Current/Load management system - Any advice please!

[Tom Nautilus]

Hi Everyone

I'm looking for any nuggets of knowledge you can throw my way on this one as I'm dealing with a few things that are new to me! Not expecting any calcs, I have only included figures to give an idea of scale.

The job brief is: Provide metering for 19 garages on a residential site, with capacity so that they can all have their own EV chargers in the future. Only one resident currently has an EV, so initially it is just making provision and getting the meters in but further upgrades can be made over time.

The garages currently have a single phase TN-C-S 100A supply cutout which has roughly 20A max demand on it already from other lights, gate control etc.

I am fine with all the basic parts of the design+install but it doesn't take a calculator to work out that 19 x 7kW loads plus whatever they have plugged in to the 1363 sockets is going to be a problem.

It's going to be all new cable anyway (existing cable is all wrong), but I would like to keep the CSA reasonable and I also don't want to run a separate cable to every garage. My thinking is to install a local load management system so that they can get a good few chargers installed before they have to consider further upgrades, this way they can make use of the existing DNO supply in the short term and plan ahead for a new supply when it's needed.

This is pretty much where my personal experience comes to an end though as I have not dealt with load management devices before and I don't even really know what they are capable of.

From my initial searches, it seems there are quite a few EVSE companies that offer a solution where the charger talks to the LLM which seems ideal, but this doesn't allow for any brand choice on chargers in the future and I don't really want to tie them in like that if it can be avoided. I am also aware that if 10 of the garages use a 'granny' cable it's going to hit 100A anyway and the LLM won't have control over the 1363 sockets. Normally we could apply some diversity, but since nearly everyone will want to charge at full power through the night I don't see that diversity can apply in the same way.

What I would ideally like to do is have the load management communicating with some kind of current limiting device before the DB in each garage so they can use the full capacity if it's there but also ther supply can be a bit 'choked' without just being turned off.

So my main questions are -
Does such a load management system exist?
Any systems that anyone can recommend?
Am I missing an obvious better solution here?

Any thoughts much appreciated!

Tom

 

[binky]

The Rolec pillar chargers I've installed have load management in the software. Whichever charger gets plugged in first gets a full supply, the others get a limited charge rate until that one is finished, it then reassigns the loading to suite the remaining charge points. All metering us done via the charge points, the user's pay via an app for leccy used. NB there's a charge for using the software system.

 

[Tom Nautilus]

The Rolec pillar chargers I've installed have load management in the software. Whichever charger gets plugged in first gets a full supply, the others get a limited charge rate until that one is finished, it then reassigns the loading to suite the remaining charge points. All metering us done via the charge points, the user's pay via an app for leccy used. NB there's a charge for using the software system.

Ok yeah the few I've looked at are similar to this, I was just hoping to avoid tying the client into Rolec or whatever brand for all future additions. Nothing against any of those brands, I just don't like the idea of it. Maybe that is just unavoidable though

 

[UNG]

Hi Everyone

I'm looking for any nuggets of knowledge you can throw my way on this one as I'm dealing with a few things that are new to me! Not expecting any calcs, I have only included figures to give an idea of scale.

The job brief is: Provide metering for 19 garages on a residential site, with capacity so that they can all have their own EV chargers in the future. Only one resident currently has an EV, so initially it is just making provision and getting the meters in but further upgrades can be made over time.

Who has given you this brief as it sounds like they are not aware of the complexities of what they are asking for

The garages currently have a single phase TN-C-S 100A supply cutout which has roughly 20A max demand on it already from other lights, gate control etc.

So do the individual garages have any power installed currently

I am fine with all the basic parts of the design+install but it doesn't take a calculator to work out that 19 x 7kW loads plus whatever they have plugged in to the 1363 sockets is going to be a problem.

It's going to be all new cable anyway (existing cable is all wrong), but I would like to keep the CSA reasonable and I also don't want to run a separate cable to every garage. My thinking is to install a local load management system so that they can get a good few chargers installed before they have to consider further upgrades, this way they can make use of the existing DNO supply in the short term and plan ahead for a new supply when it's needed.

