Sunday, November 23, 2014

Enphase AC Battery Technical Details - What's in the box & How does itwork ?

Enphase announced "a revolution" in the Energy Storage world with its new AC Battery coming mid 2015, a very exciting announcement ...

But what's in it exactly ? Let's take a look at the spec sheet provided by Enphase and try to identify its components


Specs tell us:

- Capacity: 1.2kWh  of storage in LiFePO4 batteries
- Power: 275 / 550 W
- Weight: 40lbs

That's not much, but enough to start guessing; I think :

Through GreenTech Media, Enphase unveiled their LiFePO4 cells source: A Japanese maker which should be actually cheaper than the Chinese (!) and have been providing residential storage systems (UPS): Eliiy Power Co., Ltd

Japanese Eliiy Power 50Ah LiFePO4 cell

- Capacity: the Battery pack could be composed of 7 50Ah LiFePO4 cells wired in series because 7 x 50Ah x 3.32V = 1,162Wh, which can be considered 1.2kWh, and would give a pack voltage of 7 x 3.32 = 23.24V in the range of the Enphase M250 operating voltage below

- New S275 Micro Inverter : This New Special Bi-Directional Grid Tie Inverter, Enphase's 5th generation inverter, is capable of 25W more at 275W; Here it will be charging (from AC) and discharging (into AC) the pack at 275W and this 550W probably means that 2 S275 inverters could be running in one AC Battery units to double power ouput (?)

- Weight: The rather small unit is light enough to be mounted on any wall, since it is actually lighter than some existing inverters and this could be more important than you think because people do not want to waste space in their garage or basement as seen already with Tesla / SolarCity backup only storage systems installed in California (even if this could be mounted anywhere in the house or apartment)

The AC Battery can be added any existing Solar installation, not only Enphase based ones of course; That means that the Bi-Directional Inverter is using AC only, and from what we can see on the drawing below, the Enphase Storage Solution would require Load Controllers (on the every outlet ...) like seen in the SMA Smart Manager Solution

The AC Battery units will communicate with the Enphase Energy Management System (EMS) Control called Enphase Envoy-S using power line (PLC), like it is with the existing M* Grid Tie Inverters of the brand, via their Engage AC Cables, but we also see a WiFi sign near the Load Controllers meaning they will use this to report appliances Power Use to the EMS through a new Envoy Communication Gateway (the Envoy-S that is)

This Envoy-S would know how much Power is in use at home, how much is Generated by the PV array, calculate the difference and tell the AC Battery to Charge or Discharge, to keep the Home Net Usage equal or close to 0W, by Storing surplus PV Power or Using Power from the AC Battery units, to help the PV array power appliances at home during the day and at night when the sun is down
I also think it will be capable of powering on and off these AC outlets through WiFi, triggering loads when surplus PV Power can be used directly by appliances instead of being stored in the AC Battery units

Simply mounted on the wall, these AC Battery units can be added one by one and provide more Storage Capacity and also more Power Output to cover your Home loads, in the end more savings because lower Energy bills from your utility company :)

We do not know the retail price of one unit yet, but I guess it could be around 1,000 USD (?), based on the price of the cells and existing Enphase inverters

For Report, Follow up and Analysis, the Enphase Enlighten Portal will be used, like it is already for a regular Enphase Micro Inverter install; You will be able to see how much Power is beeing stored into each AC Battery unit, how much is drawn from it, its State of Charge and all kinds of interesting graphs from any smartphone, tablet or PC, which is pretty cool :)

So, I think Enphase will indeed deliver a great solution, because it will be scalable, able to integrate to any existing PV install, using a very efficient proven inverter to Charge and Discharge the BAttery Pack, and safe because based on the LiFePO4 Lithium-ion chemistry

I guess it should be a hit !!


  1. It sounds excellent, but the most important specification - the price - is missing...

  2. Yes it does, I guess it could be between 1,000 and 2,000 USD

  3. Since this unit has an energy capacity of 1.2kWh, to be competitive in the market, the pricing should be around USD650 for the battery and inverter.

    For existing customers, Enphase should offer to replace the existing Envoy with Envoy-S for a discounted price.

    For new customers, the Envoy-S and other accessories needed for the battery should be processed around USD250.

    1. We got the pricing last week for Australia: 990 USD per unit
      For more info check out my Facebook Page, link in the upper left corner

  4. AC Battery ??? Wow, did not know that existed !!!

  5. Yes, it's the name Enphase Energy gave to their Energy Storage System

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