Vampire drain a considerable cost on the long run

[scaesare]

Anybody here owns a Roadster? My company does and it has Open Vehicles Monitoring System, OVMS in it.

I can see were it is, control the charge, etc and it uses almost nothing. The Roadster has almost no vampire drain.

I don't see a reason why Model S should. Staying connected and sending some bytes to a app doesn't use 2,5kWh a day.

A iPhone could do the same inside Model S and only use 30Wh/day.

No, something inside Model S is not very efficient.

What's interesting, is the Tegra 3 in the center console unit was designed with a special low-power core designed just to handle background tasks that would seem ideally suited for what the car needs while asleep:

Tegra 3 5th Core

I wonder if it's some other subsystem that's responsible for the signficant power usage...

 

[wk057]

Ah, that probably explains how you are only seeing ~1KWh/day vampire loss.

I find "always connected" makes a significant difference in the responsiveness of the mobile apps.

I'm actually seeing substantially less than 1kWh per day I think less than half of that when I'm actually away (no key fobs nearby, no checking mobile app, no one touching the car).

I definitely don't think eliminating the extra 20-40 seconds it takes to connect with the mobile app justifies the additional power usage 24/7. Mine usually connects in 20 seconds or less. I open the app, car wakes up and connects to the house's WiFi, then to Tesla's VPN, and it's ready to go in no time. If it jumped to > 1kWh/day just to keep a data connection... that's hundreds of kWh per year just to make the mobile app faster. Not worth it, IMO.

 

[AmpedRealtor]

I'd be happy with one order of magnitude less, which is still worse than other connected EV's which also protect their packs, and have telematics.

To be fair, the Leaf does nothing to protect its battery pack.

 

[Cottonwood]

To be fair, the Leaf does nothing to protect its battery pack.

On the other hand, nothing in the Tesla battery is changing very fast when the car is off and not charging. The battery is a large thermal mass that changes temperature slowly and the battery self-discharge is tiny over the scale of hours. This means that monitoring checks only have to happen a few times an hour. The Cellular modem is already a phone design that is optimized for very low power.

Doing low power monitoring and control equipment is not rocket science. It just takes a little care and thoughtful design.

 

[Ingineer]

To be fair, the Leaf does nothing to protect its battery pack.

It doesn't heat or cool it, but the BMS and cell balancing system is still there. Other cars that do have active thermal, such as the Volt, don't suffer the overhead. I'm only trying to show it's simply poor execution on Tesla's part. That many watts in standby is crazy-excessive.

 

[PoweredByRain]

It doesn't heat or cool it, but the BMS and cell balancing system is still there. Other cars that do have active thermal, such as the Volt, don't suffer the overhead. I'm only trying to show it's simply poor execution on Tesla's part. That many watts in standby is crazy-excessive.

I'm with Ingineer on this one. I had a LEAF, and it simply did not have this problem. I left it at the airport once for weeks and came back with almost no change in state of charge. The high standby load in the Model S is a definite bug, not a feature. It consumes at least two orders of magnitude more than it should. I really hope they fix it. (In future cars - given the design I don't think it can be made better for existing cars.)

 

[apacheguy]

What's interesting, is the Tegra 3 in the center console unit was designed with a special low-power core designed just to handle background tasks that would seem ideally suited for what the car needs while asleep:

Tegra 3 5th Core

I wonder if it's some other subsystem that's responsible for the signficant power usage...

What about the BMS boards? @wk057 - aren't there something like 16 of them, one for each module? That may be explaining some of the ancillary draw - they are wired off the 12 V system.

 

[wk057]

What about the BMS boards? @wk057 - aren't there something like 16 of them, one for each module? That may be explaining some of the ancillary draw - they are wired off the 12 V system.

The 16 BMBs are isolated and draw directly from their respective modules on the microamp level while idle. They basically use nothing.

The main BMS is powered by the 12V system, though, but I think it's power use would also be pretty negligible.

 

[apacheguy]

I don't see why the center screen display alone would account for the vampires. In my mind the idle power requirement with the display off should be the equivalent of an ipad in sleep mode. I do, however, know that there are several modules connected to it which collective comprise the MCU and I suspect these might be the main culprits.

 

[wycolo]

> The Roadster has almost no vampire drain. [widodh]

Yet if a pedestrian squeezes the door switch on a locked Roadster, the car rambunctiously fires up a fan etc for a short while. Like a race horse champing at the bit.
--

 

[kirkbauer]

Wow, I pay just $0.012 per kWh when charging at night... didn't realize electricity was so expensive in other areas.

 

[Panu]

I definitely don't think eliminating the extra 20-40 seconds it takes to connect with the mobile app justifies the additional power usage 24/7. Mine usually connects in 20 seconds or less. I open the app, car wakes up and connects to the house's WiFi, then to Tesla's VPN, and it's ready to go in no time. If it jumped to > 1kWh/day just to keep a data connection... that's hundreds of kWh per year just to make the mobile app faster. Not worth it, IMO.

In my short tests vampire drain has been 3 times higher when always connected is enabled. But when I disable it I can connect with mobile app only when the car is charging. I asked support and they adviced me to keep always connected ON.

Is everybody able to wake up the car when "always connected" is OFF? I've sometimes tried for about 15 minutes with no luck.

 

[apacheguy]

@Panu - Yep, my car wakes in under 1 minute through the mobile app.

 

[AmpedRealtor]

Is everybody able to wake up the car when "always connected" is OFF? I've sometimes tried for about 15 minutes with no luck.

Yes, but sometimes it takes a couple of minutes. My "always connected" is OFF and I lose about 2-3 miles per day depending.

 

[Ingineer]

Wow, I pay just $0.012 per kWh when charging at night... didn't realize electricity was so expensive in other areas.

Wow! About a penny a kWh?!? That's crazy! (Insane... LUDICROUS! =)

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I don't see why the center screen display alone would account for the vampires. In my mind the idle power requirement with the display off should be the equivalent of an ipad in sleep mode. I do, however, know that there are several modules connected to it which collective comprise the MCU and I suspect these might be the main culprits.

It definitely SHOULD be milliwatts instead of watts, but it isn't. They clearly architected the system to be efficient, but it appears the software just isn't using the hardware capabilities. The only other module the MUST be on is the body ECU. It's definitely an automotive-class device, with a CAN interface and it's idle power should be negligible when asleep. It supports hardware interrupts for the input system, so for instance when it receives a fob transmission or someone touches a door handle, it can wakeup and take action.