Why Do Pouch Cells Require Strict IR Testing?

Pouch cells have become increasingly common over the past few years, for everything from electric vehicles through to energy storage, but pouch cells, though they have advantages over existing prismatic or cylindrical cells, do present challenges for battery testing, and also sorting. One of these is with internal resistance (IR) testing and this is where we go next – why pouch cells require strict IR testing.
What is IR testing?
Internal resistance (IR) a way of describing how much resistance the battery ‘feels’ to the flow of electric current; it’s a crucial number, with an impact on capacity and efficiency of course. IR testing gives us the internal resistance number for a particular cell: spotting differences which might result in degradation, or worse, in certain conditions.
Why is strict IR testing important for pouch cells?
Ensuring good fit for purpose
For applications involving continuous and sustained power, as with EVs, we want to know that the individual cells within the batteries are outputting the resistance they say they are. Now, while all cells are factory tested, if there’s a problem further on, and we need to discharge the pack or (heaven forbid) eject or remove cells, everything is ruined.Pouch cells with too much internal resistance generate more and more heat each time you charge and discharge the battery, and this could just lower efficiency overall. With rigorous IR texting, manufacturers know that every single pouch cell is habituated to a specific cutoff (cutthroat LOL) for resistance, and hence performance.Excessive heat builds up in HIR cells, which in extreme instance leads to thermal runaway, like we’ve been seeing with EVs and the consumer products they power. Aided by IR tests, we know what cells are borderline overheating, and can prevent a fire or worse.Shorter lifetime of cellsMore of these nasty HIR pouch cells bite the dust earlier and faster as the battery thrashes around aging. More naughty IR means less capacity to charge and discharge strong, until kaput well too soon. Strictly testing for IR means that cells with higher than needed IR are not selecting for release.
Consistency means quality
pouch IR tests equal out every cell to relative identicals. If IR varies, so too cell performance, as pack—lots of cells in series and parallel must box as one. Rigorous IR testing converts to cells with a small delta of variance. All cells, good, consistently—extra issues will not be amplified or magnified.
Dumpling Energy Bloat!
Dumpling bloat into hot HIR cells named HIR, albeit precise in usage for last end in EVs, but the HDT pouch cells seam on. So we respect the IR value tests, so IR must be low, in otherwords higher so it elevates overall energy performance, and power.
Keep those pouch cells healthy, and you’ll be strippin’ offa the load for grosses—longer life in ivory tower, shorter charge, lower operating heat, and the works. And really blast those babies through IR testing so only a Nova or boucy cell goes forth to keep our system tuned for its energy
Avoiding danger of too much discharge
Low resistance? Right. But wait, when high resistance bent over, there go the cells in general. It happens on charge and discharge. And if you’re talking pouch cells in pack? One cell cuts too much to draw off neighbors; phew. Again, you’re, with IR testing a cell, you can’t block vault to the big leagues. Nice try, but you can’t make the cut!
And so goes your bottom line…
Ok, you a plugs-in-a-plight big cabbager beautiful production family style? And think that you going that cell through IR testing for rigor is frills and fiscal fancies?
Well, I guess cell jiggler duties on Saturday then, huh?
How the IR testing works
A small current is run through the battery, and they measure the fall in volts from discharge across the battery; in essence the voltage drop shows the battery’s resistance. Of course IR testing you can do several ways. Here are a few for you;
ConductanceTestYou discharge cells using a low current and assess readings and such.