How do people determine/measure power usage while awake topping of 12V battery?

[rrolsbe]

Several months ago I measured the 12V DC power usage while the car was sleeping with an ammeter connected in line and found the power usage to be about 7 to 8 watts. This measurement could have also been performed using a shunt. Many sources say the power usage while the car is awake (normally this is topping of the 12V battery) is about 250W +/- 50W. Does anyone know how this was instrumented or otherwise determined this range? I am curious how much the power draw differs between the DC-to-DC actively charging the 12V battery at around 14.7V as opposed to providing a float voltage of around 13.4V? I saw no parameters in SMT that showed power usage in the range of 200 to 300 watts while car was awake topping off the 12V battery.

 

[Frank99]

All the reports I’ve seen have been people estimating using range loss divided by hours - e.g. I lost 24 miles of range overnight in moderate temperatures because I left Sentry on, which works out to about xxx watts on average.

 

[GtiMart]

I woke my car up and stayed outside and then launched scanmytesla. I can see around 150-200w being consumed by looking at the "Battery Power" field. I can also look at the DC-DC output voltage/current/power and presume it's charging the 12V because those values are at 14.8V/9.2A/136w for example.
The coolant pump and other such things are variable, energy consumption might vary a bit. I presume 12V charging is variable too, these values are just what I see today, parked in a garage, after a manual wakeup (opening and closing a door) without knowing when it last woke up and charged by itself.
Separately, I guess people have looked at how their battery has drained over a day or more and were able to infer that the loss was in the 200-250wh range.

 

[android04]

I installed a battery monitor that uses a shunt to measure and calculate current, voltage, energy use in Ah, and battery SoC in %. I did this back in August. I fully charged the 12v battery while it was disconnected from the car (and with car powered down) with a smart charger until it showed 100% charged. Then I hooked up the battery monitor and programmed it so that it considers the current state as 100% SoC and a battery capacity of 45 Ah (using the number printed on the battery label).

I've observed that if the car is awake, or will be either charging or maintaining float voltage of around 13.45V (varies by temperature). It does not put a drain on the battery if the car is awake. The maximum charging current I've ever seen, even after having the car sit unused for 3 days, is less than 8 Amps. As soon as the car wakes up the charging current could be a little less than 8 Amps for a few minutes and tapers down. In 5-10 minutes it will usually be below 3 Amps. Within 1 hour of starting to charge the battery is usually full and at float voltage. When the 12v battery is at float voltage, there is less than 150mA going to it (fluctuates a little, but averages below 100mA). If the car is asleep and you don't have Sentry Mode or any other persistent feature on, the car draws about 33 mA (last measured a few weeks ago, 4 hours after finishing charging and in a 39°F garage). I remember another measurement I did last fall with the car asleep averaged around 120 mA, but it might not have been in deep sleep at that point yet or the behavior might have changed with a software update. In the half year I've been observing, the 12v battery is never drained more than about 3 Ah (out of the total possible capacity of 45 Ah) before my car recharges it again; which means that it only uses up about 6.7% of it's rated capacity (aka depth of discharge). A 6.7% DoD is perfectly fine for any old starting type lead acid battery and does not require a deep cycle battery. Keep in mind the charging and utilization behavior had changed over time with software updates because Tesla has full control of how it works and their computers can monitor all the exact things I am with my aftermarket kit. Also keep in mind that the behavior could be different from car to car, especially if Tesla uses any measurements or assumed battery age to adjust charging and utilization of the battery. For example, my 12v battery is almost 4 years old and if Tesla measures something or keeps track of something that indicates it's age, they could be going easy on it in terms of how deeply they discharge it.

