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Discussion Starter #1
I have a 2011 Range Rover Supercharged and for like 5-6 years I didn't have any problems but now when I am accelerating, the vehicle jerks when the bass from the subwoofer hits at high volumes. If I am driving at a constant speed, you can feel the vehicle lose some power; you can also see the bump in the RPM on the gauge as well. When climbing a hill, it is very noticeable too.

We first thought it was an old battery problem and replaced the battery; that didn't help. Next, we found out the alternator had issues and that was replaced with a new one; that didn't help with the jerking.

Originally the power was taken from the rear fuse box by the person who installed the system and the voltage was dropping at the rear so we thought that was causing the problem. So, I ran the 1/0 gauge wire directly from the battery to the back and connected it into the capacitor (I replaced the original capacitor a while back with the current one in case that was in issue). I tested the sound system and the jerking did not go away. Almost no difference after bypassing the rear fuse box.

Next, I installed a second battery in the back, after fully charging it first. I connected the batteries in parallel (I did not put a fuse/circuit breaker between the back battery and the amps just for testing, but there is one between the first main battery and second). I do notice a decrease in the jerking when the bass hits but it did not go away. It is probably at least half of what it was before the second battery was installed. The bass also seems to be louder/stronger with this set up as well (hopefully its not just in my head).

I am thinking about permanently installing the second battery in the back to lighten the load on the factory electrical system. If I do, should I be adding any solenoid in the setup, or fuse between the second battery and amps, or anything else to ensure proper charging and safety? I don't ever listen to my music without the truck running so I am not worried about draining the battery with the engine off.

Second, since there is still jerking when the bass hits, any idea what the problem could be at this point? Would a high output alternator solve this issue? Would it be able to solve the issue without installing a second battery?

P.S. I am going to disconnect the power wire from the main battery today so I run on the second battery only and see what happens.


The set up is as follows:

2 Alpine Type X subwoofers
2 Alpine PDX-M12 1200W amplifiers
1 Farad Phoenix Gold Capacitor

Thanks!
 

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What about your ground wires? Same size as positive?
Since it didn't used to do this and now does, did you increase the amp gain level at some point?
 

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Discussion Starter #3
What about your ground wires? Same size as positive?
1/0 from battery positive to capacitor (currently replaced with second battery), 4 gauge from capacitor to "Y" soldered joint which splits into 2 separate 8 gauge wires (1 into each amp).
The ground from the capacitor (currently second battery) is 4 gauge.

Since it didn't used to do this and now does, did you increase the amp gain level at some point
I actually decreased the gains a bit in order to avoid possible damage to the truck's electrical system. I will lower them further and see how low I need to go to make it stop if it does. However, I don't want to go too low.
 

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Discussion Starter #4
I did some further testing yesterday, I disconnected the main battery from the second battery just to test what would happen with the sound system running from only the second dedicated battery. The result was that the truck was still jerking when the bass hit. The only relation to the truck the sound system has with that set up is that the ground wire on the second battery is still connected to the chassis. The lights still very slightly dim (same as before) as well. Does this change anyone's opinion about the suggestions?

By the way, I also took the power wires out of the amp connectors since they were showing some corrosion. I decided to cut the ends, strip them back, and connect them again. I saw that both the ground and positive wires going into the amps are corroded. They are green around the outside perimeter of the wire. The center in pretty clean. The speaker wire appears to be similar from what i can see through the clear jacket but I haven't taken those apart and stripped them back. These are about 9 years old. I was thinking to replace all of the wiring perhaps and replaced the soldered "Y" connections to the amps with power distribution units while maintaining 4 gauge all over and eliminating the 8 gauge. See image attached of one of the positive 8 gauge wires going into the amp. Could this be causing a problem? The ground wire to the chassis looks good however.
284898
 

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I think you are on the right track by walking through the wires and connections. The whole circuit includes your alternator and battery as well so if any of those positive or ground wires are corroded or loose, they could cause the problem. On my P38, the battery/chasis/engine ground wire looked great. Until I removed it and it basically broke in half. Corrosion is often inside the wire.
 

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Regarding the gain adjustment, I was wondering if you are using some sort of speaker level to line level gizmo to connect the amp. If the preamp connection is too low, you will have to run more gain for listening. Higher preamp level with reduced gain could possibly help. But from the sounds of your installation, it doesn't seem like a corner like this would be cut.
 

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Discussion Starter #7
I think you are on the right track by walking through the wires and connections. The whole circuit includes your alternator and battery as well so if any of those positive or ground wires are corroded or loose, they could cause the problem. On my P38, the battery/chasis/engine ground wire looked great. Until I removed it and it basically broke in half. Corrosion is often inside the wire.
I will be checking all of the grounds in the coming day and possibly adding a 4 gauge overlay to the existing wires (after cleaning them up).

Regarding the gain adjustment, I was wondering if you are using some sort of speaker level to line level gizmo to connect the amp. If the preamp connection is too low, you will have to run more gain for listening. Higher preamp level with reduced gain could possibly help. But from the sounds of your installation, it doesn't seem like a corner like this would be cut.
I don't think there is any device boosting the preamp signal. There is a box there which has the RCA's coming out of it but I'm pretty sure it is just a line output converter. There are not settings on it.

The more i'm reading about it, I am seeing that while the engine is running, the batteries won't really do much and that the alternator output is more important...
 

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I suspect two possibiloities: 1. the alternator still has an issue of not providing sufficient power for the loads. Try turning every electrical load off, and run just the stereo while driving. 2. There is a voltage drop somewhere close to the alternator, directly affecting the output. Note: if the amplifier output is notably higher than the original, you may need an alternator with a higher output. Subwoofers draw a considerable amount of current, especially when played very loud. Ray
 

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There’s a ground strap in the right front corner from the motor to the frame. It may be worth replacing given the corrosion you discovered on your interior wires.

There’s another ground strap between the transmission (near the starter motor mount) and frame. I’d consider replacing that too.

As a temporary “fix” connect a decent quality -ve jumper cable between a good solid metal grip on the motor (SC plenum etc) and the -ve on the battery.

Drive the car and check for any change/improvement (or not).

Rob
 

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These grounds can be checked for voltage drop using a DVM. Connecting the leads between battery negative and the component, such as the transmission, or components in the rear and setting the DVM foor DC volts, any reading above .5 volts is considered a drop. The engine will need to be running, headlights on high beam, A/C on, every high current load needs to be operating. Consider a .3 volt drop per connection a high limit. The high output alternator was suggested if the stereo draw exceeds alternator output with everything else running. This can be checked using a DVM also With every high current device operating, including the stereo, look for a voltage pulsating with the bass. Connect directly to the battery terminals, not the cable ends.
Note: by high quality jumper cables, we don't maen the ones with 10 ga wire.
 
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