How do I know if my alternator is big enough to support 2 15 inch subs and 20 watt amp?

Your amp will have a peak and steady wattage specification. Then the formula is Amps = Power/14. You can make an estimate of peak and steady amps from that. It is worth noting that at a lowish voltage like 12V, high power produces high currents.

The job of the alternator is to charge up the battery, which you would know. Once the battery is charged up fully the alternator is effectively disconnected by the regulator. So to prevent the battery from running down in use the alternator needs to supply enough current to your audio amps, plus enough to run the car as well.

A typical alternator in a medium size car can produce about 14V and 50-70A, This is regulated to about 10A at 14V. So if your audio amps pull about 5A they would be developing about 5 x 14 = 70 watts steady. Peak power spikes can be buffered by the battery. Most car audio systems are nowhere near this powerful.

4ga & 6ga used in cars,
might find what you want here....or a local auto parts store.
http://www.wiringproducts.com/battery-cable

As big as you can fit, 12 inch is most likely the size that will best fit the tiny truck

Usually when this happens, there is too much power being distrubuted to the parts that the fuse is linked to. First, try using a hire amp fuse, or instead of using only a fuse, try installing a relay to run with it as well. The relay will take the majority of the power, allowing the power to the unit to be distributed evenly, and the fuse will stop being blown.

If this is not an option, try using a higher amp fuse - if it calls or a 20, use a 30 and so on.

It may be possible that you have faulty connection on the battery, ground and/or starter. Make sure these are all in good repair. Also ensure that you have the correct alternator for this vehicle installed - an alternator that produced more charge than necessary for this vehicle will cause many components to malfunction as they will receive more power than what their limited, such as the fuse in question; also make sure the battery is sufficient (big enough), to support such components, as too little power will cause this as well.

Please let me know if you need further assistance.

carsandcomps,

Guru, Premium Expert @ Fixya.com

a 1500 watt inverter draws appx 100 amps from your battery,check with your dealer and see how big in amps your alternator is rated for,if its less than 160 amps you may run short in the summer with the a/c and lights on and discharge the battery or ruin the alternator

no problem with replacing all speakers with ones that are compatable wth you new amp .. and that means the the speaker impedance has to be wtihin the range of what the amp can drive (like 4 ohm, 8 ohm, 16 ohm) .... the subwoofer needs inputs from both left and right channels .. it also needs its own amplifier and low pass filter .. this all may be built into your after market amplifier .. if so you will have an output marked sub (that will directly drive the subwoofer) .. or you may have a low level outdput marked sub that goes to your subwoofer amplifier if it has one .. .. sometimes the woofer has its own built in amplifier and filter .. it then just needs power and inputs from each channel .. since you are running 500 watt speakers, they likely already have a subwoofer component .. (speakers that extend down to 20 hz or lower .) if so, you may not need an additional sub-woofer .. just make sure all the speakers are phased correctly .. (wired to work together not fighting each other ..) .... an amplifier capable of driving 500 watt speakers can draw peak currents that are very high .. so power wiring would have to be very heavy and preferably go directly to the battery with an inline fuse right at the battery ..

no the factory alternator will not have nearly enought power to operate this amp. Yes the alternator is BOSCH and it has a rated output of 75 Amps, u need at least 140 amps, any really good auto electric shop can supply a rebuilt high output alternator custom built, but it will be very expensive.

Your best bet is to buy a cap. A capacitor is an external battery booster like device. It boost power to amp. The thicker the wire the better. Power and ground. Shorter thicker ground wire the better. Make sure it is not on a painted surface. Scrape down to metal surface!!!!

The sound system is exceeding the capacity of the Alternator, it takes allot of power to run the subwoofers, they make higher output alternators for just this situation, u will need one with at least 130 Amps output.

the stereo fuse is under the hood in fuse box and uses a five or ten amp fuse no fifteens will blow it right up