The importance of testing electric batteries in E-Mobility

E-Mobility. For your future.

The advent of electric mobility has created a new industry in need of leak testing.

These tests can be carried out with absolute pressure drop leak test instruments (preferable solution) or even mass-flow test instruments (secondary solution).

The battery pack is a complex system of lithium cells, enclosed in a protective metal chassis and requiring an efficient water and glycol cooling system.

The 2 primary objectives is to prevent dust, water and mud from entering through the protective chassis, and that the cooling circuit does not let the liquid inside it escape, causing short circuits in the underlying lithium cells.

In particular, 3 specific tests are required:

1. Battery pack cover tightness test: it is usually performed at very low pressures, between 30 and 100 mbar, often both in vacuum and under pressure with leak rates in the order of 10-1…10-3 mbar l/s. In this phase, using plastic or metal fillers, it is possible to reduce the large volume under test, thus facilitating the detection of leaks. The objective of this test is to prevent dust and liquids from entering the battery pack.

2. Cooling circuit leak test: All battery packs require a cooling circuit which will contain a mixture of water and glycol. It is obviously very important to check that there are no losses in this circuit, to avoid short circuits in the delicate underlying electronic section. This test is carried out at 2.5 bar, the volume under test is usually between 5 and 10 litres, and the permitted losses are in the order of 10-3…10-5 mbar l/s.

The objective of this test is to prevent the coolant from leaking and ending up on the internal electronics.

3. Complete battery pack leak test: After the assembly of the cover, the modules and the cooling circuit, it is necessary to test the complete assembly.

In this case, we will have an extreme test volume (up to 200 l), which makes the test longer and more difficult to detect leaks.

Having such a large volume, in fact, the pressure decay will be limited, adding to a great elasticity of the material.

All conditions that are inimical to performing a reliable and safe leak test.

The ideal instrument for these tests remains the T8090, with “Dual Absolute” patent.

Another necessary test is that of the electric traction motors, which are obviously coupled to the battery packs mentioned above.

Also in this case, the necessary tests are many:

1. Motor casing seal test: in this case the motor casing is tested, subjecting it to a test at 2-3 bar, with leak rates in the order of 10-1…10-3 mbar l/s. As with the battery pack chassis, also in this case it is possible to use metal or plastic fillers to reduce the volume under test and make the test more sensitive.

2. Cooling circuit tightness test: as in the battery pack, electric motors also need an efficient cooling circuit, therefore, it will be necessary to test that the mixture of water and glycol cannot leak. Test at 2-3 bar with maximum losses of 10-3…10-5 mbar l/s.

3. Complete motor seal test: in this case the test pressure is often 1 bar, and the maximum losses 10-1…10-3 mbar l/s. In some types of motors, where there are no fittings for blowing in air, it will be necessary to carry out a "bell" test, using the optional "Capacimeter" present on the T8090 and T8990 models.

The ideal instrument for these tests remains the T8090, with “Dual Absolute” patent.