Design of backup power supply for ground penetrating radar tester

Traditional field ground penetrating radar testers use lead-acid batteries as mobile backup power sources. Due to the disadvantages of lead-acid batteries, such as low energy density, heavy weight, low rate discharge efficiency, and non-environmental protection, they can no longer meet the backup power needs of modern portable industrial instruments and equipment. Lithium battery packs have become the first choice to replace lead-acid batteries in many industrial instrumentation and equipment fields due to their unique advantages such as high energy ratio, light weight, small size, high cycle life, high safety, and high voltage consistency.

1. Ground Penetrating Radar Tester Backup Power Supply Requirements:

The ground penetrating radar tester has the requirements of high working voltage, long working time and special ambient temperature. In terms of lithium battery cells, it adopts the domestic first-line brand BAK long-life lithium battery cells, and uses a 6-series and 8-parallel combination to meet the customer's related parameter requirements. In terms of lithium battery protection circuit protection, 6-series precision hardware protection circuit + 6-series charging balance circuit are used to achieve the maximum overcurrent of 25A, continuous discharge current of 8A, and charging balance current of 300mA for the finished lithium battery. In terms of related working environment, a high-end white waterproof box shell is used to meet the customer's waterproof environment requirements. The specific parameters of the assembled finished battery are as follows:

1) Lithium battery pack model design requirements: 18650-6S8P/16Ah/22.2V.

2) Circuit design requirements:

1. Single cell overcharge protection voltage: 4.35±0.25V

2. Single cell overcharge recovery voltage: 4.15±0.50V

3. Single cell over discharge protection voltage: 2.70±0.08V

4. Single cell over discharge recovery voltage: 3.00±0.10V

5. Combined battery overcurrent protection value (10ms): 30~35A

6. Charging balance current: 300±50mA

7. Charge balance voltage: 4.20±25mV

8. Battery over-temperature protection value (recoverable): 70±5 degrees

9. The finished battery also has short circuit and reverse charging protection.

3) Battery cycle life design requirements: 500~1000 times (national standard charging and discharging standard)

4) Battery size design requirements: refer to the outer shell

2. Design of backup power supply for ground penetrating radar tester:

1) Protection board (PCM): It is mainly designed for the protection circuit of rechargeable lithium battery packs. Due to the chemical characteristics of lithium batteries, it is necessary to provide intelligent power calculation, overcharge, over discharge, short circuit, overcurrent and other protection functions to avoid dangers such as combustion and explosion.

2) Protection IC: The main protection function chip of the design solution, which performs online and real-time monitoring of overcharge, over-discharge, over-current, short circuit and other functions of the battery cell, so that the battery cell can work in a safe, stable and efficient range.

3) Charging balancing module: balances the voltage difference of each battery cell during the charging process, enhances the consistency of the voltage of each battery cell to extend the service life of the combined battery.

4) Temperature switch: Mainly designed for temperature protection function. When the temperature of the battery itself reaches 75 degrees due to other abnormal problems, the temperature switch will be activated to achieve over-temperature protection. When the temperature drops, it will automatically recover.

5) 18650 lithium-ion battery cell / 18650 / 2000mAh / 3.7V BAK cell (long life battery cell).

6) Field Effect Transistor (MOSFET): MOSFET acts as a switch in the protection circuit, which always keeps the voltage across the load from rising or falling, thus ensuring voltage stability.

7) Schematic diagram of the design of the backup power supply scheme for the ground penetrating radar tester: