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I have a high powered audio system and I need to run another alternator to power it so I won't destroy the one I already have. I am planning on running the other alternator to charge another battery which will sit in the trunk. What type of bracket would I need and would running the hot wire from my 2nd alternator to the trunk be a bad idea because of voltage drop across that length.
Any suggestions on how to tackle this problem are welcomed.
 

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Have you thought about using a battery isolator instead of two alternators? Isolators are used in RV applications. Most motorhomes have a large 110-160 amp alternator to keep up with the current load, a starting and deep cycle battery and an isolator between the two batteries. This setup is simpler, less expensive and will leave you with more horsepower. You could upgrade your alternator if you don't have one that puts out at least 80 amps. The isolator is essentially a diode that controls the flow of power to the batteries and keeps you from discharging the starting battery when using your high current accessories while controlling the charge rate to both batteries. It keeps the starting battery fully charged and regulates the charge to the accessory battery as needed. Some larger auto parts chain stores carry them, or you could check out a local RV dealer. You should use a deep cycle battery for your accessories and a heavy 8 guage cable from the isolator to the rear battery. Make sure you cover the cable at any possible chafing points and run a separate negative cable too.
 

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Originally posted by 69Chevelle:
I have a high powered audio system and I need to run another alternator to power it so I won't destroy the one I already have. I am planning on running the other alternator to charge another battery which will sit in the trunk. What type of bracket would I need and would running the hot wire from my 2nd alternator to the trunk be a bad idea because of voltage drop across that length.
Any suggestions on how to tackle this problem are welcomed.
Have you checked into a replacement one for what you have ?. On all of the systems I've seen in competition the second alternator was always mounted with custom made brackets to the engine. If you are doing this yourself, try and keep the belt as short as possible to reduce the flapping of the belt between 2 or more pulleys and try and have at least 1/3 or more of the circumference of the pulley groove having the belt in it as this will reduce the amount of slippage.
As far as wiring, the voltage sensing wire on the alternator should be at the battery post on the battery.
If you run a large enough power wire then also have a low resistance ground return path as this will help insure good power transfer from the front mounted alternator to the rear mounted battery. If you run 1/0 wire for power, also run a 1/0 for ground back to the power source.
If you can, solder on all of the terminal ends and protect the wire with the proper sized fuses.
I'm not sold on the basic diode designed isolators because they always have a voltage drop across the terminals. A contactor or large relay will also have some amount of voltage drop across it's connections but it will be less.
Do not ground the new or old battery to the chassis of the car without adding or upgrading the connection between the engine and the chassis.
If you put on a big-ole alternator on the car and run a big-ole power wire to the battery then the battery needs an easy way to connect back to the block to complete the circuit. If the engine to chassis connection is poor then you could have limited power from the new setup and could possible fry a shifter cable as it's trying to find a return path back to the alternator.
Jim/Saint Louis
 

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I have the same issue, the most powerful alternator is 220 amp, ad that simply isnt enough to keep the voltage from dropping even with 2 extra batteries in the trunk. I think i will have to custom make an alternator bracket.
 
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