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Setting your SMA – SUNNY ISLAND Inverter to work with BigBattery 48 Volt LiFePO4 Batteries

BigBattery 48V LiFePO4

1.0 – Introduction

This Integration Guide covers the recommended set up and configuration of SMA equipment for optimizing performance with BigBattery 48V LiFePO4 batteries. More information on BigBattery products can be found on our website: www.BigBattery.com. SMA offers many products which are too numerous to be covered here. BigBattery offers energy storage battery solutions for SMA Inverters/Chargers. If the SMA 48V product you are looking for is not covered in this Integration Guide, the parameters listed here should be used as a general guide. The specific SMA products covered in this guide include, but are not limited to:
SMA Sunny Island
    • SI 4548-US
    • SI 4548-US

2.0 – Inverter Settings

Based on tests and evaluations of BigBattery 48V LiFePO4 batteries with SMA’s equipment, the following parameters (refer to tables below) have been established.

More information on SMA Sunny Island series inverter products can be found on their website:
The Sunny Island inverter manual can be found here:

3.0 – Battery Bank Sizing

A properly sized BigBattery battery bank should be at least double (2x) the kW rating of the inverter(s) and have a C/2 rating greater than the maximum charge controller rating. Depending on the specifications of the equipment used in the system, sizing the BigBattery battery bank based on these two criteria may yield different results. Therefore, the best practice is to calculate the BigBattery battery bank based on both criteria and use the greater of the two results as the minimum quantity. We can compare these two calculation methods assuming the nomenclature below:

    • Battery rated continuous power = BatkWh (typically @ C/2)
    • Inverter power full load = InvkW
    • Maximum battery charge current = IBatChrgMax
    • PV charge controller maximum = IPVChrgMax
    • Recommended minimum number of batteries = B#

Discharge equation: B#Inv ≥ InvkW / BatkWh
Charge equation: B#PV ≥ IPVChrgMax / IBatChrgMax

3.1 – Discharge Calculation: Inverter Power Bank Sizing

To optimize the BigBattery battery bank and protect against over-discharge (voiding the battery Warranty), the BigBattery battery bank should be sized at least double (2x) the kW rating of the inverter.
Discharge Example A: B#Inv ≥ InvkW / BatkWh
    • Inverter is rated at 6 kW
    • BigBattery 48V Rhino 14kWh battery is rated at 14kWh, therefore the C/2 load rating is 7 kW B#Inv ≥ 6 kW / 7 kW = 0.86
Discharge Example B: B#Inv ≥ InvkW / BatkWh
    • Inverter is rated at 6 kW
    • BigBattery 48V HSKY 5.3kWh battery is rated at 5.3kWh, therefore the C/2 load rating is 2.65 kW B#Inv ≥ 6 kW / 2.65 kW = 2.26
In example A, a properly sized BigBattery battery bank based on maximum discharge of the inverter would have a minimum of 1 battery. In example B, a properly sized BigBattery battery bank based on maximum discharge of the inverter would have a minimum of 3 batteries. This ensures no greater than C/2 battery load. If the BigBattery battery bank has fewer batteries than calculated, special care must be taken with the inverter settings to limit the load below the specified rating of the BigBattery battery. These settings are described in the following sections of this Integration Guide.

3.2 – Charge Calculation: Charge Controller Power Sizing

To optimize solar harvesting, a properly sized BigBattery battery bank should be able to accept the maximum PV charge current. To determine the minimum number of BigBattery batteries required to optimize PV, divide the output of the charge controller(s) by the “max continuous charge current” per BigBattery battery. Be sure to verify the “max continuous charge current” for the BigBattery battery model that you’re using, because it may differ from C/2, depending on the model.
Charge Example A: B#PV ≥ IPVChrgMax / IBatChrgMax
    • Max continuous charge current for our 48V Rhino 14kWh = 175A
    • PV charge controller max = 80A – B#PV ≥ 80A/175A = 0.46
Charge Example B: B#PV ≥ IPVChrgMax / IBatChrgMax
    • Max continuous charge current for our 48V HSKY 5.3kWh = 90A
    • PV charge controller max = 80A – B#PV ≥ 80A/90A = 0.89

In both examples A and B, a properly sized BigBattery battery bank based on available PV charge would have a minimum of 1 battery. This maximizes the use of available PV while ensuring the BigBattery batteries are never stressed by overcharging. If the BigBattery battery bank has fewer batteries than calculated, special care must be taken with the inverter settings to limit the charge rate below the specified rating of the BigBattery battery. These settings are described in the following sections of this Integration Guide.

In summary: When comparing the same system using these two calculations for sizing the BigBattery battery bank, the minimum number of batteries should be the greater of the two results (Discharge Calculation & Charge Calculation).

