LEAK TESTING OF COMPONENTS

Battery packs for EVs / HEVs
DESCRIPTION OF TECHNICAL CHALLENGE
The production of batteries for electrically driven cars has recently ramped up
significantly. It is very important to achieve a decent life time and performanceof the battery in this new drive train technology as to not scare away any newusers of this technology due to an initial bad experience. Typically battery cells
are pretested during the cell production process. Subsequently, the battery
cells are assembled into battery modules and then the modules areassembled into battery packs.
Both, the battery modules as well as the battery packs typically include somecooling channels which are operated either with a water-glycol mixture or withrefrigerant which is by-passed from the AC system of the vehicle. In addition,
the electronic module controlling the operation of the battery is usually also
somehow cooled, again either with a water-glycol mixture or with refrigerant.
Leak tightness is critical to avoid loss of water or refrigerant from the cooling-3system. For water-glycol cooling, typically leak rates of 10 mbar l/s (0.06sccm) are set as the threshold level. Refrigerant loops must be leak checked-5
for leaks in the 10 mbar l/s range.

Battery packs in electrical vehicles
need to be tested for loss of cooling
fluid and against intake of water.

The complete battery pack is usually mounted in a housing. This housing-3
usually must meet the IP67 standard and tested to leak rates in the 5*10
mbar l/s range.
System to be tested

Specification

Equivalent leakrate

Battery cooling circuit –glycol-water solution

No significant loss of coolingfluid~ 10-3 mbar l/s(~0.06 sccm)

Battery cooling circuit –refrigerantNo significant loss ofrefrigerant~10-5 mbar l/s(5 g/a ofrefrigerant)

External integrity of battery packhousing

IP67~ 5*10-3 mbar l/s(~ 0.3 sccm)

THE INFICON SOLUTION
Leak testing the cooling circuit of the battery packFor testing the cooling circuit of the battery pack, it is recommended to first
evacuate the cooling circuit of the battery and then backfill with forming gas(an inflammable mixture of 5% hydrogen in 95% nitrogen). Subsequently, allwelds and brazes are scanned by moving the sniffer tip of the Sensistor
Sentrac leak detector across those areas. In the presence of a leak, forminggas will escape from the leak outlet and will be detected by the Sensistor
Sentrac. The exact leak location can be determined by moving the sniffer tip
back and forth. The exact leak is found where the highest leak rate is shownby the leak detector.
For cooling circuits filled with refrigerant, leaks can also be detected when
already filled with refrigerant. In that case, sniffing with the Ecotec E3000
multi-gas leak detector is recommended for leak testing. The Ecotec E3000
will directly detect the refrigerant escaping from the leak without any crosssensitivity to other gases / liquids present.

Cooling circuits of battery packs are typicallytested in a sniffing process, directly locating
the leak in one testing step.

LEAK TESTING OF COMPONENTSBATTERY PACKS

Final leak test of battery pack housings
Two options are available for leak testing of the battery pack housing:Recommended tracergas
Typical cycle times
Battery size
Test result
Localization of leakAccumulation

SniffingHelium

Forming gas (5% hydrogen)1 – 2 min
Small to medium

2 – 5 minAll sizesleak testing in predefined areas
onlyIntegral testingNo,needs to be performed
subsequently

yes

Automated, integral testing without localization (accumulation testing)
For automated integral testing of small to medium size batteries, the housing of
the battery pack is first pumped down to about 100 – 250 mbar underpressure
and then backfilled with helium to an overpressure of 100 – 250 mbar. This
leads to a helium concentration inside the housing of approx. 20 – 50% helium.
The battery pack is then placed in a simple chamber and the lid is closed. Now,helium from any leaks will accumulate inside the atmospheric chamber overtime and the increase in helium concentration will be detected with the T-Guard
accumulation leak detector.

The integrity of small to medium size
battery pack housings may be tested in a
T-Guard accumulation system without
operator intervention.

If a leak is detected, the battery pack can be taken from the chamber and areas
prone to leakage can be scanned by sniffing these with a Protec P3000(XL)
leak detector to localize the exact leak location.
Leak testing in predefined areas via sniffing
Larger size battery packs must be tested in a manual process or by roboticsniffing. The housing of the battery pack is filled with forming gas (5% hydrogenin 95% nitrogen) and the sniffer tip of a Sensistor Sentrac sniffer leak detector is
moved along the areas prone to leakage - either by a human or by a robot. If
the sniffer tip crosses a leak outlet, it will detect the hydrogen phase of theescaping gas and detect the leak.

BENEFITS OF LEAK TESTING WITH TRACER GAS•••••

Accurate, traceable and repeatable measurements for confident leak testing-4-6
Highly sensitive testing methods, able to detect small leaks (10 .. .10mbar l/s range)
Testing independent of temperature and humidity
Dry process, no risk of water intake during testing
Option of automated, operator independent process as well as manual,
lower cost process available

For more information, please visit us atwww.inficonautomotive.com or call your nearest sales representative.

www.inficon.co mreachus@i nficon.com

Due to our continuing program of product improvements, specifications are subject to change without notice.
mial00en-04 (1903)©2019 INFICON

For larger size battery packs or for amanual process, sniffing of forming gas
with the Sensistor Sentrac hydrogen leakdetector is recommended.