Tesla charger - any known issues with occasional low supply voltage?

[bangtidy]

So I'm still trying to get my charger installation completed.

After chasing up the installers today (they'd stopped responding to my emails) I've been told they've 'done some research' and think that the Tesla charger will have the same problems as the matt:e box they supplied currently does, ie. cuts out under low voltage conditions when the supply is under a heavy load.

The matt:e box is designed to cut the power if the voltage drops below 216V which is what is happening on occasion and it requires manual intervention when it happens..

My understanding from the Tesla charger's installation manual is that its own operating range for the supply is between 180V and 230V and unlike the matt:e box will attempt to auto-recover a few times before giving up completely.

I'm waiting on a call back from the electrician to confirm what their plan is as I've made it clear that they need to remove the matt:e box and complete the installation in an alternative way or just give me my money back.

In the meantime, does anyone know if a Tesla charger has any known problems with occasional dips in the supply voltage (eg. to say 210V)?

 

[Tony Hoyle]

Mine has no problem with a voltage variation that looks like this...

I can't see why 210 would be an issue for it, if the manual says it can handle 180.

 

[bangtidy]

Thanks Tony, that answers my question and will give me something to counter the electrician's excuses.

 

[ACarneiro]

What is the source of all this variation? Is it anything you can do something about (like run a wider cross-section cable to it)?

 

[bangtidy]

Just had an interesting reply from the installers. This just strikes me as absolute bs from a company that wants to walk away from the job rather than get it sorted properly.

"I’ve had a discussion with Matt:e and taken advice from trade bodies.

A Matt:e type device is mandatory unless the installer can be reasonably certain the vehicle in question can’t be charged outside, therefore if the Matt:e is not working properly with the charge point, moving the charge point to the rear of the garage without the Matt:e would be a solution.

Given the fact we now know that the Matt:e is working as it should and is cutting out because of voltage drop (Matt:e is designed to cut out if voltage drops below 216v) relocating the charge point will not solve this.

The most likely result of removing the Matt:e and relocating the charge point is that the charge point itself will detect the voltage drop and cut out, If for any reason it doesn’t you are left with a charge point drawing more voltage and making the voltage drop worse across your home.

When voltage drops it causes resistance which causes heat and has the potential to be a fire risk, with this in mind we will not be able to relocate the charge point without a Matt:e unit, therefore we are willing to give a full refund and arrange collection of the Matt:e unit."

 

[Roy W.]

Just had an interesting reply from the installers. This just strikes me as absolute bs from a company that wants to walk away from the job rather than get it sorted properly.

"I’ve had a discussion with Matt:e and taken advice from trade bodies.

A Matt:e type device is mandatory unless the installer can be reasonably certain the vehicle in question can’t be charged outside, therefore if the Matt:e is not working properly with the charge point, moving the charge point to the rear of the garage without the Matt:e would be a solution.

Given the fact we now know that the Matt:e is working as it should and is cutting out because of voltage drop (Matt:e is designed to cut out if voltage drops below 216v) relocating the charge point will not solve this.

The most likely result of removing the Matt:e and relocating the charge point is that the charge point itself will detect the voltage drop and cut out, If for any reason it doesn’t you are left with a charge point drawing more voltage and making the voltage drop worse across your home.

When voltage drops it causes resistance which causes heat and has the potential to be a fire risk, with this in mind we will not be able to relocate the charge point without a Matt:e unit, therefore we are willing to give a full refund and arrange collection of the Matt:e unit."

I’d take the money and run, and get a decent electrician on the job!

 

[MrBadger]

When voltage drops it causes resistance which causes heat and has the potential to be a fire risk, with this in mind we will not be able to relocate the charge point without a Matt:e unit, therefore we are willing to give a full refund and arrange collection of the Matt:e unit."

Tell him the car will counter this by modulating its power draw which should allow the voltage to recover if its the car dragging down the voltage. Sounds like the Matt:e is not allowing this built in protection to function, instead taking the heavy handed approach and just tripping out.

Oh yes, the bit about being mandatory is bollocks.

 

[arg]

The Tesla chargepoint is sold across Europe, where nominal voltage goes down to 207V (it's Europe-wide at 230 +-10%, but in the UK for historical reasons the range is still 230 +10%/-6%). Cutting out at 216V doesn't guarantee operation even in the UK, because the -6% is at the supply terminals and there needs to be an allowance for voltage drop within the installation itself, with a further 5% normally being allowed.

