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High Amp Alternator

High Output Alternators provide the current you’ll need for LOUD car audio

To avoid the dreaded red light of despair in the suddenly silent night, you will need to upgrade your electrical charging system. High Output Alternators provide amperage that your stock alternator cannot produce.

If the Big Three Wiring Upgrade failed to alleviate your electrical issues in your car or truck, then upgrading the alternator might be your next step toward a high performing car audio system.

Did increasing the current flow through the system solve problems like headlight dimming or did it make them worse?

This is because your amplifier is trying to draw more amperage than your stock electrical system can create.

Boosting the flow of current in the vehicle will only increase the problem if the charging system can’t keep up.

This means your headlight dimming could worsen after upgrading your electrical charging systems wiring. That is if the alternator cannot supply adequate power for both your cars electrical charging system and stereo.

High Output Alternators increase the amperage of your system.

Relying on a stock electrical system for the massive amperage that car audio amplifiers require, while still supplying your vehicle with the current it needs will result in low voltage and other problems.

When the alternator can’t provide the necessary amperage for your system, the battery tries to make up for the amperage deficit.

When the battery cannot make up that deficit, the power supplies fail and the amplifier goes into protection mode.

Stock electrical charging systems typically fail to provide the level of current that 2,000 Watt+ car audio builds require.

Wait, wasn’t that what the Big Three was for?

Upgrading the Big Three is the first step toward a solid electrical system.

It increases the diameter of the straw our current flows through.

Adding a high output alternator is the second step. It increases the force of water that flows through the straw.

There will be costs to keep in mind and hurdles to overcome.

Depending on the current your vehicle and install require, you may need to make modifications to your engine and create space for a small power plant under your hood.

If you’re chasing numbers, prepare to play Tetris in your engine bay to make room for the alternators and the bracket that will be holding them. Championship rings don’t come easy or cheap.

If you’ve read this far and are starting to rethink 150’s, hair tricks, and broken windshields, you can still enjoy considerable bass with a single high output alternator in your car or truck.

As a general rule, you need about 100 amps of current for every 1000 watts of power generated. Add that to the base electrical requirements of your vehicle for the total amount of amp-hours you need for your system.

You can use this formula: watts/volts = amperes

Example: You plan to install a 2,000 watt amplifier. Your vehicle’s voltage is 13.5 volts. Divide 2,000 watts by 13.5 volts. The result is 148 amperes of current. If your stock alternator output is 85 amps, add 150 amps for a total of 235 amps needed to safely operate the amp.

How to choose a High Output Alternator

There are a number of reputable manufacturers to choose from. As a starting point JS Alternators  is popular. We do not advise buying an alternator on eBay.

The difficulty is that one size does not fit all and many high output alts are vehicle specific.

Your alternator’s rated output will typically refer to the amperage output at high-RPM’s like highway speeds. When you’re idling, or running at a low RPM, your alt may only be capable of providing a small fraction of that rated power.

The best practice is to do some research on what works for your specific vehicle.

Learn what hangups may be associated with that. Like what is ‘too much’ for your engine, how much amperage does your car or truck need to operate, and determining the best use of your available space.

For instance, if you have an economy car, you may be limited to 300 amps or fewer. Vehicles with small engines may not be able to effectively operate alternators larger than 300 amps.

You may find your engine dying when idling if you are using too much amperage.

It is a balancing act. Check the data available for your vehicle, your desired application, and then read the reviews.

Many High Output Alternators are made to order, so you’ll have some time on your hands while you’re waiting for it to be manufactured and shipped.

Every alternator installation will be different. Follow your manufacturer’s instructions to install yours. Don’t be afraid to ask them questions.

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XS Power Wattage Chart


Choosing which battery to use to power your audio system can be daunting when faced with all sorts of numbers and specifications that don’t seem to have anything to do with car audio at all. With our wattage chart below, the choice has never been easier! When using only one battery, refer to the “Primary” column; when using a second battery as a supplemental battery, refer to the “Secondary” column. When replacing the original battery and adding supplemental power, use a combination of the two columns to arrive at the desired level of power needed to satisfy any stereo system!

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XS Power Frequently Asked Questions


What is an AGM battery?
Absorbed Glass Mat (AGM) Batteries completely eliminate the hassles of conventional battery maintenance. There is no liquid acid in AGM batteries. All of the acid is absorbed into the compressed glass matting in the cells. They are completely Non-Spillable, so they can be shipped by mail or courier service with no hazardous warnings or extract fees. Likewise, they can be mounted in any position for special application.

