Is the car keeping my garage warm?

[jcanoe]

I don't believe that the Tesla Model Y battery management system (BMS) performs much battery warming when charging or preconditioning, certainly not as much battery warming as in earlier releases of the Tesla software. If the battery is at 4C (39F) or colder the battery will be warmed. Once the battery temperature is 10C (50F) or warmer then battery warming stops as further warming is not needed for Level 1/2 charging.

Last winter (temperature was at or below 4C (39F), while charging Level 2 (30A), after 90 minutes of charging the Tesla Model Y would initiate battery warming as soon I I activated preconditioning via the Tesla app preparing to drive. 90 minutes charging time was not sufficient to warm the battery to 20C (68F) which seems to be the BMS preferred battery operating temperature for best battery performance while driving. Preconditioning with battery warming continued for ~15 minutes.

Battery warming for Supercharging is handled differently as the optimal temperature for Supercharging is (~46C) 115F. The Tesla Model Y may perform some battery warming while Supercharging if this will improve the overall speed and efficiency of the Supercharger charging session.

 

[Vinnigan]

Okay, so I unplugged the car overnight last night since there was a thunderstorm rolling through.

There was no difference in the int/ext temps in the morning. Turn out, it's just what my garage is.

Sorry for a dumb thread, folks!

 

[dakhlkt22]

Save yourself some grief and put a thermometer in your garage and test it with and without the car in the garage.

My garage thermometer is connected to my security system so I see the temperatures whenever I look at the security system.

 

[rotarypower101]

The older design that used a 12V lead-acid battery could go ~24 hours before needing to be charged from the high voltage battery. The new low voltage lithium battery module has much less capacity than the lead-acid 12V so unless Tesla reduced the power usage in Sleep mode the low voltage lithium battery module would require charging multiple times over 24 hours. This could account for some of the increased power usage Tesla Model Y owners are observing while their Tesla vehicle is parked. The Tesla Model Y (other models too) must wake up from sleep mode, enter Standby mode so that the DC-to-DC converter can charge the low voltage lithium battery module, for perhaps 1 hour, multiple times per day. If the low voltage battery requires charging from the high voltage battery/DC-to-DC converter 4 times over 24 hours, each charging session lasting 1 hour, the estimated consumption would be ~1kWh every 24 hours just to top up the low voltage lithium battery. (All numbers are estimates.)

This seems like a very reasonable observation and conclusion, possible anyone has tested this, even if estimating from empirical data?

Is it possible the newer low amperage LV system (separate from other associated benefits) is actually less efficient for long periods of inactivity, like camping away from the grid, or away on trips?

 

[Z_Lynx]

"The older design that used a 12V lead-acid battery could go ~24 hours before needing to be charged from the high voltage battery. "

My 2020 MY appears to charge the low voltage battery for perhaps 10 minutes of most hours. I can hear the contactors engage and disengage and have observed the 12 volt battery voltage increase when engaged and slowly drop when disengaged.

At least one member had a monitoring system that generated graphs of these fluctuations.

 

[jcanoe]

I have not observed that happening in my 2020 LRMY with the lead-acid 12V battery. I receive notification on my phone every time the low voltage system is energized via Amazon Echo Auto. Echo Auto is plugged in to the 12V accessory outlet, sends the notification "Ready to Drive" when powered on. If the contactors engage then I would hear it as my Model Y is inside my garage, next to my kitchen. The contactors make a loud thunk sound when engaging.

 

[zoomer0056]

have observed the 12 volt battery voltage increase when engaged and slowly drop when disengaged.

How was this observation made?

 

[Z_Lynx]

I hooked up a connector to the battery (old batteryminder connector) whose other end rests near the wipers, from which I can remove the connector cap and read the voltage without opening the frunk. So nothing I do has any significant affect on the voltage I read with my Fluke knockoff.

The reading above was in between charge cycles, when it rises to 14+volts.

The contactors engaging and disengaging are pretty noticeable.

 

[jcanoe]

Charging the 12V battery 1X per hour (for 10 minutes) seems excessive. Perhaps the 12V battery is failing, no longer holds a charge.

