DIY a 48V 200Ah Powerwall Battery for a 10kWh Home Solar Energy System

The Powerwall battery 48V 200Ah is the most commonly used specification in our daily lives. It is an integrated battery system that stores your solar energy for backup protection, so when the grid goes down your power stays on. Your system detects outages and automatically recharges with sunlight to keep your appliances running for days. With two or three powerwall batteries, we can get enough electricity from solar power for our daily consumption.

Are you interested in the assembly process of the 48V 200Ah lithium battery? Which materials should we use to build? Please check the following detailed process!

*Note: It is recommended that you learn some basic knowledge about LiFePO4 batteries before assembling the battery pack. Keep safe when you are assembling the battery pack.

Material Used:

• 3.2V 200Ah LiFePO4 battery cells (16 pieces)

There are currently three common shapes of LiFePO4 batteries: cylindrical, prismatic, and pouch. Different shapes of batteries will have a certain impact on performance. At present, the most suitable battery DIY enthusiasts are the prismatic LiFePO4 batteries, which are very suitable for both performance and operational difficulty. 

We recommend you purchase the Grade A battery with a high quality and reliable warranty.

• BMS (Battery Manage System, 1 piece)
• Connectors (About 16 pieces)
• Others: EVA cotton, screws, ribbon cables, plastic pipes, etc.

Tool Used:

• Spot Welder
• Spot Welding Pen
• Soldering Iron
• Wire Cutter
• Wire Stripper
• Multimeter

Assembly Methods: 16 Series And 1 Parallel

• Series(S): The way of connecting the positive and negative electrodes of two different cells is called a series connection. As a result, the voltage of the battery pack will increase while the capacity remains the same.
• Parallel(P): where the positive and positive electrodes of two different cells are connected in parallel. The result is that the capacity of the battery pack increases while the voltage remains the same.

EVA cotton can protect our LiFePO4 battery cells, which are shockproof, fireproof, and insulated. Cut two EVA cotton into suitable sizes and tape them on the battery shell.

Next, we can install the port board on the side. After installing the port board, we can put the battery cells inside.

• First, we should check the voltage of each battery to ensure consistency.
• Next, we divide the battery cells into two groups and place them in order.(Each battery pack is 24V)
• Then, we should install the signal acquisition wires in sequence.

If we want a 48V powerwall battery, we can connect two 24V battery packs into series to increase the voltage. Connect the negative terminal of one battery to the postive terminal of another.

If we want a 48V powerwall battery, we can connect two 24V battery packs into series to increase the voltage. Connect the negative terminal of one battery to the postive terminal of another.

Put the epoxy resin board insulation board between the battery packs. The epoxy board is suitable for the protection and bonding of the LiFePO4 battery.

(EVA cotton can be shockproof, fireproof, and insulated)

A BMS is a really important safety feature to add to a lithium battery. Not only will it make your battery safer by protecting your cells from over and under-discharging, but it will also make the entire charging process much simpler.

(Attention: The wrong sequence may cause BMS to burn out)

Battery monitor, indicating the state of charge percentage and more data. We can install it to the cap.

This is the final step of the assembly process. After connecting the monitor to the BMS, the battery is ready for working.

Through the test, we can check that the charging value is normal and that the battery is abnormal during the charging process. We need to pay attention to the battery charging time and charging current.

The discharge test of the battery is beneficial to the battery cycle life and discharge performance evaluation. We can use a professional device(Such as a Programmable DC Electronic Load) to check whether the battery works well or not during the discharging process, which can protect our battery and devices for further daily use.

When testing, there are three factors we need to pay attention to the port voltage of the battery, the resistance of the wire between the battery and the electronic load, and the temperature of the battery.

To test if it can communicate well with the inverters. In the whole household solar energy storage system, the inverter can change the direct current into an alternating current. The battery should be compatible with the inverters, then we can make full use of the inverters, such as reading information from the inverter’s screen.