Build Your 12V/6V Car & Motorcycle Battery Tester Circuit

Description

Modern camping necessitates bringing a significant amount of electronic devices, from everyday necessities to leisure equipment. Frequently, a charged lead-acid battery and a power converter are utilized to guarantee a streamlined and enjoyable holiday, with the spouse and children happily utilizing their electric and electronic goods. It is generally advantageous – and often crucial – to assess the remaining capacity of rechargeable lead-acid batteries while traveling, to ascertain if the power source is diminishing and requires recharging. This same circuit configuration proves valuable during automotive or motorcycle excursions, enabling the verification of a 12 V (for automobiles) or a 6 V (for motorcycles) battery’s condition.

Circuit diagram:

Despite consuming minimal power, this circuit will not noticeably burden the battery being tested. The circuit incorporates the well-known LM3914 integrated circuit (IC1) to display the voltage measurement. The LED display provides a visual battery status indication: illumination of the uppermost LED signifies a fully charged battery, while the lowest LED indicates that immediate recharging is necessary. Switch S1 allows selection between 12 V and 6 V operation. A series diode, D1, safeguards the bargraph driver from reverse voltage supply. Alternatively, a color-coded LED display could be implemented instead of the standard common-anode bargraph display, offering enhanced clarity regarding the battery’s state.

Integrated Circuit – LM3914

The LM3914 is a versatile integrated circuit, often employed as a linear voltage follower and comparator. This particular IC serves as a key component in the battery voltage display circuit, measuring the voltage across the battery terminals. Its precision and stability make it ideal for accurately determining the battery's charge level. This IC typically incorporates a built-in amplifier and comparator circuit, enabling a clear and reliable voltage measurement. The LM3914 is manufactured by Texas Instruments and is available in various package types. It is widely used in hobbyist electronics, instrumentation, and automotive applications due to its robust design and low power consumption.