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Dual Alternator?

9K views 37 replies 11 participants last post by  DjPaulTheBrain 
#1 ·
Hi
Ive been wanting to add some very powerful subwoofer systems to my patriot for a long time but was not sure if my vehicle could take it. I wanted to put in a new higher output alternator but was told it would void my warranty? is this true? If it is would letting the dealership i bought it from install an alternator be ok and not mess up the warranty? I browsed around the internet awhile and noticed someone had a similar problem i was having, only he did not have a patriot. He too could not replace his alternator, so instead he bought another HO alternator and a dual kit and just used the HO to charge the extra batteries for his system. The idea sounded good but my question is if that is possible with a patriot. After pooping the hood i couldnt seem to ffind any extra space to put another alternator, but perhaps i missed something. Information would be greatly appreciated please! :D
 
#2 ·
i don't think there is room for a second alternator , you might be able to find a high output but i'm not sure what that would do to your warranty. a second battery would work but where would you mount the second battery? how much current does your amplifier draw?
 
#5 ·
"Pooping the hood?"

Anyway, setting that aside, I would go with a heavy duty alternator, capacitor and focus on a separate battery.

Not sure a second alternator is a great idea. There is not much space and you may end up putting needless drag on the engine.
 
#20 ·
"Stiffening" capacitors are pretty much snake oil. The only tile the cap would have to charge would be in between songs. One the song starts, the cap would discharge and be done until the song ends.
Extra batteries would reduce available power to a system and should only be added in cases where there is high current demand while the engine is not running.
 
#8 ·
To all it offended i meant "popping the hood haha" and yeah i didnt assume id be able to fit another in there. I have been looking around for a while but everysite i look at for HO alternators does not have one compatible with jeeps. There is however a place near my residence that will rewind your factory alternator to get more amps out of it. Right now its 120 amps. Does anyone know how strong of an alternator id need for a 4000 watt rms system?
 
#21 ·
One, you have to look at what the power rating is. If that's actually real rating and CEA standards (14.4V) you would first have to convert it the 12.5V your vehicle operates on. In this case it would be 2800 Watts. Now since music is dynamic and you won't be driving around listening to a sine wave clipped by 3db, most people use 20% of the amps power average over time. This means you will use 560 Watts average power over time. When we apply Ohm's Law to this average, we get 44.8 Amps of current assuming the amp is 100% efficient and you will not be clipping it's outputs. Since in all reality neither situation applies, efficiency with clipping will average 50% so your average current draw would be 89.6 Amps.
 
#10 ·
That sounds good. Im getting 2 Kinetik khc2000 batteries and somewhere told me i could run them off just batteries if i had a charger plugged in over night. Or run them off my current alternator but plug them into a charger overnight. And its not like id bump them 24/7 straight. Is this just a false fact or could i get away with just runnin on my alternator (120A) the two batteries if charging them overnight?
 
#18 ·
no that is about what your amps are actually going to put out. your alternator could keep up if you were wunning a second battery and a battery isolatoe and you do not run at max volume for extended periods of time, charging the second battery overnigth would help too.
 
#22 ·
Keep in mind that a 2nd battery is an additional load on the alternator so an extra battery actually reduces the available power to the audio system. The only time an extra batter makes sense for an audio system is when you need lots of juice when the engine is off.

Under normal circumstances, the alternator has to operate the vehicle's electrical system and charge the primary battery after it starts the vehicle. Add an after market stereo, and now the alternator has an additional load. Add and extra battery that needs to be charged and you now have yet another load. Don't forget about the voltage drop across the isolator too.
 
#19 ·
If the alternator's voltage regulator is ECU controlled, then adding a HO alt can damage the ECU and if not, would still be controlled by the same system. If you will only listen to the system while the engine is driving, you don't want extra batteries.
 
#23 ·
"IF" you find a way to add a second battery, here is a nice write. It explains that process nicely. The battery and/or an alternator are usually the first choices in upgrading the electrical system into adding additional power.
 
#24 ·
i like what all of you said and it makes sense that batteries would share the power from the alternator thus creating more of a load. so would adding capacitors instead of batteries be the smartest thing to do? Cause im not planning on SPL competing or anything as one said id only need the batteries in that case for running when the engine is off. The system will only be a driving audio system, for when im crusing around.
 
#26 ·
Batteries don't consume much when charging (under 1 amp), aside from a minute or two after starting the engine and recovering from that. A capacitor is a dead short until it's charged (resistance will ramp from 0 to infinity) so it will consume a LOT of current when charging, and this happens very fast. So if you discharge the cap quickly, it will attempt to replenish as quickly as possible.

Capacitors are good for short bursts of extra current and are to prevent your lights from flickering, not to add additional load capacity. Long periods of load should use a battery.

Just be careful with how much you discharge the batteries. I'm sure you already know car batteries are not deep cycle (your sound system would use a deep cycle). Not only will running down a regular battery hurt it, but it places a huge demand on your alternator right after starting the engine as it will attempt to charge very quickly.

When I run radio amplifiers, I parallel another battery with jumper cables to assist. With the larger amplifier, it's too much for the 2 batteries as the voltage drops below 11 volts....so it's necessary to have the engine running.
 
#27 ·
I cant really explain why i want so much power. In a way i guess you could compare it to why someone with a larger income would buy a fancy sports car. Its not neccessary but i guess its just for show. Not trying to show it off or anything but i am also a bass player, and as a bass player there trully is no such thing as enough bass. I mean i have 2 basson full stacks i use with my band. I just love Bass ha. I am also aware about the law on how loud your system can legally be but the cops around here are pretty lenient in regards to that. In response to buca, are you saying that i could hook up those batteries to my alternator now, but then wait a few minutes after starting the engine for the batteries to charge before i start playing the subs?
 
