I am a new owner and, at the recommendation from Tesla dealer, had an electrician install a 50 amp circuit to my home. Yet, when I try to change setting in the car, it will only go up to 40 amps as a maximum. Further, every time I try and charge, it will be reset to 30 amps and I have to manually increase to 40 amps. So, if I don't reset, I get a maximum of approx. 22 miles/ hour for the charging; if I manually increase the limit in the car up to the maximum 40 amps, then it will go to 30 miles/ hour for charging. Two questions: Can I get it to go to 50 amps? Can I at least not have it continually reset back to 30 amps as a default? Note: At a superstation, it easily seems to adjust on its own and take whatever ridiculously high voltage and amperage is available.
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Undesired reset to 30 Amps
- Thread starter Caprice
- Start date
earcandy
Member
The 40 amp limit is proper for your UMC, and a 50 amp circuit. You want the Tesla to pull a max of 80% of the circuit. (So a 30 amp dryer circuit, you would pull 24 maximum).
As for your 30 amp decrease, it sounds like you might have some fluctuating voltage. As a safety precaution, the car is automatically dialed down 25% when it senses abnormal voltage drop/fluctuations.
I'll let the tech heads chime in more on this, and what causes it.
Did you get dual chargers or a single? If you got a single charger the max is 40 Amps. It's all the charger can handle. If, however, you got the dual chargers your car can handle 80 Amps, The problem is that on continuous load the circuit is limited to 80% of total. That means if you want 80 Amps to the car you have to have a 100 Amp circuit. I am not at all sure why your car does not remember 40 Amps at your specific charging location. It might be because you have a power source that is not pristine. If the car detects voltage fluctuations it will automatically step down Amps to stay "safe".
Wow! Not only do I love the car, I love this forum. Thanks for the answers. I do have a single charger. Now, it makes sense they recommended a 50 amp circuit as 80% would give the 40 amps desired. Now, the question is why it keeps resetting back down to 30? I might have to revisit this question with the electrician.
Sounds like the car is seeing a voltage drop and is determining what amperage that the car can safely charge at. You need to have your electrician look at the circuit again and double check that the wire he used is sufficient.
Caprice,
Just to try to visualize the "reset to 30A" that you are seeing, are you seeing one of the two following scenarios?
1.
You plug the car in.
Get into the car.
You see the max current setting is at 30A.
You select the current increase until it says 40A.
You walk away from the car and it charges away.
You come back to the car all charged up, unplug and drive away.
The next time you plug into the wall you get back in and it again says 30A (and repeat from here)
2.
You plug the car in.
Get into the car.
You see the max current setting is at 30A.
You select the current increase until it says 40A.
You leave the car charging for one hour.
You come back to the car while it is still charging and it now shows you that it is charging at a maximum of 30A.
Peter
Just to try to visualize the "reset to 30A" that you are seeing, are you seeing one of the two following scenarios?
1.
You plug the car in.
Get into the car.
You see the max current setting is at 30A.
You select the current increase until it says 40A.
You walk away from the car and it charges away.
You come back to the car all charged up, unplug and drive away.
The next time you plug into the wall you get back in and it again says 30A (and repeat from here)
2.
You plug the car in.
Get into the car.
You see the max current setting is at 30A.
You select the current increase until it says 40A.
You leave the car charging for one hour.
You come back to the car while it is still charging and it now shows you that it is charging at a maximum of 30A.
Peter
strider
Active Member
Is it a 14-50 that was installed? I don't use that plug but wasn't there some talk about the UMC with a 14-50 dropping down to 30A for safety as the old 14-50 plug adapters could melt?
No, it only drops to 30A if it detects a voltage drop. The software is more sensitive to voltage drops now, however.
jkliu47
Member
How hot has it been in your garage these past few days?
I have found that with a 14-50 connector wired to a 50 AMP breaker with AWG 6 wiring, charging that normally stays at 40 A lately drops to 32-30 A after about 15 mins. That's because the plug temp goes above 165 F because of high ambient temps. (>90F)
But this problem goes away if I set charging to later at night when the garage cools off.
Note to myself - have to get rid of wife's BMW - it contributes heavily to higher garage temps
I have found that with a 14-50 connector wired to a 50 AMP breaker with AWG 6 wiring, charging that normally stays at 40 A lately drops to 32-30 A after about 15 mins. That's because the plug temp goes above 165 F because of high ambient temps. (>90F)
But this problem goes away if I set charging to later at night when the garage cools off.
