If we use an electric bicycle, we find that the electric bicycle lithium battery sometimes breaks down, even after a short change, the battery pack breaks down again. If this situation happens, it’s worth taking a closer look at the 6 factors which lead to this.
1. The “small horse pulling a big cart”phenomenon
At present, the majority of electric bicycle drive power is 300W, even up to 350-360w, but a large number of electric bicycle manufacturers and dealers in order to reduce costs, the pursuit of profit, configuration the batteries and motor power mismatch, most of them are 10Ah power lithium battery.
According to the calculation of the driving power of 350W, the average driving current is 350W/48V = 7.3(A), while the actual discharge time of the new 10Ah battery is only 90-95min(Discharge rate 7A), according to the discharge rate technology of the conventional battery. The 6-DMZ-12 Battery has a discharge intensity of 7.0 A and a discharge time is about 110-115 minutes.
The practical output of the battery is beyond the electric motor power of an electric bicycle. The phenomenon of a small battery dragging a high-power motor is often referred to as a “Small horse pulling a big cart” phenomenon. This phenomenon leads to accelerated degradation of battery capacity, vehicle mileage decreased, the lack of power also leads to user frequent complaints, impact on the reputation of vehicles and batteries.
Therefore, once the vehicle configuration is determined, it is necessary to select the appropriate battery specifications. For example, when the power of the motor is 300-350W, at least 48V 14Ah Ebike battery or above electric bicycle lithium battery is needed. If the capacity is not reached, at least 300-350W is needed according to the driving power, configure the corresponding lithium cell discharge rate, so that it can meet and can achieve the driving power of the motor. Strictly speaking, in addition to the power of the reference configuration, the battery power needs to leave a certain margin, this allows for higher output power requirements that may occur instantaneously or temporarily, such as higher current output from the battery when the electric vehicle is climbing the load. If the battery power is only matched by the motor, during the uphill, the battery stopped due to an over-current circuit and causes short circuit protection, it may appear dangerous.
2. Tight brakes
This phenomenon is common in electric vehicles with large batteries.
Because of the high capacity of the battery, the electric bike itself will become heavier. Therefore, when the vehicle leaves the factory, in order to ensure the reliable and safe braking of the vehicle, the brake is adjusted more tightly, resulting in the electric bicycle idling current is on the high side, the self-power consumption is increased.
Take an electric bicycle with a 48V 350W motor for example. In general, the normal reactive current is in the range of 1.0 ± 0.1, but at present, we are approaching the maximum reactive current of 1.5 or even 2.0 on the market, leading to an increase in battery load and a decrease in the mileage of an electric bicycle at run time.
The effective solution is to detect the no-load current after the electric bike is assembled and adjust the brake to the proper position.
In addition, here to remind you: everyone in the daily use of electric vehicles, it is best to have a brake calibration at half a month or so on.
3. Controllers power consumption
At present, brushless motor is equipped with lock and switch control circuit electric main circuit. The advantages of this structure are: first, the load of lock is reduced, the cost of lock can be reduced; the other is to avoid the lock passing through large current, and to reduce the power consumption of lock to generate heat, and extend their service life.
But its disadvantage is: easy to cause the battery to over-discharge. According to the actual situation in the market, the power consumption current of the controller is about 15-25 mA, the minimum is 5mA, and the maximum power consumption current (especially for the vehicle equipped with anti-theft alarm device) is about 150mA.
The 20Ah battery, for example, can only last 12 days and nights at 100 mA. The long-term sustainability of electricity consumption has led many Ebike dealers found that the battery was out of power before sell. By this time the battery is usually overcharged.
The effective solution is when storage the E-bike, disconnect the power box and the vehicle, or timely replenishment the power. When you don’t use an electric car for a long time, you have to disconnect the bike from the battery. New electric bikes and motorcycles now have separate switches that disconnect the battery from the car, or you can take the battery out completely.
4. Arbitrary amplification of the control current limit
Through market sampling test, the current limit value of the controller is generally too large for the vehicles produced by electric bicycle manufacturers, especially for luxury electric bicycles. It is well known that increasing the current limit directly affects battery life. This is usually the initial design, choosing battery life at the expense of manufacturing costs.
To make the vehicle “More powerful”. Often want to increase the current limit of the controller, and ignore the motor efficiency at the current limit, which is similar to the case of a small horse-drawn cart.
5.The power box sealed too tight, power fuse heating phenomenon
The current market use of electric bicycle power box is mostly enclosure,during battery charging, especially after the end of charging can produce a certain amount of hydrogen and a small amount of oxygen gathered in the top of the power box, which makes the power box security hidden danger, these combustibles can cause a fire or explosion if they spark or overheat.
Generally speaking, “Battery explosion”actually means “Power box explosion”. And the fuse (especially installed in the power box) , because it is a long time through a large current, so the fuse seat thermal loss of elasticity, resulting in poor contact, thermal softening caused the power box ABS plastic melt, resulting in sparks, could cause the power box to explode. Therefore, in addition to the design of waterproof, but also to consider the power supply box air flow, to avoid some problems caused by airtight.
6.Charger parameter drift
The first is the parameter drift in the cold and hot states, where the maximum voltage in the hot state is 0.1V-0.35V lower than that in the cold state. The problem is caused by poor electronic component selection or inadequate aging conditions.
In the second case, when the Charger is carried with Ebike, the vibration in the bike causes the charger to drift. This parameter drift occurs with a high probability, causing fatal damage to the battery. It is recommended to explain to the customer why the Charger should not be taken with them when selling the electric bike, and to take appropriate anti-vibration measures for the internal structure of the charger.
SmartPropel Original Writer:Nancy