Henley blocks in series

Okay, this is probably a terrible idea but just thinking aloud really.

We now have a home battery and an EV. The inverter system for the battery has a CT clamp that currently detects all consumption by the house and determines how much comes from the battery or grid etc.

As is common with these systems when you charge an EV at night say, one is apt to find one’s home battery has fully discharged trying to charge the EV which can be an issue if you were wanting to use your battery to power your house in the morning on cheap rate electricity stored overnight.

The “simple” solution that I read a lot about it to position the clamp so that it’s only monitoring in-house use, not power drawn by the EV charger. Easier said than done in my case.

My power lead from my meter goes into one Henley block where it splits into three. One wire for the domestic consumer unit, one wire for a mini consumer unit for the EV and the third to a consumer unit for the inverter & battery.

The clamp can only be fitted around one cable. It’s too small to squeeze two cables through.

So, if it isn’t shockingly bad practice, could one fit one Henley block to divide the power supply into two, one of the legs going to the EV charger and the second leg (with the CT clamp), going to a second Henley block supplying the domestic CU and the inverter/battery CU? Effectively the house and inverter/battery will now be getting power through two Henley blocks in series.

I’m sure that there are other solutions involving home automation and some software jiggery pokery but I like the idea of a solution that will simply “blind” the CT clamp to the demands of the EV charger.

Tim

You can't get more electricity by rewiring! So, if you don't have enough electricity to charge the car's battery there's no way to adjust things so that there's power for breakfast etc. If you simply don't charge the car then you may have enough for breakfast! :-)

I don’t think you’ve understood. This is nothing to do with getting more power. It’s about preventing the home battery attempting to charge my EV when it’s plugged in. It’s 9.5 kWhr capacity is a lot more useful as a supply of cheap rate electricity to the house during the day than pissing into a large EV battery (that would normally get charged on cheap rate electricity.

I’m not attempting to live off-grid, just to manage my power storage better.

Tim

It's possible to charge the battery (5kW here) and the EV (7.2kW here) at the same time so both will be fully charged and the battery will have more than enough power to cook the full English.

The problem described is that if the battery isn't being charged while the EV is calling for a charge then the battery will discharge into the EV. The trick is to stop that happening. One way is to charge the battery at the same time as the EV, Home Assistant offers other options.

I think you're probably describing a Sunsynk inverter & battery installation. There's a Facebook group for Sunsynk inverter owners which might be a useful source of information in resolving your problem. As long as you have single means of turning off power (isolation) from the meter to your premises (say with a 100A Wylex DP switch) I can't see a problem in what you're proposing although it might be preferable to combine the inverter mains connection and household circuit into one larger consumer unit. Setting up the timers deciding what gets charged and when in the Sunsynk is reputedly tricky but it's a topic which regularly gets discussed and I'm sure one of their gurus will oblige

A bigger better consumer unit would solve a lot of problems but I’m not gonna go there. ;-)

I could set timers every time I charge but that’s a faff. Seems simpler just to make the EV draw “invisible” to the inverter.

Tim

IANAElectrician, but I can't see why not. If this is all post-meter (I assume it must be), and the Henley block is rated for 100A (or whatever your supply is), then having a split supply like that seems ok. There will be a bit of additional resistance from each Henley block which I'm sure it's possible to calculate, but assuming that voltage drop / heating is ok then it seems fine.

Do you have a post-meter isolator? If not you could fit a 4 pole isolator:

Theo

I still fail to see how adding more junctions to the wiring can change whether the inverter 'sees' the EV. That was why I made my original comment. To actually change what 'sees' what you'll have to add some switching or, maybe, move some connections from one side of an existing switch to the other.

Sadly we don’t have an isolator and things are already rather busy with three consumer units etc. I’m not sure there’s room to fit one now without major rejigging. Must have a closer look.

We haven’t paid for our installation yet so it may be possible to get the sparky back to fit another Henley block and/or an isolator if there’s room.

Tim

Simple. The inverter “sees” demand for power by using a CT clamp on the cable that currently supplies all three consumer units.

By splitting off the supply to the EV charger CU after the meter but

No switches involved, just changing the position of the CT clamp and wiring.

Tim

There is a switch, the inverter on/off switch which is controlled by the current detecting clamp. You're doing what I meant by "move some connections from one side of an existing switch to the other".

Maybe his best bet is to have breakfast early during the cheap rate from the grid. I think he just wants to not allow current back out of his battery to his ev, but as you observe, the power has to come from somewhere, and if its not the battery then its the grid and only he can tell which is the cheapest. The problem is that to recharge the battery, either the ev or the other battery, he has to do it outside the cheap rate no matter what unless there is an accelerated charging mode its intelligent to use during the cheap rate. Brian

The inverter is either powering the car battery or it's powering your breakfast toast etc. It is thus being switched from powering one or the other.

The load is not being switched, it's pumping energy into the system it's connected to. That connection includes the car, the toaster, the rest of the world via the grid - it doesn't care, all those loads are wired in parallel, so any time it runs it powers all of them. Some of that power will be consumed by the toaster or the car - what flows past the meter counts as 'export'.

The switching happens when the inverter senses the current taken by the 'house' and decides to throttle back its output if the 'house' isn't taking enough, because export is a worse deal than saving the energy to use later. By moving the EV from inside the 'house' to the 'grid' side of the current transformer, the inverter will only power the EV when it decides to export to the grid. Aside from metering, from the inverter's point of view the EV could be on somebody else's charger down the street - it's all the same to the it.

Theo

It’s not being “switched” to anything. When the inverter is outputting power it has no control at all where that power goes. What’s changing is the ability of the inverter to detect the draw from the EV.

Clearly you’re just being obtuse.

Tim

" The load is not being switched,....", "The switching happens when ....", I rest my case! :-)

The load is not being switched, the *generation* is being switched. The control loop has a sensor (the current transformer) and a decision to turn the generation on and off.

Of course loads like the toaster and the car come and go, that's what loads do. They are not being controlled in any way by this circuit.

Theo

I didn't say anything about what was being switched, I just said

Admittedly I think we're arguing semantics rather than anything useful now. I don't think we really disagree about what's needed/happening.