SDC vs SCC. Check My Reasoning

[PianoAl]

I use Scheduled Departure Charging (SDC) instead of Scheduled Charging (SC). It's a little more likely to result in the car charging before the start of the off-peak period, but with SDC, the battery spends somewhat less time at higher SOCs.

I realize that the difference is slight, and that it may not make any significant difference in battery longevity. However, I figure, why not optimize things?

Here's an example to illustrate my thinking:

Imagine that you do your driving during the hours between 9 AM and 6 PM, and that it takes three hours of charging to replenish the battery. Let's say your off-peak time starts at midnight. Here's a simplification:

With SC, your battery sits at the lowest charge level for six hours every day (6 PM to midnight).
With SDC, your battery sits at the lowest charge level for twelve hours every day (6 PM to 6 AM).

With SC, your battery sits at the highest charge level for six hours every day (3 AM to 9 AM).
With SDC, your battery sits at the highest charge level for zero hours every day (momentarily at 9 AM).

Do you think it's worth using the slightly more complicated SDC?

 

[ewoodrick]

Scheduled Departure Charging is design for colder climates and is intended to get the battery warmed up before leaving in the morning.
Scheduled Charging is design for Time of Use billing from the utilities.

One isn't more complicated than the other, they have different purposes.

Battery longevity isn't a big issue, but may be impacted by max state of charge.

My recommendation don't use any scheduling if you are not on a ToU rate or in a cold region.

You are creating much ado about nothing.

 

[davewill]

It's a question of value, not of logic. Do you value having the car finish charging close to time of departure more than making sure you optimize charging during off-peak? My feeling is that it's unlikely to make a significant difference in 95+% of cases.

I use SDC because I wanted to try it and it works. I don't believe it creates any real benefit in the mild weather we enjoy here. My overnight charge rarely exceeds three hours so I don't end up charging outside of off-peak. The once or twice a year where that might happen is going to cost me less than a dollar, even here with some of the highest rates in the country. Not worth worrying about.

 

[jjrandorin]

I use Scheduled Departure Charging (SDC) instead of Scheduled Charging (SC). It's a little more likely to result in the car charging before the start of the off-peak period, but with SDC, the battery spends somewhat less time at higher SOCs.

I realize that the difference is slight, and that it may not make any significant difference in battery longevity. However, I figure, why not optimize things?

Here's an example to illustrate my thinking:

Imagine that you do your driving during the hours between 9 AM and 6 PM, and that it takes three hours of charging to replenish the battery. Let's say your off-peak time starts at midnight. Here's a simplification:

With SC, your battery sits at the lowest charge level for six hours every day (6 PM to midnight).
With SDC, your battery sits at the lowest charge level for twelve hours every day (6 PM to 6 AM).

With SC, your battery sits at the highest charge level for six hours every day (3 AM to 9 AM).
With SDC, your battery sits at the highest charge level for zero hours every day (momentarily at 9 AM).

Do you think it's worth using the slightly more complicated SDC?

I dont understand this line of reasoning at all, because you can set scheduled charging to start at any time you want. In your scheduled departure example, you seem to have scheduled departure for 9am every morning. You also stated that it takes 3 hours to charge, in the example.

You could simply set scheduled charging to 6am, if this was something you wanted to do (and you dont care about charging between midnight and 6am for time of use rates).

Since I am not currently under a time of use rate, I set my scheduled charging time at 6am for my car, and 4am for my wifes car. There isnt any situation where scheduled departure automatically results in a lot more, or a lot less time spent at a particular level of charge, if departure time is known.

 

[yesimon]

If you are minmaxing, then yes scheduled departure is superior.

The primary reason is either explicit preconditioning of the battery or implicit warming of the battery (from charging). Driving off with a warmed up battery will have lower internal resistance and higher regen capability both of which will improve energy efficiency. Meanwhile resting longer at a lower average SOC is a very minor marginal benefit in terms of calendar aging but still counts for something.

 

[PianoAl]

I don't understand this line of reasoning at all, because you can set scheduled charging to start at any time you want.

Quite right. And in the simplified hypothetical I gave the change you suggested would solve the issue and made SC a good option. I didn't think of that.

In my situation, however, the amount of charging needed varies widely, from zero to seven hours, so if I wanted to use SC, I'd set the start time to midnight (I can charge 8% per hour). I could change it based on how much I'd driven, but I'm too lazy for that, and if I forgot, the car might not be ready.

 

[jjrandorin]

Quite right. And in the simplified hypothetical I gave the change you suggested would solve the issue and made SC a good option. I didn't think of that.

In my situation, however, the amount of charging needed varies widely, from zero to seven hours, so if I wanted to use SC, I'd set the start time to midnight (I can charge 8% per hour). I could change it based on how much I'd driven, but I'm too lazy for that, and if I forgot, the car might not be ready.

I think your use case makes scheduled departure a better fit for you. I just dont like it myself because it seems to be flaky (or, said another way, I have never had an issue with scheduled charging, over the 5 years I have had my model 3).