This is pretty much where my personal experience comes to an end though as I have not dealt with load management devices before and I don't even really know what they are capable of.

I think you need to review your basic design, I assume that these garages are rented by a landlord or are part of a residential community with a residents management commitee
With a DNO single supply and each garage sub metered how is it intended to manage what chargepoints are / can be chosen / installed by the occupier of each garage. Multiple chargepoints on a single supply would need to be linked for load management purposes
Given that since June 2022 all domestic chargers have to be "smart" you will also have to consider making an internet connection available to any chargepoints installed
If all the garage occupiers eventually require EV charging how is intended to mange their expectations given that load management will be needed and their 7Kw chargepoint may at times deliver less than the 7Kw it can supply
I think your looped supply to each garage is flawed and in the longer term could prove to be much more expensive, then there is how it is managed how does the owner intend to get access to read the meter in each garage. If the looped supply trips / blows the fuse how will it be reset as it could cause inconvience to some or all of the garage users

From my initial searches, it seems there are quite a few EVSE companies that offer a solution where the charger talks to the LLM which seems ideal, but this doesn't allow for any brand choice on chargers in the future and I don't really want to tie them in like that if it can be avoided. I am also aware that if 10 of the garages use a 'granny' cable it's going to hit 100A anyway and the LLM won't have control over the 1363 sockets. Normally we could apply some diversity, but since nearly everyone will want to charge at full power through the night I don't see that diversity can apply in the same way.

As mentioned previously it has been a requirement since June 2022. For this project to work given all the constraints I don't see any option but to standardise on the chargepoint and I would suggest that any design for the electrical distribution is based around the probable need to upgrade the supply to 3 phase at some point

What I would ideally like to do is have the load management communicating with some kind of current limiting device before the DB in each garage so they can use the full capacity if it's there but also ther supply can be a bit 'choked' without just being turned off.

So my main questions are -
Does such a load management system exist?
Any systems that anyone can recommend?
Am I missing an obvious better solution here?

Given that load management is already built into the chargepoints why would you want to duplicate it
Is there no parking space available where a few chargepoints could be installed for communal use this would in the short term provide a solution while the bigger plan is formulated, these chargpoints could be managed by a back office software and the residents charged for electricity used

One thing that isn't clear from your brief is who is financing the work involved and what is the plan in the short term and how does the customer see the longer term plan so a cost effective design can be developed now to avoid any potentially costly mistakes moving forward

There is a lot to think about with this project and I think it needs a more detailed discussion with the customer as to what their expectations are going forward for you to be able to put forward any design proposals. The first thing to tackle is if EV charging is required does it need to be delivered at each garage

I would suggest speaking to some of the chargpoint manufacturers most do training courses and it may be beneficial to you so you can better understand how to move forward on the design

 

[Tom Nautilus]

Who has given you this brief as it sounds like they are not aware of the complexities of what they are asking for

So do the individual garages have any power installed currently

I think you need to review your basic design, I assume that these garages are rented by a landlord or are part of a residential community with a residents management commitee
With a DNO single supply and each garage sub metered how is it intended to manage what chargepoints are / can be chosen / installed by the occupier of each garage. Multiple chargepoints on a single supply would need to be linked for load management purposes
Given that since June 2022 all domestic chargers have to be "smart" you will also have to consider making an internet connection available to any chargepoints installed
If all the garage occupiers eventually require EV charging how is intended to mange their expectations given that load management will be needed and their 7Kw chargepoint may at times deliver less than the 7Kw it can supply
I think your looped supply to each garage is flawed and in the longer term could prove to be much more expensive, then there is how it is managed how does the owner intend to get access to read the meter in each garage. If the looped supply trips / blows the fuse how will it be reset as it could cause inconvience to some or all of the garage users

As mentioned previously it has been a requirement since June 2022. For this project to work given all the constraints I don't see any option but to standardise on the chargepoint and I would suggest that any design for the electrical distribution is based around the probable need to upgrade the supply to 3 phase at some point

