Electrical genius required?

[thewishy]

My gut feel is voltage sag when you're charging, and a very long cable run with perhaps smaller than ideal (in hindsight) conductors.
Why not the i4? Interesting question, but if you're operating at the margins, then odd behaviour is somewhat expected. I can see why Tesla would say it's chargable, seems like a job for a sparkie tbh

 

[pgkevet]

And there can be other factors. In my case in rural nowhere we have a pole Transformer off the 11k line to a 100amp house input. But I know not to plug in the Tesla while the immersion heater, oven, 4 top rings, the kettle, electric shower, bore hole pump, freezers and Aircon as well as a welder are all in use and the wife runs dishwasher and tumble drier....

 

[GlynG]

I'm eagerly waiting for the update on a friends Tesla being connected to see if the same thing happens as that will determine if its your car or not.

The fact the gate issue has been like it for some time does suggest the gates are drawing a lot more power than the 5amp design and you haven't said how old the gates are, A motor that has been in use for a number of years for the gates has had a fair bit of work, the likelihood is its a brushed motor and as brushes wear the motor develops a lot less torque, so it will try to draw more power.
The capacitor stores energy to a value and when a motor draws power it has the effect of lowering the voltage and at that point the capacitor discharges to negate a voltage drop and provide a little more to get the motor to spin up.
Any stiffness in the gates that resists movement will also need more current to keep going.
The length of cable to the gates is significant and its possible some moisture has got inside the insulation - which would cause the copper core to oxidise a little and this creates a resistance and therefore the cable cant provide all the power the gates need and there is insufficient reserve within the house electrics to supply more - even though the total drawn my be below the 100Amp main fuse rating, the fuse rating doesn't indicate the grid is able to supply the full 100 amps - which could also mean an issue with the capillary in the street.
A few years ago the UK was 240V but the standard now is 230V though many of us exceed the 230V supplied to our sockets but some may be a little less - 230 is just the target figure - and that too would make a difference to the watts you could draw. 240V and your 100 amp supply could drive 24000 watts - at 230 its 23000 watts - so a 1000 watts less push - which is just about the rated value of your gates.

 

[MrBadger]

I have a friend coming up tomorrow with his Tesla to plug it in and see what happens as Tesla service have kindly informed me that they will charge me if they can't find a fault with the car.

I would keep Tesla well away for the time being. Good that they have told you about any cost as I would imagine that your friends car will cause exactly the same issue and Tesla would otherwise have an expensive wasted journey.

I know a couple of people have mentioned voltage sag. Whilst it won't tell you what is at the gates, its easy to monitor in the car/app or third party app like TeslaFi. Plug the car into both charge points and before starting the charge on the other reduce the charge rate to 5A (to allow you to see the charge voltage - can't remember if you can see it anywhere without charging) and monitor the voltage. Start the charge at 32A on the other. I would expect that you will see the voltage drop and if its around 220v or thereabouts of less then I would think that you have found your answer. If you have time, then you could reduce the amps on the other car to the point that the gates start working - add back in the 5A on your car and you have probably found thereabouts the tipping point of the single car charge rate that the car can be charged at.

If it drops below ~216v, then if you were in mainland GB (NI may be different?), probably time to get your DNO involved who may up the voltage at your property although before you go that route it may be worth double checking that the DNO gave permission for two charge points to be installed... they may insist that the max charge current on the charge points are dialled back.

 

[MrT3]

Are you able to see the actual voltage and current on either of your chargers? I wonder if the BMW is strictly limiting the charging to 7.4 kWh and therefore dropping the current to 30 A if your voltage is up at 240 v or beyond, whereas the Tesla will charge up to 7.7 kWh if the voltage is high.

Possibly just enough to make the voltage sag on your gates be enough for it not to work correctly. Either way the connection at the gates needs to be checked for poor connections or insufficient connector surface area given the distance.

 

[SageBrush]

I don't know the answer -- nice riddle !

In the meantime, grease the gate hinges and have a look at the gate wiring and motor

 

[WannabeOwner]

Does Teslafi show the voltage when charging?