The spec of the Model3 itself isn't totally clear; if the on-board charger shares parts with USA models (as used to be the case with Model S), the cars there have to tolerate nominal 208V as well as nominal 240V interchangably on public chargepoints (depending on the type of supply they happen to be connected to), and so they support full-current charging well below 200V (aside from 120V charging, but that's a special case with lower current).

The car's detection of suspicious supply voltage and consequent reduction of charge current to reduce the risk of fire therefore can't rely on just looking at the supply voltage at any given moment (as the "normal" range is too wide), rather it compares the voltage seen before and after the car increases/decreases the current drawn - a large droop in voltage caused by the car starting to charge is likely to indicate a high resistance in the circuit supplying the car and so possible fire risk, while a voltage that's low the whole time just means the supply to the whole street is struggling.

 

[ewoodrick]

The car will cut back power if it sees the voltage dropping

 

[NewbieT]

Bin the matt:e and fit an earth rod?!

 

[bangtidy]

Thanks for the replies guys - much appreciated. Definitely going to bin the matt:e and if necessary will also get an electrician to install an earth rod to the garage although my understanding is that this isn't actually a requirement if the charger can only ever be used indoors - which will be the case once the charger is also moved to be the back of the garage ie. 7m from the door.

At this point I just need to get the charger working reliably and it's bloody annoying that the installer is just trying to get out of finishing the job properly.

@arg - it's the supply line to our house that appears to be the cause ot the voltage drops under load. It sounds though like the charger and car will deal with this by throttling back on the current draw - something the matt:e box won't do as it just cuts the power completely. Presumably, any attempt by the charger to draw more than 32A would also trip one of the breakers. The weakest link between the charger and the supply will be the 6mm2 cable (approx. 15m long).

 

[bangtidy]

Okay, so after going back to them again this morning, they've come back with the following

"We’re not worried about the Tesla Charge Point coping, we’re worried about YOUR SAFETY. Adding more load and making the voltage drop worse is not safe!!"

Is that really the case, if the supply voltage to our house does occasionally dip to say 210V under load, are we in danger? If so, then I guess I have to go back to the DNO again.

I do wonder how many other EV charger installs are going to run into similar issues as EVs really take off.

 

[MaDProFF]

6mm is more than adequate at that length, unless you have a load of other things connected to it.

I have volt drop issues, my run is longer to my garage, and only 4mm, but had no problems, just the car drops to charge at 24 amps or 16 instead of 32, the odd thing is if I stop it when it is charging at lower rate, and restart it a few minutes later, it seems to charge at 32A and holds.

Low Voltage is being an issue tbh especially at night oddly enough, I think the Power Companies are fiddling something on purpose to drop it at night.

 

[bangtidy]

6mm is more than adequate at that length, unless you have a load of other things connected to it.

No it's just the charger.

 

[arg]

@arg - it's the supply line to our house that appears to be the cause ot the voltage drops under load. It sounds though like the charger and car will deal with this by throttling back on the current draw - something the matt:e box won't do as it just cuts the power completely. Presumably, any attempt by the charger to draw more than 32A would also trip one of the breakers. The weakest link between the charger and the supply will be the 6mm2 cable (approx. 15m long).

The car might or might not throttle back - you don't particularly want it to, and this isn't the case which the feature is designed to catch, but it might be fooled into thinking so. Still, the throttling back probably won't stop you getting the charge you need.

The matt:e is trying to solve a completely different problem (and not doing it very well).

Drawing more than 32A would only occur if something is seriously faulty, but yes indeed breakers are there to cover just that case.

Just so you understand what is going on here:

• The box on the wall (which I would call a "chargepoint", somtimes the term "EVSE" is used) does not directly control the charging rate. It is simply a means of switching on or off the supply plus a communications module: it ensures that the cable is not live until reliably connected to a car, and then instructs the car the maximum current it is allowed to take.
• The actual charger is in the car, and will adjust the current it takes based on a whole range of factors - state of charge of the battery, temperature, charge timer etc. - but should never exceed what the chargepoint has told it.
• The "backing off" feature isn't something required by regulations or for the operation of the car itself; it is something Tesla have added as an extra precaution after some experience of overheating plug/socket arrangements. This is not triggered by low voltage per se - the car will charge happily on lower voltages than you are likely to encounter in the UK, and a low voltage before starting to charge can be caused by all sorts of factors that are unlikely to be related to the individual circuit that the car is connected to. However, if the voltage drops just as the car increases the current it is taking, then it assumes the extra drop in voltage is related to that circuit, and if excessive it reduces the charge current to reduce the risk of overheating/fire. Since the heating effect is proportional to the square of current, a modest reduction in current has a larger effect on the amount of heat produced.

