How much power do the headlights draw?

[Transformer]

How much power (watts) do the headlights draw on low beam?

I'm curious how fast they'd drain the battery if the lights were left "on" in the manual setting, and didn't find anything in the Energy app.

Ideally, info for both matrix or pre-matrix headlights.

 

[zoomer0056]

I'm just guessing here, I would think they would time out and turn off.

 

[E90alex]

I don’t know how one would measure that. But it would be in the magnitude of days with a full battery.

 

[RayK]

I don’t know how one would measure that. But it would be in the magnitude of days with a full battery.

Best case and cleanest scenario would be to find out what connector is used to attach the headlight(s) to the associated wiring harness and build a short extension cable (male and female ends) and put an ammeter inline on one of the leads. That way you could get the current/power measurement needed and there would be no evidence after the fact, like a spliced wire.

 

[Transformer]

Web sources:

• ≈100W together Leaving headlights on
• 70W together for 2014 Model S Xenons; LEDs are less How bad is a Tesla battery affected if all driving is at night with the lights on?
• 72 Watts "rated power" each (= max on high beam? so ≈half that for low beams?), Rstfa Led Headlight For Tesla Model Y/3 Headlamp 1514952-00-d 1514952 151495200d - Buy Model Y Headlight Performance Led Headlamp 12v Led Headlight For Tesla Model Y Customized,Model Y/3 Headlamp Express Delivery Headlamp,Oem Auto Parts For Model 3 Headlight Product on Alibaba.com

Even 2 x 72W x 10 hours is only 1440 Wh, which is < 2% of a 75 kWh battery pack. A full charge would last > 3 weeks.

Exiting the car with the headlights on manual gives a warning beep and a warning message. If they'll eventually time out, it takes longer than they were on for my neighbor's car before I noticed.

Interesting idea to measure the current. Replacing one requires a firmware reinstall (Tesla Model 3 (2020) DIY headlight replacement write-up), which means you'd have to figure out which leads have power.

 

[gsmith123]

leaving the lights on for an hour wastes enough energy to drive about 650 meters. Lol.

 

[MOE J]

I always switch them off when day driving. No reason they should be on full furring the day. Auto doesn’t always turn them off, especially on cloudy days.

 

[CyberGus]

I need a 8-hour Lightshow to entertain the parking lot while I'm at work, probably less power draw than Sentry Mode

 

[MOE J]

8 hour light show-what kind of light show lasts 8 hours. Aren’t they all pretty much the same: lights flash, trunk opens, music plays, Tesla projected on wall

 

[MLXXXp]

find out what connector is used to attach the headlight(s) to the associated wiring harness and build a short extension cable (male and female ends) and put an ammeter inline on one of the leads

Or, if you can isolate the wire supplying the power, use a clamp on DC current meter. Then, there's no need to insert a conventional ammeter inline.

clamp on dc current meter - Google Search

Actually, you could probably just clamp the meter around the positive wire from the low voltage battery and measure the difference between the lights on and off, provided that the base draw without the lights on wasn't too high. Inserting an ammeter inline with the positive battery wire, and using this technique, probably wouldn't be too difficult, either.

 

[RayK]

Or, if you can isolate the wire supplying the power, use a clamp on DC current meter. Then, there's no need to insert a conventional ammeter inline.

clamp on dc current meter - Google Search

Actually, you could probably just clamp the meter around the positive wire from the low voltage battery and measure the difference between the lights on and off, provided that the base draw without the lights on wasn't too high. Inserting an ammeter inline with the positive battery wire, and using this technique, probably wouldn't be too difficult, either.

While that clamp-on method can measure current, I believe it's best used on AC current measurements, rather than DC. In order to get the most accurate reading, at a reasonable cost, an inline ammeter is the best.

 

[terranx]

Dc clamp meters exist. They’re generally accurate

 

[MLXXXp]

I believe it's best used on AC current measurements, rather than DC. In order to get the most accurate reading, at a reasonable cost, an inline ammeter is the best.

Just how accurate does it need to be for this situation, where the goal is to get and idea of how fast the battery would be drained with the headlights on?

I have a UNI-T UT210E clamp style meter. This is a relatively inexpensive mid-quality brand. On the 20A and 100A DC ranges, the accuracy is ±(2% + 3 counts). For AC current, the accuracy is actually worse, at ±(2.5% + 8 counts) on the 20A range and ±(2.5% + 5 counts) on the 100A range.

https://meters.uni-trend.com/product/ut210-series/#Specifications

 

[RayK]

Just how accurate does it need to be for this situation, where the goal is to get and idea of how fast the battery would be drained with the headlights on?

I have a UNI-T UT210E clamp style meter. This is a relatively inexpensive mid-quality brand. On the 20A and 100A DC ranges, the accuracy is ±(2% + 3 counts). For AC current, the accuracy is actually worse, at ±(2.5% + 8 counts) on the 20A range and ±(2.5% + 5 counts) on the 100A range.

https://meters.uni-trend.com/product/ut210-series/#Specifications

Okay, I'll admit that DC current clamp-on meters exist and some are more accurate than my Craftsman True RMS Multimeter (81079); accuracy of +/-2.5% + 5 digits in the 4A and 20A ranges, but maybe not as accurate as my HP E2373A (+/-1.5% + 2 digits in 10A range).

However, I still like my inline adapter method...