Using the greater of the two results for both example systems A and B:
    • System A would need 1 Rhino battery in that system.
    • System B would need 3 HSKY batteries in that system.

3.3 – SMA Inverter/Charger Battery Bank Sizing Examples

The two examples below apply to the two SMA inverters identified below. Calculations are for the minimum recommended number of BigBattery 14kWh-48V batteries. More batteries should be added to increase BigBattery battery bank capacity.

3.3.1 – SI 4548-US Battery Bank Sizing
The SI 4548-US has a power rating of 4,500 Watts and includes a battery charger with 100 Amps DC of maximum battery charging current.
Discharge Example A:
    • Inverter is rated at 4.5 kW
    • 48V Rhino 14kWh battery is rated at 14kWh, therefore the C/2 load rating is 7 kW
B#Inv ≥ 4.5kW/7kW = 0.64 – Use ≥ 1 48V Rhino 14kWh battery
Discharge Example A:
    • Inverter is rated at 4.5 kW
    • 48V HSKY 5.3kWh battery is rated at 5.3kWh, therefore the C/2 load rating is 2.65 kW
B#Inv ≥ 4.5 kW/2.65 kW = 1.70 – Use ≥ 2 48V HSKY 5.3kWh batteries
Charge Example A:
    • Max battery charging current = 100A
    • Max continuous charge current for 48V Rhino 14kWh = 175A
B#PV ≥ 100A/175A = 0.57 – Use ≥ 1 – 48V Rhino 14kWh battery
Charge Example B:
    • Max battery charging current = 100A
    • Max continuous charge current for 48V HSKY 5.3kWh = 90A
B#PV ≥ 100A/90A = 1.11 – Use ≥ 2 – 48V HSKY 5.3kWh batteries

Battery Bank Sizing
The minimum recommended battery bank size is 1 – 48V Rhino 14kWh or 2 – 48V HSKY 5.3kWh batteries. More BigBattery batteries should be added to increase overall battery bank capacity.

3.3.2 – SI 6048-US Battery Bank Sizing

The SI 6048-US has a power rating of 5,750 Watts and includes a battery charger with 130 Amps DC of maximum battery charging current.

Discharge Example A:
    • Inverter is rated at 5.75 kW
    • 48V Rhino 14kWh battery is rated at 14kWh, therefore the C/2 load rating is 7 kW
B#Inv ≥ 5.75kW/7kW = 0.82 – Use ≥ 1 48V Rhino 14kWh battery
Discharge Example A:
    • Inverter is rated at 5.75 kW
    • 48V HSKY 5.3kWh battery is rated at 5.3kWh, therefore the C/2 load rating is 2.65 kW
B#Inv ≥ 5.75 kW/2.65 kW = 2.17 – Use ≥ 3 – 48V HSKY 5.3kWh batteries
Charge Example A:
    • Max battery charging current = 130A
    • Max continuous charge current for 48V Rhino 14kWh = 175A
B#PV ≥ 130A/175A = 0.74 – Use ≥ 1 – 48V Rhino 14kWh battery
Charge Example B:
    • Max battery charging current = 130A
    • Max continuous charge current for 48V HSKY 5.3kWh = 90A
B#PV ≥ 130A/90A = 1.44 – Use ≥ 2 – 48V HSKY 5.3kWh batteries
Battery Bank Sizing
The minimum recommended battery bank size for these examples are:
  • 1 – 48V Rhino 14kWh battery
  • 3 – 48V HSKY 5.3kWh batteries
More batteries can be added (In Parallel) to increase the battery bank’s overall capacity.
  • The batteries do not need to be the same ‘model’ to be connected in parallel.
    • They MUST be the SAME:
      1. CHEMISTRY
      2. CELL CONFIGURATION
      3. VOLTAGE

4.0 – SMA Sunny Island Program Settings for BigBattery Rhino & HSKY

In order to maintain the BigBattery Warranty, it is critical to ensure that the appropriate settings for the desired Warranty are programmed in all of the system components. This section will cover the basic concepts and settings in the SMA Sunny Island equipment. Refer to SMA’s Warranty document regarding Sunny Island Warranty Exclusions, including the “use of battery types not certified for operation with SMA battery inverters”: https://d3g1qce46u5dao.cloudfront.net/supplier_document/com_res_gbed_en_44_warranty.pdf.
Without communication between the BigBattery BMS and the Sunny Island, VRLA settings are used instead. Due to the fact that these settings may need adjustment post commissioning to better match the system’s operational environment, BigBattery highly recommends that installers configure the Sunny Island with the Sunny Webbox* for remote programming capability: http://files.sma.de/dl/4253/SWebBox-BA-US-en-34.pdf. Otherwise, settings adjustments must be made on-site.
*The Sunny Webbox requires an internet connection.

