Car keeps resetting to 30 Amps

[Erandhawa]

It could definately be other loads turning on causing it a/c, fridge compressor etc. I would check the wiring one more time and make sure everything is tight but not so tight that it seperates the contacts.

 

[ken830]

I am charging on a NEMA 14-50 on a (dedicated) 50 amp breaker and had the car set to charge at 40 Amps but it reset to 30. At first I thought it was the recent software update but it did it again today. I seem to recall someone else posting about this but couldn't find it. Any ideas?

Yeah. There have been several threads over the years. This (Anyone Still Experiencing Charge Current Limiting (40A->30A)?) was the latest.

I have had this issue with my car since the Dec 2013 firmware update.

My setup is perfectly-wired (performed to code by my electrician father and inspected by Tesla-endorsed electrician, dedicated-circuit, dedicated-meter, only a short <1-foot run of wires. The voltage reading is regularly between 240-246V and is super-stable as there is nothing else on the circuit and everything is brand-new and short.

Tesla could not solve this and I have pretty much resolved myself to living with it.

 

[jfoxny]

Yeah. There have been several threads over the years. This (Anyone Still Experiencing Charge Current Limiting (40A->30A)?) was the latest.

I have had this issue with my car since the Dec 2013 firmware update.

My setup is perfectly-wired (performed to code by my electrician father and inspected by Tesla-endorsed electrician, dedicated-circuit, dedicated-meter, only a short <1-foot run of wires. The voltage reading is regularly between 240-246V and is super-stable as there is nothing else on the circuit and everything is brand-new and short.

Tesla could not solve this and I have pretty much resolved myself to living with it.

Thanks for the thread link. It's good to know that I am not alone. My car, wiring, charger, plug, etc. are all new and everything is correctly installed. So it must be a quirk of the software or an overly cautious safety check. Oh well, good to know its normal-ish. Thanks.

 

[msnow]

Thanks for the thread link. It's good to know that I am not alone. My car, wiring, charger, plug, etc. are all new and everything is correctly installed. So it must be a quirk of the software or an overly cautious safety check. Oh well, good to know its normal-ish. Thanks.

I thought you weren't getting 240V or more, no?

 

[scaesare]

The pilot signal is what tells the car which adapter is connected. The UMC reads a resistor from the adapter, figures out the corresponding amperage, and then generates a J1772 pilot signal for that amperage. Without a pilot signal, the car would have no idea what it could safely draw, it could be far below 30A, or the EVSE could be trying to indicate an error over the pilot wire.

Right you are. My bad.

I'd guess the car is defaulting down to 30A upon seeing 240 then.

I get some port locking weirdness as well, which makes me think flakey connection...

 

[mikeash]

Defaulting to 30A for 240V would be dangerous, given the existence of the 6-15 adapter and the occasional J1772 station that puts out less. I still think it's a contact problem on the power lines. However, I certainly could be wrong. I've seen it happen to other people and I figure it could happen to me someday too!

 

[AB4EJ]

Could it be the constant plugging and unplugging of the cable that is causing it to not have as good of a connection?

Plugging and unplugging can introduce metal dust and oxidation into the interface between the mating surfaces and create a sort of resistor there. In olden days (1970s) I worked for Packard Electric (now Delphi Packard, GM's old wiring division), and one of the ways we could get connectors to fail (especially when they carry a lot of current) was to mate and unmate them a few times.

That said, I think the connector surfaces in the Tesla connectors are silver-plated. (That's true, isn't it?) Silver is unusual in that its oxide is also very conductive, so these connectors should be able to tolerate a lot of connections before the interface degrades enough to cause problems (although at the high current levels used in the Tesla, it won't take much to cause problems); so house wiring problems (i.e., too small gauge wire, wrong wire type, etc.) would be where I would look first if Tesla is dropping current levels.

 

[jfoxny]

I thought you weren't getting 240V or more, no?

You are correct. I was seeing 230V, but, my understanding is that +/- 5% volts is an acceptable variation.

 

[supratachophobia]

I

You are correct. I was seeing 230V, but, my understanding is that +/- 5% volts is an acceptable variation.

Have constant 239-243v

 

[roblab]

Me, too! Me, too! (waves hands)
I used to charge at 40 amps. I put in my own circuit a decade ago. I charged my RAV4EV on it, and my Sig S85 charged for years at 40 amps. Then all of a sudden, it would trip back down to 30. Plugging in at other 14-50 outlets, it charges at 40 amps again, but when I come home, bip, back to 30. I can sneak it up to 32 and it doesn't know it.
I've changed breakers, checked connections, everything I can think of. The only thing I might guess is that Tesla did some firmware changes to detect extension cords, and everybody started complaining at the same time. Service has checked my charger, and report it's fine.
For the record, I have a fairly long run of #6 wire, but it's within NEMA recommendations. Nothing ever gets warm when I charge.
Either way, it charges fine at night. I'm not ever in any hurry, so big deal, and maybe the slow charge is being nicer to the battery.

 

[murphyS90D]

It's not just the run to your 14-50 outlet. If a big air conditioner starts up it puts an instantaneous load on the whole panel. That may be what the car is seeing. Your A/C probably isn't running much at night. There could be a flaky connection anywhere between the power pole and your panel that would result in excess drop when the A/C starts.