Tesla Model S Software Update 5.8.4 Reduces Charging Current by 25% If Input Power Fluctuations Are Detected


Tesla Motors is quick to react when safety might be an issue.

Take, for example, the latest Model S software update.  Officially called Version 5.8.4, this Model S update includes the following charging-related modifications:

What’s New in Release v5.8.4

Tesla Model S Gets Software Update

Tesla Model S Gets Software Update

Automatic Charge Current Reduction

If the Model S onboard charging system detects unexpected fluctuations in the input power to the vehicle, it will automatically reduce the charging current by 25%. For example, this will reduce a 40 amp charge rate to 30 amps.This change is designed to help protect you even when a problem exists that is outside of the car or charging electronics. It should significantly increase robustness and safety in the unlikely situation that a home wiring system receptacle, adapter or cord is unable to meet its rated current capacity.

The software update was rolled out at approximately 4 pm on Saturday and was first reported on the Tesla Motors Club forum.

Version 5.8.4 was no doubt put out in response to the garage fire from November 15.  Oddly, Reuters waited until December 18th to report on the garage fire.

What this shows us is that Tesla takes safety seriously and that even when a Model S is not the cause of a fire, Tesla responds by attempting to do what it can to ensure that a home’s faulty wiring/poor connections won’t burn the house/garage to the ground.

Hat tip to Sven!!!

Source: Tesla Motors Club

Categories: Charging, Tesla

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17 Comments on "Tesla Model S Software Update 5.8.4 Reduces Charging Current by 25% If Input Power Fluctuations Are Detected"

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It would be nice if other appliances had this feature like space heaters in that this is most likely how a lot of space heater fires get started were the heater over loads the circuit. So this is good that this tech exists for something to sense when it’s over loading a house’s wiring.

The fire investigator’s report seems to say that the Tesla(?) wall connector unit was wired to a dual 50A breaker through a 240V plug and receptacle. It seems to imply that this is where the fire started.

It’s my understanding that code (at least here in Portland, OR) requires that, with a 40A breaker or higher, the wall unit must be hard wired back to the breaker. i.e. no plugs/receptacles.

Am I reading this correctly? Sounds like good advice anyway.

Even if that’s the case, there’s no reason a properly connected plug/socket in that situation isn’t just as safe as a hard-wired installation. I’m not saying everyone should ignore the code, but a hard-wired installation is not somehow magically safer than a portable pone.

Except in this case,

No , any Jurisdiction subscribing to the NEC allows 50 amp branch circuits in a home, they even can have multiple outlets. MOst range outlets are 50 amps. The Leviton 400 40 amp charger dock has a nema 6-50 plug on it.

If I had a model s, the first thing I’d do is chop off their hot running attachment plug and put on a good nema 14-50 p that didn’t generate any heat of its own.

I got this update and hope they put a lot of effort into testing it. It had to be a pretty fast turn.

I do think the concept is a great idea though there are many ways that overloaded circuits can cause a fire that don’t result in something detectable at the load point. A stuck or oversized breaker will overheat an undersized wire to the point where it starts a fire – no fluctuations until it’s too late.

Except that had nothing to do with the last house fire. It was conservatively installed (100 amp subfeed,and a 50 amp breaker as recommended) by a licensed electrician.

How’s this for a novel thought: how bout Tesla make something just a little BETTER than it has to be the first time? The first “mobile connector” rated at 30 amps was discontinued for the roadster because it ultimately didn’t work.

The second “Universal Mobile Connector” (40 amps) kept burning out.

The 3rd UMC for the “S” has a troublesome attachment plug as seen by the melted plugs shown by DaveR.

Maybe their fourth mobile connector will actually work?

I was told by Tesla I was the only 220 volt charging roadster customer that has not purchased their UMC or HPC at the time I purchased my car.
Everything asssociated with my charging apparatus remains COLD after 8 hours.

In my view, this is the target Tesla should shoot for on try # 4.

