Getting bad headlight dimming, what to do?

[blue07]

My setup consists of:


-Big 3 done in 1/0 AWG
-1/0 going to a distribution block, with a single 4 gauge run coming out, and a single 8 gauge run coming out. (everything is fused properly too)
-Proper grounds.
-PDX 1000 (very efficient that's why I chose it)
-MRP 250 (mids and highs, very small amp)
-gains turned down
-stock battery




I haven't had it too long, maybe 1 week, and I don't play it much due to the dimming.


What should I do to fix it? My friends say get a cap, while it will fix the dimming, there is still a problem, and I'd rather not go down that route.


So far my options seem to be:


-Get a yellow top up front
OR
-add a second battery to system



Which one should I go with, or is there anything else I should consider besides upgrading the alternator, which I do not want to do for such a small daily setup.

[quickfit]

get a stonger alternater

your alternator is teh waekest link in the system.
-a second abttery can only hold as much poer as is being supplied ot it (from the alternator)
- unless your OEM battery is bad, no need to upgrade it.

[HsOffRoad]

First off, a link to my DIY on headlight dimming - it should answer all of your questions:

DIY - Understanding Voltage Drop (Headlight Dimming)

Second, Quickfit is incorrect. A bigger alternator is not the way to go about addressing your problem. You need to upgrade your battery to a larger unit (or multiple larger units, depending on how much power you are running), and make sure your power/ground/big three wiring is good quality 100% copper cable, and all connections are solid and tight. If you haven't alreay done so, I would consider running a main amp ground back to the negative battery terminal, the same way as you ran the main power wire (A single run of 1/0 AWG from the negative battery terminal to a distribution block, then from there 4 AWG and 8 AWG to the ground connections on the amps).

Having a bigger alternator is nice for keeping the charge up in large battery banks (like when you have a group of 8 or 10 deep cycle batteries for very high-power SPL-type audio systems), but is certainly not necessary for what you have going on. In high-draw situations, regardless of what kind of alternator you have, you will be relying on the battery bank's reserve capacity to provide the necessary current and keep voltage stable.

The DIY has formulas for determining things like the gauge of power wire you should be using, and the size/number of batteries necessary to properly power a given number of watts.

Like I said, it should answer your questions... but if anything is unclear, just ask.


Hans

[blue07]

My amp can't take anything bigger than 4 gauge, so I can't use 1/0.

That DIY is very helpful, thanks.

The power I'm running is ~1300 RMS.

According to that DIY, I need a battery thats capable of 80 AH at least.


Which one should I get? I plan on using it under the hood, so it cannot be too big. Will a yellow top be enough?

[HsOffRoad]

I understand that your amps can't accept 1/0. What i was getting at was upgrading your ground wiring by running a single run of 1/0 from the negative battery terminal to a distribution block, and then from there using 4 AWG and 8 AWG to connect to the amps themselves. The reason for this is that flow through a circuit is limited by its point of highest resistance, which means that if you are currently grounding the amps to the chassis, that may be part of your dimming problem.

For example:

Lets say you are running big, 1/0 AWG power cable from the battery to your amps, but grounding them to the chassis. That means that the metal of the chassis now has to complete the circuit back to the battery. Now if the metal in the chassis only conducts as well as say, 4 AWG power cable... the fact that you are running 1/0 for power is useless, since the circuit can only flow as well as its point of highest resistance... the chassis. You follow? If thats that case, you could upgrade the power wire to huge, 4/0 cable and your headlight dimming wouln't get any better, since the chassis would still be limiting flow through the circuit as if it were a 4 AWG wire.


By running a dedicated run of 1/0 back to the negative battery terminal, and grounding the amps to that, you guarantee that the flow is the circuit is maximized... because in this case, you know for sure that the ground wire and the power wire both have the same resistance. Its like having a 4-lane superhighway for the current running through the amp grounds to get back to the battery.

It does cost something, but its definitely the best way to go if you have a high-power setup with 1000+ Watts RMS.


As for what battery to go with, it depends on where you want to put it, and what you can get a good deal on. You will want to start by upgrading the underhood battery to a larger, deep-cycle style unit. A group 34 size battery is about the largest thing you can fit under the hood of our cars (approx. 10" long X 7" wide X 8" tall). Many companies offer batteries in this size, although not all of them call it a group 34 (it doesn't matter what they are calling it, if its close in size to 10" X 7" X 8", it will work). Companies like XS Power, Optima, Kinetic, SVR, & Xstatic (batcap) all make deep cycle batteries of that size that are specifically designed for audio applications. Sears sells a group 34 size Diehard Platinum thats not marketed as an audio battery, but its not a bad unit for the money. You can also use batteries designed for other, non-stero applications. Many SPL competitors use telecommunications style batteries, such as the Northstar NSB series.

