The wattage a car battery can handle for a subwoofer isn't a single number; it depends heavily on your vehicle's electrical system, specifically the alternator's output. Most standard car alternators produce between 90 to 150 amps. A typical aftermarket system with a 1000-watt amplifier can draw around 70-80 amps at full power. If your total audio demand approaches or exceeds your alternator's capacity, you'll risk draining the battery and causing dimming headlights.
The key is to match your subwoofer amplifier's power draw to your car's charging capability. Amplifier power is listed in two ways: RMS (Root Mean Square), which is the continuous, realistic power it can produce, and peak power, a marketing-focused maximum. Focus on RMS wattage. For a system with a 1000-watt RMS subwoofer amp, you should ensure your vehicle's electrical system can support the additional load, often requiring a high-output alternator for vehicles over 1500 watts RMS.
Here’s a general guideline for system power and electrical requirements:
| System RMS Power (Subwoofer Amp) | Typical Alternator Requirement | Recommended Upgrade |
|---|
| Up to 500 watts | Standard factory alternator (90-120A) | Usually sufficient |
| 500 - 1000 watts | Standard to robust factory alternator (120-150A) | May be sufficient; Big Three upgrade advised |
| 1000 - 2000 watts | 150A - 200A+ | High-output alternator often necessary |
| 2000+ watts | 250A+ | Essential to upgrade alternator and battery |
To prevent damage, always install an in-line fuse on the power cable near the battery, rated for the wire's capacity, not the amplifier's peak power. If you're planning a powerful system, consult a professional installer who can measure your alternator's output and recommend the necessary upgrades, like a high-output alternator or a secondary battery.
