Using a Zappi V2 and a Mk2pvRouter together?

Using a Zappi V2 and a Mk2pvRouter together?

Hi all.
I have had a Mk2pvRouter installed and working perfectly for over 8 years.
Now I want to add a Zappi V2 ev charge point and have it permanently on the Eco setting where it only uses solar energy.

I am looking at the wiki on multiple diverters here Learn | OpenEnergyMonitor

I am having problems understanding this diagram and how/if it will work with the Zappi V2 as it has an extra CT on the solar feed.
Would it be better to use a non-smart charger perhap or at least one that doesn’t have a solar setting?
Could anyone advise me please.



Looking at the Zappi 2 installation instructions:

Installation of a CT to monitor the Grid connection point is required for ECO modes. Other CTs are optional and can be purchased separately.

Therefore, it would appear that the c.t. on the solar infeed is only there to provide information to feed the display.

Thanks I hadn’t noticed that! I wonder though what the other ct’s would be for?
My other option would be to build the open the EmonEVSE kit as that’s got solar diversion built in as well. Is there someone on here that I could contact and ask them for advice do you know?



There’s quite a lot written here about Emon EVSE - but if you want the excess PV to be split between the two, you’ve got roughly the same problem whichever you use - decide which has priority, and how to share, bearing in mind that (from what I’ve read) the EV won’t like being switched on and off.

I think Glyn is the EV expert. if you can’t find what you need from searching the forum.

Thanks I have sent a private message to Glynn :grin: Not heard back yet :slightly_frowning_face:

I have an Open ESVE and a commercial solar diverter (not the Mk2 version) and they work “fine” together. As long as the diverter’s export threshold is increased to say 100W it does not upset the ESVE or my battery storage. Priority is gained by the diverter not kicking in till after something else has grabbed that 100W. Basically I have it wired according to the last diagram here Learn | OpenEnergyMonitor with the battery storage having a 3rd export CT with a back to front extra immersion wire as per the last diagram. It is not perfect and the export and immersion may not be quite as well controlled as in pre EV days. But perfectly adequate.

As I don’t have the emons system to measure currents (the diverter provides these) the house battery and EVSE need a separate microcontroller to tell the battery and the EVSE what to do. But I see no reason that a emons, ESVE and diverter config would not work although can’t be sure as don’t own them all.

Bear in in mind that both the car and house battery change their current quite slowly whereas the diverter (if it’s a decent design) is fast acting. So there will be short periods when the immersion grabs the export before the car/house ramps up to their powers. And, because the power reporting is only averaged over a minute, odd figures like negative house loads may be briefly reported, but it’s not a real negative.

Also due to the extra back to front wire through one CT some power levels reported by the battery may not be correct even if the export is controlled well, as immersion power is subtracted off the export.

1 Like

Thankyou! That’s very interesting.
As I understand it The EV Charger doesn’t kick in until there is at least 1.2kW export ?
so just leaving without assigning priority.
The Mk2pvrouter seems to start working on tiny amounts of export so I think it will kick in well before the Charger anyway. The charger will wait for the export to get over 1.2kW before trying to grab any spare Export current so what will happen then I just don’t know.

Assigning priority to the Zappi.
If I run the output to the tank through the Zappi grid CT then I would think that the Mk2 will continue to have priority up until the solar production tops 3kW ? or 4.2kW? yes 4.2KWbecause the immersion heater will take 3kW and the EV needs at least 1,2kW .
Or when the demand for hot water is satisfied.
Does that sound right to you ?

If I try to give the EV charger priority I’m not sure what will happen will I be wasting any power up to 1.2kW ?
Or :smiley:
will the MK2 nick anything up to 1.2kW then if the EV Charger kicks in will it then rob all of the power to the mk2 ? : My head hurts :slightly_frowning_face:

TBH: I’m not sure I have got my head around that properly?

Also I’m not sure at the moment whether I want to give priority to the Hot Water or the EV?

I do have an emonTx3 reporting my Solar Production, Diverted Power though the Mk2 and Grid Flow. from which I can calculate My actual imports and exports as well. I think I have another spare input into the emonTx so I can possibly use that for the EV charger.
I will have to look at the software to do that though :slightly_frowning_face:

1 Like

It does. It requires zero “export bias” and reacts on the second mains cycle following a change in the grid power flow.

I know the feeling. The trick is to recognise what each “controller” sees as its “priority load”. In the simplest case - just the Mk2 or just the [name your brand] - it’s the house and all the other appliances.

If you now add a second controller downstream of where the first one measures the current, that too becomes part of the priority load.

If you can’t physically get the priorities right, this is when you must take a load backwards through the c.t. so that the load current is cancelled inside the c.t; so the load is effectively upstream of the controller.

Not sure it’s exactly like that but come what may the diverter will use the 1.2kW and not waste it. But if you don’t set the priority there is a danger that the immersion takes the 3kW rather than the car. So on mine the car has priority over both the diverter and house battery. But because the car current changes slowly the battery, for short periods, is often part charging the car. Until the car drops enough to match the export.

If you have gas heating for your water it’s usually best to let the car have the electricity and use gas for the water as its cheaper (ignoring any green arguments). But this is not always true if you have very cheap overnight electricity, like Octopus Go, or in the summer where some gas boilers are not that efficient at operating for short periods to heat water.

By the way how fast does the Zappi and the Open ESVE (on its standard software) ramp up/down their output current? On my Open ESVE I have set my bespoke software at a 1 amp step per minute. But a Leaf can accept a lot faster than that I believe, maybe any level of change every 1 or 10 seconds. As long as you don’t turn it on and off completely (below 6A) too often the Leaf is happy. I have set 10 minutes as a minimum on and off time.

My brain hurts too but I suspect that if I did not have the house battery as well as the car I would not need the 100W threshold on the diverter. The house battery threshold is about 30 W so the combined system it’s not “wasting” the full 100W export.

Or has anyone tried cascading three systems with 2 of them having back fed wires from other ones? That might work for me although there is a limit to how many CTs and wires one can squeeze inside a consumer unit or string around the house!

Just to let everyone know for now and maybe someone in the future.
I got mk2 working well with the Zappi :slight_smile:
How did I do it?
Well after I actually got the Zappi I realised that I only needed to switch the Hotwater on/off
As the Mk2pvRouter always took precedence and the Zappi would not kick in until I had a surplus Solar Production Of 1.4Kw.
If the HotWater was on and needing the Power then the Zappi won’t start until I had 3kw for the H/w and 1.4Kw for the Zappi.
So I rigged a simple relay that cut the internal trigger to The Mk2 (with some advice from Robin Emley who as always was very helpful !) . That was the only hardware I need to make.

I then wrote a Program with which I could prioritise either the Hot Water or the Zappi.
Giving priority to the Hotwater was simple as with the relay in it’s resting position that’s what happened .
So I just needed to find out the HotWater temperature and switch to the Zappi when over my set limit.
Giving priority to the Zappi was a bit harder as I didn’t want to waste any energy below 1.4Kw.
so as the solar power fluctuates above and below 1.4Kw it switches between the two.
But I also had to take account of the Car reaching 100% full which was a little tricky but I found a way to find out if that happened.
I only got a good chance to test it properly yesterday as the weather had been too good!
100% Sun ! :boom:
Yesterday did go back and forth between sunny and cloudy and it all seems to work fine Thankfully :slight_smile:
So thanks for everyone’s advice