Introduction
It is a known issue that charging your EV will typically empty your home battery in doing so – some owners are aware and happy about this, but for others it comes as an unpleasant surprise; for a general discussion of the issue and various remedies see How To Configure a MyEnergi Zappi or Other EV Charge Point With a Home Battery System.
The MyEnergi Zappi, which is the main solar charge point that we offer and install, is one of the few that has built in configuration options to help remedy this issue. We’ll cover the process here for solar charging, and hope it helps new battery owners, for example if you had solar and a Zappi previously installed and have recently added a home battery.
Note the following:
- This method applies to solar charging (Eco and Eco+ modes): if you force the Zappi to fast charge then it will ignore the battery saving setting.
- This method assumes you have a separate AC attached battery: if you have a hybrid then there is no way for the Zappi to know just what the battery is doing (the output will be combined with solar).
Hardware
First of all a CT (current transformer) clamp needs to be added to the Zappi system. There will always be one already installed for reading the grid import and export, and very often there will also be a second one installed for reading the solar generation, so this will typically be a third clamp.
It needs to be fitted around the Line or Neutral cable from the AC battery inverter to the main consumer unit, with the arrow marked on its side pointing towards the consumer unit if on Line, and reversed if on Neutral. The loose end of the wires are connected into the CT3 connections inside the Zappi.
Zappi Configuration
During original installation the grid CT is usually configured as CT1, and if there is a solar CT it would usually be configured as CT2. Here we will configure the battery CT as CT3. The process to set it depends on how the Zappi system is arranged, and particularly whether there are any Harvis (CT extenders) in the system, and here we assume it is physically connected to the Zappi CT3 connectors.
Zappi Main Screen (Image: Tanjent)
From the main screen the menu sequence is as follows (note on the Zappi the Menu key is marked by three horizontal lines and also functions as a Back key, and the Enter key is marked with a ‘+’):
Menu -> Other Settings… -> Advanced -> enter password (default 0000) -> CT Config…
Zappi CT Config Screen (Image: Tanjent)
In this example, one we prepared earlier, we can see the Grid is CT1 and the battery is CT3. In fact the solar generation is set as CT2 but it’s connected via a Harvi so it’s CT2 on the Harvi. It’s not shown here as the Harvi is a separate Myenergi Device and so shows under the Device menus.
To set this up if it hasn’t been done before, on the CT Config… screen select CT3: with the up (^) and down (v) keys, and Enter (+):
Zappi CT3 Config Screen (Image: Tanjent)
Select Type: and then with the up key cycle through the options (None, Grid, Generation Only, Storage Only, Gen & Battery, Monitor) and select AC Battery, Enter. Then back up (Menu key).
With the CT set now correctly we can check the value of what it is monitoring via the CT Config/Readings… menu showing at the bottom of the main CT Config screen:
Zappi CT Config/Readings Screen (Image: Tanjent)
We can see here that CT3 is picking up the battery power correctly, it is discharging at 462W with a power factor around 1. When charging up the power reading is still positive but the power factor value is around -1.
To confirm that the Zappi knows that this value is for battery power we can go to the main System/Readings… menu. Use the Menu button to go back to the main screen, then the sequence is as follows:
Menu -> Readings… -> use the down arrow to get to page 4:
Zappi System/Readings Screen (Image: Tanjent)
Note this is the first point that we have confirmation that the Zappi is seeing this CT reading as a Battery. The value is positive if the battery is discharging and negative if it is charging.
Battery Saving
Next we need to tell the Zappi what to do with the battery reading, so we go into the Network… menu and set the Battery value to Avoid Drain. Note this is a tricky menu to find as its location does not relate to its function (it should really be under the Charge Settings… menu). The menu sequence is as follows:
Menu -> Other Settings… -> Advanced -> enter password (default 0000) -> Supply Grid… -> Network..
Zappi Supply Grid/Network Screen (Image: Tanjent)
Here we need the Battery setting to be Avoid Drain.
To test this solution, set the Zappi to charge an EV when there’s excess solar. Typically the battery will start to empty, then the Zappi spots this and reduces the charge rate down until it (approximately) matches the solar only that’s available, and then the battery (largely) goes back to sleep. Of course, there will be fluctuations in the various power readings as the solar generation changes and the Zappi adjusts its charging rate to compensate.
