from chemistry to pack
Jerry Wan’s post (right) asks whether cell design has a “golden ratio” for aspect ratio. He concludes that there isn’t a universal one, and that’s right. But the reasons are worth working through, because the best shape changes completely depending on where the tabs are and which edge the heat leaves by. A ratio that … Read more
AION Engineering INC When you open the datasheet of a lithium-ion cell, one of the first values to catch your eye is the internal resistance. Typically, it sits there as a single, proud number: ACIR: 15 mOhm. Many engineers look at this number, validate the “quality” of the cell, and integrate it into their vehicle … Read more
AION Engineering INC In lithium‑ion battery design, internal resistance is one of the most critical parameters governing power capability, heat generation, fast‑charge performance, and overall efficiency. The difference in internal resistance between wound (spiral/jelly‑roll) cells and Z‑stack (stacked) cells is often misunderstood as a chemistry issue, while in reality it is largely a current‑path and … Read more
Cylindrical lithium-ion cells have long used metal tabs to connect the current collectors to the terminals. These tabs act as the path for current to flow out of the electrode layers and into the external circuit. While this design has been reliable for decades, it introduces a few well-known limitations, particularly for high power applications. … Read more
The Galvanostatic Intermittent Titration Technique or GITT as most know it in the world of battery chemistry and modelling as it is used to estimate diffusion coefficients, OCV, over-potentials and resistance. First described by Weppner and R. A. Huggins [5]. The GITT measures the transient voltage change and open circuit voltage (OCV) change during the charging … Read more
When looking for the best performing battery pack the internal resistance of the cell plays a significant role. Simple Ohm’s Law shows that as we deliver a voltage we get a voltage drop equal to the current times the resistance. The heat generation in a cell is a summation of Joule and Entropic heating. At … Read more
Often cell datasheets are limited in data, particularly when it comes to internal resistance. So how do we go about estimating cell DCIR? Although cell datasheets don’t explicitly give the DC internal resistance of the cell, they do often show the voltage versus SOC discharge curves. Within this data is the DCIR value for the … Read more
Cold climate EV range is determined by a number of factors. First of all though, let’s look at the range results as conducted by Motor.no in their winter range tests. An impressive test with 29 different electric vehicles. Read the full description of the tests on the Motor page and there you can see some … Read more
Internal Resistance: DCIR and ACIR:- Let’s take a tiny step and understand how IR is measured in the first place. How are resistances measured? A small current is injected into the component and voltage is measured across it and then resistance is calculated by R=V/I; yes! This is how a multimeter does its’ job; it’s … Read more