Description / Abstract:
This SAE Recommended Practice describes a procedure for
measuring gaseous hydrogen emissions from the aqueous battery
system of a battery-powered passenger car or light truck. The
purpose of this procedure is to determine what concentrations of
hydrogen gas an electric vehicle together with its charger will
generate while being charged in a residential garage. Gaseous
emissions are measured during a sequence of vehicle tests and
laboratory tests that simulate normal and abnormal conditions
during operational use. The results of this test may be used to
determine whether or not forced air ventilation is required when a
particular electric vehicle and its associated battery and charging
system are used in a residential garage.
Gaseous emissions are measured in an enclosure during charging
cycles at temperature extremes simulating garage charging at the
manufacturer's recommended upper and lower operating limits of the
battery under test.
To prevent damage of the battery under normal operating
conditions due to ignition of gases within the battery by an
external spark or flame, battery systems that are vented shall be
equipped with a suitable flame arresting system. A flame arrestor
may be provided either for each individual cell or at the outlet of
a battery venting system.
Because certain failures in the charging system could cause
gassing to be many times the normal rate, the measurement of
hydrogen during the test should include appropriate abnormal
conditions such as single point failures in the charging control
subsystem.
These are tests of the charging system which may involve
components both on and off the vehicle. It is also expected that
there will be a wide variety of designs to accomplish battery
charging. It is therefore required that great care be exercised in
the detailed execution of these tests so that their intent is
preserved.
The Scope of this document is intended to cover all battery
conditions which may maximize gassing. However, it does not include
the testing of batteries at their end of life. It is generally
accepted that aged batteries will emit more gas while charging and
the achievement of the aged condition by accelerated means would be
difficult to control and the test results would not be
reproducible.
Rationale—This Recommended Practice defines a
procedure for measuring gaseous hydrogen emissions from the aqueous
battery system of a battery-powered passenger car or light truck.
The purpose of this procedure is to determine what concentrations
of hydrogen gas an electric vehicle together with its charger will
generate while being charged in a residential garage. Hydrogen is
generated from aqueous batteries during charge. Today's use of
aqueous batteries is limited to Neighborhood Electric Vehicles or
special military vehicles.
SAE J1718 is not relevant to the new fleet of general purpose
electric or hybrid electric vehicles that are being developed with
advanced battery technology, which are sealed battery systems with
a different chemistry that does not produce hydrogen on charge.
Aqueous batteries don't have sufficiently high energy density or
specific energy to be competitive with today's advanced battery
technologies that will be used in the new vehicles under
development. Furthermore, procedures that address hydrogen safety
in fuel cell vehicles are addressed elsewhere.