Installing Solar Batteries to an Inverter: A Technical Guide

Introduction

Solar batteries have become increasingly popular as homeowners seek to maximise their energy independence and reduce reliance on the grid. This guide will provide a technical overview of installing solar batteries to an inverter, including essential considerations, safety precautions, and component sizing.

Understanding the Components

• Solar Panels: These convert sunlight into direct current (DC) electricity.
• Inverter: This converts DC power from the solar panels into alternating current (AC) power compatible with household appliances.
• Solar Batteries: These store excess solar energy for use during periods of high demand or grid outages if you have a compatible installation.

Key Considerations for Battery Installation

1. Inverter Compatibility: Ensure your inverter is compatible with battery storage. Some inverters are specifically designed for battery integration, while others may require upgrades or additional components or manual settings.
2. Battery Chemistry: Choose a battery chemistry (e.g., lithium-ion, lead-acid) that suits your needs and budget. Lithium-ion batteries are generally preferred for their high energy density, long lifespan, and low maintenance.
3. Battery Capacity: Determine the appropriate battery capacity based on your energy consumption patterns and desired backup time.
4. Safety Precautions: Adhere to all electrical safety codes and regulations. Always disconnect the system from the grid before working on it.
5. Professional Installation: It is highly recommended to have a professional installer handle the battery installation to ensure proper wiring, grounding, and safety measures. They can also manually set the inverter and communications settings.

Cable Sizing and Breakers

The size of the cables and breakers required for the battery system depends on the inverter’s power output and the battery’s voltage and current rating. As a general rule, it’s crucial to:

• Use appropriately sized cables: Undersized cables can lead to excessive voltage drop and heat buildup, potentially causing fire hazards.
• Install circuit breakers: These protect the system from overcurrent conditions and short circuits.

Refer to the following table for a general guideline on cable sizing and breaker selection:

• The information provided is Our cables, not all cables are the same!
  Currents vary from inverter to inverter based on the system voltage and power output.

Battery SAFETY

The British Standards Institute (BSI) recently issued new recommendations (PAS 63100:2024) that discourage the installation of solar batteries in lofts.  

• Key Points:
  • Not a ban: This is a recommendation, not a strict regulation.  
  • Safety Focus: The recommendation aims to enhance safety by minimizing fire risks. Lofts can pose challenges like limited ventilation and potential for flammable materials.  
  • Existing Installations: Systems already installed in lofts prior to the March 2024 publication of PAS 63100 are generally not affected.  
• Important Considerations:
  • Safety is paramount: If you’re considering a loft installation, prioritize fire safety measures. Ensure adequate ventilation, fire alarms, and easy access for maintenance and emergency response.
  • Battery temperatures should for LFP be between 10oC and 40oC which lofts may not be most of the time.

Common failure points in solar batteries can be categorised into three main areas:

1. Cell Degradation:
   • Capacity Fade: Over time, the battery’s ability to hold a charge diminishes. This is a natural process, but excessive heat or deep discharges can accelerate it.  
   • Internal Short Circuits: These can occur within individual battery cells, leading to reduced capacity and potential safety hazards.  
   • Maintenance and lack of.
2. System-Related Issues:
   • Overcharging: If the battery is consistently overcharged, it can lead to premature wear and tear, reduced lifespan, and even safety hazards.  
   • Undercharging: Chronic undercharging can lead to sulfation in lead-acid batteries, reducing their capacity and efficiency.  
   • Temperature Extremes: High temperatures can accelerate cell degradation, while extremely low temperatures can reduce battery performance.
   • User error charging and failure to balance cells. 
3. Manufacturing Defects:
   • Faulty Cells or Modules: Occasionally, batteries may have defective cells or modules from the manufacturing process.
   • Poor Connections: Loose or corroded connections within the battery pack or between the battery and the inverter can lead to performance issues and safety risks.  

Signs of Potential Battery Failure:

• Reduced Battery Life: The battery doesn’t hold a charge as long as it used to.
• Slow Charging Times: The battery takes significantly longer to charge than usual.
• Unusual Noises or Smells: Clicking, hissing, or unusual odors coming from the battery could indicate a problem.  
• Physical Damage: Visible signs of damage, such as swelling, cracking, or leaking, warrant immediate attention.  

Preventive Measures:

• Regular Monitoring: Use a battery monitoring system to track performance and identify potential issues early on.  
• Temperature Control: Keep the battery in a cool, well-ventilated area to minimize heat buildup.  
• Proper Charging and Discharging: Avoid deep discharges and overcharging, and follow the manufacturer’s recommended charging and discharging cycles.
• Regular Maintenance: Conduct periodic inspections to check for any signs of damage or corrosion.
• Top up: lead acid battery fluid needs to be maintained.
• Equalise and balance: cells in a battery drift over time and they need to be balanced.

Tools for batteries – From RenewSolar

Batteries are a costly part of solar and management of the battery is essential. While we would like to rely on the hardware, some times its a good idea to add some extra protection.

• Battery Auto Charger: Grid charger that monitors the battery, if the voltage drops it will start charging the battery automatically.
• Discharge Cut off: Protect your battery for over discharge with a automatic disconnect
• Heater: For LFP and other battery systems that should not be charged in the cold.
• Temperature monitor: Battery room temperature monitoring online/phone app.
• Active battery cell balancer: Balance batteries faster, improving battery life and capacity.
• 300 Amp Bus bar: Share the load on quality bus bars.