# Thread: what size alternater should i upgarde to

1. ## what size alternater should i upgarde to

I have a stereo system in my suv that totals 5000 watts with all speakers, amps and cd player. My lights are dimming if i turn the base up. i was told i need a higher amperage alternater, How do i Know what size to get? or how to calculate amps from watts with dc volts.

2. Somewhere in a range of 420 amps. I think you'd do better with more batteries.

3. Originally Posted by kedarganesh29
I have a stereo system in my suv that totals 5000 watts with all speakers, amps and cd player. My lights are dimming if i turn the base up. i was told i need a higher amperage alternater, How do i Know what size to get? or how to calculate amps from watts with dc volts.
P=I * E

Where:

P = watts
I = amperage
E = voltage

5000 = I * 13.5
I= 370 amps

You need an addition 130 or so more for car electrical, so 500 amps should do it.

4. Thanks But can you run 2 batteries in series on the same alternater would it charge

5. Originally Posted by kedarganesh29
Thanks But can you run 2 batteries in series on the same alternater would it charge
No, 2 batteries in series would require twice the voltage to charge them. Two batteries in parallel however, that might work.

You're still gonna need a huge whacking great alternator though, batteries are just a reservoir, not a source of power.

6. Batteries are only able to produce a finite amout of charge before it drains out. The batteries main function is for starting the car, and while the car is running it is used for regulating voltage.
On the other hand, once the engine is on the altenator is producing the neccessary current to run all of the electronics in the car while recharging the batteries (obviously constrained by the specified amperage output of the altenator).

If the OP were to just add batteries as suggested, with power consumption of the stated 5000 watts, it would not be able to keep up with the power demands of those higher power components.

7. a higher amperage alternator will take away from your horse power tho. i amd more of a fan of having 2 batterys

8. Question to the OP. Is the wattage that you added up the ratings of the devices at the advertised wattages, or PEAK wattages. Or was the wattages the sum of the true power, or RMS wattages.

Originally Posted by 20mg
a higher amperage alternator will take away from your horse power tho. i amd more of a fan of having 2 batterys
Very true. Which begs the question you ask yourself, "All show, or all go?"

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