Multi-Chemistry Battery Charging

Multi-Chemistry Battery Charging Using the Array 366X series Programmable Power Supplies

The increasing demand for portable electronic devices has resulted in a wide range of battery chemistries in use by virtually all areas of consumer and industrial instruments. It is therefore extremely difficult to maintain a complete line of battery charging solutions to keep batteries at the most efficient charge levels.

The Array 366X series of programmable power supplies can easily accommodate the varied battery charging characteristics by programming it for various complex modes of operation.

After determining the proper charge algorithm for the battery chemistry in use, a simple Mat Lab program was written for each of the battery types. This now eliminates the need to procure and maintain multiple battery chargers and keep track of which charger is required for the different batteries being used. The various charging requirements will now be listed and the corresponding program described.Battery Charging with the Array 3363a Programmable Power Supply

Lithium Ion batteries are quickly becoming the most popular battery type due to the large energy density capacity, but….the charging algorithm is the most complex and is extremely critical from a safety standpoint. Incorrect charging could potentially result in the release of harmful gasses and could even result in spontaneous combustion of the cells.

The discharged battery must start off being charged in CC (constant current) mode at a rate equal to one half the mAhr current rating of the battery. The voltage of the battery is monitored and the power supply mode of operation is switched to CV (constant voltage) mode when the battery voltage reaches the full charge voltage of 4.2 volts per cell.

At this point, the supply current is monitored and the charge is terminated when the current supplied is less than 10% of the initial charge current.

The attached Mat Lab program was written for a dual cell Lithium Ion battery pack rated at 7.4 Volts and 4500mAhr.

Therefore the initial power supply settings are CC mode, 9.0 volts, and 2 Amps. The CC mode at 2 Amps is maintained until the battery voltage reaches 8.4 volts at which time the operating mode is switched to CV (constant voltage).

The charging is now continued at this rate and is maintained until the supply current drops to 0.2 Amps. At this point the battery is considered fully charged and the output of the power supply is switched off.

Although this example was written for Li Ion batteries, it is a simple matter to modify the program to accommodate any other battery type such as NimH, NiCad, or lead acid.

This technique could be used with any programmable power supply, but the Array 366X series of programmable power supplies was found to be an exceptional candidate for this application due to its use of the SCPI (Standard Commands for Programmable Instruments) control language.

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George Leger has a Masters in Electrical Engineering from Stanford University, worked in private industry pioneering surface-mount technology and in government research labs for twenty years, published several papers on surface-mount technology, co-authored papers published in national symposiums on accelerator technology, was past president of SMTA and an adjunct professor at the community college level, holds a patent, and is a certified microchip design partner, serving as a consultant to many companies developing electronic circuits.

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