Overnight Charge: Fast vs. Slow?

[BillRadio]

I decided to install a dedicated circuit to charge my M3 LR in the garage. I called 3 electricians to bid on installing a 14-50 socket. When the first electrician opened the breaker panel, pieces fell out and found it in bad shape. Now that I'm facing a whole new panel, the prospect of installing a Tesla wall charger, instead of a 14-50, seems like an insignificant part of the project. So now that I will be able to do a full 48 Amp. charge each night, I'm wondering when to charge. Our off-peak period starts at 8pm and at 48 Amp. with Scheduled Charging it would be fully charged shortly thereafter. So it may be wiser to use Departure charging instead and have the batteries warmed and ready for use in the morning. However, I work from home so departure time varies.

For those of you that have tried different methods, have you established a preference?
1) Schedule Charge it at the beginning of "Off Peak" so you're always ready to go?
2) Departure Charge so you're warmed and ready at, say, 9am?
3) Charge overnight slowly (less than 48 Amps), say over 8 hours, so that you're not drawing maximum power and the battery is "warm" through most of the morning?

 

[jjrandorin]

I dont use scheduled departure, I use scheduled charging, and have it set to 3am in the morning. The whole "warmed battery" thing only really matters if you are going on a trip and anticipate needing the additional range. For regular use, a warm cabin is super nice, but a warm battery is not necessary.

There is no benefit to "slow" charging less than 48amps, as far as battery life expectancy is concerned. All home charging (including 48amp) is slow charging, to the car.

The reason I dont use scheduled departure is, I am not a super fan of "things trying to figure out stuff for me" which is what that feature does. It also appears to be quirky as there are always posts from people who have issues with it starting, or not starting, or stopping, not filling to desired percentage, etc etc.

Contrast that with "Start charging at X time" which always works for me, and for me, that makes scheduled charging a slam dunk. I have it set to 3am in the morning because my car will always be full by 6am.

Since your departure time varies, I would just set it to start charging in the middle of the night sometime, and not worry too much about "warm battery" unless you anticipate needing a charge when you are on that days drive, away from home.

Its not like that energy to warm the battery is free, the reason people talk about it as far as trips is, if your battery is warm, the car will be able to accept a faster charge, and also wont use energy while on the road heating the battery, leading to more range on a road trip. For non road trip use, a warm battery doesnt matter, imo.

 

[dmurphy]

I dont use scheduled departure, I use scheduled charging, and have it set to 3am in the morning. The whole "warmed battery" thing only really matters if you are going on a trip and anticipate needing the additional range. For regular use, a warm cabin is super nice, but a warm battery is not necessary.

Boy, living in beautiful Southern California must be nice.

The value of that warm cabin on a cold day can’t be overstated. We’re in the middle of a cold snap here and it’s truly one of the mostest bestest features of the car.

For battery management, I agree - doesn’t make a hill of beans of difference whether you charge at 4.8 or 48 amps…. But it sure is nice to have the cabin warmed up as if I’m in my livingroom!

 

[jjrandorin]

Boy, living in beautiful Southern California must be nice.

The value of that warm cabin on a cold day can’t be overstated. We’re in the middle of a cold snap here and it’s truly one of the mostest bestest features of the car.

For battery management, I agree - doesn’t make a hill of beans of difference whether you charge at 4.8 or 48 amps…. But it sure is nice to have the cabin warmed up as if I’m in my livingroom!

Lol.. I pre heat my car out here during "winter" (or what passes for it anyway lol). I love having the car itself be at temp when I get into it. I park in my garage and it only takes about 5 minutes for my car to get to temp, so I start it about 5-10 minutes before I am ready to go.

Regarding your cold snap.... its going to be 76 degrees at my house today /e ducks

 

[BillRadio]

After researching this, including in the TMC forum, I find little difference in battery performance among different home charging rates or hours. These are the most important caveats:
1) Don't overuse Superchargers.
2) Level 1 (110V) charging is somewhat inefficient, but not harmful.
3) If there is an enemy of batteries, it is heat.

That tells me 24A to 48A charging rates are pretty equal in their battery effects.

Next, I will be looking at how charging affects the home electrical system. If I set my charge rate at 40A and I feel any heat in the breaker, wire or Wall Connector, I'll consider backing down the rate to 32A.

 

[Bouba]

I dont use scheduled departure, I use scheduled charging, and have it set to 3am in the morning. The whole "warmed battery" thing only really matters if you are going on a trip and anticipate needing the additional range. For regular use, a warm cabin is super nice, but a warm battery is not necessary.

There is no benefit to "slow" charging less than 48amps, as far as battery life expectancy is concerned. All home charging (including 48amp) is slow charging, to the car.

The reason I dont use scheduled departure is, I am not a super fan of "things trying to figure out stuff for me" which is what that feature does. It also appears to be quirky as there are always posts from people who have issues with it starting, or not starting, or stopping, not filling to desired percentage, etc etc.

Contrast that with "Start charging at X time" which always works for me, and for me, that makes scheduled charging a slam dunk. I have it set to 3am in the morning because my car will always be full by 6am.

Since your departure time varies, I would just set it to start charging in the middle of the night sometime, and not worry too much about "warm battery" unless you anticipate needing a charge when you are on that days drive, away from home.

Its not like that energy to warm the battery is free, the reason people talk about it as far as trips is, if your battery is warm, the car will be able to accept a faster charge, and also wont use energy while on the road heating the battery, leading to more range on a road trip. For non road trip use, a warm battery doesnt matter, imo.

Does warming your battery increase range when the ambient temperature is above 50F ?

 

[jjrandorin]

Does warming your battery increase range when the ambient temperature is above 50F ?

I have zero idea, because I never turn on my climate control to "warm the battery". I turn it on 5-10 minutes before I leave to warm the cabin. I do know that, even though ambient temp may be 50 degrees (as an example), its likely that it was colder than that overnight, so its entirely possible for the cars battery to be colder than ambient temps at the time.

 

[Bouba]

I have zero idea, because I never turn on my climate control to "warm the battery". I turn it on 5-10 minutes before I leave to warm the cabin. I do know that, even though ambient temp may be 50 degrees (as an example), its likely that it was colder than that overnight, so its entirely possible for the cars battery to be colder than ambient temps at the time.

I was also thinking that any surface would stay colder than air temp except when it gets really hot...but in normal winter temperatures (around and slightly above freezing) how much range does Tesla claim can be gained by pre heating before a long trip?

 

[Kimmi]

“If I set my charge rate at 40A and I feel any heat in the breaker, wire or Wall Connector, I'll consider backing down the rate to 32A.”

First thing I would do would be calling a electrician to check it out.