Building A DIY Lithium Battery

With the Van Build coming to an end, several important projects need some attention. Today I’ll start working on the battery bank of my solar system. Originally, and that was at the beginning of the van build, I installed two 6V Golf cart batteries. This netted me only ~100Ah at 12V nominal. Sufficient for only the most basic usage. At the time also more than sufficient, with only a minimal number of trips planned.

Overview

The main reason however, was that only 3-4 years ago, Lithium battery technology was hardly existent and very expensive. As I look back now, much has changed. We know now, that charging a Lithium battery at below freezing temperatures, is a big No-No, cell balancing must be part of the setup and many more issues are better understood. The development of low priced BMS’s (Battery Management Systems) has also made the DIY setup a possibility.

3.2V – 272Ah LiFePO4 cells

Meanwhile, drop-in Lithium batteries have become a standard and brands like Battleborn, Relion, Lion and Renogy, have established a new market. But prices haven’t really come down, which has led to a thriving DIY community. Using cheap Chinese LiFePO4 cells of 3.2V each (4) can be easily put in series, to create the 12.8V battery we are so used to. These individual cells vary in capacity from 60Ah to 280Ah and with the latter, one can create a 560Ah battery bank from 8 cells at less than $100.00 each, including shipping, tax and duties. With additional tools to put it all together and materials like BMS’s, cables, studs, lugs, fuses and switches added into the mix, a 560Ah Lithium battery bank is within reach for anybody with a reasonable amount of understanding of 12V electricity and insight into the issues surrounding Lithium technology.

I have to admit, that my knowledge of it is very limited and I understand that I may end up with a dummy, either because the goods from China don’t show up or I run into complications like calibrating the batteries or incorrectly programming the BMS. Fortunately, with the information that can be found on the DIY Solar Power Forum and YouTube videos from Will Prowse, I found the confidence to take a big risk and start with this project.

Assembly

I bought eight 3.2V – 272Ah Lishen LiFePO4 battery cells for $69 each plus $198 shipping; added 16 busbars to double up and to top balance the cells after they arrive in the USA. With some trusted advice, I found the Overkill 120A BMS (resold in the US $115), but chose for the Chinese version at half price. This adds some risk to it, but I couldn’t resist a good deal. BTW I have only heard good things about Overkill and that might have been a safer option.

120A BMS

I chose for two BMS’s as they each have a maximum charge/discharge of 120A at 1C. Where 120A at 12.8V makes ~1540W at peak discharge, two of them together offer enough power to use my induction cooktop or water heater. I will create two 12V (4 cell) batteries with each its own BMS. I intended to create a box for each unit, with a built-in fuse, connected to a red positive and one black negative stud and both batteries connected to an On/Off switch before the cables hook into the existing solar system. Because of space limitations, I am forced to use a separate fuse and switch.

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Outlook

Multimeter & DC Power Supply

With the battery cells underway and the two BMS’s on order, I have started to buy all the tools and materials, needed to finish this project. I needed a specific multimeter and a DC power supply to do, at minimum, a top balance of the LiFePO4 cells. Then many electrical items as specified in the material list below; these items may differ for each installation, but it gives a good overview of what will be required. By the time that the cells arrive, I hope to be ready and able, to put it all together.

Tools*

*These are just some of the tools that I will use during this installation

Material List*

*Materials vary by installation. Always independently verify what you need for a safe installation.

Resources*

Alibaba Battery Cell suppliers:
BMS Suppliers:

*These are a variety of resources that I used to accomplish this project. I have no business relationship with any of them. Buy safely. Your credit card or Paypal may offer additional assurance. Business practices in China are different from those in the USA. Buy at your own risk.

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