Alternator and electrical upgrade can it be done??

[rennocneb]

Ok so i have read conflicting reports about whether or not we can step up to a higher output alternator. Some say due to pcm control we can not? im looking to run about 1300w rms stereo system using not very efficent JL Slash series amps, so im thinking the stock electrical system is going to be crying for momma. I know the first thing to do is a big 3 upgrade, but then ive read that putting a big power wire from the alternator output to our batteries positive terminal is a no no as well? just need to clear up can a big 3 be safely done on the liberty, mine is a CRD by the way. Also will a higher output alternator work as designed with the pcm control? if so whats the options out there for alternators?

 

[chris03kj]

I've got a 1200w rms system in just two 12inch subs, I also have a capacitor for a constant voltage. I get a lot of dim if I have the heated seats on, the fans on, and the headlights and fog lights on. If I only have the headlights on, the dim is way smaller. during the day I notice no issues. I have the 3.7 though, which may have a different alternator


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[rennocneb]

that dimming is what im trying to avoid, voltage drop is ******* stuff. Ive also heard a stiffening cap wont do much for you in the long run.

 

[dude1116]

I've heard that just getting a better, higher quality battery will help with those voltage drops. I'm pretty sure the issue tends to be with the battery not the alternator, although I can see where you're coming from and it can be a possibility. I'm sure someone with a little bit more experience will chime in.

 

[chris03kj]

I originally ran without the capacitor, and I really got dim in the lights, it would almost be impossible to drive at night with a deep long hit of the subs. Dimming (from what I've discovered) is a result of the voltage drop. (Correct me if I'm wrong). I've got a 1.2 Farad renegade cap leveling my voltage out. It helps with the dim A TON.


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[tjkj2002]

mine is a CRD by the way.

Pretty sure there is no option but a OE spec'd alternator for a CRD.

 

[rennocneb]

mine is a CRD, so not sure it makes any differences as far as engine grounding needs. I plan to run 0ga for a battery postive to alternator post, and battery negative to like the shock tower bolt perhaps id think that would be a good ground point, now how about the engine ground does it need to run back to the battery negative from say the alternator bracket, with 0ga as well? lastly i leave all the factory wiring alone and simply add the new correct? Also do i need to fuse any of these links im adding? and if so at what rating?

 

[Cardhu]

Do you really believe going to a thicker wire is going to cut down on power loss compared to the stock cables from alternator to battery that are ~5 feet in length max?

as for the dimming, most have had better luck with a better battery. with the stock mopar, mine would have the headlights dim when i rolled down windows. Similar story when traction control would kick on.

If that doesn't work, then run your 0G back to second battery mounted under driverside rear seat.

I'd normally say run a VSR (voltage sensitive relay) but i have no idea how it would act with subs. It will work well with a trolling motor.

 

[CactusJacked]

Look up Mean Green. They have 200+ amp alternators but don't have one ready made for a CRD. They do offer custom made alternators (which I'm sure might cost an arm and a leg). When you're up there in amps, it's strongly recommended to run new thick gauge wires/cables for battery supply (from the alternator) and ground. It's not to prevent power drop to the battery as much as it is to prevent the factory wires from having a melt down since they weren't designed to carry those many amps. Too small of a gauge of wire causes resistance, and heat.

 

[LibertyTC]

rennocneb, This reply may get a bit lengthy. I have had a Pc-1500DT Odyssey battery in my KJ and at idle notice my interior lights still dim when operating power windows. IMHO it is not so much the ALT that is in question as it is the small diameter wiring used in harnesses that is the problem. What I would like to know is when u crank your stereo system up, what does the voltage drop to at idle and at 1400 rpm? at both the battery terminals and from an interior accessory socket as well. (someone with the right testing equipment may be able to view the ALT load draw/diagnose) see final comment.
It also should be noted that as the ALT's amp draw is increased it is normal to see the voltage drop a bit. More amps output = less voltage is normal!
If at idle is the problem and not so much at 1400 rpm, you would be well served to understand that most ALTs do not work well with large draws at idle and the fix is utilizing a smaller diameter pulley and new re sized belt,as the ALts dont produce enough driven amps at even 800 rpm, and a smaller dia pulley spins the Alt faster bumping up the ALT pulley rpm sufficiently, & in most situations work better than ordering a new High output ALT. Which can have the same problem with lower rpm ranges without the right diameter pulley.
AS I have experience with H/O ALTs (not in KJ) but my options loaded car with powerful stereo, on board air compressor for leveling etc, and have upgraded my ALt there using a quality power custom built from California.
This link will explain a lot from Quality power: Alternator Frequently Asked Questions FAQ
The other issue is how the vehicles low voltage or regulating sensing system works.
In a KJ I can not speak of that Maybe Troy can? In my car a sensing wire mod took place and voilla, all is so much better now.
Hope This Help ya all...
For my car I also built a Ancor marine grade (tin/copper) 2ga wire with an in line 200amp wafer fuse, runs from back of alt directly to the + battery terminal & ..( Troy re kJ?)
there was a slight improvement. Also upgraded the ground wires as well...nice!
I would highly recommend before you do anything, consult with a good tech at one of your local high end custom stereo installer shops as well.
And Lastly, always ensure that your existing alt is diagnosed properly to include: ALT AMPS/loaded/unloaded output at variable rpm's and a Diode performance test/check.
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[Billwill]

Ok so i have read conflicting reports about whether or not we can step up to a higher output alternator. Some say due to pcm control we can not? im looking to run about 1300w rms stereo system using not very efficent JL Slash series amps, so im thinking the stock electrical system is going to be crying for momma. I know the first thing to do is a big 3 upgrade, but then ive read that putting a big power wire from the alternator output to our batteries positive terminal is a no no as well? just need to clear up can a big 3 be safely done on the liberty, mine is a CRD by the way. Also will a higher output alternator work as designed with the pcm control? if so whats the options out there for alternators?

