At Voltaiq we’re often asked for recommendations on how to best set up and record data from a battery or capacitor test. If you’re like us, you probably built your first test program using a template created by someone else — without first thinking through the implications of each recording step. At the end of this post we'll provide some best-practice cycling procedures to produce rich data sets with minimal noise, delivering powerful insights from your battery data.
When setting up a battery test, you want to set your recording conditions to balance the volume of data generated with the value of the information you're looking to extract from the device. While the most obvious types of high-level data from a test are per-cycle statistics — capacity, energy, efficiency — we’ve previously shown that even greater insight can be extracted from time series data, using techniques such as differential capacity analysis. However the design of your test protocol can have a major impact on the quality of data produced, particularly when using these advanced analysis techniques!
Take a look at the next two plots. This first one shows differential capacity (dQ/dV vs. V) generated using data from a "standard" cycling protocol, of the kind we routinely see in use across the industry.
Not so easy to tell where those peaks are on charge and discharge, is it? Turns out the cycling procedure is to blame.
This next plot shows the same type of analysis generated from data using our recommended cycling procedure.
In this second plot, multiple peaks are clearly visible over charge and discharge, and each one can be precisely located. This is why we test batteries!
The best thing about using our recommended cycling procedures is that you'll get access to this powerful analysis without needing fancy new equipment. You can use them with commercial equipment — Arbin, Maccor, and others — to generate high quality data.
Follow the link below to find recommended constant current, constant voltage charge (CCCV) and constant current charge (CC) cycling procedures for two common equipment brands, Arbin Instruments and Maccor.
For those who aren't familiar, CCCV is the most commonly used battery charging procedure in lithium ion and lead acid batteries. At the start of charge the battery management system in the charger uses a constant current. As the battery charges it's potential rises up until it hits the maximum potential — typically between 4.2 and 4.35 V — and switches to a constant voltage charging mode where there current is allowed to trickle into the battery. The constant voltage charge step is implemented so that the battery potential doesn't rise above the maximum potential, a point after which the battery can degrade rapidly or fail catostrophically.
Some researchers also prefer to test their batteries using a CC charging procedure. In CC battery charging the battery is charged using a constant current up until the maximum potential where the charge is then terminated.