 

[Z_Lynx]

It has done this for over a year (first noticed last year when I was working on my carport). Turned off Tezlab to make sure it was not being awoken. Explored Virginia Mileage Choice metrics. I think of this behavior as operating like a trickle charger to keep it topped up.

Example of a Tesla owner using a data logger for the 12V battery:

12v battery is now charging 24 hours / day

Ah, found the post: https://teslamotorsclub.com/tmc/posts/5387679/ Now, doesn't this mean that on pre-2015 contactors stay closed and 12V battery is charged with the "regular" DCDC? On post-2015 contactors are open and MCU is powered from the standby DCDC.. Anyway, I'll measure how my 12V...

teslamotorsclub.com

I'll look into the possibility it is charging even more frequently. All voltage checks indicate a "healthy" battery.

 

[jcanoe]

If the Tesla Model Y is in Standby mode, as when Sentry mode is active, then I could understand the 12V battery being topped up every hour (for 10 minutes) as the DC-to-DC Converter is already powered on. If the Tesla Model Y is in Sleep mode, then powering up the low voltage system actuating the high voltage contactors, powering the DC-to-DC Converter would use a lot of power (this would be like constantly opening the Tesla phone app and waking up the Tesla vehicle.)

The original 12V flooded lead-acid battery is rated 45Ah (I believe this is a deep cycle battery, designed specifically for use in Tesla 3, Y vehicles.)

Assuming 25W power consumption (when in Sleep mode), that is ~12.6V X ~2 amps.

2Ah X 12 hours = 24Ah. Assuming a deep cycle 12V lead acid battery can be discharged 50% without being damaged the 12V would need to be charged ~2X per 24 hours, not 24X per 24 hours.

 

[Z_Lynx]

This happens at home, sentry off, everything that could cause battery drain off. It sometimes skips an hour but mostly once an hour for perhaps 10 minutes last year when I started exploring this and manually logging the behavior. Last year, I could set a clock by how regularly it turned on.

If you have a good book (or a project to work on) and want to be in your garage for an afternoon, note the contactor times (on and off). It annoyed me greatly when I realized how often this was happening but it seems to be the norm.

 

[Chookman]

It's just not necessary to keep the car plugged in. One benefit, pointed out by @father_of_6 , would bf using house current for batteru conditioning instead of the battery. But I believe thats only if there is a departure scheduled.

Everybody knows charging to 100% and letting to car sit is bad for the battery.

May I ask if the last statement, "Everybody knows charging to 100% and letting to car sit is bad for the battery.", it's referring to lithium ion or lithium phosphate batteries?
My M3 is 14 months old and over the last 3 months,it seems to be indicating a drop of 1% per month as seen via the battery range/percentage indicator on the touchscreen and app.
I have been trying to charge only from solar or my Powerwall2 but that means sometimes I don't reach a full charge on every charging session. Could that be the reason?
Thanks
Chris

 

[Chookman]

May I ask if the last statement, "Everybody knows charging to 100% and letting to car sit is bad for the battery.", it's referring to lithium ion or lithium phosphate batteries?
My M3 is 14 months old and over the last 3 months,it seems to be indicating a drop of 1% per month as seen via the battery range/percentage indicator on the touchscreen and app.
I have been trying to charge only from solar or my Powerwall2 but that means sometimes I don't reach a full charge on every charging session. Could that be the reason?
Thanks
Chris

My apologies, in my post I referred to losing 1 % per month, which is incorrect. I meant to say, 1km per month as indicated...
Chookman

 

[zoomer0056]

May I ask if the last statement, "Everybody knows charging to 100% and letting to car sit is bad for the battery.", it's referring to lithium ion or lithium phosphate batteries?
My M3 is 14 months old and over the last 3 months,it seems to be indicating a drop of 1% per month as seen via the battery range/percentage indicator on the touchscreen and app.
I have been trying to charge only from solar or my Powerwall2 but that means sometimes I don't reach a full charge on every charging session. Could that be the reason?
Thanks
Chris

I only know half of everything and I usually talk about the half I don't know. @AAKEE knows a LOT more. Search for his posts and you'll learn a lot.

