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Battery Current Indicator Circuit – Current Dependent Charging

Battery Current Indicator Circuit – Current Dependent Charging

In this post we learn about a simple battery current sensor with indicator circuit which detects the amount of current consumed by the battery while charging or by any other load and displays it through discrete LEDs.

Battery Charging by Detecting Current

Commonly most battery charging indicators utilize the voltage level of the battery to indicate its charging condition, here instead of voltage the current (amps) magnitude is used for measuring the charging status.

Using current as the measuring parameter enables a more accurate assessment of the battery charging status. The circuit is also capable of indicating the instantaneous health of a connected battery by translating its current consuming capability while its being charged.

Circuit Operation

Referring to the shown circuit, we can see four opamps configured as comparators where each opamp has it own presetable current sensing inputs.

A high watt resistor Rx forms the current to voltage converter component which senses the consumed current by the battery or the load and translates it into a corresponding voltage level and feeds it to the opamp inputs.

Setting up the Presets

P1 upto P4 are adjusted such that the A1 to A4 opamp non-inverting inputs become higher than their respective inverting inputs in response to the decreasing current consumption by the battery as it reaches it full charge status.

For instance P1 may be adjusted such that A1 pin3 becomes slightly higher than its pin2 when the battery consumes the highest amount of current (a known specified level), that is when its fully discharged.

P2 may be adjusted identically when the battery gets charged to some a slightly higher voltage level and its current consumption is reduced proportionately.

Similarly P3 and P4 may be adjusted for the next lower voltage levels across Rx in response to the battery's increased charge level until it's fully charged.

These various current consumption levels from maximum to minimum is indicated by the corresponding LEDs connected across the outputs of A1 to A4 in a sequential manner, wherein only a single LED lights up at any given instance for indicating the relevant battery current levels.

Circuit Diagram

Parts List for the proposed battery current indicator circuit

R1----R5 = 1k

P1-----P4 = 1k presets

A1-----A4 = LM324 IC

Diode = 1N4007 or 1N4148

Rx = 0.6/specified battery charging current

How to set up the circuit

Initially keep all the preset slider arms towards the ground end.

Disconnect the P1---P4 connection with Rx and connect it with an external variable voltage source which can be simply made with a 1K pot.

For making the variable power supply, take a 1K or a 10K pot, connect its outer terminals with the supply rails and connect its center terminal with the free end of P1---P4 which was disconnected from Rx.

Adjust the pot and create a 0.7V at the center lead of the pot.

Now adjust the P1 such that the white LEd just lights up.

Increase the pot center lead voltage to 1V and set P2 such that the yellow LED just lights up, shutting off the red LED.

Next, increase the pot center lead voltage to 1.3V and subsequently to 1.5V and adjust P3 and P4 identically as done for P1, P2.

Once the setting is completed the pot may be removed and the P1----P4 end reconnected to the Rx point.

The above range of 0.6V to 1.5V will be subject to the selected Rx value and the desired current range, where 1.5V may be assumed to the maximum voltage across Rx generated for an equivalent maximum desired charging current for the battery or any other load.

For example, a 1 ohm resistor selected for Rx will generate 1.5 V across it when a current of 1.5 amp is passed through it, whereas the same voltage will be generated for a 5 amp current if Rx is selected as 0.3 ohms and so on.

The formula for selecting Rx = 1.5/maximum charging current.


About the Author

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials. If you have any circuit related query, you may interact through comments, I'll be most happy to help!

5 thoughts on “Battery Current Indicator Circuit – Current Dependent Charging”

  1. Explanations regarding this circuit is a little hard for me whose language is not English. Perhaps it appears easy but I wish there was a video exlaining to set up circuit at least. I want to use this circuit for 12V battery of my solar energy system.

  2. Hi sir,
    Your work is great.This circuit is very
    Well work on simulation sofwear.
    I use variable current source in
    Place of charging battery.

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