A very common question is "how do I set up my myenergi devices so that they work with a battery?"
Although we can't control a third party battery directly, the myenergi devices have been designed so that they "play nicely" with a battery if one is fitted. As the battery and the myenergi devices are both trying to control the power flowing to / from the grid they can fight each other, leading to unexpected results.
The exact answer depends on what sort of battery has been fitted:
- a standalone battery that is completely separate from a PV panel or other renewable generation
- a "hybrid" battery where the battery and the PV panels both feed into a single "inverter"
In both cases, most customers want to avoid emptying their battery into their EV or hot water when the myenergi devices should be working from any spare PV (or other) generation that this available.
Please note - if zappi or eddi are "boosting", or zappi is FAST mode then power will always be taken from your battery, unless the battery is turned off.
The simplest setting
The simplest way to stop your eddi or zappi draining the battery is to set an "Export Margin".
This means that the myenergi devices will not start to divert power until they measure power being exported that exceeds this level. The battery then has a chance to control first, taking the surplus generation.
There is a small drawback in this approach as, once the battery is full, you will see a small amount of power being exported to the grid.
To set an export margin, the menu is
- Zappi: Settings - Advanced - Supply Grid - Network - Export Margin
- Eddi: Setting - Advanced - Supply Grid - Export Margin
A value of 50W or 100W should be suitable.
If you have more than one myenergi device this setting needs to be set on the "master" device
Note: If you have the Export Margin set then, on zappi, the "Minimum Green Level" or "MGL" needs to be set at 100%.
With a standalone battery, you have the option to install an extra current transformer (CT) on the wire from the battery to your consumer unit. With this CT, your myenergi devices can measure the power flowing to / from the battery and then ensure that the zappi / eddi does not take power from the battery when they should be using any surplus renewable generation.
The CT will normally need to be installed by an electrician and should be connected back to your zappi / eddi - either connected directly or via a harvi wireless transmitter. If needed, extra CT's can be bought through the myenergi website at myenergi.com.
Once the battery CT has been connected, the following needs to be set in the zappi/eddi
- Set the CT type to "battery"
- Tell the zappi / eddi to "avoid draining" the battery. The menu is
- Zappi: Settings - Advanced - Supply Grid - Network - Battery
- Eddi: Settings - Advanced - Supply Grid - Battery
If you have more than one myenergi device the battery setting needs to be set on the "master" device
When you have a battery CT fitted, you will also be able to see the live battery power flows in the myenergi app.
Hybrid Battery and PV Inverter
With a hybrid battery system it's not possible for your myenergi devices to work out whether the power is coming from the PV panels or the hybrid battery. In this case the only option is to set the "Export Margin" (see Hybrid PV and Battery - How to stop your myenergi devices draining the battery in ECO+)
If you decide to fit a CT on the output from the hybrid inverter then you can still monitor the live power flows from the inverter in the myenergi app. The CT type should be set to "Generation + Battery"
Depending on where the battery and myenergi devices are connected in your electrical system it may be possible to wire them so that they work better together. This article provides examples from two myenergi customers: Hybrid Battery Installation - Alternative Connection Arrangements
Shouldn't the article also mention that the export margin and avoid drain only work with ECO+ with MGL100%?!
What about a basic timer function so we can set the charger to only charge at night when we know our battery is not discharging? All modes I set my unit to seem to use my house battery even if a schedule is set!
[Ed: There's the Scheduled Boost in eddi and zappi that do this - turning on the output at a defined time. However the battery also needs to be "off" or set to charge during the same time period, otherwise the battery will always be drained]
I previously had my Zappi (in my garage, separated from main house and Consumer Unit) and my Hybrid inverter (also installed in garage) wired separately to the mains/meter board, and both worked independently, splendid. But for various reasons I had to re-wire, and one heavy mains cable now takes power from the CU to both the Zappi and the Hybrid Inverter. So now I have the problem of my 10kWh Li batteries discharging whenever I want to charge the car.
One simple solution is to disconnect the Hybrid inverter's CT from the main power line in to the CU, the Hybrid Inverter then does not 'see' all the energy that the Zappi is using, and so does not attempt to compensate by discharging the battery to get that power. I will probably install a simple 'on off' switch on the cover of the box in which the CT is installed.
Before I read this article. On an ac coupled battery and PV system I set the eddi export to 500w because I had noticed the battery drainage. This adjustment was not successful. When the eddi starts increasing its water charge rate with exported PV generation, and the PV output subsequently drops off, it does not seem to differentiate between PV exported output and energy from the ac coupled battery. This results in an increasing drain on the battery as the PV output drops off. This is taken from direct observation of Kw flow within my ac coupled battery and PV system.
[Ed: This will be a problem with the installation / location of the CT's. Please try posting a message on the myenergi forum (https://myenergi.info) or sending and email to email@example.com]
Why does a third party battery have no settings yet Zappi logs flow to and from the battery. Solar panels, grid and home have no settings yet they are all logged for the myenergi app?
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