Plugged in Re-Charging Rates

Plugged in Re-Charging Rates

I'm wondering what other MS owners are experiencing with recharge rates. Mine don't seem to be what is advertised by TM.

I've installed a NEMA 14-50 outlet. The MS steps that Down to 40A at 236v. I'm supposed to recharge at 31mi/hr yet the best rate I've gotten is 22mi/hr which is ~66% of advertised. Normal range at beginning of recharge session has been between 140-180 miles left in battery.

When I used the SC in Gilroy I got a recharge rate of 112 mi/hr at the start of the session and ended at 88 mi/ hr. In actuality the beginning rate was 2mi/min for ~15 min, however the last 5 miles of charge took 11 minutes, well below 88 mi/hr.

I know there are efficiency losses in the system.

Do you think the meter is reading actual or theoretical re-charging rates?

What's your experience been?

jat | 10. Februar 2013

The 31mi/hr rate is in ideal miles -- presumably you have selected rated miles. Note also that the maximum rate is achieved at 40A@250V - with 236V, you are getting less. 40A@236V is 9.44kW, or 94% of the maximum charge rate. Finally, the charging rate slows down as it nears a full charge (particularly so in a max-range charge -- the last few percent take more than twice as long).

In rated miles, 22-24mi/hr is what you should get from 40A, and a bit less as you near the end of a standard charge.

For the supercharger, that is displayed using your preference of rated miles, and it only charges at full speed up to 50% state of charge. Beyond that, it gets progressively slower to protect the battery. I haven't used a SC yet being in Georgia, but others have reported going from 50-90% takes over an hour, while 0-50% takes 30 minutes.

kent | 10. Februar 2013

My normal recharge rate on the Nema 14-50 is 24 Miles per hour. Voltage is @39/240 @ 40 Amps.

Hills | 10. Februar 2013

I have Nema 14-50 that is always at least 240V to start, sometimes as high as 246V. However, within a minute of plugging in the Model S, the voltage always drops, to as low as 230 V, range is 230-236 when charging. I don't know why.

The charge rate displayed in the instrument panel and the 17" screen is rated miles, not ideal miles. Thus, 31 x 0.8 = 24.8. (240/300=0.8).

My normal charge rate starts at 22, but I've noticed that if I come back in 30 minutes the charge rate usually goes to 24 or so.

I normall only charge 60-70 rated miles at a time (to get to 240). However, two weeks ago, I allowed the battery to get down to 60 rated miles, and noticed that my charge rate went to 28 miles. I had never even seen 26 miles/hr before and I've had the car for 7 weeks at that point. Even when the battery got to 200 miles, the charge rate was still 28. Eventually it slowed down to 25 miles at the end.

Since then, I still usually see 24 miles/hour after 30 min of charging.

Finally, the charge rate stated by the instrument panel always seems to understate actual miles charged. For example, If the instrument panel says charge rate is 24 miles per hour, if I come back four hours later the number is always more than 96 miles charged, usually well more than 100 miles.

Hills | 10. Februar 2013

Just now,
Car was at 220 rated miles.
Plug car in, voltage starts at 244 V, Amp zero.
Within a minute, AMP gets to 39-40, bounces around. Voltage goes down to 233V.
Come back 10 minutes later, Amp at 40, Voltage 234
Charge rate according to instrument panel and 17" screen: 25 miles/hour (better than usual)

This is on 4.2.
Don't have 4.3 yet.

jat | 10. Februar 2013

@Hills - the voltage drop is a normal consequence of drawing a load. E=IR, so the voltage drop across a circuit is equal to the current times the resistance. If the voltage drops too much, it is a sign your wiring has too high resistance (such as bad connections) -- that is why they say if your lights dim when you turn on a heavy load, it is time to call an electrician, as those high-resistance wires generate heat and enough can melt insulation or cause fires. In your case, it is within the desired range of 5% or less.

lov2krz | 10. Februar 2013

Thanks for the insight. Should of asked more questions when ordering would have considered the 90 amp dual charger setup.

Hills | 10. Februar 2013

You are good! I asked the service center and they did not know the answer. In my case, I estimate that from the Nema 14-50 to my panel is 125 feet of cable. The contractor bought expensive high quality cable, but still 125 ft is a long way. At the Menlo Park service center, I noticed that voltage is 225 when charging my car.

jat | 10. Februar 2013

@lov2krz - you can add the second charger now, though it costs you more, and the HPWC is no extra cost to get after the fact (though you will probably get it much later than you would have).

lov2krz | 10. Februar 2013

Thanks. I will consider my options.

nickjhowe | 10. Februar 2013

@Hills - assuming the electrician used #6 wire you should see no more than a 4V drop over 125 ft.

nickjhowe | 10. Februar 2013

I have a 50 ft #6 AWG run and I see 239-241V at the car during charging

Hills | 10. Februar 2013

Don't remember what gauge, but it was very thick and very expensive. The cable material was at least $200. At the outlet we get 40 amp and always 240 V or higher measured by meter and confirmed by Model S. I have decided not to worry about the voltage drop during charging.

portia | 10. Februar 2013

@lov2krz it doesn't seem you drive that much, and the charging using the NEMA14-50 would take oonly 5 hours, plenty of time overnight to get that done. I have dual charger, and wanted the HPWC at first, but it wasn't yet available when I got my car in Oct, and my friend talked me out of it, saying There was no reason to charge twice as fast based on my usage pattern. Besides, my home would require a major electric upgrade to get the additional 100 amps to the house, so I thought to just use the NEMA14-50 and maybe get the HPWC later. Now that I have had the car for a few month, I do not think I will get the HPWC, no need for that. At the superchargers, you don't need dual charger, the charge rate may have more to do with the electricity at the charger than anything else, and yes, if you are close to empty, it will charge faster as already noted by others.

