On July 30, the Shenzhen fire rescue team and SmartPropel energy system conducted a destructive experiment on electric bicycle batteries.
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The safety test simulated the battery overcharge, short circuit, and collision of electric bicycle in daily life, and carried out three experiments, namely battery overcharge experiment, acupuncture experiment, and short circuit experiment.
In each experiment, two groups of samples were chosen for comparison: one group was a qualified lithium battery provided by SmartPropel Power, and the other group was a three-none product collected by Shenzhen fire protection on the market. In the experiment, three none products in the over-charge, pin inserted, such as the case, the instant explosion, burning, and the normal battery provided by SmartPropel power only appeared a trace of smoke, and there is no drum, burning.
The aim of the test is to simulate what happens when an electric car’s battery is recharged after it has been fully charged.
The experimental method is based on the national standard GB/T 36972-2018“Lithium-ion battery for electric bicycle” published in 2018. After the battery pack is fully charged, remove the protective board and continue charging for 90 minutes at the specified current and voltage. The standard requires that the battery pack should not catch fire or explode.
Because the overcharge experiment takes a long time. In this over-charging experiment, SmartPropel power supply provide the protection of the circuit board in accordance with the standard requirements removed in advance. It is worth noting that the general lithium-ion battery is equipped with a protective circuit board, the role is to avoid battery charging, over-discharge, short circuit, over-current, and so on. And the three non-battery that Shenzhen fire fighting collects in the market after disassembling, there is no protection circuit board inside, quite dangerous.
From the experiment, we can see that the battery provided by Smartpropel power only appears the phenomenon of the bulge and so on, no fire and explosion. Three non-products appear obvious fire and explosion phenomenon.
The aim of the acupuncture experiment is to simulate the sharp object penetrating the cell under extreme conditions and to investigate the safety performance of the cell.
This experiment is based on QB/T 2947.3-2008“Batteries and Chargers for Electric bicycles-part 3: Lithium-ion batteries and chargers”. The object of the acupuncture experiment is a battery cell. When the battery cell is fully charged, a steel needle with a diameter of 3 mm is used to puncture the battery cell and stay for 30 seconds. The standard requirement is no fire, no explosion.
From the experiment, we can see that the battery provided by SmartPropel is very safe, and there is basically no response to acupuncture. (Description of test phenomena: there is no fire, no explosion, and even little/no smoke.) And three none battery products followed by smoke and fire burning after the steel needle insertion.
There are two main reasons for the differences: one is that lithium-ion batteries are relatively safe compared to NCM batteries, which is determined by the material system itself; the other is that most of the batteries given to the three non-manufacturers are products B and C that have been eliminated by the major manufacturers, even have a lot of ladder use of the cell, quality can not be guaranteed.
Short Circuit Experiment
According to the national standard issued in 2018, after the battery pack is fully charged, the protection device is removed, and the short circuit is carried out using 80mm ± 20mm outer circuit until the battery pack voltage is less than 0.2V.
From the experiment, we can see that the appearance of the battery provided by SmartPropel has no obvious change. Three non-products appear obvious fire phenomenon.
Vincent Yang, CEO of SmartPropel said that the safety of lithium batteries produced by regular manufacturers is safe, and users needn’t worry too much about safety as long as they ensure the correct use method.
Finally, Shenzhen Fire also based on this experiment gave a few suggestions:
- Do not put the electric bicycle in the home or corridor to charge, do not charge around flammable and explosive materials;
- The battery should be fixed in the electric bicycle to avoid shaking or vibration of the battery. Do not use cardboard, foam and other inflammable materials instead of tape or as a filler into the battery box;
- If the vehicle is not used within a week, it is recommended to disconnect the air switch on the vehicle to reduce battery consumption. Long-term unused vehicles need to recharge their batteries every 1-2 months to avoid overcharging;
- Avoid high temperatures (such as direct sunlight) when charging a battery;
- Avoid using inappropriate charger to charge the battery, such as: lead-acid charger to lithium battery charge, 60V charger to 48V charge, please use the original charging;
- Electric bicycle batteries should also pay attention to waterproof protection, if touch water, should timely drying, to ensure that there is no performance failure.