How do I charge an AGM Battery?
AGM batteries should only be charged with AGM compatible chargers. Please view our full XS Power 1004 16V and 1005 12V/14V/16V charger manuals for complete instructions.

Could you explain “MAX amps”?
CA and CCA have been used since 1914 as a definition for battery performance. CA is defined as a measurement of the number of amps a 12 Volt battery can deliver for 30 seconds at 32°F and not drop below 7.2 volts. CCA is the same test at 0°F. These tests were meaningful for the cars of yesteryear that had to be cranked for a long time to get started. Back then CA and CCA numbers were very meaningful; however, for mobile audio use, immediate burst output is more important. XS Power batteries, when compared to the batteries of yesteryear, deliver much more power more quickly. This instant burst energy is what we call “MAX amps”.

Could you explain “amp hours”?
People often wonder what the term “amp hours” means when referring to batteries. Many people assume that “AH” (amp hours abbreviated) is a standardized rating for a battery’s ability to discharge current; a true statement. The actual method for de terming the AH rating is more often times not fully understood by the automotive enthusiast.
AH capacity is measured in hours. AH is most commonly used to rate deep-cycle type batteries, or any type of battery used for relatively low discharge rates across an extended period of time. Most batteries, including XS Power batteries, are tested in a 20 hour cycle. AH tests can be performed for 10 hour cycles at a higher amp load, but results are not as useful for determining long term capacity.
An AH test can easily be conducted by the end user, which is why we at XS Power are so adamant about strict honesty regarding all of our battery ratings. To conduct your own AH test, simply calculate 5% of the AH capacity, and use that number as the amp load. Make sure the battery maintains the standardized 25°C temperature for the duration of the test. The idea is that the battery needs to maintain that load for 20 hours without falling below 10.5 volts. Please note that 16 Volt batteries would be tested to 14 Volts.

Here is an example for a 30 AH 12 Volt battery:
5% of 30 (amp hours) = 1.5 amps.

A 30 amp hour battery should be able to maintain a 1.5 amp draw for 20 hours at 25°C without falling below 10.5 volts.
When a manufacturer is initially determining AH, the calculation is done in reverse. The amp draw is multiplied by the test cycle length in hours as evidenced by the example below.
1.5 amps x 20 hours test = 30 AH

The AH rating is most useful for determining how well a deep cycle battery can maintain a relatively low amp load across an extended period of several hours, as the example above illustrates. This information is especially important to customers who plan to use XS Power batteries in Recreational Vehicles (RVs), boats, show vehicles, or any other application vehicle that will need to sustain a low draw for extended periods without being charged.

What does BCI Group Number mean?
The BCI Group Number defines a battery by describing the following characteristics:

A.) Its maximum dimensions (L x W x H)
B.) Voltage (6 volt or 12 volt)
C.) Post configuration
D.) The type of terminal used (top, side, flag, etc.)

It should be noted that the BCI (Battery Council International) Group Number does not designate a battery’s capacity, it merely defines the above listed physical characteristics.

Could you explain reserve capacity minutes?
Reserve Capacity is yet another standardized battery rating useful in selecting the proper battery. Usually abbreviated “RC,” reserve capacity is measured in minutes. Battery Council International defines RC as: “the number of minutes a new, fully-charged battery at 80°F (27°C) can be discharged at 25 amps and maintain a voltage equal to or higher than 1.75 volts per cell.” This works out to 10.5 volts for a 12 Volt battery.

For example, the XS Power S925 battery has a rated RC of 55 minutes. This means that with the S925 starting at a full charge at 27°C, it can maintain a 25 amp load (similar to a large cooling fan) for 55 minutes before battery voltage drops to 10.5 volts.
It is easy to see how this rating is very important in determining how well a battery will operate accessories in the event of a charging system failure, if the vehicle is not properly equipped with an alternator or if the vehicle’s engine is not running.

How do I determine the state of charge of my battery?
By measuring the open circuit voltage (OCV) of a battery that is not connected to any loads, it is possible to determine what percentage of capacity is remaining by referencing the chart below.


Are all 16 Volt batteries tested alike?
Unfortunately, no. XS Power is a member of BCI (Battery Council International) and tests all our batteries to BCI specifications. We test our 16 Volt battery to 16 Volt specifications. Other suppliers of 16 Volt batteries test to 12 Volt specifications. If XS Power batteries were tested the same as our competitors, our CA numbers would be considerably higher.

Why do XS Power batteries cost more than flooded batteries?
XS Power batteries are manufactured using only virgin lead, 99.99% pure compared to most batteries that use recycled lead. The pure-lead design means better performance. In other words, MORE POWER!

