¿Por qué el amplificador de automóvil agota la batería y cómo solucionarlo?

Muchas personas se quejan de que después de instalar el sistema de audio del automóvil, el subwoofer agotó la batería del automóvil, pero ¿realmente este problema es causado por un subwoofer?

Investigué un poco para averiguar si un amplificador de automóvil puede agotar la batería y los resultados son bastante interesantes.

Entonces, ¿puede un amplificador agotar la batería? La respuesta simple es sí, pero la batería de un automóvil solo puede agotarse cuando envía más energía de la que recibe de un alternador. En otras palabras, la batería de un automóvil se agota cuando no está lo suficientemente cargada, lo cual es un problema común cuando se usan amplificadores potentes. Además, el amplificador agotará la batería cuando esté conectado directamente a la batería, sin un cable remoto que vaya al estéreo. En este caso, el amplificador agotará la batería del coche, incluso cuando el motor esté apagado.

Averigüemos qué significa y cómo solucionar este problema común.

¿Por qué un coche necesita batería?

La función de la batería en un automóvil es arrancar un motor y, cuando el motor no funciona, la batería suministra electricidad al aire acondicionado, las luces, la radio y otros equipos del automóvil.

A diferencia de lo que mucha gente piensa, la batería de un coche no produce energía, sino que almacena y alimenta los equipos eléctricos del coche con la energía que produce un alternador. El alternador, cuando el motor está en marcha, suministra al automóvil la electricidad necesaria y carga la batería al mismo tiempo.

Simplemente no puede arrancar el motor sin una batería. Sin embargo, puede intentar empujar un automóvil para que arranque desde la colina, pero necesita una transmisión manual para hacerlo. Ponga una segunda marcha y, después de unos pocos metros, su automóvil funcionará correctamente.

Pero volvamos al tema principal de este artículo y hablemos de las baterías.

¿Qué significa cuando se agota la batería de un automóvil?

Cuando intenta arrancar un motor, y después de girar una llave, no escucha nada o solo escucha un sonido débil de un motor de arranque durante un segundo o menos, lo más probable es que su batería esté agotada. También podría ser un motor de arranque averiado, pero en el 99 % de los casos, cuando no se puede arrancar un motor, el motivo es una batería descargada.

Me pasó muchas veces, sobre todo en los años 90, cuando conducía mis primeros coches con baterías de segunda mano, correas del alternador flojas, etc.

El motor no puede arrancar porque la batería no tiene suficiente energía para hacer funcionar un motor de arranque y hay varias razones por las que la batería se está descargando:

• Tiene un potente sistema de audio con un alternador estándar o el propio alternador está dañado

• El equipo del automóvil consume demasiada energía cuando el motor no está funcionando. Por ejemplo, cuando dejó las luces durante la noche o escuchó música durante mucho tiempo

• El nivel de agua en la batería es demasiado bajo o los terminales de la batería están empañados

¿El sistema de audio de mi automóvil es demasiado potente para mi batería?

Es una pregunta común cuando, después de instalar un amplificador potente, comienzan a aparecer problemas con las baterías. Las capacidades de las baterías montadas en fábrica están diseñadas para adaptarse a un automóvil en particular con equipo estándar. Al agregar amplificadores adicionales, aumenta los requisitos del sistema eléctrico, según la potencia del amplificador.

Para calcular el amperaje exacto de su amplificador, debe dividir el RMS total de su amplificador (no por canal) entre 13,8 V. La siguiente tabla muestra el amperaje de los amplificadores para automóviles. Usé para este ejemplo una eficiencia del 70 %:

Amplificador RMS (vatios)	Amperaje necesario si el amplificador fuera 100% eficiente	Amperaje real necesario (al 70 % de eficiencia)
100	7	10
200	14	21
400	29	41
600	43	62
800	58	83
1200	87	124
1600	116	166
2000	145	207
2400	174	248
2800	203	290
3200	232	331
3600	261	373
4000	290	414

The table shows how high amperage has to be supported by car alternators, in addition to the standard car equipment.

If your total amperage demand in a car exceeds what your alternator is capable of producing, even the most durable battery will be dead because it always has to support an alternator. In effect, it will never be charged unless you will turn a radio on, and power demand will drop.

When looking at the battery label, you will see two important symbols with numbers behind them. It is worth remembering what they mean.

• Ah – Ampere Hours , that means for how many hours, your battery can supply your car with 12V power. For example, battery Ah65 can continuously provide 1amp for 65 hours or 10amps for 6.5 hours until is fully discharged.

• CCA – Cold Cranking Amps mean how many amps your battery can deliver consistently for 30 seconds in temperature 0°F until voltage will drop below 7.2V.

The table below shows popular conversions between CCA and Ah and how powerful amplifiers you can connect to your battery without further modifications. Assuming that 40% of the battery amperage powers car equipment, and the remaining 60% you can use for car audio amplifier.