DouglasR | 10. Februar 2013

A number of Roadster owners got HPCs but didn't need them in the garage, so they donated them as "public" Tesla chargers. The Roadster HPCs charge at 70 amps, not 80 amps, but this is still very useful for long distance trips. It forms the basis of the "Tesla Highway" running from Vancouver, B.C. to San Diego. I would love to see a network of public HWPCs as well.

lov2krz | 11. Februar 2013

Portia, thanks for your insight. I think the thing that bothers me the most is if I have to use a public (Charge Point, etc.) charger at level 2 charging rates I will be stuck at the charger for several hours if I need an additional 100 miles while on trip. I also know that having a dual charger in the car won't help in this situation.

I was planning on taking a trip in the MS 85kW battery to Fort Bragg, CA from the South Bay (Morgan Hill), there are no super chargers along Highway 101 north and based on my calculations I'll need 1 stop at a public station in Gyserville or Ukiah, CA for 3 hours to make it to Fort Bragg So I'm taking the Prius. There are no charging stations in Fort Bragg so I'd be using a 120V outlet at the hotel.

I love the car but adding 3-4 hours wait time each way isn't fun, but doesn't have anything to do with this thread. Thanks for letting me vent.

jat | 11. Februar 2013

@lov2krz - another option is charging at RV camps, where you can get 40A@240V pretty easily, or the same as you get at home.

Brian H | 11. Februar 2013

Or get a friendly EE to make a MI-EVSE for you, and get 80A at an RV camp!

KendallPB | 11. Februar 2013

I'm glad I saw this thread. I wasn't sure if my charging ever hit 31 (I've only had the car 2 days and don't remember to check). Two things:

1. I checked after reading the above and I was getting like 12! I went out and it was flashing yellow, which I think means not plugged in all the way? I ejected from the car end and plugged it in again, firmly to make sure it was in all the way, and it went to the green flash. Yay! Moral: Always check the color of the flash after plugging in, to make sure it's in all the way. (blush)

2. Now, fluctuating 39-40A and 239-240V, I see 26 miles. Reading the above, this is very good. The range listed is "rated," so I presume this is a good charge rate.


Brian H | 12. Februar 2013

"Rated" means on the assumption you would drive as though a full Max charge would get you to 265 miles, like the EPA did. Another thing to watch: that miles per minute seems sometimes to under-report actual charging. If you watch the totals and do some arithmetic, it may be actually higher than that shows.

lov2krz | 12. Februar 2013

Brian H., thanks for the referral to Peters trip notes. It was not clear if the MI-EVSE referenced is for use on a Model S that has only one charger in the car.

Also thanks for reminding me that there are lots of RV parks that would have NEMA 14-50 outlets.

I'll send a note to Peter and ask for his MS configuration and some specs on the MI-EVSE

jat | 12. Februar 2013

@BrianH, lov2krz - you will need dual chargers to charge the car from AC power at anything more than 40A.

I would still be nervous about the MI-EVSE approach - while in general it should be safe, the only thing keeping the current balanced between the two 50A receptacles is the resistance of the wires and the other loads on those circuits being approximately the same all the way back to a common point (typically a breaker panel, though if they are on different meters it will be the grid itself).

The more dissimilar those paths are, the more likely there will be an imbalance in the current. Each one is only rated for 40A continuous, so you would be relying on the breakers to trip to prevent overheating the wires/receptacles, and breakers have been known to fail (not to mention the annoyance of coming back and finding your charge isn't complete because a breaker tripped).

Personally, if I were going to do something like that, I would dial back the current to something like 60A to make sure one leg didn't handle too much current, or have current monitoring built into my adapter.

lov2krz | 12. Februar 2013

@jat, thanks for your comments. Since 95% of our driving is local my MEMA 14-50 gets the job done at night. It's the occasional trip that brings concern for a faster fill-up. Living in the Bay area and traveling south to LA or even Vegas (I'd probably fly anyway)isn't a concern since the SC are located along the route to those places. It's the trips not currently serviced by SC. But as I'm leaning from this forum it going to take some time and patience to fully utilize the wonderful exciting capabilities of this magnificent automobile.

My MS is less than 5 days old and I'm really new to the EV world. I understood from the beginning that long distance driving would require a slightly different mind set than driving a ICE auto. It's more closely related to riding motorcycles, they have limited tanks and require more frequent fill ups than a ICE auto. In fact most of my long trips by road are on my motorcycle ('05 Goldwing) and I do just fine but can fill up in 8 minutes and be on the road again.

Brian H | 12. Februar 2013

Good luck getting Peter's specs! Many, many readers are waiting for those. It may well be you need an attached EE to make it work. ;)

Vawlkus | 13. Februar 2013

Maybe I'll start doing that. I need a hobby anyway }B)