To always charge or not?

[SSedan]

On the refresh models the 12volt can be charged from wall current. HVAC on all can run from wall power. By keeping it plugged in you reduce the small incremental discharge cycling.

I think this is why I believe Tesla says to keep it plugged in.

If the car unplugged losses 2% a day to cabin overheat and other non-driving energy use at the end of the year that is 730% 7 extra full discharge cycles, ignoring the shallow vs deep discharge elements of the discussion. Keeping it plugged in overnight can halve that. In real life with normal cabin over temp and preheating seasonally I believe keeping it plugged in saves many more discharge cycles than I suggested above.

Think of it like keeping your tire pressure right, 5 pounds low won't destroy the tire today, but long term it will wear out faster. Not exactly the same but with the battery more cycling will wear it out sooner, won't hurt for today, but there is a small shortening of life.

 

[obie_fl]

I've never fully figured out the charging routine on the refresh models. I do know my HV battery pack only re-charges when it drops by 3%. I've often charged to 80% and if I don't drive it soon enough it will often be between 77% - 79% when I leave. Are you saying the 12V is always trickled and the HVAC is actually on shore power when plugged in?

 

[jerry33]

When I first got the S85, I charged to 80% daily. However, the displayed range went down. I then charged to 90% daily, and it went back up. (in both cases there was the odd 100% charge and set the charge to end about the time I start driving). Now at 117K miles and 5 2/3 years, the displayed degradation is just under 4% (varies somewhat with temperature). So I see no reason to not charge every day to 90% (the maximum daily setting). A plugged in Tesla is a happy Tesla.

 

[SSedan]

I've never fully figured out the charging routine on the refresh models. I do know my HV battery pack only re-charges when it drops by 3%. I've often charged to 80% and if I don't drive it soon enough it will often be between 77% - 79% when I leave. Are you saying the 12V is always trickled and the HVAC is actually on shore power when plugged in?

Not always on trickle but I believe it does recharge off shore power. I have a 2014 so I have not observed this myself just seen it posted here.
The HVAC definetly runs on shore power, you can see it if you have the charging screen up and go to get something out of the car. It will wake up and you can see a few amps being pulled.

I have mine set to mileage and yeah it is always a few miles down from 80% when I get in if it had been anything more than a few minutes since finish. I think some of it might just be system cooling when done charging I can see the chargers needing this. Temperatures affect battery output as well so the pack cooling to ambient might be a factor.

 

[bob_p]

Incorrect. But thanks for playing.

Whether plugged in using an HPWC, 14-50, or UMC (to 110, 30A or 50A), the vehicle will lose some charge and periodically restart charging to bring the battery pack back up to the desired charging level. Evidently Tesla decided this is better for the battery packs, than to constantly keep charging and maintaining a specific charge level constantly.

Even with the smaller amount of power from a 110 outlet, it should still be enough to slowly charge the car - and when it hits the desired charging level, maintain that level (with the periodic drops in charge, as the software allows the battery to discharge a small amount, and then resume charging to replenish that).

In most cases, a 110 outlet won't charge quickly enough (2-3 miles of range per hour) to do much good. But, if you are going to park the car long-term, it's enough power to keep the battery close to the desired charging level and not have much impact from vampire drain.

 

[TexasEV]

Whether plugged in using an HPWC, 14-50, or UMC (to 110, 30A or 50A), the vehicle will lose some charge and periodically restart charging to bring the battery pack back up to the desired charging level. Evidently Tesla decided this is better for the battery packs, than to constantly keep charging and maintaining a specific charge level constantly.

Even with the smaller amount of power from a 110 outlet, it should still be enough to slowly charge the car - and when it hits the desired charging level, maintain that level (with the periodic drops in charge, as the software allows the battery to discharge a small amount, and then resume charging to replenish that).

In most cases, a 110 outlet won't charge quickly enough (2-3 miles of range per hour) to do much good. But, if you are going to park the car long-term, it's enough power to keep the battery close to the desired charging level and not have much impact from vampire drain.

Thank you for clarifying that for the folks at home. It’s a better explanation than saying you avoid losing any charge when you’re plugged in to 120V.

 

[tga]

In most cases, a 110 outlet won't charge quickly enough (2-3 miles of range per hour) to do much good. But, if you are going to park the car long-term, it's enough power to keep the battery close to the desired charging level and not have much impact from vampire drain.

Unless it's cold enough to activate the 6kW battery heater. Then you're screwed.

I've never fully figured out the charging routine on the refresh models. I do know my HV battery pack only re-charges when it drops by 3%. I've often charged to 80% and if I don't drive it soon enough it will often be between 77% - 79% when I leave. Are you saying the 12V is always trickled and the HVAC is actually on shore power when plugged in?

My pre-refresh 2014 does the same thing. Vampire loads slowly drain the battery until it's 3% below the setpoint, then it kicks in and charges to the setpoint. If it stays plugged in, it'll bounce between (setpoint-3%) and setpoint indefinitely.

 

[SSedan]

I can see how my post could lead someone to think a wall connection eliminates vampire load, I did not mean to imply that, but it definitely can reduce vampire losses particularly if large draws happen like cabin heating or cooling and battery heating.
For those of us who live in cold climates the warming the battery from shore power can make a BIG big difference. Think it was 28f when I got up this morning and come winter and average one means -15f some mornings and I have seen -25f. If the battery has to warm from battery power when you start driving, you have severely reduced power, no regen and HUGE energy use while it warms up

 

[Candleflame]

Not sure about it being cold but if its warmish a Model 3 can probably easily last 12-18 months if charged to 90%.

As for being plugged in. A plugged in Tesla can only run the AC charger, HVAC or Aircon and maybe the battery heater from the charger directly. Everything else has to come from the 12v battery which can only be topped off from the high voltage battery. So even when plugged in it will cycle through the battery but the long term damage will be minimal due to relatively small cycles of 1-2%.