48V 100Ah Lifepo4 Powerwall Battery Assembly for Household Solar Energy Storage System

With the surging price of electricity, more and more people decide to build a household solar energy storage system. We can build a solar energy storage system with an inverter, several powerwall batteries, and rooftop solar panels. Powerwall gives you the ability to store energy for later use and works with or without solar. 48V 100Ah powerwall battery can meet your 5kWh daily consumption, such as the air-conditioning, hair dryer, coffee machine, etc. You can increase the total capacity by connecting no more than 10 pieces of powerwall batteries in parallel.

Compared with a diesel generator or lead-acid battery, the powerwall battery is lightweight and modern. With 5,000 cycle times, it can work exceeding 8 to 10 years. If you have a chance to DIY a LiFePO4 battery, would you like to have a try?

*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 100Ah 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

EVA cotton can be shockproof, fireproof, and insulated, which can protect the battery cells well.

Laser welding is a process used to join together metals or thermoplastics using a laser beam to form a weld. Welded contact connections between the individual battery cells, for example, have proven to be more reliable, sustainable, and above all cost-effective than bolted contacts or the use of bimetallic busbars.

To connect a group of batteries in series you connect the negative terminal of one battery to the positive terminal of another and so on until all batteries are connected. Connecting the battery packs in series will increase the voltage. In our example, we connect two 25.6V battery packs in series, we will get a 51.2V battery pack.

The epoxy board has a high density, with excellent heat insulation and corrosion resistance. After the cells are assembled, the whole battery pack needs to be fixed with insulating sheets. The reason why the epoxy sheet is selected as the outer casing of the battery pack instead of steel or aluminum is that although these materials are beautiful and sturdy, it is hard to guarantee a good combination of the battery cells. If handled improperly, the battery cells might probably be scratched, which will cause battery leakage and safety accidents. Therefore, the epoxy sheet is very ideal for li-ion battery insulation and packaging.

EVA cotton can be shockproof, fireproof, and insulated, which can protect the battery cells well.

A BMS is one of the most important elements in a LiFePO4 battery, like the brain of the battery pack. It calculates the State of Charge (the amount of energy remaining in the battery) by tracking how much energy goes in and out of the battery pack and by monitoring cell voltages, which can prevent the battery pack from overcharging, over-discharging, and balancing all the cells voltage equally.

There are two main sets of wires we need to install, the thick wires and the thin wires. The thick wires are your charging/discharging wires and the thin wires are your balance wires. Not every BMS is the same, but most are similar. Your BMS will likely have 3 thick wires or 3 pads to solder on your own heavy gauge wires. These are the B-, P-, and C- wires (or pads for adding wires). We usually start with the B- wire. We can connect the B- of BMS to the negative pole of the battery pack.

The wrong sequence may cause BMS to burn out.

The battery capacity, or the amount of energy a battery can hold, can be measured with a battery analyzer. If you’re doing a capacity test, be sure to charge the battery until the battery reaches 100%. Then discharge the device until the battery is fully depleted. The charge and discharge rates of a battery are governed by C rates. The capacity of a battery is commonly rated at 1C, meaning that a fully charged battery rated at 100Ah should provide 100A for one hour.

The discharging test of the battery is very helpful 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.