Good action by Tesla.

I think that Elon and his PR team could also use some advice from Zen or compassionate-listening experts.

Admitting to something – not guilt/liability, but at least to ownership of ways to mitigate safety problems – is not only more truthful (since Tesla does seem to have modified things both in response to the impalement fires and to this garage fire), but will more importantly go a long way towards winning the PR battle over such incidents.

The current take-no-prisoners, kill-the-messenger, all-our-drivers-are-perfectly-happy-so-screw-U approach they seem to be following, is backfiring spectacularly.

I have a feeling they can find some “soft skills” experts in Northern California, can they not?

What’s to backfire? Tesla just wants the media to report the truth, without an anti-EV bias. I commend Tesla for creating a well designed product, sticking to the facts, and continuing to refine the vehicle in response to real world use. 🙂

In all cases, Tesla does something for the customers to lower the risk, but they are not “soft” either. And it hasn’t really backfired on them really. All it does is make journalists think twice before writing an inaccurate article about them (as Tesla has shown they will go to extreme measures to prove you wrong).

This is good and smart safety measure. Tesla has been quite bold with their software updates that they honestly admit that there are risks involving Tesla electric vehicles, but Tesla does not try to deny them, but they try to minimize them.

I would also like to have smart charging that Tesla would adjust charging rate as such that it would help to stabilize the grid. Namely, it would try to automatically optimize the use of off-peak power for charging. This is especially important when solar and wind becomes more dominant, because off-peak power means the days or nights when wind power production is the most abundant. And in sunbelt region naturally off-peak means the midday when solar power peaks.

We’ll, thats gunna suck when you’re charging then the laundry dryer kicks on!

Exactly Querty. Not that it was the case in the house fire last time, but they didn’t say anything about detecting arcing faults either, just ‘pwr changes’ and since the current is regulated, that means voltage changes only. But all that does is make installations that have very long runs with large pressure (voltage) drops safer. A proper installation with relatively large voltage drop is no more dangerous or safer than one with no voltage drop. The voltage will drop when the car goes to charge, and then it will revert to 30 amps, making charging safer, which could be done on other cars (making them safer) at any time. I know the purpose of the software change is to hopefully detect a connection getting worse. This might work some of the time, but it is rather like Tesla’s fix of the model S battery to have “Tesla Air Suspension – Now with more Air!”. Installations with very short runs from a very stout feeder remain unprotected, since a drop at the outlet/attachment plug can still generate alot of localized heat without tripping the point in the software to reduce the current to 30 amps. To me its a bit… Read more »
Dr. Kenneth Noisewater

Hmm, for a dedicated 100A Tesla charger I’d reckon on at least hardwiring with 6ga or larger? I have 3′ of 6ga wire for my CS-60 hardwired into its breaker, done by a licensed electrician (was def worth paying for, considering that a number of circuits needed to be consolidated to make room for that breaker!)

I would think it’s too late for a minor reduction if the wiring is so damaged that you can detect a significant drop. You wouldn’t detect the cable being in fire for instance. To cause a detectable drop you would need a short from melted insulation or broken wire and I’m not sure that dropping from 100 to 75A will do the trick.
I’d guess it would be better to advise all customers again that the house wiring need to be capable of what’s asked of it.

Please Dan, Tesla seems to be having problems with 40 amps, of course it is never their fault, ever. Please lets not have a 100 amp design. You have to walk before you can run.

My Roadster was obviously designed by the group of engineers that died. There will never be any problem with that car since right off the charging cord there are 2 – 150 ampere rectifier (fast-acting) fuses that open at the slightest duration fault. Of course, that won’t happen at my house, since my 2- 60 amp rectifier fuses (also fast acting) coordinate with the 150’s such that they will always shut down first.

The anomoly here of course is that I think some s’s can charge at 322 amps temporarily. I wonder if anyone notices any hot spotting, or whether things are just perfectly fine.