Note to myself - have to get rid of wife's BMW - it contributes heavily to higher garage temps
Do you have a dedicated circuit? If not, that could be a contributory factor as well.
caddieo
Member
My thoughts as well. I have a dedicated circuit and have no problems holding the amp settings.
mitch672
Active Member
Watch the voltage reading as the car starts charging, if it drops significantly (more than %8-%10), that's when the charger will drop down the charging current by %25 (and prevent garage fires due to outlets melting). This was done to prevent overheating of outlets/circuits.. You should have you electrician check the outlet and breaker lugs to make sure they are tightened properly. If they are, then it could be the transformer feeding your house can't deliver the power without too much voltage sag, or the overall length of the power drop to your house could also be the cause. Really all of the terminations from the meter on need to be checked to make sure they are tight, somewhere you are getting voltage drop, and that's the cause of the automatic %25 current lowering.
^^ what Mitch said.
If you are getting a voltage drop, it may be because your electrician used thinner (=cheaper) wire, e.g. 8 gauge instead of 6 gauge. How long is the run from your circuit board to the plug? Do you know what gauge wire was used?
If you are getting a voltage drop, it may be because your electrician used thinner (=cheaper) wire, e.g. 8 gauge instead of 6 gauge. How long is the run from your circuit board to the plug? Do you know what gauge wire was used?
jkliu47
Member
Good point shelbri, but I don't think so because I have been monitoring the AC usage (via Nest reports) in the house lately to determine how the new PV system's performance is affecting the electric bills (so far so good, the meter has been running in reverse the last two months!). And the AC (highest power usage since I don't have a pool) doesn't come on if at all, until later in the evening just before the sun sets. I had been charging the Tesla right after usage earlier in the day.
I noticed the drop in charging current (via Visible Tesla graphs) only after I installed the replacement UMC and after the latest software revision. I have never seen this happen before. But then that was before the weather started warming up, and the temp in the garage started inching up.
No matter, whether its due to higher ambient temp or daytime household power usage, the change in charging schedule to midnight has cleared up the issue.
Last edited:
Cottonwood
Roadster#433, Model S#S37
I don't think that it is a maxing out of current issue for the whole house, because that would probably pop the main circuit breaker. What I have seen when charging at a motel, is the current be reduced from 40 to 30 Amps on the motel 14-50 long after I plugged in, but during the busy evening activity at the motel. I reset it to 40 Amps later that night and it stayed at 40 Amps until charging completed.
My theory is that other large load(s) can drop (or wiggle) the Voltage of the entire facility enough to trigger the new twitchy current reduction into action. @jkliu47: This could be your AC coming on in correlation with the garage getting warm. The AC turning on could cause enough Voltage drop at the MS to cause the current reduction.
jkliu47
Member
Cottonwood - you are right. I re-checked my Visible Tesla and Nest charts for one specific occurrence - and wouldn't you know it, the charging current dropped from 40A to 35A just around the time the A/C came on.
I'm dealing with a similar issue, and am hoping someone has some insight. At the outlet, we were seeing a consistent 245-7 volts. But the minute we started charging, that quickly lowered to about 235 volts, thus prompting my 85 to default to 30 amps as a safety mechanism. We've checked the logs and the hardware. Everything checks out fine.
My service advisor thinks it could be an issue with out electrical service, specifically a transformer. Has anyone dealt with, or heard of this possibility?
My service advisor thinks it could be an issue with out electrical service, specifically a transformer. Has anyone dealt with, or heard of this possibility?
mitch672
Active Member
Yes. My unloaded line voltage was 239 volts, when my 75A OpenEVSE was running at full power, line voltage dropped as low as 211-213 volts. All of my connections where checked, the power company told me the transformer was 500 feet away, they changed the drop wire to the house to the largest they provide, didn't help much. Eventually they installed a 50Kva transformer at the pole right by my driveway, dedicated to just my house. Problem solved.
laalan
Member
I live in Orange CA. At 10:20 pm, my neighbor and I both noticed the same voltage fluctuation. Starting charging after 10:20 eliminated problem. Seems to be a SCE utility problem.
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