 

[MaDProFF]

"The car might or might not throttle back - you don't particularly want it to, and this isn't the case which the feature is designed to catch, but it might be fooled into thinking so. Still, the throttling back probably won't stop you getting the charge you need."

I disagree, the whole reason I upgraded from a 16A for a 32A (first car was a hybrid) was to make sure I got an over night charge on off peak electric, If I get home late in the evening at say 20% it takes hours before it gets back to 90% for next morning drive, on 16A even 24A but 32A it is like 6/7 hours which is a good time. It has on numerous occasions throttled back over night and the car no where near charged to 90% in the morning, in my case it pretty well makes no difference as my daily miage generally is a lot lower, it is only a couple days a week I do like 200 mile on a 90% charge.

 

[bangtidy]

@arg - thanks - really appreciate the feedback.

The supply to the house (100A) seems okay (ie. 230V) until it's heavily loaded eg. 40A+ when the induction cooker and kettle are at full tilt etc at which point the voltage might drop to around 215 - 220V. Adding the charger obviously makes that situation worse and the voltage can then drop to around 210V. At that point though the matt:e drops the power completely so I've not been able to see what happens after if the power to the charger wasn't cut.

So based on what you've said, I guess the problem would be if the voltage is consistently low while the car is charging at 32A as this could drag our entire property's supply voltage down to a point where there could be a danger of overheating cables attached to any high load anywhere in the house or garage especially if this were over a long period.

Does that sound that right?

How low a voltage is actually dangerous in this kind of situation?

Am I likely to have the same issue with any other electrician being cautious in this way? ie. are the installers being reasonable or are they just trying to walk away from a job that's causing them more hassle than they want?

Such a frustrating process!

Regardless of this installation, I will be looking to stick an opensource current/voltage monitor and logging as close to the supply feed as possible so that I can go back to the DNO if neccessary, but the fact is that replacing the supply line to our house would seem to involve digging a trench across the neighbour's garden so this isn't really something I want to deal with if possible.

Thanks again for all the advice on here!

 

[.jg.]

What worries me is that your electrician(s) seem to be dodging the question of why the voltage at the charging point has dropped so much.

 

[bangtidy]

What worries me is that your electrician(s) seem to be dodging the question of why the voltage at the charging point has dropped so much.

Just to be clear, I can see that the voltage drops in the house without the charger so I'm pretty sure that this is a supply issue and nothing to do with a problem with his installation. I also had the DNO come round and they weren't surprised that we have a low voltage issue under load as our supply line is long and probably a bit undersized. Unfortunately though, that's not an easy fix at all.

So I can't really blame the installer for not wanting to investigate the voltage drop any further. But I just need to understand whether they're simply being over cautious or whether I actually have some fairly insurmountable problem with the supply.

If it comes to just restricting the charger to 16A then so be it, I can cope with that. I just hate the way the installer has been responding.

This was the same installer that told me that registering the install with the DNO was a formality, and then told the DNO that we had a max load of 130A (which is way beyond what we actually need). The installer then blamed the DNO for the delay this caused because the DNO said we need to pay for a new 3 phase supply.

Eventually when I spoke with the DNO myself, they said the only reason they couldn't sign off the install was because of the 130A figure the installer had put on the form. When I sent the DNO a spreadsheet of our meter readings for the last 5 years, the DNO immediately said there wasn't a problem and gave it the okay once the installer had put a more reasonable figure on the form.

 

[Tony Hoyle]

I'd definitely get a second opinion from someone who is a good installer.. these guys sound.. well, did they wear ten gallon hats?

Voltage variation isn't unusual and lots of chargers will be installed right now with much similar variations. The only reason you noticed it was because the matt:e doesn't do its job properly. If they'd just installed an earth rod like any normal installer would you wouldn't be needing to worry about any of it.

I'd expect there to be less variation overnight anyway (if you look at my graph after midnight it's relatively stable - people in other houses are asleep and so less demand on the line between me and the substation (I think.. not an electrician but that seems to make sense)).