The 2005/6 CRDs have a regulator built into the alternator....not like other KJs that are regulated externaly by the PCM so the ECM for the CRDs has nothing to do with it other than sending a "wake up" signal to the alternator.
This is according to Keith from GDE although the circuit diagrams do not show this...from other forums where this has been discussed I believe that Keith is correct and that the 2005/6 CRD circuit diagrams are wrong!

Also bear in mind that the thick wire going from the alternator to the battery has a built in "fusible link" so you cannot simply replace this wire with a thicker wire.

So I believe that any alternator that has its own built-in regulator will work provided you upgrade the thickness of all the wiring....and watch out for the fusible link!

Maybe better to add a second battery and have thicker wiring....the "How To" section here has some ideas regarding this :icon_cool:

 

[Birdman330]

^ Run a ''Slave Battery" though if you have a Diesel you should be able to put on a higher heavy duty amp alternator. Even if you have a 3.7 most gas engine alternators are PCM controlled but a higher amp alternator can be installed to help with a heavy duty battery such as an Optima Yellow Top which is highly suggested for heavy electrical loads. Its my understanding that the computer will read a higher amp alternator and adjust the charging capacity from it. I could be wrong. I've noted that on my 3.7 that the TCS really kills the power especially with this winter. As in heater fan slowing and lights dimming out terribly. I've been considering doing a slave battery myself to help out for next winter. I've never seen a vehicle act like that when TCS alone is engaged even on a manual transmission.

 

[Billwill]

^ Run a ''Slave Battery" though if you have a Diesel you should be able to put on a higher heavy duty amp alternator. Even if you have a 3.7 most gas engine alternators are PCM controlled but a higher amp alternator can be installed to help with a heavy duty battery such as an Optima Yellow Top which is highly suggested for heavy electrical loads. Its my understanding that the computer will read a higher amp alternator and adjust the charging capacity from it. I could be wrong. I've noted that on my 3.7 that the TCS really kills the power especially with this winter. As in heater fan slowing and lights dimming out terribly. I've been considering doing a slave battery myself to help out for next winter. I've never seen a vehicle act like that when TCS alone is engaged even on a manual transmission.

The alternators that do not have a built in regulator...such as all the gassers...do indeed get their regulation from the PCM.

The PCM does not have any way of knowing what current the alternator is capable of supplying nor does the PCM or any other component actually measure the current being drawn.

What happens is that the PCM measures the battery voltage at a certain point. As the current through all the wiring increases so this point suffers a voltage drop due to the voltage drop across all the wiring.

The PCM then increases the amount of current flowing through the field coil inside the alternator....it does this by increasing the pulse width of the ground side of the field coil...called Pulse Width Modulation. When the current draw gets too high the ground side of the field coil is no longer pulsed but is now firmly down to ground. If you continue drawing this amount of current the battery goes flat and you grind to a halt!:icon_smile:

 

[Birdman330]

So then any higher voltage aftermarket alternator is then snake oil for a gasser engine.

 

[tjkj2002]

So then any higher voltage aftermarket alternator is then snake oil for a gasser engine.

No such thing as a "higher voltage" alternator for a KJ,that would be very.very bad for all the electronics plus the PCM(or ECM for the CRD's) will kill the power to the alt anyways if it reaches 15 volts or more.

 

[Birdman330]

Eh I should have worded that more properly cold meds do wonders but leave the brain cloudy, I should have said higher amperage.

 

[Billwill]

Eh I should have worded that more properly cold meds do wonders but leave the brain cloudy, I should have said higher amperage.

I do believe that a higher rated amperage alternator can supply the larger current required by add on audio. The renegade has a higher rated alternator for the gassers.

As long as thicker wiring is used throughout it should work...the alternator simply ups the output voltage to compensate for the voltage drop across the thinner wires when large current is being consumed but once the field coil has its maximum voltage applied then the alternator will not be able to supply any further demand.

 

[the_dealer]

I did the big 3 by adding on to the existing wiring. For the 0ga wire from the alt., just put in an inline fuse. I use 150a. At idle with your system at full tilt, check your voltage drop at the battery. Then do the same at the amp. If you are getting more voltage drop at the amp then your power/ground wires are undersized. There's charts that show wire size, wire length, and draw on www.the12volt.com

When doing the big 3, DO NOT, replace the factory wiring with your upgraded wiring. Always add to them, and always run at least an 80a in line fuse from the alt to the battery

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[Billwill]

I did the big 3 by adding on to the existing wiring. For the 0ga wire from the alt., just put in an inline fuse. I use 150a. At idle with your system at full tilt, check your voltage drop at the battery. Then do the same at the amp. If you are getting more voltage drop at the amp then your power/ground wires are undersized. There's charts that show wire size, wire length, and draw on Car Alarm, Car Stereo, Mobile Video, and Cruise Control Info for Installers

When doing the big 3, DO NOT, replace the factory wiring with your upgraded wiring. Always add to them, and always run at least an 80a in line fuse from the alt to the battery

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Yep this^^^^^ is the way to do it; an 80 A inline fuse in the additional wiring will do just fine.:icon_cool:

 

[tjkj2002]

I'd do a much higher amp fuse then 80a if using 0awg wire,major chock point and easily blown since the alternator can produce much more then 80a.