Given that load management is already built into the chargepoints why would you want to duplicate it
Is there no parking space available where a few chargepoints could be installed for communal use this would in the short term provide a solution while the bigger plan is formulated, these chargpoints could be managed by a back office software and the residents charged for electricity used

One thing that isn't clear from your brief is who is financing the work involved and what is the plan in the short term and how does the customer see the longer term plan so a cost effective design can be developed now to avoid any potentially costly mistakes moving forward

There is a lot to think about with this project and I think it needs a more detailed discussion with the customer as to what their expectations are going forward for you to be able to put forward any design proposals. The first thing to tackle is if EV charging is required does it need to be delivered at each garage

I would suggest speaking to some of the chargpoint manufacturers most do training courses and it may be beneficial to you so you can better understand how to move forward on the design

This is a great reply and gives me a lot to think about, I was contemplating the idea of putting communal chargers in instead as they do have parking spaces as well and I think this is probably a better solution.

To answer your questions, it is a residential set of flats in a gated community type setup. There is also a second set of 16 garages but I left that out of the OP to keep things simple.

Yes they do have supply to the garages already but it's all 2.5T+E (+1.5 for the lights) pinned outside in sunlight and all hanging off one MCB with no DB in each garage. Replacing that with something more suitable is all in my comfort zone and I'm considering a few options, but I will get into the details and calcs for all that once I have a basic concept in mind. All parts of my design will be planned out on ElectricalOM anyway.

The big question for me was managing the potential load of all these chargers. If I knew they would all be needed right away then I would have started the conversation with new 3ph DNO supply but the reality is they only need one right now and probably only a handful for the next few years so it's a massive outlay that might not be required for years. If the chargers go where the parking bays are (not by the garages) there is an alternative 3ph supply that has almost nothing connected I can make use of. They could have 3 or 4 for now and supply all 25 or so bays in the future if needed with the load management looking after them all. This seems like a much better idea.

I sort of had an idea of doing that but it had not become a fully formed thought until you suggested it so thanks again! Back to the drawing board for me!

 

[UNG]

This is a great reply and gives me a lot to think about, I was contemplating the idea of putting communal chargers in instead as they do have parking spaces as well and I think this is probably a better solution.

To answer your questions, it is a residential set of flats in a gated community type setup. There is also a second set of 16 garages but I left that out of the OP to keep things simple.

Yes they do have supply to the garages already but it's all 2.5T+E (+1.5 for the lights) pinned outside in sunlight and all hanging off one MCB with no DB in each garage. Replacing that with something more suitable is all in my comfort zone and I'm considering a few options, but I will get into the details and calcs for all that once I have a basic concept in mind. All parts of my design will be planned out on ElectricalOM anyway.

The big question for me was managing the potential load of all these chargers. If I knew they would all be needed right away then I would have started the conversation with new 3ph DNO supply but the reality is they only need one right now and probably only a handful for the next few years so it's a massive outlay that might not be required for years. If the chargers go where the parking bays are (not by the garages) there is an alternative 3ph supply that has almost nothing connected I can make use of. They could have 3 or 4 for now and supply all 25 or so bays in the future if needed with the load management looking after them all. This seems like a much better idea.

I sort of had an idea of doing that but it had not become a fully formed thought until you suggested it so thanks again! Back to the drawing board for me!

So you now have a slightly different design issue when you say there is an alternative 3 phase supply available although you don't say what capacity this has you could now maybe look at 11Kw chargers which for those cars that can charge at that level and improve the charging times. Having the chargepoints on the parking bays also makes it accessible to visitors who could be charged for what they use via a back office software setup

With regard to having a network connection I believe some chargepoints can by supplied with a GSM module for internet connection and if linking a number of chargepoints for load management they can all share one GSM connection

I went on a course about 12 months ago at Garo in Birmingham that was arranged by a wholesaler I use that was probably the most informative one that I have come across as part of it dealt with multiple charger configurations for car parking sites and how to optimise the supply use across a number of chargers using load management to deliver the maximum charge down to the minimum 6A charge to meet the legislation and it also gave options on back office management and charging for the electricity used by each chargepoint user

