/topoff the aux battery more often when plugged in.

Put even a Bluetooth OBD adapter's parasitic drain on an ICE, forget that you left it connected, come back to a heavily sulfated battery 2 weeks later. Modern "smart" vehicles have even more parasitic drain than that - fortunately they also usually have a gigantic main battery.

 

[jjrandorin]

12V lead/acid chemistry can sit for a month without needing to being topped off. And it is definitely not going to freeze unless we get one of those "polar vortexes".

Setting the charge level to 50% might be a reasonable strategy, but a bit of a nuisance. As long as one sits or moves somewhere within the gentle portions of the optimum curve, I don't see that it should make any appreciable difference.

If you are not going to leave it plugged in, please dont come back here talking about "lost range" or "degradation". The car will also slowly balance the battery over time when plugged in, and most people who are wailing about "degradation" are not leaving the car plugged in.

I have "gained" back 3 miles that I "lost" because the car has been sitting plugged in for basically the past 2 weeks with only minimal driving.

 

[neurocutie]

If you are not going to leave it plugged in, please dont come back here talking about "lost range" or "degradation". The car will also slowly balance the battery over time when plugged in, and most people who are wailing about "degradation" are not leaving the car plugged in.

I have "gained" back 3 miles that I "lost" because the car has been sitting plugged in for basically the past 2 weeks with only minimal driving.

ok, deal... (I've never done that).
But do you actually have any evidence that "MOST" people who don't leave their cars plugged in AND keep the car at least a minimum of 30% SOC actually come here to complain about lost range, as compared with people who do leave their cars plugged in? I highly doubt it.

Good that you've "gained", but have you shown that that gain is real, or just noise in the numbers presented? I've "lost" and "gained" a few miles here and there and I seriously doubt that it is meaningful or real.

I get that its good advice to tell everyone to leave their Tesla's plugged in as much as possible. Remember that one of the earlier realizations in the issue of energy conservation and climate change is the fact that most of us burn many kwh leaving TV's plugged in VCR/DVR, game consoles, chargers, etc, etc. So I don't think it is unreasonable to examine, with specificity and real engineering specs, advice that something should be left plugged in 24/7. I think its ultimately consistent with Tesla's mission.

 

[Rocky_H]

Uh, I don't see what you are talking about. I live up here in Sparks at about 4,000 feet and it gets really cold in the winter. Most nights are below freezing. In 4 years I have NEVER seen the car need to warm the battery while charging at home on the wall charger. That has been the case whether the car is plugged in or not.

And yet despite your not having "seen" this, I assure you it for certain is happening.

I'm not sure by what criteria you think you will "see" this battery heating. But Tesla cars absolutely will not charge the battery while it is below freezing. That would cause irreversible damage, so they just don't do it. So when it is time to begin a charging cycle, it will instead, start pulling energy from the house circuit to run warming systems for a while to heat up the interior of the battery pack to get it up to a safe enough temperature that it can then start sending some of that energy toward recharging the battery cells. It will still continue splitting that energy, further warming up the pack and gradually increasing the amps of the charging rate as the temperature in the pack continues to rise.

 

[Zoomit]

If you are not going to leave it plugged in, please dont come back here talking about "lost range" or "degradation". The car will also slowly balance the battery over time when plugged in, and most people who are wailing about "degradation" are not leaving the car plugged in.

I have "gained" back 3 miles that I "lost" because the car has been sitting plugged in for basically the past 2 weeks with only minimal driving.

Incorrect-- brick balancing occurs independent of the car being plugged in. It occurs based on SOC above ~85%. Here's the section from the Model 3 Service Manual with the key sentence in bold:

Brick Balancing

Note that the capacity of a pack is limited by the brick with the lowest capacity. When that brick is charging, it will gain voltage faster than other bricks. The HVBMS will stop charge when any brick reaches its ceiling voltage (~4.2V). If one brick has a significantly lower capacity that others, the pack will be limited by that brick which will get to 4.2V faster than the other ones. We refer to the brick with the lowest capacity as: min CAC. In periscope, its value can be seen by viewing the signal: 'BMS_cacMin'
Another limitation could come from bricks being imbalanced, or some bricks with a voltage higher/lower than others. This would limit ability to charge the pack as the brick with a higher voltage than others would reach the ceiling voltage early. Same idea when discharging, the brick with the lowest voltage would hit the floor voltage early which would cause the HVBMS to open contactors from low power

To mitigate this imbalance, Batman has some bleed resistor that can be placed and removed in parallel of each brick via a FET relay. Batman can put that resistor across the brick with the highest voltage which would slightly discharge that brick and bring it back to the level of the other bricks. Batman closes a FET which puts that resistor across the brick. The HVBMS will order Batman to put that bleed resistor across the brick with the highest voltage when Delta V is > 5mv MinBrickV > 4.0v (~85% SOC) && HVBMS State == STAND BY.

Note that Batman can also do balancing when the HVBMS is asleep.

The best way to balance the Model 3 pack is to set charge limit to 90% or higher and let the vehicle sit idle for hours (plugged in or not). 24 hours of balancing can reduce imbalance by 1mV.​