Also available on the APP when charging - just tried mine and as it ramps up from 0-32 AMPS the voltage fell from 240V to 235V - I have a very skinny cable from pole to house

 

[init6]

Also available on the APP when charging - just tried mine and as it ramps up from 0-32 AMPS the voltage fell from 240V to 235V - I have a very skinny cable from pole to house

It would be interesting to see if there is a BMW equivalent. I suspect the BMW is either not charging at 32A or is not dropping the voltage as much.

 

[GPDP]

My friends Tesla does exactly the same as mine does when plugged in...... at 32 amps the gates don't work, at 16 amps they do work.
Teslafi tells me that when charging is set to 32 amps that the voltage max is 232, voltage average is 229 and max amps is 32 and average 31.2, if that means anything to anyone?
I have cancelled the Tesla ranger appointment, don't want to pay the £100 for them to tell me the same thing I already know.
I have no way of knowing what current the BMW is actually using as I don't know of an data logger like Teslafi for non Tesla's, I just know the car is set to charge at 32 amps. The next time I put the BMW on for a long charge I will see how many KW's it uses to calculate the KWh usage, I suspect it will be quite a bit less than 7KW's per hour, therefore the likely reason that it doesn't cause issues with the gates.
I will have to engage an electrician to test voltage drop etc, but it is likely to show a new larger supply is required and then it will mean digging up the garden etc, so will contact the local automated gate installers and see if they can provide a solution using lower voltage motors or a battery back up or something.

Thankyou all for your replies and advice, it has been educational.

 

[Regulo]

Do you know how the cable supply to the gates was run? In the past I've come across PVC sheath cable in iron conduit, in plastic waste pipe and even simply buried in sand! All these gave weird effects before finally going bang, or simply going open circuit. They should be run in the correct armoured cable, and properly protected from any chance of damage from digging, animals etc. If you have to have it re-done, put in a much larger cable than strictly necessary, that would negate voltage drops, to a large extent.

 

[GPDP]

Do you know how the cable supply to the gates was run? In the past I've come across PVC sheath cable in iron conduit, in plastic waste pipe and even simply buried in sand! All these gave weird effects before finally going bang, or simply going open circuit. They should be run in the correct armoured cable, and properly protected from any chance of damage from digging, animals etc. If you have to have it re-done, put in a much larger cable than strictly necessary, that would negate voltage drops, to a large extent.

Hi Regulo,

I don't know how the cable was run as it was installed before we purchased the house. We did replace the gate system when we moved in around 7 years ago, but just connected to the existing cable.

 

[LiamPope]

Are you getting similar voltage readings with the Tesla on both chargers?

Also, what if you dial down the charging not all the way to 16 A, but try dialing down amp by amp in the app or car charging current limit and see when the gates come back to life.

Volt drop within the installation (in cable from house to garage and from garage to gate) seems most likely and the 'gut feeling' of many. A double whammy of volt drop when you are charging on the garage charger and operating the gate. Then you have Vdrop in the cable from house to garage with charging current plus gate motor inrush current, and further Vdrop in the garage to gate cable with just motor inrush current.

But if that's the cause then we'd expect it to be OK when charging with your new charger that is not on the garage circuit. Because in that situation there is no more volt drop in the house-garage-gate circuit than when the car is not charging at all.

The alternative, and only thing that as making much sense to me, is that this is primarily external voltage drop in the supply. That's why I asked if you are on a TT installation. If the external supply cable is oddly long and undersized then a large current draw on any circuit could drop your voltage at the origin due to Vdrop in the supply cable. Then add to that Vdrop in the cable to the gate under inrush current. This would help to explain why it happens on both chargers.

But then that doesn't really explain why the BMW doesn't cause it! But maybe it draws just a little bit less and that makes the difference - that's why I ask you to try the Tesla at 31, 30, 29, etc limit. But external Vdrop also seems unlikely since you are on a 100 A supply fuse and you measure a healthy 230 V at the car when charging.

So I'm as stumped as ever. Maybe the focus should be on the gate. Would be interesting to know the length and csa of the house to garage cable, and the csa of the 40 m gate cable. Also how old is the motor? Maybe an old or failing motor plus mechanical gate mechanism not in good shape is causing epic inrush current and combined total Vdrop then enough to stop the controller. But then why with only the Tesla!!

