I Have Some N00B Battery Questions

[ghsnick!]

I took delivery of my SR+ last week and it’s an absolute blast!

I have some questions about the battery and best charging practices.

1) I charge it to 85% every night...I’ve read that between 80-90% are best. Correct me if I’m wrong.

2) When I first charged it to 85% the estimated mileage was 204 miles. 85% of 240 is 204...so the math was perfect. Over the last week the estimated range of 85% has decreased to 190 miles...why is this happening?

3) Should I charge it every night? It only gets to about 40-50% before I recharge it...not sure if I should let it get lower.

4) Should I leave it plugged in all night? Or unplug it once it gets to a full charge? I want to do what’s best for the battery, but I don’t want to waste power and have a higher electric bill.

5) I plug it in at 8pm and leave for work at 8am...I find it normally becomes fully charged around 11pm. Should I start the schedule charge at 3am so it fully becomes charged at 6am...so it’s sitting fully charged for less time?

Any advice/feedback would be appreciated

 

[duanra]

Apparently the best to a battery is to operate on a lower range eg between 60 and 75 % with once every 3 month a full charge to recalibrate the battery. Lots of litterature on internet with people far more educated than myself.
Also it is best to keep it plugged in. I recommand to read your owner manual...enjoy your new car !

PS: I am not saying that the 60-75 thing is practical but in theory i read that it is the best.

 

[TexasEV]

Any advice/feedback would be appreciated

My advice/feedback is you and all new owners who ask a version of these questions almost daily should RTFM. At least read the battery section. Then don’t think about the battery again and just enjoy your car.

 

[DavidElg]

I charge to 90% overnight, every night. Elon himself said this was fine/recommended. It's always best to keep the car plugged in when not in use. The car will only charge when needed. As I understand it, the car will adjust the range based upon recent driving conditions. I'm thinking that as a new owner you may be checking out how well it accelerates (don't blame you at all BTW) and the car is adjusting range accordingly.

 

[Krugerrand]

OP, read the manual. Believe what the manual says. Do what the manual says.

For quick reference: A happy Tesla is a plugged in Tesla. And yes, charging to 85% every night is good and fine. But do read the manual. It’ll answer your battery questions (and many others).

Welcome to the Tesla family! You now own one of the badasses best cars ever made, second to only another Tesla. Thanks for taking the step toward sustainable transport and saving future generations of hopefully less stupid humans.

 

[srs5694]

1) I charge it to 85% every night...I’ve read that between 80-90% are best. Correct me if I’m wrong.

That's the charge level that most people seem to be citing as optimal.

2) When I first charged it to 85% the estimated mileage was 204 miles. 85% of 240 is 204...so the math was perfect. Over the last week the estimated range of 85% has decreased to 190 miles...why is this happening?

With most EVs (including my current car, a Chevy Volt), the estimated range is adjusted based on your last trip (or last few trips), so if you push the car hard, a drop in the estimated range is understandable. That said, I'm still waiting on delivery of my Tesla, so I don't know from personal experience if Teslas work in the same way. If not, it could be you're seeing something else.

3) Should I charge it every night? It only gets to about 40-50% before I recharge it...not sure if I should let it get lower.

It's probably best to charge every night, at least normally. Every few months, a deeper discharge should help the BMS keep itself calibrated.

4) Should I leave it plugged in all night? Or unplug it once it gets to a full charge? I want to do what’s best for the battery, but I don’t want to waste power and have a higher electric bill.

One of the disadvantages of Teslas vs. other EVs is that Teslas have more "vampire drain" -- their batteries discharge even when the car is parked. This happens in part because of powering the Tesla's on-board computers, which like to wake up and send data back to Tesla on a regular basis, among other things. Sentry Mode greatly increases vampire drain, too, BTW. Teslas will also keep their batteries warmed or cooled for optimal performance, which contributes significantly to vampire drain, particularly in winter or in summer heat waves. Vampire drain happens whether or not the car is plugged in; but if it's plugged in, it can recharge the battery immediately once the battery drains by a small amount. This factor alone argues strongly for leaving the car plugged in. To be sure, vampire drain won't completely drain the battery in a day or two -- people leave their cars for a week or more and still have plenty of charge left. The drain will slightly reduce range, though, which might be a nuisance if you want to go on a road trip or something after leaving the car unplugged for a while.

5) I plug it in at 8pm and leave for work at 8am...I find it normally becomes fully charged around 11pm. Should I start the schedule charge at 3am so it fully becomes charged at 6am...so it’s sitting fully charged for less time?

Some utilities charge different rates depending on the time of day. With them, charging only during the off-peak times will save money. IIRC, there's a way to tell the Tesla about this so it will charge at the optimum time. (I didn't pay too much attention to this since my utility offers only flat-rate plans; and I can do the same thing via my network-enabled EVSE, which I originally bought for my Volt.) I've also seen claims that keeping a battery fully charged for extended periods can result in more rapid degradation, which argues for timing it to finish charging just before you want to drive. If you're only charging to 80-90%, though, this may not be much of a factor.