#29 ·
Oops...missed your reply.

You just need to be aware of the recharging current placed on an alternator. More than 1 discharged battery will place a considerable load on it, so if you add an extra battery don't crank up the system until you give it a few minutes to recharge the batteries (the recharge current will sharply drop off).

And remember, batteries are 12V. Alternator is 14V. As the voltage goes up, current goes down. That means running your system with the engine on will require less current than running it just with batteries to achieve the same power usage. The alternator also offers voltage regulation so when the voltage drops under load, it will compensate.

Also keep in mind that the continuous current capability of batteries differs. Like I mentioned in my previous example, my battery delivers a huge amount of current to operate the starter.....but giving it a 50A load continuously will drop it to 11V within seconds. 10-11V is insufficient to power my equipment and the protection relay will activate shutting it down, voltage rises because there's no load, the relay unlatches, equipment pulls a load again.....rinse, repeat. You don't want to damage your gear.
 
#28 ·
i know someone who can help you out...look at dc power alternators, mechman alternators and if you scared of ecu voltage both vendors will turn them into external regulators for you and if you dont want that then you can google missing link audio. It is a module that will crank your voltage up to as high as 15.5....here are the links:

http://www.missinglinkaudio.com/
http://www.mechman.com/mobileaudio.html
http://www.dcpowerinc.com/

just email them and get a quote...also let me know if they will do a dual alt bracket for you and how much it would be....you can call or email them....very good guys to work with
 
#30 ·
Haha its no problem man.
Yeah that makes sense though. The more you pull from the batteries the lower the voltage would be. The two batteries i was looking at were either (2) Kinetik HC2000 or (2) Powermaster XS D3100. Im not quite sure how to gather useful informoation on batteries.

The specifications for the Kinetiks are:

Specifications
Weight: 61 lbs.
Ah: 102
Amps: 2250
Dimensions: 12" x 6.5" x 8.2"

•AGM Technology
•Sealed Non-Spillable Design
•Mount In Any Position
•Ultra Low ESR
•More Plates For Stronger Energy Density
•Higher Voltage Under Load
•Tightly Packed Cells
•Superior Heat & Vibration Resistance

--The Specifications for the Powermaster just says 2500 max amps and 117Ah, so not alot of information. But i see those batteries used all the time in professional setups. Any advice on these?
 
#31 ·
Ah = "amp hours". It means that you can pull 117 amps for 1 hour before the battery will be discharged. Works the same way with those rechargeable AA batteries. Let's say the capacity is 2500mAh (milliamp hours), which is 2.5 Ah. It means you can pull 2.5 amps from them for 1 hour and then they'll be discharged.

So if the battery was rated at 117 Ah and you wanted to run your system with an average load of 11.7 amps, it would last about 10 hours. Likewise, if your average load was 23.4 amps, it would last about 5 hours. And of course if you pull 117 amps, it would last 1 hour.

To calculate its life, divide the Ah rating by the number of hours:

117 Ah / 1 hour = 117A
117 Ah / 5 hours = 23.4A
117 Ah / 10 hours = 11.7A

Adding 4 batteries in parallel with 117 Ah capacity would give you 468 Ah of capacity, which equates to:

468 Ah / 1 hour = 468A
468 Ah / 5 hours = 93.6A
468 Ah / 10 hours = 46.8A

Sounds great, right? Well, it's not actually the case. The continuous current rating of the batteries will usually not provide you with 117 amps for an hour. It varies from manufacturer to manufacturer and by battery type. Their calculation methods may also be different. That's why you need to check for the continuous current rating as it may not necessarily match the Ah rating. Like always, YMMV.

Don't forget to calculate efficiency into your power requirements. An amp with 50% efficiency would require TWICE the power of its rated output, which means a 5,000 watt amp would require 10,000 watts of power (10,000W / 12V = 833 amps). This is an instantaneous calculation, which means you'd need 833 amps continuously. You'll probably find its efficiency in the specifications.
 
#33 ·
Ok so i went to the lanzar website and looked at the model mxa242 amplifiers, and in the specifications it did not state the efficiency of the amps. I also went to hifonics and looked and there specifications for the model zxi1010 also does not have it listed. Now i recall a while back in this post a member had told me for the lanzar amps i would need 90 amps capacity for each. so for 3 amps, based on his information, i would need 270 amps available, or at least 540 if these amps have at least a 50% efficiency rating. So 3 d3100 batteries would give me 351 Ah when wired in parallel? Also the batteries do not state continuous amps. The (2) Kinetik are 2600 amps 128 Ah. The D3100 says 1200 Cold cranking amps @ 32 F 200 min reserve capacity but nothing about continuous amps. Ive come to notice amp draw, efficiency, and continuous amps are extremely hard to find when it comes to amps and batteries.
 
#34 ·
The amplifier specifications will usually list current requirements instead of efficiency. A good class D amplifier will have good efficiency. For example, you said a particular amplifier has a 90A current rating at max output. 90A * 12V = 1,080 watts. So if the amplifier is rated for 600 watts, it's 55% efficient (600/1080 = 55%, which is pretty bad). A good quality amplifier with decent efficiency will help reduce your current requirements and cooling requirements.

Based on your figures, 3 batteries at 128 Ah would seem sufficient.

And that's a LOT of sound. :wow: Be careful you don't overwork the alternator with the added load of battery charge current.
 
#35 ·
Right thats what most people have been saying. I would love to change it but that instantly voids my warranty. Would there be anyway of possibly being able to put a switch there to charge the extra batteries, for instance whoul I be able to play them loud off the charged batteries then turn it down and press or flip a switch to send a current to charge them up again from the alternator?
 
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