How to Assemble a 15kWh LiFePO4 Battery?

Assembling a lithium battery seems like a difficult task, let alone a 15kWh LiFePO4 battery, a huge power source with 16 314Ah cells inside.

After reading this article, I guarantee you will be able to assemble batteries of any voltage, including a 15kWh LiFePO4 battery.

What Components Does a 15kWh LiFePO4 Battery Include?

Let's first understand what components a 15kWh LiFePO4 battery must include.
The two most important components of a lithium battery are the BMS and the battery cells.

BMS

BMS stands for Battery Management System, a PCB used to manage the entire battery pack and individual cells.  A 15kWh LiFePO4 battery typically uses a 16S 200A BMS. The BMS has the following functions:

• Cell balancing function. Controls the voltage difference between cells within a certain range.
• Cell overvoltage protection during charging.
• Cell undervoltage protection during discharging.
• Battery overcurrent protection during charging.
• Overcurrent protection during discharging.
• High temperature protection.
• Low temperature protection.
• Short circuit protection.
• And other functions.

As shown in the image below, the JK PB2A16S20P BMS is quite popular in Europe.

Battery Cell

The 15kWh LiFePO4 battery will use LiFePO4 prismatic cells, with typical capacities of 280Ah and 314Ah. 16 cells are connected in series to form a 51.2V battery, resulting in a 15kWh battery.
The battery cells mainly provide energy for the battery pack.
EVE MB31 Cells

How to Assemble the 16 Battery Cells?

We will use the Wistek 15kWh DIY box as an example to explain the principle of assembling a 15kWh LiFePO4 battery.
As shown in the image below:

Wistek 15kWh DIY box

Currently, most suppliers on the market provide pre-assembled casings. DIY enthusiasts only need to place the prismatic cells in order and tighten the bolts to complete the assembly.

Step 1:

Identify the total positive terminal or the total negative terminal of the battery cells. (That is, after the battery cells are connected in series, the cell with a voltage of 51.2V is the total positive terminal of the battery pack.)
The total positive terminal of the battery pack will be connected to the circuit breaker interface.
As shown in the figure.

The total negative terminal of the battery pack will be connected to the BMS B-.
As shown in the figure.

Step 2:

Based on the total negative terminal of the battery pack, place the prismatic cells in order.
Adjacent cells in a vertical row are placed in opposite directions:
As shown in the figure.

Step 3:

Place the busbars.
Install in series mode (+-), placing them on top of two battery cells.
As shown in the figure:

Step 4:

Install the signal wires.
The B1 signal wire will be installed on the positive terminal of the cell with a system voltage of 3.2V.
The B2 signal wire will be installed on the positive terminal of the cell with a system voltage of 6.4V.
…
Refer to the BMS installation diagram.

Actual pictures are as follows:

Step 5:

Tighten the flange nuts. We recommend using a torque of 5-6 N.m.

Finally, you will get the following battery pack image:

Lithium Battery Assembly Tips

1. If several cells are connected in parallel inside our battery pack, we can first treat the parallel cells as a whole, and then connect them in series with other wholes.
2. Determine the total negative terminal of the battery pack. It is recommended that the total negative terminal be close to the BMS B- port.
3. The BMS signal wires will be installed on the positive terminals of the battery cells, in the order of the series voltage.
4. Since home energy storage batteries are placed inside a house or a small cabin, the overall size of the battery pack is not very important. For other applications, the size of the battery pack needs to be considered.

Lithium battery assembly belongs to the power system and has certain dangers. Before assembly, please take protective measures and carefully check the assembly manual.

15kWh LiFePO4 battery

Lithium batteries are dangerous goods. During the assembly process, you can clearly understand which steps or details will affect the performance of the entire battery pack. One advantage of self-assembly is that you can clearly understand the materials you use and replace existing materials at any time. DIY 15kWh LiFePO4 batteries are currently very mature in the market, and following the assembly process strictly will likely prevent problems.