CAUTION: If a firmware update is executed on SMA equipment, ALL the settings must be reverified. The programmed settings shown in the following table must be applied based on desired Warranty/cycle life. The recommended is 80% Depth of Discharge.

4.1 – Inverter/Charger Settings

Table 1.0 – Settings for BigBattery 48V Rhino 14kWh & 48V HSKY 5.3kWh battery w/SMA Sunny Island 48V Inverter/Charger

SUNNY ISLAND  SETTINGS 
Setting > Battery > Property 
221.01 BatTyp VRLA
221.02 BatCpyNom (Ah)276Ah per 48V Rhino 14kWh battery
103Ah per 48V HSKY 5.3kWh battery
221.03 BatVtgNom VRLA 48 V
221.04 BatTmpMax (°C) 49 (Requires coms)
  
Setting > Battery > Charge 80% DoD 90% DoD 100% DoD

222.01 BatChrgCurMax (A)
222.01 BatChrgCurMax (A)

175A per 48V Rhino 14kWh battery 
90A per 48V HSKY 5.3kWh battery

222.02 AptTmBoost (Minutes)  90 min  
222.03 AptTmFul (Hours)  1.5 hr  
222.04 AptTmEqu (Hours) 1.5 hr
222.05 CycTmFul (Days) 30 days
222.06 CycTmEqu (Days)2 & 3 30 days
222.07 ChrgVtgBoost (V)  2.43 V  
222.08 ChrgVtgFul (V)  2.33 V  
222.09 ChrgVtgEqu (V)  2.33 V  
222.10 ChrgVtgFlo 2.27 V
222.11 BatTmpCps (mV/°C) 0 mv/°C
222.12 AutoEquChrgEna2 & 3 Disable
Setting > Battery > Preservation 
223.05 BatPro1Soc 21%  
223.06 BatPro2Soc 20%  
223.07 BatPro3Soc0%
Notes:
    • 1. Per BigBattery – These settings are calculated by multiplying the nominal value per each battery multiplied by the # of BigBattery batteries. For other batteries, refer to the Specification Sheet for the specific model. Refer to Section 3.0 herein for BigBattery bank sizing.
    • 2 & 3. Reduce to 7 days and Enable Automatic Equalization Charge if needed. The Sunny Island remains in the Float Charge phase until the battery bank’s state of charge (SOC) drops below 70%. If the system’s nighttime energy demands do not result in the battery bank’s SOC dropping below 70% overnight (i.e. nighttime demand is low relative to the battery bank’s capacity), then more frequent Equalization charging ensures that the battery bank is topped off periodically.

      • If more frequent Equalization charging is needed, then Enable parameter 222.12 AutoEquChrgEna.

      If nighttime loads are significant enough to reduce the battery’s SOC below 70% overnight, the Sunny Island will automatically initiate a Boost Charge for the battery the following day, and an Equalization Charge is therefore unnecessary.

    •  4. According to the Sunny Island Manual, “the first [battery preservation] level is used to switch the Sunny Island into standby mode at times when the energy is not necessarily required (e.g. at night).
      • You define the start time using parameter ‘223.01 BatPro1TmStr’
      • You define the stop time using parameter ‘223.02 BatPro1TmStp’.”
    • 5. According to the Sunny Island Manual, “the second level of the battery-preservation mode ensures that the Sunny Island is started regularly every two hours only in the time period during which energy supply is expected and that it attempts to charge the battery from the AC side. For PV plants, this is during the day. In this case:
      • You define the start time using the parameter ‘223.03 BatPro2TmStr’
      • You define the stop time using the parameter ‘223.04 BatPro2TmStp’.”
    • 6. According to the Sunny Island Manual, “the third level ensures that the battery is protected from deep discharge and thus protected against damage. In this case, the Sunny Island is switched off completely.”
      • Levels are typically based @ 25°C and may need adjusting at temperature extremes.
      • Always refer to the BigBattery ‘Spec Sheets or Product Manual’ for model specific information.

CAUTION: When the battery quantities change, the capacity & charge/discharge current settings must be reassessed. Failure to do so, may void the Warranty.

5.0 – Specifications & Warranty

See BigBattery48V Rhino – LiFePO4 – 276Ah – 14kWh (SKU FWRHN-48140-G1) Specifications sheet and Product Manual.

See BigBattery 48V HSKY – LiFePO4 – 103Ah – 5.3kWh (SKU FHSKY-48053-G1)Specifications sheet.

See BigBattery’s 10-Year Warranty; Failure to adhere to installation protocol will void Warranty.

6.0 – BigBattery Technical Support

For technical support related to your BigBattery product, please contact us directly at: