EV Charging and Lamp Posts

1/ Ask the person who has "decided" if they actually realise the additional costs to themselves, they may then decide to just carry on with the original contract of wiring lampost lighting.

2/ Consult lamp manufacturers about your actual expected voltages/fluctuations.

3/ Will changing from LV to ELV (and battery back up for instance) mitigate results

I'd wonder if it would make more sense to keep the EV and lighting circuits separate - you'd have better resilience if a fault on the EV circuit didn't take out the light as well, and the additional cost of an extra cable when you've already got the trench/ducting open would be minimal.

  - Andy.

The EV charging load will almost certainly be many times the lighting load. So basically this is an EV charging installation with the addition of a little lighting. 7 kw single phase chargers are pretty much standard unless something faster is specified. 7000 VA charging and perhaps 100 VA lighting. 3 phase 22 kw chargers are another possibility.

Street lighting equipment is almost certain to be LED these days which is generally fairly tolerant of voltage variations and should be fine with a 5% voltage drop. It might however be a better design to limit the voltage drop to 3% or less on economic grounds. Remember that each 1% of voltage drop represents the loss of 70 watts, for which someone is paying and deriving no benefit.

Reducing the losses from 5% to 3% will save about 150 watts per charge point during the hours for which it used. 1000 hours use a year is 150 kwh saved per year per charge point. 150 kwh cost about £75 at say 50 pence a unit which is about the going rate for non domestic.

The size and layout of the cables will depend upon many factors.

Hi Andy,

This was the first consideration, and we are carrying out a cost comparison exercise.

The ducts are already in place...which is another issue.

I’ve been getting up to speed with the code of practice for EV charger installations recently as I’m going on the C&G 2919 course in a matter of weeks. I actually logged in to ask an EV question myself. I haven’t got it to hand but from memory I’ve got two things to say but first I’ll give myself a get out of jail free card that I’ve not yet attended said course and I’m a house basher, I don’t do street furniture 

so voltage drop being a product of current and resistance, as per usual your three options when faced with this problem are as follows, 1) increase cross sectional area of your conductors. 2) and or decrease your design load, can a 3.5KW charger be installed instead of a 7KW one? 3) don’t install the circuit.

Now I’ve been looking in the code of practice yesterday and I’m sure it says in there somewhere that EVC installations should be supplied individually but it can supply multiple EVCs, perhaps with this in mind utilising a street lighting circuit would not be appropriate.

Just to give a bit of history.

The lamp posts are to be fitted and will be fed from the landlord's supply.

The EV points are an afterthought, and will utilise the existing ducting; which limits the number ands size of the cables.

Each EV point will be 5Kw and supplied via open PEN protection. This is all to be supplied and fitted by the EV Installation/Supply company.

We are just responsible for installing the cables and making sure they are the correct size.

Currently my view is that we wire the lighting separately, or the client agrees to a blanket 5% volt drop.

You'll need to decide what charging rate to offer.  Standard ones are 3.6kW single phase, 7.2kW single phase and 22kW 3-phase.  Lower rates are available, but with car batteries getting bigger every year, trying to charge a 50kWh battery off a 2kW public charger starts getting a bit pointless.

The charging side is not my responsibility.

Apparently the client has asked for 7Kw chargers that are throttled down to 5Kw, which they have asked us to base our figures on.

The design, and in fact the whole idea has not been thought through. Do you have a 3 phase supply, and how big is it? How many cars fit the car park? How many chargers are envisaged? This idea to supply some odd level of chargeing is daft. I suggest a large transformer, and a ring main or several, around the car park, probablly 300mm al conductors. The place to start is a 500kVA (or more) TX with TNS distribution, and 3 phase chargers, then it is simple. The lighting circuits should be separate because the cable cost will be less than the cost of jointing. Follow DNO practice. Perhaps the car park is for 10 cars, in which case ignore the charging altogether.

This is rather like expecting a mini to pull a circus caravan. By all means co-locate the lights with the charge points, so folk can see if they want to plug in at night, but unless there are very few charge points indeed, then there will need to be far more to consider than a slightly thicker cable. I'd start by verifying the available supply capacity with the DNO and go from there. The costs of more cable to handle voltage drop will pale beside any  requirement to subsidize a new substation transformer. You'd probably want to pull all 3 phases and neutral to each point.

you cannot do this with out involving the design of the charger install and the DNO , so you need to liaise.

Mike.