Battery testing calorimeter

Battery Testing Calorimeter (BTC) from the Process Safety Experts

The Phi-TEC is able to study : -

Battery components (anode, cathode, electrolyte, SEI)
Complete batteries
Overcharged or over discharged battries
Charged, discharged and cycled batteries

Even large batteries (EV and HEV, for example) can be directly tested to obtain safety, lifecycle and electrochemical efficiency data.
BTC is a special version of the Phi-TEC I Adiabatic Reaction Calorimeter, modified to enable easy and reliable safety testing of Li-ion batteries of different sizes. This is possible under different conditions of battery use as well as undesirable modes of use.
Depending on battery size to be tested, “standard” and “customised” versions of the BTC are available.

Stability Testing
Lowest temperature at which battery starts to self-heat can be accurately determined in the standard Heat-wait-search test. To assist with chemical development, the kinetics and energy release can be easily qualified.

Phi-TEC also has a second test modes where the sample is ramped and this provides quick screening data during battery development

Testing to “destruction”
It is a also possible to place batteries in a pressure “cell” so that the decomposition can be allowed to proceed to “destruction” – allowing gas rates and temperature increase to be measured in the event of the battery decomposing in a closed space.

BTC Design Choices

"Standard” Calorimeter
Compact design that can be used for battery types : -

18650
Prismatic
Polymer
Coin
AA
3/4A
4/5A
Battery packs
Prototypes

“Custom” Calorimeter
The Custom Testing Calorimeter is used for batteries larger than 18650.

This Calorimeter will allow batteries up to 35cm x 35cm to be tested, and typically includes batteries for EV and HEV, military use, space aircraft and also large packs of smaller batteries.

Technical Advantages of Phi-TEC BTC

Controlled heating
Phi-TEC is able to evenly distribute heat over the body of a battery while heating to higher temperatures, ensuring that data is representative of natural slow heating and that results are realistic – especially important in large batteries.
Direct temperature sensing
Wall and internal temperature can be sensed and either can be used for judging the battery stability. This is critical in large batteries where wall temperature can be very different to the internal value.
Battery “abuse” simulation
Either of the two BTCs can be integrated with an electronics unit that can simulate battery shorting and overcharging (to 24V) using the calorimeter control software. Stand-alone (customer supplied) cycler units can also be used with the BTC to determine the effect on battery safety and performance.

Low temperature stability testing of Li-ion batteries

Increasing amounts of research into Li-ion batteries is performed at low temperatures while standard thermal screening calorimeters work only above room temperature. HEL’s phi-tec adiabatic calorimeter (ARC) has recently been extended to enable battery testing from sub-ambient temperatures and this feature relies on two important components:

Mechanical changes to enable the test section to be cooled, very simply and quickly using any available chiller which determines the lowest operating temperature.
Control software that allows stability testing from any initial temperature, without any need for
recalibration.

In effect, the combination of above features immediately extends the working range to whatever the chiller is able to achieve. This means that a phi-tec designed for low temperature operation can be run in exactly the same way as standard systems without any influence on the normal, high temperature testing.

Typical data for a chemical test is shown below where the evaluation starts at around -20°C (labelled as “can” temperature, representing the test sample) and step-wise heating is performed with an assessment at the end of each step until exothermic activity is finally detected (at round +20°C ) and from that point the sample is allow to self-heat exothermically. A battery or components of a battery could be tested in the exactly the same way.

Safety, Calorimetry, and Process Hazards