 

[johnb2713]

3 Phase wallboxes are usually 22 kW, the 11 kW is down to many EV's that have 2 phase chargers installed.

 

[Tom Nautilus]

So you now have a slightly different design issue when you say there is an alternative 3 phase supply available although you don't say what capacity this has you could now maybe look at 11Kw chargers which for those cars that can charge at that level and improve the charging times. Having the chargepoints on the parking bays also makes it accessible to visitors who could be charged for what they use via a back office software setup

With regard to having a network connection I believe some chargepoints can by supplied with a GSM module for internet connection and if linking a number of chargepoints for load management they can all share one GSM connection

I went on a course about 12 months ago at Garo in Birmingham that was arranged by a wholesaler I use that was probably the most informative one that I have come across as part of it dealt with multiple charger configurations for car parking sites and how to optimise the supply use across a number of chargers using load management to deliver the maximum charge down to the minimum 6A charge to meet the legislation and it also gave options on back office management and charging for the electricity used by each chargepoint user

More great info cheers!

 

[binky]

3 phase supply means faster charging, ergo you need less charging points as cars can be moved after only an hour or two, rather than sat there overnight. The residents will probably prefer fast charging anyway, and software for the billing side quite often has a facility to text users when the car is fully charged, so less blocking of charging points.

 

[rjp44]

Another way to look at this may be to look at the total daily charging requirement across all 19 garages at a point in the future when everyone is using an EV. This is presumably within the lifetime of whatever solution, certainly cabling, you put in now. Look at the likely average daily mileage of each car. This will be very different for e.g. retirement flats (low) vs urban professionals (low) vs small town families (high) then divide by 3 to get the number of kWh needed each day. Most cars are in the 300wh/mile ballpark - may get better, may get worse if ESUVs take hold. Most people will want to charge overnight so divide that by 12 (say 7pm-7am) to get the average overnight hourly load.
I suspect utilising that 3ph supply, and cabling for at least 16A average/garage will start to look essential.

 

[rjp44]

3 phase supply means faster charging, ergo you need less charging points as cars can be moved after only an hour or two, rather than sat there overnight. The residents will probably prefer fast charging anyway, and software for the billing side quite often has a facility to text users when the car is fully charged, so less blocking of charging points.

Not at all sure about this. Fast charging then moving is a proper PITA, wouldn't want to do it at home (can't have a drink with dinner because car will need moving soon etc). Most people will want to arrive home, put car on charger, forget it until the morning. Shared fast chargers in a residential location will just be perennially blocked by people who are charged but have better things to do with their time than move their car.

 

[binky]

Not at all sure about this. Fast charging then moving is a proper PITA, wouldn't want to do it at home (can't have a drink with dinner because car will need moving soon etc). Most people will want to arrive home, put car on charger, forget it until the morning. Shared fast chargers in a residential location will just be perennially blocked by people who are charged but have better things to do with their time than move their car.

It's upto the residents to 'co-operate' easier said than done, but it can work, and certainly more likely to work with fast chargers.

 

[UNG]

Not at all sure about this. Fast charging then moving is a proper PITA, wouldn't want to do it at home (can't have a drink with dinner because car will need moving soon etc). Most people will want to arrive home, put car on charger, forget it until the morning. Shared fast chargers in a residential location will just be perennially blocked by people who are charged but have better things to do with their time than move their car.

I suppose a lot depends on what your definition of fast charging actually is, an 11Kw chargepoint is hardly going to be fast if it is charging a nearly drained EV battery that needs the best part of 80Kw

Given the limited EV charging requirement that the residents have currently It probably offers a more cost effective solution to have a shared charging solution at the moment and create a long term plan to increase the charging capacity in the short term as @binky says it is upto the residents to be sensible and co-operate

 

[Phoenix]

And bearing in mind that not all vehicles have a 3ph charger on board, you could find, that having fitted a load of 11kw points that all the load ends up on L1 anyway, I did think you could shuffle the phases along at each point to try and ensure it kept it balanced, but then if you have a load management system of some description going in, it would probably confuse the poor thing unless there was a way to set up what was done, I'm waiting for someone to make a point that can automatically shuffle a car that inists on pulling a single phase load onto the most appropiate phase, but not sure it'll happen

