Battery Storage Knowledge Bank

MyEnergi Battery System ('libbi')

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MyEnergi libbi

About MyEnergi

 MyEnergi focuses on creating products to help homeowners make the most of their solar, the main ones to date being the Eddi hot water diverter, and Zappi car charger. Many of our customers have installed these alongside solar PV, because they will automatically turn the hot water immersion / car charger on and off to take advantage of excess solar.

In January 2023, MyEnergi is launching the 'libbi' battery storage system; thus the main suite of MyEnergi products will be as follows:System Overview - MyEnergi


You can read about the other products on these links: Eddi hot water diverter,             Zappi car charger.

Overview of MyEnergi battery storage ('libbi')

The full product launch for MyEnergi's storage system - called libbi - is in January 2023, At the time of writing (December 2022), we are therefore missing one or two details.

However we do know that the system is available with:

  • 3.68kW or 5kW AC output power;
  • modular storage capacity: 5kWh, 10kWh, 15kWh or 20kWh.

    Note that the usable capacity for each 5kWh battery module is 4.6kWh, giving a maximum usable battery size of 18.4kWh.

    The battery chemistry is the superior lithium ferro phosphate (LiFePO4) which is now standard for all of our lithium batteries, apart from the Tesla Powerwall which is lithium manganese cobalt (Li-NMC). Lithium ferro phosphate is preferable for two reasons:
  • much longer life expectation for LiFePO4: ~8,000 - 10,000 lifecycles as opposed to more like 4,500 lifecycles for Li-NMC: this in turn leads to a much much lower 'cost per kWh storage slot':  9p per kWh for the libbi versus 16p per kWh for the standard Li-NMC storage battery;
  • reports of child labour being used in Cobalt mining for Li-NMC batteries, which is leading us to seek alternative battery products to offer our customers, other than the Powerwall.

In terms of location, the battery and inverter are IP65 rated and can go inside or out. The controller needs to be indoors,

Use Cases

The libbi is very flexible in that it can be used:

  • with existing solar systems which already have their own inverter (AC coupled storage);
  • with new systems, in which case a separate solar inverter is NOT required and panels will be connected directly to the DC side of the libbi system (DC coupled solar / storage);
  • to add both storage and additional solar panels to an existing solar system; in this case the additional panels can be connected directly to the DC side of the libbi system (AC coupled original system, DC coupled extension system / storage).

    Note that solar panels produce DC electricity and batteries charge and discharge with DC. Therefore it is most efficient if panels are coupled to the DC side of the system.

    Functionality and Monitoring

    The libbi has two main functions:

  • storing excess solar power for use when the solar is insufficient to cover the load;
  • charging from the grid to 'buy cheap', 'use peak'.

    Back-Up / Power cut functionality: Before buying any storage product, it is important to understand functionality in a power cut - does the storage work, and will the solar continue to work?

    The libbi datasheet says that the system offers "Optional Blackout Back Up - Instant energy availability to a dedicated socket or lighting circuit in the event of a power cut. Additional installation costs will apply."

    That's as much as we know as of December 2023, but we will update when we find out more. 

    Monitoring and Management: all MyEnergi products are managed through their APP.


Sample pricing is as follows:

3.68kW power / 5kWh storage: ~  £6500 + VAT.

5kW power / 20kWh storage: ~ £14500 + VAT.

VAT is 0% if you purchase storage with one or more solar panels, and 20% otherwise.

The approximate installed cost of the libbi system runs from £788 + VAT per kWh.

With an expectation of 10,000 lifecycles (i.e. 10,000 storage slots of 1 kWh for each kWh of storage capacity), that equates to a cost of around  7.9  + VAT pence per kWh storage slot. 

With electricity prices currently running at around 23.72 pence per kWh, it is clear that storing excess solar is cheaper than exporting excess to the grid when there is too much solar and then buying back later off the grid when you don't have enough electricity from the solar. 

So a battery investment makes sense as long as there will be sufficient use of the battery overall (i.e. the storage slots purchased upfront actually get used). This comes down to proper sizing.

If you are in our installation area and request a quote from us, we will model the optimal battery based on the output of your solar system, usage and usage profile. You can also use our battery calculator).