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Ev charging point for car with limited power supply
Dave Thomas
27 Posts
Question
Guy rang me yesterday, He wants to plug his EV in and charge it overnight at his static caravan. He only has a 2OA supply: that's fine he can in theory plug in via a 13A socket and trickle charge. What he wants/needs is some sort of management system that will turn off his charger if he turns on say kettle and toaster first thing; I don't even know if this sort of thing is available, I would think it would have to be installed at the CU and won't be cheap. I think I'm going to tell him he needs to speak to a registered EV point installer, as (before I even look) there's probably all sorts of issues here with liability, and additional earthing requirement/ RCD issues, but any thoughts?  It''s an interesting and not unreasonable question, and  i guess likely to be commonplace in the future. You have a static: how do you charge your car when you're there?
10 Replies
mapj1
3413 Posts
Load shedding switches are a fairly common item on the continent, especially in the warmer south where electric heating is rare, and supplies are thinner.
(An example from eaton) This 15/32A unit closes its relay contact (rated at 1A only) when the load through its sense coils exceeds 15A, though it will take loads up to 32A without damage. Other sensitivities are available and may be better suited.
IF the charger will stand being cut off and then reconnected, sensing the socket circuit loads and using the current sensor relay contact to drop a  contractor in series with  the supply to the charger socket might be an easy way to tackle the maximum load issue.
Sort of thing will require a small DIN box enclosure for the sensor and the contactor - how easy that is will depend on the space available and the layout of the wiring. And do not sense the load that will be dropped, or it will oscillate 🙄.
If the charger needs something less brutal than a power cut such as an ethernet or RS232 command to be sent, then a current transformer and an Arduino may be the way forward for those who can program in C, an option not for the faint of heart however.
Mike
 
Matt Hunt
5 Posts
Hi Dave, we at 'matt:e' have a little load curtailment unit for EV Chargers, effectively you put the CT around the incoming supply tails and if it approaches its factory set limit then we stop charging to the EV unit, it can come with a factory fitted Type A RCBO or even a full Type B RCCB if required.
Dave Thomas
27 Posts
Thanks Mike'
i'm trying to work out what these actually do: I need something that will switch off the supply to the EV charger when the power in the other circuits totals say, 10A. not sure if this will do that? I it seems like they switch on /off  when a particular load or combination exceed a total value, unless I get that wrong?
Dave Thomas
27 Posts
Matt thanks:  that sounds like it might work, assuming that the ev charger will automatically re-start when it's re-energised  up-stream. Do you have a link to this? What is the sort of price/availability, is it something I can fit (electrician with little EV experience)?
dave 
mapj1
3413 Posts
Hi Again
- the sort I linked to have 4 terminals, 2 for a sensing coil - you might put that in series with the live supply to the socket that feeds the kitchen for the toaster, kettle  etc. and 2 that are just a switching contact, like a relay.

When the current in the sense coil exceeds 16 amps in in this example the contacts change state, and do not reset until the current in the sense coil falls below some lower value, perhaps 8 or 10 amps for this specific device, but ones with other preset or adjustable limits exist. This is your 'kettle or toaster detector'

The contacts you use via a relay or contactor or whatever  to wind down the charge in some way (or in the continental house to disconnect the water heater or whatever discretionary load is to be shed while the kettle boils.)

A dedicated unit as implied by Matt:e is probably far better, but you'd need something that can interface with your chosen make of charger and cable.

Mike.

 
Matt Hunt
5 Posts
Hi Dave/Mike

Our units are often used on garage type boards for switching off individual loads, if the full load of the garage supply reaches 40amps for instance then we isolate whatever load runs through the contactor. We could programme the CT for a maximum of 20amps and whatever runs through the contactor will be isolated if 20amps on the incommer is reached until the supply falls below 20amps. We use this product a lot with EV Chargers and have not heard of a car charger yet that does not restart on power loss. The units come with over and under voltage protection and the controlled circuit can have an MCB, Type A RCBO or even a full Type B RCCB, of course you can have no circuit protection or indeed have an IP65 Version, you pay your money you take your choice.

As an example of pricing, a double pole MCB integrated unit would cost  £152.50 ex VAT ex Carriage.
Matt Hunt
5 Posts
Yes Dave they are very easy to fit, you can check out CEF online for the product description which is SP-EVCP-MC/RC although we would need to programme a special 20amp PCB for you.
Dave Thomas
27 Posts
Thanks guys: I Iike to learn about new products and EV has clearly a big future, but as a 60 yo part time spark in a rural area, I can really do without the hassle of any issues that may come up with this, so will probably chicken out. I'm sure you're right about the restart on power loss Thinking about it you'd be pretty pi **ed if you got up for work to find your EV was flat 'cause one of the kids had tripped the RCD, reset it and gone to bed ! 
I'll probably go and see the guy, have a chat, and if he really can't get another spark, sort it out for him, but it might be best left I think. 
Dave  



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Matt Hunt
5 Posts
No problem Dave, good luck and stay safe.

Matt
Hello Dave Thomas,
Electric cars in the automotive world, they are powered by batteries installed inside the car, so it is necessary to charge those batteries that the car has traveled a certain distance.
It is forbidden to use a household multi-plug extension conductor when charging the electric vehicle. If you need to use an extension conductor, use only one that is suitable for external use such as a coil cable.
  • Buy a charging cable from a reputable retailer or directly from the manufacturer who has tested such and other products in strict tests to ensure that they meet safety standards in the UK.
  • If you are charging a 13A electrical outlet in your home, make sure that the wiring in your property is checked before performing this operation. Old wiring may not be helpful and may cause a flare-up.
  • I suggest going to the link:
  • https://www.gov.uk/government/collections/government-grants-for-low-emission-vehicles#electric-vehicle-homecharge-scheme
  • This is helpful for anyone who wants to understand more about charging an electric vehicle.
Good luck....

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