Grids are thinner. This allows for more grids which means more surface area in a smaller package. More surface area means MORE POWER!
AGM (Absorbed Glass Mat) design means longer life, vibration resistant, deep cycle and can be mounted in any position (except upside down).

Why XS Power Batteries?
We believe that to create a superior product you must have a vast knowledge of your product offering. For this reason we have invested a great deal of time and money into the development and understanding of our batteries and the markets we supply. This task could not be completed with run-of-the-mill test equipment. We worked in cooperation with one of the worlds largest and prominent battery testing equipment manufacturers to develop a one of a kind test lab that would enable us to duplicate circumstances realized in real world battery applications. Our battery tester is capable of being programmed to simulate a wide range of scenarios like the dynamic current loads from an amplifier for daily driving, or the insane power demands from top sound pressure competition vehicles. We are convinced that in-depth testing and quality control is a must for any manufacturer that is serious about delivering quality batteries to the mobile audio market. Buy from the people who understand both the market and the product – XS Power!

Battery Comparison: 
Get more continuous amps for less weight! Why drag around extra weight for less power?

Ultra Low Internal Resistance:
XS Power batteries design allows for extreme amounts of discharge current, as well as super fast recovery and recharge rates. XS Power batteries are ideal when you want to add that extra boost for your stereo without having to upgrade the entire electrical system.

Greater Performance:
Don’t let the small size and weight of XS Power batteries fool you. The cranking power of XS Power Batteries can be two to three times the power of a flooded battery of equal size. Take for example the XS Power Battery Part Number S925. It will often out perform and last longer than the bigger battery that comes original equipment on a new car. This makes XS Power the ideal battery for race cars, street rods, and daily drivers.

Since there are no external vents on an XS Power battery, there is no fear of mounting it in a passenger compartment, below a seat, or inside a glove box. No leaks mean no corrosion or damage to chrome or paint. We are so confident in the safety of XS Power batteries that we guarantee no acid leak even if damaged.

Extreme Vibration Resistance:
Rigorously tested to withstand insane amounts of vibration allows XS Power batteries to be installed inside the harsh environments of the trunk or hatch areas where sound vibrations can ruin the average battery.

Sealed Design:
The perfectly sealed design of the XS Power AGM Batteries allows safe, maintenance free operation, allowing them to be used in nearly any position without sacrificing life expectancy or performance. This means there is no need to constantly check and refill the electrolyte and no more corroded terminals to clean!

Excellent Storage Life:
XS Power Batteries are perfect for show cars or situations where the batteries are left unused over a long period of time. A fully charged XS Power battery can sit for up to a year at room temperature and still have the power to produce when you’re ready.

Still Have Questions:
 If you would like to speak to an XS Power professional immediately, please call 888.4XS.POWER.

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Need help finding shorter belt for your JsAlternators High Output Alternator?

Need help finding the required shorter belt for your JsAlternators High Amp Alternator?
Check out Dayco for vehicle belt length lookup.

belt part number link:

Vehicle belt lookup:


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Installation Instructions


High Amp Alternator Installation Manual
Safety tips:
-Wear eye protection
-Remove jewelry or any loose items
-Allow car to fully cool before starting installation

Steps to installing alternator:
*Batteries must be fully charged before installation.
1. Make sure vehicle is off and engine is cool.
2. Disconnect the negative cable from the battery/batteries.
3. Disconnect all other wiring from the alternator.
4. Remove the belt (note the belt routing before removing).
5. Remove the bracket bolts and original alternator.
6. Mount the new alternator. In general, the original bolts will be used.
7. Inspect he belt and replace if there are any signs of wear. We suggest you replace the belt with a .5 to 1-inch shorter belt when installing a high output alternator. Install the belt.
Make sure routing is correct and the belt is aligned to all pulley grooves.

Continue reading Installation Instructions

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Need help finding shorter belt for your JsAlternators High Output Alternator?

Need help finding shorter belt for your JsAlternators High Amp Alternator?
Check out Dayco for vehicle belt length lookup.

Vehicle belt lookup:

belt part number link:

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Why do I need a shorter belt for High Amp Alternator?

JS Alternator Alternator

Slipping belt – Each of our high output alternators come with smaller overdrive pulley. This pulley is made to increase low RPM charging for maximum output. It is custom for the diameter of the overdrive to be less than your factor pulley, depending on the kind of vehicle you own. If the belt provided does not suffice, you may get the right length from your local parts store. In using the belt and the pulley system, ensure that each part of the pulley system is free of oil or grease, this will help its efficiency.