Why LiFePO4 Battery Balancing?
A LiFePO4 battery balance is simply the process of balancing the voltage and charge of each battery cell in a battery pack. It is often impossible to get enough power from a single battery cell, so we usually assemble a group of cells together as a power source.
Ideally, these cells are supposed to be in pristine condition, with identical voltage and capacity. Unfortunately, when they arrive from the factory there can be discrepancies in how much charge they contain, due to various transportation factors. These differences become magnified as they cycle through use and must be addressed through LiFePO4 battery balancing so the complete battery can run at its optimal level.
To give a simple example, a LiFePO4 battery with a smaller capacity will charge quicker while other cells in the same battery pack will not be able to draw as much current. Similarly, the discharge rate of the smaller cell will be faster, limiting overall output from this battery pack. The voltage of the higher capacity cells also differ, resulting in performance that is not optimal. This phenomenon can be summed up by barrel effect – the weakest cell dictates the total wattage available and the most powerful sets the cut-off voltage. However, generalizing this theory does come with certain risks as it could potentially lead to overcharge or overdrain all cells connected in this battery pack, causing irreparable damage. To ensure correct usage and safety when using LiFePO4 batteries, balancing is vital.
How to do LiFePO4 Battery Balancing?
To begin with, we need to be aware that there are two traditional ways to balance a battery; these are top and bottom cell balancing. However, with the ever increasing progress of technology, many opt for scientific approaches in tackling such complicated tasks. As of now, the preferred device is a balancer. This equipment is proficient in LiFePO4 battery balancing and is more accurate and effective than manual operations. Nevertheless, if one does not possess the necessary tools, manual balancing remains the only option.
Top balancing requires charging all the cells to full and then connecting them, which is beneficial for charging optimization. On the other hand, bottom balancing necessitates discharging the cells to a safe minimum level and then connecting them; this is best suited for discharge optimization. Ultimately, your choice of top or bottom balancing should be based on how you intend to use your LiFePO4 battery pack – but in both cases, balance is the key factor.
Manual balancing is not so hard after all. We begin by using the multimeter to measure the voltage of every cell, writing down their respective values as we go along. Then, order the cells from low to high or high to low – whichever way you prefer. It’s best to link them together in a parallel connection rather than series – that’s safer when it comes to balancing the cells. The arduous part is keeping an eye on them for an extended period while (the) higher-voltage cells pass on their charge to the lower-voltage ones until they become equalized.
Don’t forget to use a multimeter to test the voltage and capacity of your battery pack before deciding on a top or bottom balance. A Balancer is highly advised, as not using one could mean that balancing batteries will be a daily task. Installing an efficient BMS also provides several advantages: it can detect parameters in your battery pack, avoiding issues such as overcharging, over-discharging or an over-current problem; additionally, it helps maintain cell balance.
Summary
It is common for DIY LiFePO4 battery novices to overlook the importance of battery balancing, but the condition of the battery can have a direct effect on the battery pack in the future and its effectiveness. Make sure the battery cells are balanced before using the battery pack.