Normal voltage drop in a house

[cerbfan]

I've an issue in our house with voltage drop whilst charging.

Background is:
2 electric cars BMW iX on a 7kW charger and a Model Y on a 13A charger. These are both timed to start charging at 23:30.

For around that time we also have the Dishwaster and Washing machine timed to come on. The 3kW immersion heater is time to come on at 02:45 daily. On top of this the other large power draw would be the hot tub 1.5kW heater which comes on randomly when needed and heating pumps as required. So probably looking at a max draw of up to 80A at times during the night, Supply is 100A.

What I notice is that often the Tesla drops back to 8A charging from 10A due to the voltage dropping sometime as low as 215V. This is a real pain as once it drops it never comes back up again even once the BMW charge is complete and the voltage comes right back up again.

Question is, is this level of voltage drop normal / acceptable and is there any way around this drop of charging current to the Tesla or getting it to increase the charging level once the voltage recovers?

Also it is not the extension lead to the charger as when the 7kW charger is not charging the BMW and not much other load on the house the the Tesla sits at around 232V whilst charging.

 

[init6]

Why not schedule the other items for later times? Even if they do drop the voltage, say at 5am, you'll have had most of your change at a higher rate.

 

[Jason71]

Not sure what is normal but what I would say is that it is normal that when the Tesla detects low voltage it drops the current and never increases it again.
If it does this from the off than maybe stagger the start time so it does not coincide with the BMW starting charging.
If it randomly happens later like when the hot tub kicks in then that is more of a problem.

 

[init6]

If it randomly happens later like when the hot tub kicks in then that is more of a problem.

Unless you do the dishes/washing while you're in the hot tub

 

[cerbfan]

This could be a winning idea apart from I'd need to have the jets on in the hot tub to get a thorough job done which would add another 30A to the load

 

[cerbfan]

This is all where I see the idea of having a heat pump and batteries is going to fall down. A 100A supply is just not enough for a modern house with 2 electric cars, a heat pump heating system and batteries when you are trying to cram all the useage in a 6 hour period when electricity is actually affordable.

 

[ACarneiro]

This is all where I see the idea of having a heat pump and batteries is going to fall down. A 100A supply is just not enough for a modern house with 2 electric cars, a heat pump heating system and batteries when you are trying to cram all the useage in a 6 hour period when electricity is actually affordable.

True. I’m almost maxing out my supply with heat pumps, immersion heater, batteries and one EV. Two EVs would have been impossible to fit into the 6 hour slot (obviously depends on mileage).
I suspect three phase supplies will have to be the way forward in the future.

 

[Durzel]

All you can really do is get on to the DNO and tell them you are experiencing voltage drop at well below the 100A expected.

It could be a problem at the pole supplying the house, or at the entry point to the property, or elsewhere. Not very helpful, but it's a fault finding game at this point.

 

[qwickshot]

All you can really do is get on to the DNO and tell them you are experiencing voltage drop at well below the 100A expected.

It could be a problem at the pole supplying the house, or at the entry point to the property, or elsewhere. Not very helpful, but it's a fault finding game at this point.

This basically.

 

[Jason71]

A workaround might be to sign up to Tessie.
Not only will this notify you if the charging speed is reduced but you could schedule it to stop charging and re-start it a couple of times through the night.
Sadly I don't think there is a way to tie a restart into the current drop.

 

[gsmith123]

You could use scheduled iOS shortcuts to reset the charge current

 

[Irata]

What I notice is that often the Tesla drops back to 8A charging from 10A due to the voltage dropping sometime as low as 215V.

Given your unloaded voltage is 232v, that's only a 17 volt drop for what is around 220,000 watts.

I see a similar voltage drop when the total load in my home approaches 100A. But my unloaded voltage is 245v and so it doesn't cause any issues.

Does your smart meter show incoming voltage on its display, with a few button presses.

 

[gsmith123]

Given your unloaded voltage is 232v, that's only a 17 volt drop for what is around 220,000 watts.

220,000 watts is 220kW. Unless you have a Supercharger in your house you probably meant 22kW. Except very few Tesla's support over 11kW AC charging (and OPs Model Y is not one of them).

 

[Irata]

220,000 watts is 220kW. Unless you have a Supercharger in your house you probably meant 22kW. Except very few Tesla's support over 11kW AC charging (and OPs Model Y is not one of them).

Yes, thank you, of course I meant 22KW.

No need for a sarcasm. Some of us have a disability, that despite proof reading 20 times we still make a mistake.

 

[pdk42]

Consider yourself lucky. At our property, with minimal other current draw, the Model 3 charging at 7kW pulls the voltage down from 240V to 210V. Most nights the car throttles to 24A and some nights it terminates due to “pcs-a054: Charging stopped due to large voltage drop”. The DNO is promising a new PMT but I’ve been waiting four years for landowner permissions. I’m pulling my hair out with it.

 

[Durzel]

Yes, thank you, of course I meant 22KW.

No need for a sarcasm. Some of us have a disability, that despite proof reading 20 times we still make a mistake.

To be fair I didn't take their reply as being malicious, just pointing out the factual inaccuracy. No harm done.

Love your avatar I've still got my 520STE in the loft

 

[browellm]

The UK's nominal voltage specification is 230V and the regulator allows a range of 216V to 253V.

If it's regularly falling a below that for a sustained period, definitely contact the DNO who will put some measuring equipment on it to gather some accurate data.

 

[Adopado]

The UK's nominal voltage specification is 230V and the regulator allows a range of 216V to 253V.

If it's regularly falling a below that for a sustained period, definitely contact the DNO who will put some measuring equipment on it to gather some accurate data.

Yes it needs to stay within spec. However I would think that the problem with the car ramping back or ending a charge will be due to a voltage drop relative to the voltage it is presently charging at. This means that the UK specification range (as far as the car is concerned) may not be at issue (in fact I've seen my car successfully charging at 207v in the past!) I would expect that if during a charge the car measures a significant voltage drop it's going to be set to back off the amps. The car can't know that the voltage drop is not due to a wiring fault so will just act in the interests of safety. The OP's experience seems to demonstrate this.

 

[MrT3]

Yes it needs to stay within spec. However I would think that the problem with the car ramping back or ending a charge will be due to a voltage drop relative to the voltage it is presently charging at. This means that the UK specification range (as far as the car is concerned) may not be at issue (in fact I've seen my car successfully charging at 207v in the past!) I would expect that if during a charge the car measures a significant voltage drop it's going to be set to back off the amps. The car can't know that the voltage drop is not due to a wiring fault so will just act in the interests of safety. The OP's experience seems to demonstrate this.

This makes sense and it may be that all is required to alleviate the issue is to schedule the Tesla to start charging just after the BMW so time has been given for the 7 kW charger to fully ramp up and therefor the Tesla only sees a lower initial voltage. Then the extra 3 kW from the immersion shouldn't cause enough of a drop to trigger a back off.

 

[browellm]

However I would think that the problem with the car ramping back or ending a charge will be due to a voltage drop relative to the voltage it is presently charging at.

Possibly, but there is a related situation with solar charging where the car will quite happy current surf up and down between 5A and whatever the array maximum is. Now I do appreciate here that a voltage sag is a different condition that the car may react differently to, but again Tesla will know about what in spec for each for each country's electricity network and for the BMS to act accordingly.

I do agree with the advice of staggering the loads more across the off-peak window. A huge demand spike at the start of these off-peak periods is very bad for the grid in terms of instantaneous load, CO2 etc. Why is why EVSEs are now mandated to have an offset built into them switched on as default, and Octopus developed the likes of IO, etc.