You do need to get a spark to investigate the gate circuit more than Tesla to look at the car, imho. Maybe a new motor with soft start controller and a lube of all the mechanicals will sort this. Good luck, most interesting thread on here, would watch the movie!

 

[init6]

you measure a healthy 230 V at the car when charging.

Does he though? His max is 232 and average of 229 so he could quite feasibly have bigger drops - even for a short period.

@MrBadger does Teslafi record the voltage throughout the charging period? Like this Teslamate graph:

 

[SageBrush]

There are parts to this wiring story I do not follow since the language in the UK is different than the US.

Could OP draw the branch circuits involved ?

 

[LiamPope]

Does he though? His max is 232 and average of 229 so he could quite feasibly have bigger drops - even for a short period.

@MrBadger does Teslafi record the voltage throughout the charging period? Like this Teslamate graph:
View attachment 901638

I rounded up! 229 average may as well be 230. Seems healthy if that is with a 32 A charging load plus whatever is going on in the house. On the other hand, if his voltage at the origin (fuse box) is 245 with no charging load, then 230 at the car under charging indicates some serious volt drop going on. It'd be useful to know the origin voltage on and off charging load as well as voltage at the car charging on both chargers. Also details of the house-garage cable and garage to gate cable. Then we could get a good picture of where volt drop is occuring within the installation or externally in the supply. It's all speculation at the moment without all the necessary data. But we're in electrican investigation territory now. Just following for interest.

Motor inrush current could be as high as 10x rated current, so depending on the size of this long cable to the gate, voltage could be tanked at the gate during startup causing it to stall which sounds like what is happening. Throwing a new motor at it could be a lucky fix, maybe the cable to the gate isn't up to the task.

 

[init6]

I rounded up! 229 average may as well be 230.

I was just concerned with the maths If the max is 232 and average is 229 then the min must be less that 229

How much less may give a clue as to what's going on.

If it stops raining I'll stick mine on charge on my Podpoint to see if it records voltage. OP may be able to use this to monitor the BMW.

 

[SageBrush]

depending on the size of this long cable to the gate, voltage could be tanked at the gate during startup causing it to stall which sounds like what is happening

That was my first thought too, but I don't understand why the charging Tesla would have any effect on a different branch circuit, or why the other car does not cause the same problem. Since the Tesla has to be derated to 16 Amps to let the gate operate, the other car charging at "32 Amps" is surely higher than 16 Amps.

I've vaguely read that the UK requires extra control/safety equipment in the circuits, I think mostly to ID ground faults but perhaps other conditions also. Perhaps the Tesla is activating this equipment ?

 

[Tony Hoyle]

Even on a branch there's only one source of power and you can get voltage drop - sometimes outside the operating range of the charger (although in this case the charger keeps working so it's not that severe).

As to why the other car doesn't.. it could be only drawing eg. 30A, it might be seeing the voltage drop and deliberately scaling back its charge rate to compensate, it might ramp up slowly enough it doesn't affect the gate.. without someone monitoring what's happening at the gate side in real time it'd be near impossible to know.

 

[LiamPope]

That was my first thought too, but I don't understand why the charging Tesla would have any effect on a different branch circuit, or why the other car does not cause the same problem. Since the Tesla has to be derated to 16 Amps to let the gate operate, the other car charging at "32 Amps" is surely higher than 16 Amps.

I've vaguely read that the UK requires extra control/safety equipment in the circuits, I think mostly to ID ground faults but perhaps other conditions also. Perhaps the Tesla is activating this equipment ?

Yeah I mentioned this earlier. If it is volt drop in the installation we'd expect it to be OK when he uses the new charger on a separate branch circuit ('radial' in UK ). But if we have volt drop external to the installation - i.e. undersized/too long supply feeder, then a high draw on any circuit in the installation could drop the voltage for the whole installation. Possibly that's what is happening.

Your second point is why I ask the OP to try the Tesla at 31, 30, 29, etc and see when the gates come back to life, not just down to 16. That could help understand why only the Tesla(s) are causing this.

 

[init6]

Does your BMW have this option?



I wonder if it is limiting the current even if set to 32Amps.