Fitting A Second EV Charger

[Onoff]

I currently have one EV charger on my detached, double garage and am looking to fit a second, identical charger so there'll be one either side of the garage. Symmetry and practicality etc. My charger is a UK made Indra Smart Pro. 

 

The single phase, overhead, mains electricity supply comes into the main house. After the incoming 100A fuse the supply is split via Henley blocks to the house consumer unit and a 60A switch fuse.

 

At the 60A switch fuse is a 100mA Type S RCD. This then feeds the garage.
 
From the switch fuse a 16mm², 3 core, SWA goes to a new garage consumer unit. I've used the 3 cores for live, neutral and earth. The steel wire armour is also earthed.

 

For the current EV point I have a 40A, C curve, 30mA, double pole, bidirectional, RCBO fitted in the garage consumer unit. The EV point is fed from there via a 10mm² SWA.

The EV charger has current sensing. A cat-6 cable runs all the way from the EV charger to the house consumer unit where it terminates in a current transformer on the house incoming live cable. This ensures the EV charger cannot draw too much current if the house demand is high.

 

I'm mulling a second charger from the garage consumer unit, again with a cat-6 cable running back to the house incoming live cable?

 
I'm trying to think how it would work, but gut feeling is it's a non starter.

 

The charger(s) is 7.2kW so a little over 30A hence the 40A RCBO. Two together would be over 60A so I'll likely need to up the switch fuse to 80A. Presumably if one charger was charging and you plugged in the second, the second would limit it's charging. 

 

If though in say the dead of night you had both chargers going at full chat then at the house whacked on say a 40A electric shower what would happen? Would both chargers see the increased draw at the house and limit their output? 

 

There are I think intelligent, third party current balancing devices for when using multiple EV chargers. As time goes on, this will undoubtedly be a thing. Something like this maybe:

 

https://www.tlc-direct.co.uk/Technical/DataSheets/SYEV/EV_Balancer_Instructions.pdf

 

Anyone else done it?

[Nickfromwales]

Do you plan on 2 EV’s? Both charging simultaneously?

 

I thought the whole point of the CT clamps was that these give the house loads mains priority and the EV charger is told to use the remaining capacity, only until the house has its fill, and thus modulates fully?

 

If they both have such functionality then the mains should be split 3 ways, and the max never exceeded. I can only assume that you would tell the EV charger what the incoming supply fuse is rated at so it can ‘do the maths’?

[Onoff]

3 hours ago, Nickfromwales said:

Do you plan on 2 EV’s? Both charging simultaneously?

 

Well, at least having two plugged in simultaneously. 

[torre]

I think what you propose would work okay, I'd expect the first charger to see the house load and the second to see the load of the house plus the first charger. So only the second chargers output is likely to be limited. 

[Nickfromwales]

7 hours ago, Onoff said:

 

Well, at least having two plugged in simultaneously. 

Does the manufacturer say these can talk to each other, and go 'master' and 'slave'? Eg your car for work at 06:30 MUST be charged, but SWMBO's can be at 50% and that'll do for 08:00 for any run to the shop (kinda thing).

[Onoff]

28 minutes ago, Nickfromwales said:

Does the manufacturer say these can talk to each other, and go 'master' and 'slave'? Eg your car for work at 06:30 MUST be charged, but SWMBO's can be at 50% and that'll do for 08:00 for any run to the shop (kinda thing).

 

I've asked this specific question over on the OVO forum:

 

"Can two Indra Smart Pro chargers each be fitted with their own CT clamp on the same incoming meter tail, allowing independent load curtailment on a single-phase installation, or do the chargers require a dedicated multi-charger load-sharing configuration?

 

 

[Nickfromwales]

3 minutes ago, Onoff said:

 

I've asked this specific question over on the OVO forum:

 

"Can two Indra Smart Pro chargers each be fitted with their own CT clamp on the same incoming meter tail, allowing independent load curtailment on a single-phase installation, or do the chargers require a dedicated multi-charger load-sharing configuration?

 

 

Beautiful words, softly spoken.