For a variety of boring reasons, I probably can’t easily put a charger on my home. Or at best I can get a nema 14-50 and would need an extension cord which I know is a no-no. I do however have a free volta charger 2 blocks from my house. I drive about 5 - 7 miles a day on average - thus, it’s concievable that a full charge once a month is sufficient for me. That got me thinking, once every few weeks top off at Volta, occasional trickle charge here and there and I may not even need the home charger. But then that got me wondering - how well does the battery hold charge when idle? Am I going to lose 25% a week no matter what?
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Battery draw when idle?
- Thread starter M3PKid
- Start date
on average I believe Tesla says 1% per day on average, if you only drive 5 to 7 miles a day a regular outlet would suffice easily
Nothing wrong with a extension cord as long as it’s a large enough gauge of wire, in your case if you had a 14-50 and an extension cord just turn the charge amperage down in the car to say 20 amps or so.
Nothing wrong with a extension cord as long as it’s a large enough gauge of wire, in your case if you had a 14-50 and an extension cord just turn the charge amperage down in the car to say 20 amps or so.
No, its not conceivable that a full charge once a month will be sufficient for anyone with one of these cars.
If you drive 7 miles a day that will likely be 15 or even 20 "miles" lost off the cars range meter every day, not counting any battery drain while parked. Lets examine exactly how often you will have to re charge (it absolutely, positively 100000% is not "once a month".
I have posted this more than a few times, but this is, in my opinion, the single biggest mistake prospective tesla owners make (" oh, I dont have home charging, but I only drive X miles a day, and the battery is Y big, so I will be able to charge only once every 2-3 weeks and have plenty left over").
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A US model 3 (which used to be called Model 3 SR) has a EPA range of 267 miles when brand new. "EPA" range is important because you wont ever achieve that, but thats what we have to start with for looking at how much you might "actually" need to charge.
Even if you get a LFP model 3 and its recommended to charge to 100% (at least once a week per teslas information), Charging to 100% at a supercharger is going to take you quite a bit of time because of the charging curve at the top. It slows down as you get near full, when supercharging (but not when home charging because ALL home charging is "slow charging").
Anyway, Even if its a LFP model 3 and you start with EPA range 267, you are not going to run it down to 0, no one does that in an EV. You are at most going to run it down to, on average, around 20%. 20% of 267 is 53.4 (lets call it 54), so what you will actually be calculating as usage is 100% to 20%, or 267 - 54 = 213.
Ok, now we know that you have 213 miles of range you will actually have to use on a regular basis (to start). Your 7 mile daily commute, being so low range, will likely use 15 miles of range from your car, maybe even more in the winter for starting up, normalizing cabin temperature, etc. Lets use a fairly conservative number of your 7 mile commute using 15 miles of range (which will be mostly accurate, except it will likely be more in the winter).
You will be losing 15 miles of range from your battery every day, and you have 213 miles of range to use (see above). Thats 14 days (not a month). This does not count any usage you might actually have sitting in the car waiting for someone, etc. Nor does it count SENTRY mode, which, people who park outside and dont have home charging almost always want to use.
Sentry mode uses between 1 and 2 "miles" an hour. Lets use 1 mile per hour as a conservative estimate, and you parking outside at your home for 9 hours a day, and sentry mode of 1 hour used "elsewhere" during the day for a total sentry mode usage of 10 hours a day, and 10 miles of range used.
Add that 10 miles of range sentry mode uses, to the 15 miles of range your car will use on those short trips, and you have 25 miles of "range" used a day for your 7 mile commute, with sentry mode being used. 213 miles to use, 25 miles a day used, for an actual "I need to go fill up" time of about 8 days.
TL ; DR -- If you use the car like almost everyone else who does not have home charging and turn on sentry mode, you will need to "fill your car up to 100% full" every EIGHT days (and be at a supercharger over an hour to do that), no where near "once a month".
If you DONT use sentry mode, EVER and you use the car, you will fill up every 14 days (still no where NEAR once a month". There is no usage of the car you will do that will have you fill up once a month. If thats your expectation, dont buy the car. You should not buy this car unless you are OK with the fact that you WILL be spending up to an hour at a supercharger (or even longer if its L2 charging) every 8-14 days.
Back to the question you specifically asked. If you DONT use sentry mode, you will lose 1-3 miles of range a day if you dont drive the car and DONT use sentry mode. If you DO use sentry mode, you will lose approximately 1 mile an hour of range for every hour you use sentry mode, so in a 24 hour period of being parked (not touching the car at all) you will lose around 15-20 miles of range, when using sentry mode.
So, if you use sentry mode and dont drive the car for 7 days, your car will have lost somewhere between 140 miles range, and 200 ish miles of range (depending on if you have cabin overheat protection on, as well). This doesnt count you actually driving the car. The reason I keep mentioning sentry mode, is people without a garage are usually the ones who want to use sentry mode.
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Gauss Guzzler
Safety Score = 42
My car takes a few days to lose 1% when parked in nice shade with sentry off. But as others said, parking “in the wild” is a whole different thing - for example it might decide to keep the battery warm overnight and use a couple percent to do so.
