Car & Motorcycle Battery Tester

Posted on Feb 5, 2014

Most of the time a charged lead-acid battery and a power inverter would be used to ensure a smoothly organised holiday where ideally the missus and the children cheerfully use their electric and electronic gear! With rechargeable lead-acid batteries it`s invariably useful if not essential to determine whether the power source you`re hauling along on your travels is losing capacity and needs to be topped up.

Car & Motorcycle Battery Tester
Click here to download the full size of the above Circuit.

The same circuit would also come in handy when going on a car or motorbike trip as it can check the status of a 12 V (car) or a 6 V (motorcycle) battery. Although the circuit draws so little power that it will not notice-ably load the battery under test, it should not be left connected permanently. The circuit employs the familiar LM3914 (IC1) to display the voltage level. The LED readout creates a battery status readout: when the top LED lights, the battery is fully charged. When the bottom LED lights, the battery needs imminent charging! Switch S1 selects between 12 V and 6 V operation. A series diode, D1, protects the bargraph driver from reverse supply volt-age. A colour coded display with individual LEDs could be used instead of the common anode bargraph display for better indication of the state of the battery.

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