Battery charge meter for cars

In this article, Chica Mecánica makes a simple circuit that can measure the charge of a car battery. Very simple to do and economical.

BATTERY CHARGING METER


Hello my dear subscribers, today I am introducing another of my simple assemblies and that for me are very useful to have at home or the workshop. In this case it is a battery charge meter, which has three status diodes that are: discharged (red LED), half load and full charge.

This small device works perfect for those who have medium power sound equipment in their cars or who do not have a capacitor that tells them the battery voltage. Then, with good high brightness LEDs you can see at a distance if our battery needs charging or not. Even making a few small variations can be placed a relay that automatically turns off the sound equipment if the load falls below a certain threshold.

It also serves as a complement to the battery charger that you mount here, so that you can see how much charge the battery has.

Anyway ... it can be used in many ways; so, without further ado, I tell you the materials:

Necessary materials:

R1: Resistance of 50 ohms 1/4 W

R2, R3, R4: Resistance of 380 ohms 1 / 4W

R5, R6, R7: Resistance of 660 ohms 1 / 4W

Q1, Q2, Q3: 2N2222 bipolar transistors

DZ1: 10.1V 1 / 2W Zener Diode

D1, D2, D3: Silicon rectifier diodes 1N4007

LED1, LED2, LED3, LEDs Green, Yellow, Red.

Two alligators, red and black.

Cables, tin and as always a lot of enthusiasm.

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The circuit:

circuito medidor de carga de baterrías

As always, you can see the enlarged image by clicking secondary to the image and selecting to see image in the contextual menu.

Operating mode:


When connecting the circuit to the battery, the LEDs will light up as an indicator bar. Red indicates that the battery is already discharged and that you can no longer start the car when the engine is started. Yellow is to indicate that the charge level is medium and that it is time to charge the battery. And finally the green to indicate full load. If you do not turn on any led, then the download is deep and it is necessary to use a static charger to recharge it.

How does the circuit work?


Well is the voltage division section that I call "stable reference" that allows the exact measurement of the voltage of the battery consisting of a Zener diode and several rectifier silicon diodes in series with a resistance of 50 ohms that serves to protect to the Zener.

Circuito simple medirdor de carga baterias

As you can see in the previous figure, connecting the alligators to the battery will produce a stable voltage drop that does not depend on the voltage of the battery limited in current by the resistor R1. Then we have these reference voltages in each of the stages marked with arrows. As you can see it is possible to add or remove stages in our circuit. Resistor R1 is calculated in such a way that the Zener diode is protected by overcurrent and in turn ensures that the base current absorbed by the transistors does not influence the regulation voltage of the system. That is why I put a 50 ohm, which is possible to lower even more if we assume that we will not exceed 14.5V of battery charging voltage.

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The second part is the voltage comparators that I built using the transistor-resistance-diode kit, as you can see in the following figure:

Desglose nro. dos del medidor de carga de baterías

In this case, as can be seen in the diagram to the right, the base-collector current only circulates when the input voltage to the base exceeds the voltage passing through the PN semiconductor of the transistor, which in this case is a bipolar transistor. 0.7V. Then for the red LED diode stage for the diode to turn on it needs to exceed the voltage of [10.1 + 0.7 +0.7] V (Zener voltage, Rectifier diode voltage, base-collector junction voltage). Finally, the resistances of this zone are placed for the protection of the transistor and the led.

It is quite simple to take it to 24V, you just have to change the Zener for a 22.1V and add the stages with rectifier diodes to the voltage they want to sample.

I encourage you then to make this small circuit, very economical and simple to put together.

Well it's all for the moment, if you have any questions or comments, because below is the question box where you can do it.

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Questions or suggestions

In the box below questions below.

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Realizado por

Dennis García

Chica Mecánica

08/02/2018

Grade 
03/02/2018

Muy buen artículo.

Muy bueno y facil.

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    Battery charge meter for cars

    Battery charge meter for cars

    In this article, Chica Mecánica makes a simple circuit that can measure the charge of a car battery. Very simple to do and economical.

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    • Asked by hector rangel
      on 04/21/2018
      Hola , sta Denis soy hector rangel me encanta el medidor de carga de baterias que publicastes es genial solo que quiero que me envies como apagar automaticamente el cargador cuando la bateria este ya cargada es un cargador de 12v dc y muchas gracias por tu ayuda y quisiera saber si dictas algun curso de electronica automotri mi numero es 0414 5800774 soy de guacara edo carabobo Answer:
      Que tal Hector, no doy cursos : (. Pero es interesante tu pregunta, voy a ver si redacto un artículo de ello. Es bastante simple de implementar lo que mencionas.
    • Asked by willian
      on 05/12/2018
      hola que tal, es muy bueno su circuito pero quisiera saber la función la explicacion del circuito del porque se prende el verde cuando esta completamente cargada o cuando se prende el amarillo cuando esta mediamente cargado y el rojo cuando tiene bajo voltaje de antemando gracias Answer:
      Willian, en el articulo lo explique. Está por etapas la 1era es de 10V y las demas de 1,4V aproximadamente.
    • Asked by Rodolfo Carrasco
      on 07/06/2018
      Hola que tal, me gustaria saber un poco mas de información. Despues de leer el funcionamiento no me quedo claro del todo. Si me pudieras dar una explicacion de como cada led se acciona me vendria bien. De antemano gracias Answer:
      Caramba Rodolfo, tienes que hacerme una pregunta en especifico.
    • Asked by a guest
      on 07/28/2018
      Como quitar el anti look de caravan 93 Answer:
      Caramba....allí si no te puedo ayudar.
    • Asked by margarito
      on 08/05/2018
      amiga como puedo hacer una punta logica con multimetro, como los power probe que vende y es costoso,me puedes proporcionar el diagrama para poder hacer mi punta logica a este mail. mramirezo6@hotmail.com Answer:
      Que tal margarito. Caramba vi esos power probe y son bastante completos y complejos. Hacer uno resultaría complicado. : (
    • Asked by enrique
      on 09/06/2018
      hola chica mecánica te dejo mi correo te agradecería si me mandas diagramas como estos y si tienes un curzo de electrónica me lo agas saber. Answer:
      Que tal enrrique. Los diagramas los puedes descargar directamente desde el blog. Y cursos la mayoria que tengo son revistas y libros. No tengo nada asi digital. Pero me gustó la idea de mandar ese tipo de regalo a la gente que me lo pida....voy a preparar un material.
    • Asked by Alejandro March
      on 10/23/2018
      Estimada Srta. Denis. Me gustó mucho tu circuito, es simple y fácil. Me gustaría adaptarlo para un sistema solar, el cual carga una batería y a la noche enciende 4 leds de alto brillo, la idea es que a medida que se descarga la batería, los leds se vallan apagando para que los que queden encendidos sigan recibiendo los voltages correctos. Ahora están en serie y se encienden bien, pero cuando la batería llega a 8 voltios, se apagan todos. ¿Mi idea es posible usando como base tu circuito? Desde ya, muchas gracias. Answer:
      Alejandro, entendi creo que quieres que el spam de tensión sea más extenso. Y si, con menos de 9V se apagan todos los leds. Si quieres bajar la tensión de medición debes en ese caso bajar el valor del diodo zener. En mi diseño como es una batería de carro, y necesita de carga para dar arranque al motor no puede bajar mucho, y por eso coloque ese ajuste. Pero para tu caso imagino que no necesitas de gran cantidad de energía para iniciar un proceso. Puedes entonces bajar el diodo a unos 5,1V y colocar dos etapas más de encendido.

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