The ultimate guide to choose batteries for inverter

Battery for inverter

Thinking of buying a storage battery? You might have heard and be confused: what exactly are AGM batteries, Gel batteries, lithium batteries, lead-acid batteries? What are the differences between them?

This article will revolve around the solar rechargeable batteries that can work with solar energy systems to help you make an accurate decision.

What different types of battery for inverter are there?

Currently, there are mainly two types of battery on the market: lead-acid battery and lithium battery, both of them have their own advantages and disadvantage and can be subdivided into several types of batteries, and here we will introduce the more common batteries in the solar industry.

Lithium battery

Lithium battery is light weight, high energy storage, no pollution, long service life, driven by sustainable development, it will become increasingly popular.

  • LiFePO 4/LFP:

    One of the most popular batteries, whose main features are no harmful elements, low cost, the very best in safety and cycle life up to 6000 times.

    Lithium battery-LiFePO4

  • LiCoO 2:

    The most mature lithium-ion battery with the advantages of high specific capacity, good cycling performance and simple synthesis process. However, the material contains more toxic cobalt elements and is more expensive, making it difficult to ensure safety when making large power batteries.

  • LiNiMnCoO 2/NMC:

    The positive electrode material of NMC combines nickel and manganese, and this material can be balanced and regulated in terms of specific energy, cyclability, safety and cost.

Lead acid battery

Lead acid batteries are mainly composed of positive and negative plates, spacer plates, sulfuric acid electrolyte, battery tank and other components, but they are not designed to be fully discharged all the time (i.e., only 50% of the depth of discharge).

  • Flooded lead acid battery:

    This kind of battery has a cap at the top which can ventilate and block the liquid spill. In the process of use, due to the loss of water evaporation and decomposition, the cap needs to be opened periodically to add distilled water and adjust the electrolyte density, so it is customarily called "open type traction battery".

  • Valve-regulated lead acid battery:

    Valve regulated sealed lead-acid battery, also known as maintenance-free battery, is divided into two types: AGM and GEL battery. The electrolyte inside the battery is in a non-flowing state, and the battery remains gas-tight and liquid-tight during normal use.

  • Tubular battery:

    The technology used in tubular batteries seals the active material in a polyester tube called armor, rather than affixing it to the surface of the cell plate. As a result, there is no peeling or corrosion, ensuring a long battery life.

What is battery for inverter and how does it work in solar system?

Generally speaking, batteries are an indispensable part of a solar power system because they allow us to store power generated by the solar panel in the battery, ensuring that the user has power available when the solar panels and the grid are running low. In summary, the battery plays the following three roles in the solar system:

Store the electricity during the day

Since people's demand for electricity is not high during the day, the power generation time of the PV system is not equal to the load power consumption time. The direct sunlight collected by the solar panel is transformed into DC electricity, part of the electrical energy is converted to AC electricity for load operation by the inverter, and the remaining electrical energy is stored in the battery.

Power appliances at night

The output power of the inverter reaches its highest at noon, but the demand for electricity is not high at that time, while at night is the peak of electricity consumption, the public's demand for electricity rises, the battery releases power to the load.

Stabilize the power of the solar power system

PV input voltage and output voltage of the inverter are not always the same, PV input voltage is affected by radiance and is in a fluctuating state, and the load side is not very stable.

Energy storage battery can be regarded as a power balancing device at this time, when the PV input power is greater than the load power, the inverter dispenses the excess energy to the battery bank for storage, when the electricity generated by the solar panel cannot meet the needs of the load, the inverter diverts the electricity from the battery to the load again.

How to Calculate Battery Size for Inverters

Configure the battery for the inverter mainly considering the following three factors:

1. The output voltage of the lithium battery should be the same as the input voltage of the inverter battery terminal.

2. Configure the battery capacity according to the load charging time.

The battery capacity is calculated according to the load backup time. Therefore, the capacity of the battery should have enough power to meet the maximum power supply of the inverter.

Let assume your inverter input DC voltage is 12 volts only then you may require one or more batteries connected parallel to control the loads to the device.

Assuming a maximum utilization of 50%, The 3000-watt inverter with a 20 amp battery will produce 12 volt DC to 110 Volt AC. As a thumb rule, the flooded cell batteries will require double the charge that is 6000 watts.

3. The maximum battery discharge voltage should match the inverter's rated supply voltage.

Let’s say you want to run a 4000 watts inverter which is a 4kW energy supply. It will draw a good amount of energy in the amps at 12 volts and 24 volts.

Presumably, you will connect the inverter to the 48 volts. Thus, you may require 4 x 12-volt batteries in the series of connections to power the 4000 watts of the inverter.