BRIEF ANALYSIS OF NEW AND OLD REGUL ATIONS
Compared with the previous regulation AIS-048, the new regulations AIS-038 / AIS-156 were changed greatly in terms of regulatory framework, technical requirements, and test methods. The previous regulation AIS-048 could test at the cell module, and battery pack levels, and no environmental test item was included. The new regulations AIS-038 / AIS-156 got closer to EU standrds, and were added with environmental tests and thermal propagation. Test objects became mainly the battery system, subsystem and even the entire vehicle. Besides, nail penetration was removed which was the most concerming test item before.In the process of the Indian AIS-038 electric vehicle traction battery test witness, the following tests have a high non-conformance rate, which should be paid special attention to:
1. Four protections
The four protections refer to over-temperature protection, over-current protection, over-discharge protection and over-charge protection. These four protection tests are in line with the new China national standard (GB 38031-2020) and the EU (R100 Rev 2) requirements, with the following key points to note:
Over-temperature protection tests require removal of the cooling system;
Over-current protection needs to confirm the test parameters;
Over-charge protection and over-discharge protection need to confirm the charge and discharge strategy.
At the same time, attention should be paid to avoid fault signals of non-test items being alarmed in the test process, which will affect the observation of the under-testing items.
The common cases like during the over-temperature protection test, because the battery pack internal temperature difference is too large, the battery management system BMS reported a fault signal for the temperature difference is too large, which affects the test of the over-temperature protection error signal detection; and during the over-current protection test, due to the improper charging current setting, the BMS did not report a error signal. The setting of these parameters will affect the detection and judgment of test witness to a certain extent.
2. Fire resistance
The specific test process of fire resistance test is: preheat for 60 seconds; direct exposure to flame for 70 seconds; then indirect exposure to flame for 60 seconds (or continue direct exposure to flame for 60 seconds); Leave the fire at last.
The main non-conformance in the test was the battery pack caught fire or ignited during combustion (endangering the safety of the occupant). A small area of fire occurred in some parts of the battery pack shell during the test, which can be judged to meet the test requirements under the condition that the safety of the passengers is not endangered.
3. Thermal propagation test
Referring to the test method of UN GTR 20 Phase 1, the recommended initiation method for thermal propagation test of AIS-038 includes nail penetration, heating and overcharging initiation method.
India AIS - 038 thermal propagation test to determine the standard of battery pack has the following two kinds: no thermal runaway occurs; in case of thermal propagation of the battery pack, the battery management system BMS shall send out an error signal in time to remind the passenger to leave the vehicle, and within five minutes the battery pack will not appear fire, explosion and other hazards to the safety of the passenger.
The thermal propagation test is a test with the highest non-conformance rate in the whole AIS-038 certification in India. The main problems include: when thermal propagation occurs, the error signal is delayed; when the thermal propagation does not occur, the error signal is false; within five minutes after the error signal reported, the battery pack smoke and there is a risk of entering the cabin which endangering the safety of passengers; These are all common non-conformances in the testing process.