This is my 68W load tester. I'm going to use it to measure the actual capacity of my 24Ah 12.8V LifePo4 battery I got on sale.
So, I wrote the customer service department, and it ended up being a pretty good summary of how this is going.
Hello,
I recently ordered two of the following batteries:
As they are four cell LiFePo4 batteries, I would expect them when fully charged to reach a float voltage of approximately 13.6V. I have fully charged both batteries, reaching a cutoff charging voltage of 14.4V. However when removing them from the charger, they have floating voltages of 13.23v and 13.28v, indicating that they are only 70-90% full. This limit seems to be enforced by the internal BMS, as when I measure the charging current, they seem to be taking approximately 3A of current, then abruptly fall to zero current, and reach the charging voltage of 14.4v, taking no additional current.
I am doing some expected load testing at the moment, and have completed the testing on the first (13.23v float) battery. In this test, I place a constant 6A load (0.25C) across the battery, and I expect the battery should last for approximately four hours, based on the rating. However in my first test, the battery cut out after approximately 2.5 hours, meaning that the usable capacity was just over half, or around 15Ah of the rated 24Ah (62.5%).
I am currently running the test on the second battery, but with the lower-than-expected float voltage, I also expect it to fall short of the rated 24Ah.
Is this behavior expected? If not, what steps could or should I do to determine if my batteries are in fact defective?
We'll see how this goes :D
