Video: BDC

Video transcript

What a capacity test tells you about a battery, and how the BDC runs one, from the first connection to the final report. A battery on float charge can show the right voltage for years, and still fail to carry the load the day the mains goes. Its real capacity only shows under load. So you discharge it at a known, constant current, and measure how long it lasts. The BDC holds the discharge current constant with a high-frequency IGBT regulator, from zero to the model maximum, while it watches the battery voltage. Any chemistry:

lead-acid, nickel-cadmium or lithium. The range comes in 7 models, from 48 volts at 200 amps to 600 volts at 15 amps, all in the same wheeled cabinet. You choose by the nominal voltage of the battery. From the outside there is little to it: the control panel, the main switch, the two battery leads, marked positive and negative, and the mains cable. A handle and heavy-duty castors,

because the discharger goes to the battery, not the other way round. The display shows voltage, current, elapsed time and the ampere-hours discharged. Up and down scroll, enter selects, and 4 LEDs show whether it is discharging, finished, stopped by hand, or in fault. It turns the battery's energy into heat, so give it room: 80 centimetres at the sides, 45 front and back. A dry place, a non-combustible floor, and a supply that matches the rating label. With the discharger switched off, earth the cabinet first. Then the battery:

the positive lead to the positive terminal, the negative lead to the negative. The mains plug goes in last. Only then switch on: the unit checks itself and recognises the battery. Two values define the test. The current: the manual recommends one 5th of the five-hour capacity, so a 100 ampere-hour battery is discharged at 20 amps. And the end voltage: 10.2 volts for a 12 volt block, 40.8 for a 48 volt string. Programming takes less than two minutes.

Hold enter to change a value, adjust it with the arrows, and hold enter again to confirm: current, end voltage, capacity, maximum time. Then press up and down together, and the test starts. Once it starts, the current stays where you set it, and the battery voltage falls: slowly at first, then faster near the end. When it reaches the end voltage, the discharger stops by itself. The ampere-hours delivered up to that point are the real capacity of the battery.

A battery with the wrong voltage is refused, reversed polarity leaves the unit in safe stand-by, and an optional probe stops the test if the battery overheats. To disconnect during a test, hold up for 5 seconds first. Never pull the leads under load. The results do not need a PC. The unit keeps the last 150 tests: voltages, date and time, ampere-hours, duration, and a code that says why each one ended. The datalogger records the whole curve.

At the end of the test, switch off and disconnect the battery, then connect the PC and download. Do it before the next test: a new discharge clears the logger. In the software, the test becomes curves of voltage, current, power, capacity and energy, and a report with the final result, ready to print, to save, or to export to a spreadsheet. When one unit is not enough, put several on the same battery. Each one works independently, with its own pair of leads.

Afterwards the software merges their files into a single report: currents, capacity and energy are added up, and the voltages averaged. There is no upper limit. And the rules that matter around batteries: qualified people only, the unit off before any connection is made or broken, a ventilated room with no sparks or flames, eye protection, and no rings or metal tools near the terminals. It is built for the stationary batteries of substations and power plants,

for acceptance and periodic tests to I triple E4 50, I triple E 11 88 and IEC 68 96, and for battery workshops and manufacturers. Battery maintenance, from Amperis.