Expanding Enphase system to include Solar Batteries
Lately, we’ve had quite a few enquiries about expanding micro-inverter system with batteries so much so that i’ve put those emails into a blog to save time in the future. It’s available on the Sunoxi website and also below.For simplicity the below examples are single phase connections.
Power & Water Corporation PV Sizing Rules
The first consideration is Power Water Corporation’s sizing rules.
A single phase property can have 10KVA of inverter capacity, 5KVA being of hybrid or battery management capability. PWC permits you to have 5kW of micro inverters. These can be made up with the many combinations of enphase products that have been released over the years.
Some examples below. Bare in mind the individual Enphase microinverter AC output is measured in VA.
Enphase IQ8HC
VA of 384 Watts = 13 *384 = 4.992kW couple these with 440 watt solar panels and you have a 13*440 = 5.72kW PV system.
See IQ8 Series Micro-inverters (Enphase site)
Enphase IQ7A
VA of 366 Watts = 14 *366 = 5.124kW couple these with 390 watt solar panels and you have a 14 * 370 = 5.40kW PV system.
IQ7A Series (Enphase site)
Enphase IQ7+
VA of 295 Watts = 17 *295 = 5.015kW couple these with 370 watt solar panels and you have a 17 * 390 = 6.290kW PV system.
IQ7+ Micro-inverters (Enphase site)
Enphase S270
VA of 270 Watts = 19 *270 = 5.130kW couple these with 300 watt solar panels and you have a 19 * 300 = 5.700kW PV system.
S270 Microinverters (Enphase website)
Enphase S230
VA of 230 Watts = 22 *230 = 5.06kW couple these with 280 watt solar panels and you have a 22 * 280 = 6.160kW PV system.
S230 Microinverters (Enphase site)
Adding a Solar Battery
10kW Sonnen
The problem arises when you want to add a battery. The 2 solar battery configurations are DC coupled and AC coupled (for more information on AC or DC coupling read this page at MC Electrical).
Generally speaking, an AC coupled battery cannot take more solar panels. The internal inverter (typically 5KVA) will convert the battery DC to issuable AC with no connection to the existing PV system.
Examples of AC couple batteries are;
- Telsa PW2
- Alpha ESS
- Enphase
- Sonnenbatterie
With this in mind I wouldn’t use up your 2nd available 5KVA on a system which can’t add more solar panels as this would leave you short on the cheap energy needed to charge the battery or other future home consumption.
A common fault once a AC battery has been added is the battery not making its full charge (ie. topping out at 80%). This is often down to there not being enough Solar capacity on the roof to supply both the household load, plus charge the battery. Setting changes can be made to charge the battery from the grid however this un-does the intended work of the solar system in providing savings from expensive grid bought electricity.
This is the reason why we prefer DC coupled batteries.
DC Coupling
DC coupling a solar battery only requires power conversion once (rather than three times). It uses DC power from the solar panels to charge the battery. It then converts the DC power from the battery back to AC power to be used by the home.
Both steps normally happen with what is commonly called a “hybrid inverter”.
Hybrid Inverter
A hybrid inverter is simply a battery charger, and a solar inverter put together in one box. The battery charger must communicate with the battery to charge and discharge the solar battery at the right rate.
DC coupled battery systems are certainly my preference and more specifically the Fronius Gen24 inverter series coupled with BYD battery.
DC Coupling Options
Fronius Gen24 / BYD Combination
This Fronius Gen24/BYD combination is a premium option available to the market. The inverter allows for expansion of the PV system to accommodate more than enough of the average household average consumption plus charging a solar battery and, should the need arise, for the charging of an EV(electric vehicle).
The BYD battery is also expandable with a Gen24 inverter able to take up to 22kWh of battery capacity. Each block of BYD battery is 2.76kWh meaning you can start with 11 or 13kWh and add as you require.
Configurations
Enphase 5KVA + Fronius Gen24 (hybrid)
5KVA = 10kVA (6.6kW of enphase PV + 7.5kW of PV onto Fronius Gen 24 and 11-22kWh of BYD Battery)
Goodwe / BYD combo
Goodwe is a Chinese inverter manufacturer who makes single and three phase inverters from 2kW to 100kW in their range. Their products are mid-range budget options. You can pair their inverter with a premium BYD battery.
Configurations
Enphase 5KVA + Goodwe (hybrid)
5KVA = 10kVA (6.6kW of enphase PV + 6.6kW of PV onto Goodwe and 11-22kWh of BYD Battery)
Sungrow / Sungrow
Sungrow is also a Chinese inverter manufacturer and considered the best of the Chinese products. They’re are also the second most installed inverter in Australia.
Their Inverter battery pairing is also proving popular.
Sunoxi is not currently offering these and has not installed these products so wevare unable to comment on their ease of install and functionality.
Configurations
Enphase 5KVA + Sungrow (hybrid)
5KVA = 10kVA (6.6kW of enphase PV + 6.6kW of PV onto Sungrow and 11-22kWh of BYD Battery)
In Conclusion
The above configurations are examples. The PV connected to the gen24 could certainly be scaled down to accommodate available roof space, consumption profile or budget.
The total capacity of the PV system would be required to be curtailed to only export to Power Waters grid 5kVA of the inverter capacity. This is not an issue and ensures the battery always makes it back to 100% charge.
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