Suddenly slower charging speeds

Suddenly slower charging speeds

I have a 2016 S90D and charge at home using 40 or 50 amp circuit. Please excuse my electrical ignorance, i can confirm specifics if asked.

Anyway, since getting the car, its consistently been charging at around 30 miles/hour. It has recently decreased to 22-24 miles/hour. This speed is true even after several hours of charging.

I haven't made any changes to the electrical system in my home and continue to use the same plugin cable the car came with from Tesla. Any ideas on why the charging speed would suddenly have dropped?

Bighorn | 5 novembre 2019

Is you garage getting colder?

jordanrichard | 5 novembre 2019

"several hours of charging".....? Just how low are you getting your battery down to, before charging?

Qwiksilver | 5 novembre 2019

Same happened to me this summer.

Qwiksilver | 5 novembre 2019

Have you tried supercharging since this recent occurrence?
Did you get throttled there as well? | 5 novembre 2019

@greg - Did you check the amperage value while charging? Let's say you have it set to charge at 40 amps, if there there is a significant drop in line voltage when charging starts, it drops down to 30 amps or so as a safety mechanism. It may indicate a connector problem (NEMA 14-50), connections to the receptacle or breaker problems, or undersized wires.

If it was working before, undersized wires are not likely. If you used aluminum wires on the circuit, and they were not properly prepared at the connection points, this is exactly what will happen. The connections can weaken over time and is one reason copper is recommended.

I don't think the temperature has anything to do with it.

bryan.hopkins | 5 novembre 2019

Did the max amps on the screen get accidentally lowered?

greg | 5 novembre 2019

So many good replies, thank you so much.

Some answers:
- yes, its getting colder out. i am in ohio
- i have recently supercharged but dont recall the amps dropping there except when the station was full
- unsure on aluminum vs copper wire
- i got the car in march and have charged since then/until now at 30mi/hr

The car is currently charging at 24mi/hr, 240v, "30/40 A". Unfortunately, i do not recall what the amp settings were before, but do know that it used to consistently be 30mi/hr and 240v.

Any advice based on that?

Are there any settings i may have changed in the car (unlikely) i should change, and to what?

Bighorn | 5 novembre 2019

Bump up the amps to 40 again. They drop to 75% when unstable power is encountered.

greg | 5 novembre 2019

Thank you. i will try this the next time i charge.

Is this a sign that i need to call my electrician?

Yodrak. | 5 novembre 2019

"charge at home using 40 or 50 amp circuit."

Which is it, 40 amp circuit of 50 amp circuit? Or do you have both available and sometimes use one and sometimes the other?

Bighorn | 5 novembre 2019

Just monitor. It could be as innocuous as an appliance coming on, causing a temporary voltage sag.

brianjdivine | 8 novembre 2019

I've got a 2015 Model S 85D and I am noticing much slower charge rates...not at home, but at Supercharger stations. I use one station frequently that is close to my house and I am charging at literally half the rate I used to...even if I am the only car there. Did Tesla throttle back the cars with free supercharging for life? I've spoken with model 3 owners at the station who pay and they are charging at the rates I used to get. Anyone else experience anything like this?

Bighorn | 8 novembre 2019

Charging slowed around 17 kW for my 85 kWh Model S. Model 3s are able to charge 2-3 times quicker than old Model Ses.

NCC1701S | 8 novembre 2019

About two weeks ago I charged at the Greenville, South Carolina supercharger on Tuesday. With my 2015 S 85D, the charge rate on Tuesday was around 104 KW and on Wednesday the rate was down to 54 KW at the same SC. Yesterday at the Acworth supercharger the rate started at 54 kW and quickly declined to 44 kW. Tesla support even had me change chargers which then slowed to 34 kW. Needless to say they had no explanation for any of the declining charge rates. In all fairness, by the time they had me change chargers yesterday the batteries were 60 miles from 90% full. This is starting to seem like software throttling either at the car or corporate level.

dborn | 9 novembre 2019

See many threads on this. My 2014 car has been throttled, allegedly due to a single fire in Hong Kong and “to preserve the life of the battery cells”. I also have free for life supercharging. I favor the conspiracy theory, being that this is a corporate ploy.

Qwiksilver | 9 novembre 2019


Welcome to the club.

jordanrichard | 9 novembre 2019

Dborn, how about favoring some history. Though you have a 2014 car, I don’t know if you bought it new or used, but just a quick historical note here. Back when there were incidents with debris hitting the front vertical part fo the packs, causing fires (3 fires) Tesla quickly stopped people’s ability to lower their cars ( air ride cars) just as a precaution until they came up with a fix. Everyone started crying foul, figuratively approaching the gates with torches ready to sue Tesla for taking away a feature they paid for. Once Tesla had a fix for this, they re-enabled the air suspension. So is it now possible that Tesla is working on a solution for the 85’s and will at some point “un-cork” the charging speed. BTW, I too have an 85. Took delivery in Mar. 2014.

NCC1701S | 9 novembre 2019

Not sure that I like the "hazing" practices in your club. | 9 novembre 2019

@NCC1701 - As a long term owner, you do know the charging power varies depending on the SOC? If you were near 90% SOC, the most that it can accept is about 20-30 kW. See this chart for a rough idea of normal tapering (it's for 90/100 packs, but your 85 will be similar. At 75% SOC, I'd expect around 50 kW. There are other variables, such as the battery temperature that can also have a major effect on the charging rate.

The other huge factor is if the SC module power is being shared with another car. That will almost always limit the power you'll get. Here's a bunch more on that:

So the big question between the two days you visited the SC - was your SOC the same when you started charging? Was the temperatures similar? And are you sure it wasn't paired with another car so that you had limited power? If everything was the same, it's less clear what might be going on.

NCC1701S | 9 novembre 2019

I get the variables, over the years the rates have been all over the place. On the Tuesday charging episode there were actually more users constantly on the chargers than there were Wednesday. Temps were within 10 degrees both days and oddly the paired charger was in use Tuesday and still got a faster rate. At this particular SC in the summer we actually got 120 kw (or there abouts) for a few minutes on a couple of trips. It was an unexpected and welcome surprise to charge so fast. On the faster charging day, the batteries were about 50 miles more depleted. The only real differences that I can think of have really been the software version changes over the summer, but not on that one trip. I accept that between 85% - 100% the charging rates comes to a crawl.

The whole gripe is that: Tesla nicely opened up the charging rate for a few months then seemingly without notice or cause or software change, within 24 hours, the charge rate is cut in half.

But, what the heck. It adds about 20 minutes to the charging time which is more time to make new Tesla friends. Still Grinning.