Technologies and know-how

Восстановление аккумулятора

Efficient use

Technique and equipment

In order to verify the electronic separator efficiency we have designed and manufactured charge-discharge test benches of 500 W and 6 kW maximum power. With the help of these test benches we’ve studied discharge characteristics of several types of lead-acid and Li-ion accumulators, as well as that of two-layer and hybrid supercapacitors.

The first test bench is intended for discharge of test chemical cell through electronic separator (ES) and has the following specifications:

  • maximum load power in short-time/long-time mode – 500 W/350 W;
  • input voltage range 7.5 – 15 V;
  • ES output voltage range 7.8 – 12 V;
  • maximum operating current 37 A;
  • mass and dimensions 215x150x110 mm, 1 kg.

ES output voltage is stabilized. The current through the studied chemical cell is measured by precise Hall sensor. Low-resistance current shunt (0.75 mOhm) is intended for load current measurement, shunt voltage is measured by analog or digital millivoltmeter. Powerful wire resistors or incandescent lamps are used as load. The second test bench was designed for testing of high-voltage supercapacitors and accumulator batteries.

It has the following specifications:

  • maximum load power in short-time/long-time mode – 3 kW/6 kW;
  • input voltage range 95 – 400 V;
  • ES output voltage range 90 – 220 V;
  • maximum operating current 24 A;
  • mass and dimensions 62x57x42 cm, 30 kg.

See diagram

Schematic diagram of charge-discharge test bench with 6 kW power

From the functional point of view, the test bench consists of charger utility power source, charger, 4 electronic separator modules connected in parallel, microcontroller control module, 4 output electronic switches with independent control and switching devices. The test bench provides chemical cell discharge through electronic separators or directly on the load, and charge (common, or by decreasing direct current, or with the help of electronic separator) of chemical cells. Thermoelements with 1 – 1.5 kW power are used as load.

Power supply of test benches (except charger) is executed directly from testing current source, that’s why even at maximum load power their efficiency is rather low – 85% for test bench with 500 W power and 92% for test bench with 6 kW power. At minimum load the power efficiency falls down till 78 – 80%.

For common discharge of a chemical cell (without electronic separator) the load is connected through electronic switches (for 6 kW test bench) or directly to chemical cell terminals through a mechanical contactor. According to the required power, thermoelements, powerful wire resistors, incandescent lamps or automobile DC/AC convertors (invertors) can be used as load.

As far as the output voltage of electronic separator prototypes which we have designed, is stabilized, the discharge of the testing chemical cell through electronic separator is executed in constant power mode. Meanwhile, the accumulator rated discharge curves are usually obtained in galvanostatic mode (discharge by direct current). That’s why in order to obtain comparable results, we use the following method: in the mode when a chemical current source (CCS) is discharged through electronic separator, we measure not only constant output voltage and load current, but also falling voltage directly on terminals of a testing CCS and the current through it. These values are followed up during the whole discharge period with the help of digital oscillograph Tektronix TDS 1012 (in recorder mode) or usb-recorder Velleman PCSU1000, are then processed by appropriate software. CCS voltage and current are measured in the same way during its discharge without electronic separator. Thus it’s possible to make a high confidence calculation of the energy extracted from the CCS during its discharge through electronic separator and without it. Total uncertainty of calculation doesn’t exceed 2–3%.

As far as energy characteristics of different accumulator types largely depend on accumulator working temperature, this parameter must be constantly controlled (thereto we use digital multimeters with thermocouple sensors). The data obtained after comparison tests on CCS discharge in two ways described above, are corrected according to temperature coefficient.

Comparison tests on discharge of Li-ion and lead-acid accumulators are executing with electronic load Aktakom ATH-8301. This device provides constant load power that allows discharging accumulator under the same conditions through electronic separator and without it. The ES efficiency shows itself in a longer discharge time till target voltage. Accuracy of voltage and current measurements is controlled by a precision digital multimeter Fluke 187.

Now is developed and tested in the electrochemical laboratory "SWEL energy" new effective charging device ("SWEL-ECD") that realizes an algorithm of decreasing the polarization component of the CCS internal resistance. Using of this device gives an opportunity to charge batteries quickly and to a increased capacity than in common regime. Charging of the batteries with aqueous electrolyte (e.g., lead-acid) can be provided at low voltage, so that can practically eliminate gassing during charging. Prototype of the SWEL-ECD has a maximum charging capacity of 200 watts and efficiency 90-98%.

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