Where to Get Cell Venting Data and PRV Flow Data

Three curves carry almost all of the physics in this model, and between them they decide what pressure a battery pack sees during thermal runaway. Everything else you type is a scalar. This page covers where each curve comes from and how good it needs to be.

The Cell Venting Curve

What it is. Cumulative moles of gas released by one cell, against time, from the start of venting.

Cumulative, not rate. The curve only ever rises or stays flat. The solver takes its slope to get the generation rate, so a smooth, well sampled curve gives a better answer than a coarse one.

Where it comes from.

• Cell venting tests, where a cell is driven into thermal runaway inside a sealed vessel of known volume and the pressure and temperature rise are converted into moles.
• Accelerating rate calorimetry combined with gas collection and analysis.
• Published literature for a comparable cell chemistry, format, and capacity.
• Your cell supplier, though this data is often treated as confidential.

What to watch for. Venting behaviour depends strongly on how thermal runaway was triggered, on state of charge, and on cell format. A curve measured by overcharge on a 50 % charged cell does not describe a nail penetration event on a fully charged one. Note the provenance of your curve, because it is the single largest source of uncertainty in the result.

Units accepted. Time in seconds or minutes, gas amount in moles.

The Valve Flow Curves

What they are. Volumetric flow through one valve, against the pressure differential across it. Two curves per valve: one for the closed state and one for the open state.

Where they come from. The valve manufacturer, measured on a flow bench. Ask for both curves explicitly. Datasheets often publish only the open curve, sometimes only a single flow figure at one differential pressure, which is not enough. A single point cannot describe the shape, and the shape is what sets your peak pressure.

What to watch for. Check the pressure range the curve covers. If your case reaches 30 kPa differential and the curve stops at 10 kPa, the tool has to extrapolate flat beyond the last measured point, which understates relief and biases the peak upward. That is the safe direction, but it may reject a valve unnecessarily. Ask for measurements across your full range.

Units accepted. Pressure in kPa, Pa, bar, or psi. Flow in L/min, m³/s, m³/h, or CFM.

The Gas Temperature Curve

What it is. Average gas temperature inside the pack, against time. Optional. It replaces the constant temperature when you switch Temperature Mode to Given Test Data.

Where it comes from. Thermocouples in the pack gas space during a pack level venting test. Note that this is the temperature of the gas, not the cell surface temperature, and the two differ considerably.

What to watch for. Unlike the other two curves, this one may rise and fall freely. Only the time column has to increase. Every value must convert to a positive absolute temperature.

Units accepted. Time in seconds or minutes, temperature in °C, K, or °F.

The Built-in Sample Entries

The tool ships with two cell entries and two valve entries, listed under Demo Company.

These are fabricated sample data. They were written to exercise the tool and to give you something to click through while learning the workflow. They are not measurements, they do not correspond to any real product, and they must not be used for design decisions. Every response from the tool carries a notice saying so.

Use them to learn the interface, to reproduce the tutorials, and to check that your understanding of the workflow is right. Then switch both data sources to User Defined and load your own curves. See Cell Venting Data and Valve Characteristic for the upload procedure and the file format.

If You Do Not Have Data Yet

You can still get value from the tool before your test programme delivers.

Run a bracketing study: take a plausible venting curve from the literature for a comparable cell, scale it to your cell capacity, and run your candidate valves against a range of gas generation rates. What you learn is not the peak pressure of your pack. It is which valves are obviously inadequate, how sensitive your design is to the venting rate, and how much margin you need. That is usually enough to shorten a supplier conversation and to specify what your own testing has to measure.