Battery CCA	Battery Ah	Max amplifier RMS
410	45	246
550	100	546
650	100	546
680	100	645
710	120	655
730	115	628
740	115	628
750	120	655
760	120	655
850	140	764
900	160	874
950	190	1037

From the above, you see how powerful amplifier you can install in your car, without facing any later issues with the battery being drained.

For example, when you have a car battery CCA710, you will be OK with a 650W amp, but for a 900W amplifier, this battery is a no-go.

If you listen to the music nonstop while driving, the battery will never be charged by the serial alternator, and it is a matter of time before it will eventually die.

Strong amplifiers do not only cause drained batteries but also you may notice dimming headlights or flickering dash lights. Also, it can happen that the amp will not receive full power, so your bass will be weak.

How to Keep an Amplifier from Draining Battery?

When you have a powerful amplifier, or more than one, and to make sure that your battery will never drain because of the car audio, you have to consider replacing an alternator with the powerful one. This way, you will be able to supply enough energy for your car’s audio system, and at the same time, your battery will always be charged.

A few months ago, I replaced in my wife’s car standard amplifier with Mechman 370A, and it works great. I have had no problem with batteries since then, and she is using a quite powerful Rockville RXH-F5 with 1600W RMS. (link to Amazon opens in the new window)

The new alternator cost me over $500, and yes, it is expensive but when I put this price against risking often battery replacement, and time for a regular charging battery at home, it balances out.

Typical alternators mounted in an average passenger car can produce between 80 – 120A depending on the model. This 80A will support around 660W RMS from the amplifier, and if you do not have more power, you do not need a stronger alternator.

But what will happen when you add a 2000W amplifier to your car for a subwoofer?

This is an additional over 100A, which a standard amplifier simply cannot produce. Many people went through this many times, and the effect was always the same.

A brand new battery was installed, and with a standard alternator after a few weeks or months, the battery was gone, and the process of regular daily recharging at home begins. This is not the way I want to go, I want to have in a car enough power to support my car audio.

When you listen to music mainly when the engine is on, adding a powerful alternator is the only solution to keep your battery in good condition and the whole system without energy shortage.

Before you start making electrical changes in your car, you need to know if this is really necessary, especially when your amplifier is not the most powerful, so its power consumption should be supported by standard car equipment. The best way to find out is to test both a battery and an alternator.

How to Test Battery And Alternator?

Testing the battery voltage and alternator charging quality is the best way to find out how healthy both are.

To perform the test, you need a voltmeter and no more than 5 minutes of your time, you will also need someone to start your engine while you make a test and the whole test can be done at home. I am using Crenova MS8233D digital meter and I am happy with it.

Before the test, make sure both battery terminals are clean and without corrosion. If you notice corrosion on the terminals, you need to clean them.

Take the leads off and clean using sandpaper, then when clean, put them back together. I use it for cleaning sandpaper grids 100 or 120 , and it works well. After that, spray both with a WD40 . This will prevent terminals from getting rusty.

Check alternator wires for any corrosion, if they sit well in the pockets. Also, check if the alternator belt is tight, and if it is not, this will cause a problem while charging a battery.

• Turn headlights on and run it for around 2 minutes

• Do not turn a radio on, or anything else in a car

• Set the voltmeter to value over 12V DC. Depending on the model, it can be 16 or 20V.

• Connect a red voltmeter wire with the positive battery terminal

• Connect a black voltmeter wire with the negative battery terminal (ground)

• Read the value on the voltmeter, for the good battery, you should see over 12.4V, in most cases closer to 13V.

• Do not unplug the voltmeter and start the engine, during start value on the voltmeter should drop to around 10V, and then jump right back to over 13V.

Test Results

When you start an engine and voltage drops below 10V, that means your battery is weak. And if drops below 6V, your battery is dead and needs to be replaced.

If your engine works and you see voltage always between 13.2V and 14.7V, that means the alternator is in good condition and is charging the battery. In this case, you have nothing to worry about, both parts are working great.

• The next step is to turn your electrical equipment on, lights, AC, fan, radio, The value on the voltmeter should drop to over 13V. If you see over 13V with your car audio on, your alternator and battery are in excellent condition.

But, if you see a voltage below 12.7V, that means an alternator does not produce enough power for the demanding equipment in your car and does not charge a battery at the same time. In this case, an alternator should be replaced.

Related Questions

Do I Need a Capacitor For My Car Audio?

Adding a capacitor helps to stabilize voltage in a car. This is especially important for powerful car audio systems, where together with loud bass , you notice dimming headlights. An amplifier and battery cannot handle such a spike in energy demand, so an external capacitor is needed.

In this article , you will find more information about car audio capacitors, which ones to use, and how to connect them.

Do I Need an Extra Battery For Car Audio?

Adding a second car battery works only when you listen to the music with the engine turned off. Extra battery , depending on the amplifier’s power consumption, can extend the listening time from a few minutes to another hour.

When the additional battery is connected in parallel between an original one and amplifier, the whole system works exactly like a standard battery but with extra capacity. To know more about additional batteries for car audio read this article .