LiFePo4 Battery Pack – Test Phase
After building the battery pack, it’s easy to assume the cells will provide the advertised capacity.
Being a skeptic in many ways, I want to measure it to know for sure. I have a blatant distrust for these things.
To measure a battery’s capacity, you can measure how much energy it gives out to a load device, or measure how much energy is accepted when you charge it from a fully discharged state. Or better still, measure both. They should probably be equal, but let;s be thorough in our testing.
To facilitate these measurements you need a device that can apply a constant load to the battery and measure (and record) current and voltage, and derive the Amp/hours produced by the battery.
On the charging side, a similar constant current supply is needed.
There are all sorts of ratings you can use, but Amp/hours is the most meaningful. If you really want to know the capacity in Kilowatt hours or some other term, go ahead and simply calculate it out into any unit you prefer.
I’ve been giving some thought to the equipment to perform these tests, and have settled on buying a (mostly) prefabricated solution. It is microprocessor-controlled, and provides a screen display showing all the important characteristics that it can measure. And it works on both the charge and discharge measurements.
It requires an external load resistor, which I selected to provide a representative load to my batteries which can approximate my radio in full power mode.
At the moment, I am waiting for the balance of the test apparatus parts to arrive, so there is nothing further for the time being. I’m also contemplating an enclosure design that’ll accommodate and dissipate the heat given off by the load resistors.
I’m looking to design and 3D-print a sort of console mount for the display.