 

[UNG]

Another way to look at this may be to look at the total daily charging requirement across all 19 garages at a point in the future when everyone is using an EV. This is presumably within the lifetime of whatever solution, certainly cabling, you put in now. Look at the likely average daily mileage of each car. This will be very different for e.g. retirement flats (low) vs urban professionals (low) vs small town families (high) then divide by 3 to get the number of kWh needed each day. Most cars are in the 300wh/mile ballpark - may get better, may get worse if ESUVs take hold. Most people will want to charge overnight so divide that by 12 (say 7pm-7am) to get the average overnight hourly load.

There are many ways to look at this project and assess what the load may be now but by the time we move to a mainly EV using society I believe that a lot of expectations may be more demanding especially the EV charging.
Your calcs make a lot of general assumptions and make no allowance for seasonal variations which could impact the charging requirements especially during the colder months also given that all EV chargepoints are generally smart devices it cannot be assumed that you can charge between 7pm - 7am if the grid load needs to be reduced to prevent power cuts the charge rate may be reduced or switched off to maintain the supply

I suspect utilising that 3ph supply, and cabling for at least 16A average/garage will start to look essential.

Sounds like a minimal solution only capable of delivering a little over 3Kw which would not be that good if you are expecting to fully charge overnight in 12 hours

And bearing in mind that not all vehicles have a 3ph charger on board, you could find, that having fitted a load of 11kw points that all the load ends up on L1 anyway, I did think you could shuffle the phases along at each point to try and ensure it kept it balanced, but then if you have a load management system of some description going in, it would probably confuse the poor thing unless there was a way to set up what was done, I'm waiting for someone to make a point that can automatically shuffle a car that inists on pulling a single phase load onto the most appropiate phase, but not sure it'll happen

It is usual to rotate the phase connections in co-located chargepoints and that connection information is programmed into the load management for each chargepoint so it can manage the load properly

 

[rjp44]

There are many ways to look at this project and assess what the load may be now but by the time we move to a mainly EV using society I believe that a lot of expectations may be more demanding especially the EV charging.
Your calcs make a lot of general assumptions and make no allowance for seasonal variations which could impact the charging requirements especially during the colder months also given that all EV chargepoints are generally smart devices it cannot be assumed that you can charge between 7pm - 7am if the grid load needs to be reduced to prevent power cuts the charge rate may be reduced or switched off to maintain the supply

Sounds like a minimal solution only capable of delivering a little over 3Kw which would not be that good if you are expecting to fully charge overnight in 12 hours

It is usual to rotate the phase connections in co-located chargepoints and that connection information is programmed into the load management for each chargepoint so it can manage the load properly

I think you misunderstood my calcs, I said 16A/charger average over the 12 hour night time period, to use in diversity calcs for cable and supply sizing. That is around 40kWh/car/day (1ph) or over 120 (3ph). For that not to be enough, all 19 garages would need to be stabling EVs that are all doing more than 120-400 miles a day (44,000-134,000 miles per year!). I guess if every single one of the 19 flat owners is an EV taxi driver then you may get there.
Seasonal variation is down in the noise within my 333Wh/mile pessimistic assumption for energy use.

 

[Tom Nautilus]

Thanks to everyone for all the thoughts on this, there were definitely a few gaps you highlighted in my knowledge, so after consideration I decided to get booked on the new 2921-31, 32 + 33 so I have all the up to date training for everything EVSE related up to large scale stuff. The client is not in any hurry so I will make my final design after that. I had been pondering it for a while anyway but all your comments have helped me move to that most important state of mind - conscious incompetence! I'm planning to start 2396 at the start of next year too so this will be the perfect thing to get those particular neurons firing.

I will try to remember to post the final designs on here when this comes around so you can have fun picking some more holes

 

[binky]

I will try to remember to post the final designs on here when this comes around so you can have fun picking some more holes

It's constructive criticism