Most of the small pumps produced by our company use DC power supply. In order to be better suitable for mobile portable or handheld instrument application scenarios, some of the models are specially optimized for mobile portable battery power supply scenarios. The purpose of this article is to help customers understand the working characteristics of the small pumps in the mobile power supply scenario and the selection of the small pumps and power supply mode.

1.Battery lifetime

Calculation formula and unit for measuring battery power supply capacity:

1)Battery discharge current (A) × battery discharge time (h) = battery capacity (Ah) = 1000mAh

2) Battery voltage (V) × battery capacity (Ah) = battery energy watt-hour (Wh)

The working time (life time) of the battery is:

3)Battery capacity (Ah) ÷ battery discharge current (A = 1000mA) = hours (h)

4)Power supply capacity (Wh) ÷ electrical power (W) = hours (h)
Take our company’s C15 small pump as an example. Its rated power supply voltage is 5V (it can work with a wide voltage power supply of 3.2v-6v), the current is 250mA, and the rated load power = rated voltage 5V × load current 250mA = 1.25W. If using 1 section 18650 Lithium battery power supply (can be recharged and used repeatedly), its standard voltage is 3.6v, nominal capacity is 2500mAh, it can be calculated that the battery power supply capacity = battery voltage 3.7V × battery capacity (2.5Ah) = battery energy 9.25 watt-hours Using the above-mentioned battery for power supply, battery life = battery energy 9.25Wh ÷ rated load power 1.25W = 7.4 hours.

The above data is the continuous working life calculated at the maximum load current. It should be noted that under normal working conditions of the C15 small pump, the operating current is about 100 to 200mA, which is less than the load current. The actual battery life is greater than the above calculated value. The actual measurement time of the above lithium battery is about 12 hours.

2. Battery discharge characteristics

Generally, when conducting theoretical analysis of battery power supply systems, the battery will be simplified as an ideal voltage source with constant voltage and zero internal resistance. However, in fact, during the charging and discharging process of any battery, the voltage will fluctuate with the remaining capacity. The following common batteries For example:

Lithium-ion battery: rated operating voltage 3.7V, full voltage 4.2V, depleted voltage 2.75V

Lithium iron phosphate battery: rated operating voltage 3.2V, full voltage 3.6V, depleted voltage 2.5V

Lead-acid battery: rated operating voltage 12V, full voltage 14V, depleted voltage 10.8V

According to the above data, in actual engineering applications, the output voltage of the battery power supply system gradually decreases as the capacity decreases. This characteristic of the battery requires consideration of two aspects:

1) Battery voltage drop. In the absence of a voltage stabilizing circuit, the voltage supplied to the small pump drive motor will gradually decrease. In this case, the small pump motor speed and torque will also decrease with the voltage drop, thus causing the small pump to malfunction. The flow rate and load capacity change. In situations where heavy load and constant flow are required, it is recommended to add a voltage stabilizing circuit to the power supply circuit, or to use a small pump with a built-in voltage stabilizing circuit.

2)Over-discharge of the battery will cause damage to the battery capacity and seriously shorten the battery life. For example, the fully depleted lithium-ion battery voltage is 2.75V, but fully depleting the battery capacity will damage the battery itself. Therefore, the battery generally has a built-in over-discharge protection circuit that stops discharging when the voltage reaches 3.6V or 3.3V to avoid Over-discharge situation. When selecting a battery, it is necessary to consider both the depletion voltage of the battery and the minimum discharge voltage of the protection circuit to match the input voltage of the small pump.

3. Selection of micro pump

4.Selection of power supply battery

1)For the C15, D15, and S15 series products with a wide voltage supply of 3.2V~6V and built-in voltage stabilizing circuits, they are especially suitable for mobile power supply scenarios. The built-in voltage stabilizing circuit can ensure that the pump is stable even when the supply voltage fluctuates and continues to drop. Flow and parameters remain stable. And when the battery discharge voltage is lower than 3.2V, the pump automatically stops working, which can also avoid battery over-discharge and help protect battery life; taking into account the small size of the power supply battery, it is especially suitable for use with various types of polymer lithium Ion batteries and 18650 lithium batteries.

One 18650 battery the size of a AA dry cell can drive the C15 series products to work continuously for 7 to 12 hours. If you need longer battery life, you can use 26650 or 32650 size lithium batteries. Generally, the battery capacity exceeds 5000mAh, which can support longer power supply. Multiple 18650 cells can also be connected in parallel according to the actual situation to effectively increase the battery capacity.

2)For C13 products with a wide voltage power supply of 3.7V ~ 6V, and D25S products with a 5V power supply, you can choose a single lithium battery with a rated voltage of 3.7V to drive it, or connect two lithium iron phosphates with a rated voltage of 3.2V in series according to the actual power supply circuit conditions. Battery for driving. It should be noted that because it does not have a built-in voltage stabilizing circuit, a built-in protection circuit is required to prevent battery over-discharge, and the flow rate and load capacity of the pump will decrease as the battery is discharged. If stable flow is required, a voltage stabilizing circuit is required. .

3) For pumps powered by 12V and 24V, you can choose lead-acid batteries or lithium batteries with a rated voltage of 12V or 24V. Generally, these batteries are larger in size and are mostly used for vehicle-mounted equipment. Considering the discharge voltage drop and vehicle-mounted voltage fluctuations, it is recommended Add a voltage stabilizing module to the power supply circuit to ensure stable operation of the micropump;