 

[Chookman]

I only know half of everything and I usually talk about the half I don't know. @AAKEE knows a LOT more. Search for his posts and you'll learn a lot.

Many thanks zoomer0056. I also seem to be piecing things together as there are a number of variants with the constant evolution of technology combined with an ever growing knowledge base from the growing owner base. The main thing is that we are all rowing in the same direction.

 

[tgrobbo]

May I ask if the last statement, "Everybody knows charging to 100% and letting to car sit is bad for the battery.", it's referring to lithium ion or lithium phosphate batteries?

My M3 is 14 months old and over the last 3 months,it seems to be indicating a drop of 1% per month as seen via the battery range/percentage indicator on the touchscreen and app.
I have been trying to charge only from solar or my Powerwall2 but that means sometimes I don't reach a full charge on every charging session.

May I ask if the last statement, "Everybody knows charging to 100% and letting to car sit is bad for the battery.", it's referring to lithium ion or lithium phosphate batteries?
My M3 is 14 months old and over the last 3 months,it seems to be indicating a drop of 1% per month as seen via the battery range/percentage indicator on the touchscreen and app.
I have been trying to charge only from solar or my Powerwall2 but that means sometimes I don't reach a full charge on every charging session. Could that be the reason?
Thanks
Chris

A km a month is ok. I think the average is 4% loss over 24 months, (and by ‘average’ I mean virtually every two year old LFP car on the planet) so, as long as it slows down slightly over the next 10 months, you’re somewhat on track. It will bounce around a lot, especially with charging from different %. Do you try to charge it up to 100% every day? I wouldn’t do that if I didn’t have to. Once a week is fine. (Pretty sure once a month is actually fine too)

 

[tgrobbo]

Okay, so I unplugged the car overnight last night since there was a thunderstorm rolling through.

There was no difference in the int/ext temps in the morning. Turn out, it's just what my garage is.

Sorry for a dumb thread, folks!

Well no it’s not a dumb thread, it’s the one I found most interesting out of all the new posts tonight. I note your car was still in the garage when it was unplugged - this only proves the car generates the same heat whether plugged in or not plugged in. A true test would be the garage temp with no car in it…. ;-)

 

[Chookman]

May I ask if the last statement, "Everybody knows charging to 100% and letting to car sit is bad for the battery.", it's referring to lithium ion or lithium phosphate batteries?


A km a month is ok. I think the average is 4% loss over 24 months, (and by ‘average’ I mean virtually every two year old LFP car on the planet) so, as long as it slows down slightly over the next 10 months, you’re somewhat on track. It will bounce around a lot, especially with charging from different %. Do you try to charge it up to 100% every day? I wouldn’t do that if I didn’t have to. Once a week is fine. (Pretty sure once a month is actually fine too)

Since I bought it 14 months ago I've been charging at 10amps at home mostly and mostly daily topping up 6Kw (10%) which is my daily drive. For this I have (in the brighter half of the year) drained my Powerwall2 of excess power, which then charges the next day. In a couple of days in having 32 amp circuit installed so I can charge up to 40Kw over night on the AGL EV Night Saver plan. I will track the 100%/ km rate over the coming months and see if fewer charges but charging more Kw makes a difference.
I'll post some updates for those interested.

 

[drtimhill]

It's my learned understanding that the chemical composition is most at the equilibrium state at 50% SoC, and the charging/discharging of a li-ion battery is basically a chemical reaction that occurs across the cathode and anode via the electrolyte layer. This means that the closer to the equilibrium point, the less violent the the chemical reactions, and the less stressed the batteries are.

Well strictly the battery is in "equilibrium" when it is not charging or discharging .. since at these times there are no reactions occurring within the battery (ok, a few leakage ones but that is always the case for everything). As others have noted the best strategy for battery health is complex and there is no one size fits all, even with the same battery chemistry (since ambient temps, driving style and environment all factor in). Pretty much the only thing everyone can agree on is avoiding the extremes (though some chemistries are fine with 100%).