 

[ewoodrick]

Apparently the best to a battery is to operate on a lower range eg between 60 and 75 % with once every 3 month a full charge to recalibrate the battery. Lots of litterature on internet with people far more educated than myself.
Also it is best to keep it plugged in. I recommand to read your owner manual...enjoy your new car !

PS: I am not saying that the 60-75 thing is practical but in theory i read that it is the best.

I don't think that I've ever heard those numbers. Generally charge 80-90 and comments from Elon indicate that 90% may be a better number.

 

[srs5694]

Apparently the best to a battery is to operate on a lower range eg between 60 and 75 % with once every 3 month a full charge to recalibrate the battery. Lots of litterature on internet with people far more educated than myself.

Although this might be a theoretical optimum for lithium ion batteries, it appears that it'll confuse the Tesla's BMC to no end, which will cause problems. Kim on the LikeTesla YourTube channel was using a lower-than-80% charging regimen and ran into this problem:

 

[ewoodrick]

I took delivery of my SR+ last week and it’s an absolute blast!

I have some questions about the battery and best charging practices.

1) I charge it to 85% every night...I’ve read that between 80-90% are best. Correct me if I’m wrong.

2) When I first charged it to 85% the estimated mileage was 204 miles. 85% of 240 is 204...so the math was perfect. Over the last week the estimated range of 85% has decreased to 190 miles...why is this happening?

3) Should I charge it every night? It only gets to about 40-50% before I recharge it...not sure if I should let it get lower.

4) Should I leave it plugged in all night? Or unplug it once it gets to a full charge? I want to do what’s best for the battery, but I don’t want to waste power and have a higher electric bill.

5) I plug it in at 8pm and leave for work at 8am...I find it normally becomes fully charged around 11pm. Should I start the schedule charge at 3am so it fully becomes charged at 6am...so it’s sitting fully charged for less time?

Any advice/feedback would be appreciated

Welcome to the club!

Don't put so much worry into the battery numbers, there's a lot of factors that impact it. You may want to overnight charge to 100% to let the batteries balance and reset numbers. I only recommend to do this every few months. For me, it is done as I take a long trip every few months, so I don't really worry about it.

3-4) You will get all sorts of responses on this one. Indeed the manual indicates that a happy car is a plugged in car, but I recommend taking that with a grain of salt. I plug in every few days, mainly because I only put 20 or so miles on the car each day.
But for those who follow the manual, I sometimes think that they really want to pull a generator so that it can stay plugged in even while they are driving. I am quite sure that Tesla did not suggest plugging it in ALL of the time. They are probably taking into consideration people working during the day and only plugging in for charging at night.

Do what's convenient for YOU. If you are driving a lot every day, then I wouldn't feel bad skipping some nights. If you put on 50+ miles per day, then you probably would want to charge each evening.

But MOST IMPORTANTLY, Tesla designed the battery so that you really don't have to worry about it, so don't.

The only real rules are, don't continuously charge to 100%, you will get a notification. Don't take it to 0%

 

[TexasEV]

As I understand it, the car will adjust the range based upon recent driving conditions.

Then you don’t understand what rated range is. The battery meter displays rated range, meaning the EPA rated range. Period. Full stop. It has nothing to do with your recent driving. You’re thinking of the trip meter which bases projected range on your past 5, 15, of 30 miles of driving.

 

[duanra]

Here is the ref.

 

[duanra]

Also..
Jeff Dahn's recommendation on long term battery preservation

 

[tga]

Back in 2014, Elon was asked 90->40 or 80->30 when daily commute uses 50% of the battery). He said 80->30: Elon Musk on Twitter

Most important thing you can do to maximize battery life is keep it in the 20% to 90% state of charge range as much as possible. That doesn't mean don't charge to 100% before a trip and run it down to 10% on arrival, just time the charge to finish right before you leave, and plug in and charge to at least 20% ASAP after you get there.

If you want to be really obsessive, plan your charging and usage to keep the SOC averaged at 50%. Or don't obsess over it; it likely won't make much difference.

Most of my driving is long road trips, with little day-to-day mileage (<15 miles). I tend to charge to 70% in the summer, and 80 or 90% (depending on my mood) in the winter (less degradation in the cold). I often charge to 100% right before a road trip. After 72k, I've lost < 4% range (256 at 100% vs 265 new).

Key takeaway - Don't worry about it.

 

[JayNJ]

I charge to 90% overnight, every night. Elon himself said this was fine/recommended. It's always best to keep the car plugged in when not in use. The car will only charge when needed. As I understand it, the car will adjust the range based upon recent driving conditions. I'm thinking that as a new owner you may be checking out how well it accelerates (don't blame you at all BTW) and the car is adjusting range accordingly.

No the car will not adjust its range based on past driving behavior. It is purely a function of how full the battery is and assuming 240Wh/mi. When you navigate, the percent remaining at destination is based on actual driving behavior during that route.

 

[BestHand]

One thing more: schedule the charge closer to your morning drive, that way your battery will be a bit warmer, it helps for winter driving. Also, if you want a bit savings, use NEMA 14-50 240V 32A instead of 120V outlet. It is not just faster, but more effective also.

 

[ghsnick!]

Thanks for all the tips! I appreciate everyone’s awesome input.