Today, after a two month long wait, I received my Lithium battery cells form China. I’ve done period purchases through Alibaba and AliExpress now for the last 2 years, mostly below $20.00 each and haven’t had any issues so far. That gave me the confidence to try a $750.00 buy on Alibaba for eight 3.2V – 272Ah Lishen Lithium battery cells. I spent another $200.00 or so on other components, to make it all work. That included a good Multimeter, a small power station to top balance the batteries, heavy wiring, bus bars, switches, BMS’s and lots of lugs, bolts and nuts.
Four 3.2V battery cells will compose a 12V unit (12.8V), each in combination with its own BMS (maximum discharge rate 120Ah) and fuse. As I put them together, I may include a heating pad connected to a temperature controller, to keep them warm during (for me severe) cold spells as they should not be charged below ~0°F. At these temperatures discharge rates tumble as well. Fortunately, I have no intentions to travel under these circumstances, so I may not install heating pads, unless necessary.
I will install 4-5 temperature controllers for these heating pads and for 12V computer fans at the battery bank, for fridge air movement and at my built-in computer.
When I received the battery cells, I immediately checked the cells individual voltage: 3.272V – 3.275V – 3.275V – 3.275V – 3.276V – 3.276V – 3.276V – 3.276V. Well within my requirements. The improve the status of each battery and level the voltages, I will now do a top balance by connecting the eight positives together and the eight negatives. The cells SOC is probably around 50%, which is a requirement for transportation, so they willl stay connected to a small lab power supply for 2-3 days until fully charged. I anticipate future usage to be between 15-20% and 80-90% SOC for a longer battery life.
The biggest issue has been to find a good working, yet affordable BMS (battery management system). The cells allow a discharge rate of 272A at 1C, but is limited by the BMS to only 120A. For a well-balanced system, with a 3000W inverter/charger, the two 12V batteries will have a max. discharge rate of 240A or 3072W, although I will likely never use more than about 2000W.
With a cost of less than $1000 for a 550Ah battery bank, including all the components for the install, I would have an approximate cost of $0.15 per watt. A 100Ah Battleborn is approx. $0.70 per watt. That is a big savings, but… There is always a but. There goes much work into development of the BMS and the entire system as a whole. Then there is the risk of a DIY installation; it’s easy to make a mistake or miscalculation. That is a risk I’m willing to take in return for a cheap Lithium battery bank. But, will it be a good choice for you?
In the upcoming weeks, I will be posting multiple videos on how I put everything together, in great detail, as usual.
Disclaimer: I’m not an expert at this and I’ll probably make some mistakes that I have to correct. Always consult an expert if you ever think of doing this yourself.