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!

You need a split charger and a leisure battery to smooth the peaks and troughs that the alternator is seeing on its load. I did suggest this in your last thread.
Also, what rating is your capacitor? Many, many years ago when I had a big audio setup, I ran 2x 1 farad capacitors and still had a little of what you mention. It was noticeable as a drop in revs on idle. After installing a 2nd battery with split charger and running all the power from that 2nd battery I actually achieved an additional 4dB and the problem went away.

I read up about split chargers and understand how they work now. I read that they cause about a 1V voltage drop when wired into a system and that a alternator regulator is recommended. I also read that they are built into alternators. Is this something that I would need?

I suppose the above could ensure my batteries are properly charged. Remember though, I am not concerned about the batteries going flat since I only listen to the sound system or use electrical components with the truck started. I am thinking that the alternator would be needing to feed the system more amperage while its started? My capacitor is only 1 farad but the replacing it with a second battery instead was in effort to try to eliminate the capacitor being the issue (i've tried two different capacitors).

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 the opinion about the suggestion?

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 everywhere and eliminating the 8 gauge. See image attached in gallery 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.[/quote]

Connecting two batteries together will create a different scenario to introducing a split charger between them.
With two batteries you're working the alternator to charge both simultaneously whereas with a split charger you'll replenish the vehicle battery first and then supply charge to the 2nd.
If your audio is only connected to the 2nd you're effectively using the vehicle battery as a capacitor to support the discharge of the 2nd while also keeping the vehicle moderated. They need to be isolated to not allow the separate systems to pull from one another especially if one battery is holding a lesser charge than the other - the current flow may become higher than the battery can accept and you'll end up in a world of trouble with both pretty quickly.

That's probably not a great explanation but I hope you get what I mean.

Just an update:

I did some testing with a clamp meter for current today. I’m not sure if it was done incorrectly or not but I set it to AC 400A and I was getting the reading jumping all over but it looks like it was generally staying under 20A.

Here are some results for the voltage tests I can do more if needed:

1. Sound system turned completely down:

14.7v at the battery, fuse box under the hood, rear fuse box, and capacitor. These locations were all consistent with each other for the tests below as well.

2. Sound system high volume:

Voltage drops to around 12v and stays around there. It recovers to a higher number when the there is a break in the bass but comes back down when the bass starts hitting again.

3. Sound system turned all the way down but multiple accessories on (fan full, heat up, front two heated seats on with rear heated seats off, heating steering wheel on, heated windshield on, everything else off like wipers, rear fan, and sound system):

Consistently at 12v, even dropped to slightly under 12v momentarily.

4. Accessories on as indicated above and sound system turned up, not even near full volume:

Didn’t check voltage but sound started clipping out (including factory speakers) so I turned it down before damaging anything.

Looks like the truck can’t maintain a consistent even 13v+ with only the accessories on.

You absolutely sure you're not tapping your right foot in time to the beat....

I’ve thought of a lot of crazy things, like my head and body are just vibrating and therefore I think the RPM needle is lol.. or the vibration in my body is making me feel like the truck is jerking.. but I’ve ruled those out! Lol

I’ve thought of a lot of crazy things, like my head and body are just vibrating and therefore I think the RPM needle is lol.. or the vibration in my body is making me feel like the truck is jerking.. but I’ve ruled those out! Lol