Clean out your garage or run an extension cord. Your usage would be fine with a 120V outlet but you’d have to keep it plugged in a lot, which might be inconvenient. Otherwise maybe a 50ft 30A extension cord from your dryer outlet might be a better compromise.
Clean out your garage or run an extension cord. Your usage would be fine with a 120V outlet but you’d have to keep it plugged in a lot, which might be inconvenient. Otherwise maybe a 50ft 30A extension cord from your dryer outlet might be a better compromise.
Transformer
Do the math. Save the world. — Mark Leon
It's reasonable to investigate the extension cord or a long charging cable. Still, letting the car charge for free a few hours 2 blocks away sounds good.
Sentry mode should draw somewhat less power than we have data for since a recent software update turns off most of the audio amplifiers for sentry. If you get the update with that (undocumented) feature rather than the later update which also turns the amps back on afterwards, you'll discover most of the speakers off and the sound tinny. Don't sweat. Ask service to push the bug fix and meanwhile do the two-thumb reboot each time it happens.
Another surprising thing is Tesla's software update arrangements. It can take several weeks to receive an update and there are many different releases in the field at any time since we're all beta testers. Never expect to be on the latest release.
Sentry mode should draw somewhat less power than we have data for since a recent software update turns off most of the audio amplifiers for sentry. If you get the update with that (undocumented) feature rather than the later update which also turns the amps back on afterwards, you'll discover most of the speakers off and the sound tinny. Don't sweat. Ask service to push the bug fix and meanwhile do the two-thumb reboot each time it happens.
Another surprising thing is Tesla's software update arrangements. It can take several weeks to receive an update and there are many different releases in the field at any time since we're all beta testers. Never expect to be on the latest release.
I appreciate the responses, particularly the Beautiful Mind calculus mathematics. These are good points. Sounds like I should suck up a nema plug, spring for the ultra bulky as snot 8 gauge extension cable for extra comfort, and probably just build a garage eventually, but also sounds plausible to make this work.
Re sentry mode im in a pretty well heeled neighborhood, I’d be pretty surprised if I really need it, but we shall see.
Re sentry mode im in a pretty well heeled neighborhood, I’d be pretty surprised if I really need it, but we shall see.
The reason for all the math was to lay out "Why" when I say " You think you will be able to charge once a month, but it wont work like that at all, at best its going to be every couple of weeks". If you dont use sentry mode, then you will likely only need to charge every couple of weeks based on the usage you mentioned, but you arent getting anywhere near once a month unless you simply park the car and never drive it at all.
Yea, point well taken.
Im going to get a nema 14-30 or something and a properly graded extension cord until I can build a garage. Appreciate all the help and advice here.
ATPMSD
Active Member
Make sure you can find a 14-30 extension cord that Is long enough first! And be sure you are looking at 14-30 and not the twist locking version (L14-30).
ATPMSD
Active Member
A better idea, maybe.
Run a 60-amp wire from the breaker box to the outlet. This will allow you to upgrade to a Tesla Wall Charger at a later date and be able to utilized the full 48-amp capacity.
Install a 6-50 outlet and a 50-Amp breaker. With a 14-50 you are running 2-hots, a neutral and a ground. EV chargers do not utilize the neutral so unless you plan to buy an RV the neutral wire is a waste of money.
Now you can get a 6-50 extension cord. The 6-50 seems to be more available (?) then the 14-30 since the 14-30 is really a dryer extension cord. WIth this setup you can charge at 32-Amps, which is the maximum the Mobile Connector will support as opposed to 24-Amps with the 14-30 version.
Run a 60-amp wire from the breaker box to the outlet. This will allow you to upgrade to a Tesla Wall Charger at a later date and be able to utilized the full 48-amp capacity.
Install a 6-50 outlet and a 50-Amp breaker. With a 14-50 you are running 2-hots, a neutral and a ground. EV chargers do not utilize the neutral so unless you plan to buy an RV the neutral wire is a waste of money.
Now you can get a 6-50 extension cord. The 6-50 seems to be more available (?) then the 14-30 since the 14-30 is really a dryer extension cord. WIth this setup you can charge at 32-Amps, which is the maximum the Mobile Connector will support as opposed to 24-Amps with the 14-30 version.
Just a reminder that DC will definitely get cold enough for a few weeks a year where charging with a 120v outlet outdoors will be nearly impossible. The car will need to use power to keep batteries above a certain temperatures, and when it's like -15c or lower, it'll basically use up all the power from a normal 120v plug to do so, leaving very little to actually charge the batteries.
That said, you're not far from a faster charger, so it's probably not enough of a problem to be of real concern.
SilverString
Member
There is nothing wrong with a proper extension cord - that is essentially what all runs from your breaker box are... I did this for a time and would say keep your amperage turned down to maybe 75% of the rating of the extension cord, and when you first connect it make sure nothing is getting hot, especially at cord plug points.
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