Here are a few pictures of my setup and battery monitor


Readings while car is asleep








Readings when car is awake and battery fully charged

 

[rrolsbe]

I installed a battery monitor that uses a shunt to measure and calculate current, voltage, energy use in Ah, and battery SoC in %. I did this back in August. I fully charged the 12v battery while it was disconnected from the car (and with car powered down) with a smart charger until it showed 100% charged. Then I hooked up the battery monitor and programmed it so that it considers the current state as 100% SoC and a battery capacity of 45 Ah (using the number printed on the battery label).

I've observed that if the car is awake, or will be either charging or maintaining float voltage of around 13.45V (varies by temperature). It does not put a drain on the battery if the car is awake. The maximum charging current I've ever seen, even after having the car sit unused for 3 days, is less than 8 Amps. As soon as the car wakes up the charging current could be a little less than 8 Amps for a few minutes and tapers down. In 5-10 minutes it will usually be below 3 Amps. Within 1 hour of starting to charge the battery is usually full and at float voltage. When the 12v battery is at float voltage, there is less than 150mA going to it (fluctuates a little, but averages below 100mA). If the car is asleep and you don't have Sentry Mode or any other persistent feature on, the car draws about 33 mA (last measured a few weeks ago, 4 hours after finishing charging and in a 39°F garage). I remember another measurement I did last fall with the car asleep averaged around 120 mA, but it might not have been in deep sleep at that point yet or the behavior might have changed with a software update. In the half year I've been observing, the 12v battery is never drained more than about 3 Ah (out of the total possible capacity of 45 Ah) before my car recharges it again; which means that it only uses up about 6.7% of it's rated capacity (aka depth of discharge). A 6.7% DoD is perfectly fine for any old starting type lead acid battery and does not require a deep cycle battery. Keep in mind the charging and utilization behavior had changed over time with software updates because Tesla has full control of how it works and their computers can monitor all the exact things I am with my aftermarket kit. Also keep in mind that the behavior could be different from car to car, especially if Tesla uses any measurements or assumed battery age to adjust charging and utilization of the battery. For example, my 12v battery is almost 4 years old and if Tesla measures something or keeps track of something that indicates it's age, they could be going easy on it in terms of how deeply they discharge it.

Here are a few pictures of my setup and battery monitor
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Readings while car is asleep
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View attachment 764054

Readings when car is awake and battery fully charged
View attachment 764062

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View attachment 764058

What shunt are you using and where did you purchase it? Where did you purchase the Energy and Focus device shown in your pictures?

Thanks Very Much
Regards, Ron

 

[rrolsbe]

I woke my car up and stayed outside and then launched scanmytesla. I can see around 150-200w being consumed by looking at the "Battery Power" field. I can also look at the DC-DC output voltage/current/power and presume it's charging the 12V because those values are at 14.8V/9.2A/136w for example.
The coolant pump and other such things are variable, energy consumption might vary a bit. I presume 12V charging is variable too, these values are just what I see today, parked in a garage, after a manual wakeup (opening and closing a door) without knowing when it last woke up and charged by itself.
Separately, I guess people have looked at how their battery has drained over a day or more and were able to infer that the loss was in the 200-250wh range.

The lions share of the 200-250wh of energy used by the so called phantom drain is used in topping off the 12V battery and all the systems requiring energy while doing so, as apposed to the energy used while the car is actually sleeping.

 

[android04]

What shunt are you using and where did you purchase it? Where did you purchase the Energy and Focus device shown in your pictures?

Thanks Very Much
Regards, Ron

The shunt and monitor are from Amazon, Aili brand but there are many other brands that are exact clones. Here's one https://smile.amazon.com/AiLi-Voltmeter-Ammeter-Voltage-Motorhome/dp/B07CTKYFTG/ and here's another https://smile.amazon.com/gp/aw/d/B08HWFPGL5/. You would have to use some battery post clamps to bolt onto the shunt.

The "Energy and Focus" is a tin with mints that have caffeine and other things to help with energy and focus . They are sold by Neuro, and they also have it in gum form and in "Calm and Clarity" variant. Neuro Gum and Neuro Mints | Energy and Focus