Tommy completes the LiFePO4 battery build and begins load testing. Emile runs Multi-applications on his shack Pi. The Cheapmunks drop by for a high frequency Christmas. Canadian and Creole holiday Food tasting. www.amateurlogic.tv
Great show and happy holidays to you all. Emile you won’t regret building the DigiPi by KM6LYW, it’s a great little project and works a treat.
A BMS just adds unneccerary complexity and leakage to a battery pack. It helps you get every cell topped up to the maximum voltage allowed which is just nonsense. The last few 100mV voltage increase of a LiFePO4 cell means almost nothing in energy storage and is mainly driven from the lead-acid batteries era where you should indeed top-up as high as possible. This is not the case with LiFePO4 batteries. It is perfectly ok to use these between 20% and 80% state of charge, or between 10% and 90%. As long as you do not exceed the minimum and maximum cell voltages. If you bottom-balance your LiFePO4 cells to 2.8V per cell (connect them in parallel and discharge the pack to 2.8V), you ensure that all cells are "empty" at the same time, at the sam cell voltage, at a pack voltage of 11.2V. If you then charge them in series for the first time, keep an eye on the cell voltage and stop charging when the highest cell voltage is 3.65V. At that point you consider the pack as fully charged. Then you measure the pack voltage and enter that as "end of charge" voltage in your charger. After this process, you have a pack that is bottom balanced, where all cells reach "empty" state at the same voltage and you have a know "full charge" voltage. You don't need a BMS and your pack can be used this way for 1 to 2 years if not abused. After that period, you bottom-balance the pack again if you notice more than 10 mV difference in "empty" state. The benefits: you don't need a BMS and you don't have the discharge current of that BMS.