Some batteries cost more than others, and some claim more power for their size... but anything is going to be a huge step up over the stock unit. Like I said, a lot will depend on what you can get a good deal on.

If after replacing the underhood battery with a group 34 size unit, you still have dimming, you will need to look into mounting additional batteries in the trunk or rear-floor area of the car.

Everyone hates spending money to upgrade their electrical system, but if you want to run big amplifiers, you have to do it. An amplifier can only produce as much power as it has coming into it, so buying some huge 8000W amplifier is worthless if you are running a tiny battery and cheap, aluminum 4 AWG power cable.


Hans

[HsOffRoad]

Group 34 and 34/78 yellow tops are rated at 55 AH. You can start with one of them (or a similar size unit from another manufacturer) in the stock location, and see how it works for you. It should be fine at low volumes, and will definitely be a HUGE improvement over the stock battery... but at high volume, especially with extended use, you may still get significant dimming.

At that point, if you have upgraded your ground wiring like I mentioned and still have dimming, there's really no way around it other than adding a second battery in the trunk or rear floor of the car, or turning the gains down on the amps to limit the amount of power they are making.


Hans

[blue07]

I currently have the 4 and 8 gauge negative runs going to a distribution block, out to 1/0 to the chassis. I will look into making a neg. run to the battery, very good advice.


I can get a Yellow Top for $160, is that a good deal?

I will look into batteries within those dimensions at Sonicelectronix, hopefully I can find a good deal on one there....is there any other stores online cheaper?

If I still get dimming with an aftermarket battery, I will get a small HC800 for the trunk.


But lets just say I did get an aftermarket under hood battery, would it make a difference in the sound of my system? I'm guessing it would be louder?

[HsOffRoad]

What the amp is doing is in essence converting the power from the battery into sound.

So if the battery can only produce enough power to make, say, 500 Watts RMS, then anything above that will cause substantial voltage drop, headlight dimming, and possible damage to the equipment.

Since you are dealing with voltage drop now, you know that the battery is limiting the amount of power that the amps can effectively make.

So yes, if you install larger, more powerful batteries, then your amps will be able to produce more power than they can with the weak, factory battery.

If you only upgrade the underhood battery, you may still have issues though, because the amp may still require more power than the single battery has to play at full output. In this case, you would either need to turn the gains down on the amp so it makes less power, or add more battery power to support the needs of the amps.

Do you understand how amp gains work, and how to set them mathematically?


Hans

[blue07]

I'm pretty sure I'm going to get the yellow top from my local shop, it's $20 cheaper than online not to mention i gotta pay for shipping if i order online.


It's rated at 55 AH, but if my alt is 70A, and half is used for other electricals in the car, I will have around 90A which seems good to power the amp....

EDIT: we posted at the same time.


If I still have problems, I will order a HC800, and make a 1/0 run to it from under the hood....I really don't think I will have anymore dimming though, because I also have the big 3 done, and my amps aren't too big, together they draw like 80 amps tops after efficiency (if there 70% efficient, they won't pull the full 110 A)


If I get an aftermarket battery for the rear later down the road, will I be ok with the stock alternator?

[HsOffRoad]

The stock alternator will be fine... but the efficiency calculation doesn't work that way.

You can use the efficiency adjustment figure a few ways, but I'll try to explain how it would apply to current draw and output power.

First, look at the fuses on your amps, and add up their total amperage. Obviously, this is the highest amount of steady current your stereo will be able to draw for any extended period of time - any more and it would blow the fuses. So lets just say your fuses add up to 100 Amps.

In a perfect world, assuming zero loss (100% efficiency) and a steady 13 volts of signal pressure, the amplifiers could convert that 100 Amps of current into exactly 1300W RMS of power. (100A X 13V =1300 Watts). That is the definition of 100% efficiency... perfect power conversion, with no loss whatsoever from heat or other parasitic physical drains.

Unfortunately, we live in the real world, where things don't work like that. Obviously there are going to be losses whenever you convert energy from one form to another. Some amps (and amp designs) are more efficienct than others, and they all tend to be more efficient at higher impedances than they are at low ones... but to be safe, we can assume 70% efficiency... meaning 70% of the power that the amp takes from the battery actually gets turned into sound.

You can think about this two ways. First, we can apply the efficiency figure to our theoretical wattage value, and get a realistic idea of how much power an amp is really capable of producing with a certain amount of input currrent.

In this case, if we use our initial figure of 100A of fuse having the potential to make 1300W RMS with no loss, we can apply the efficiency figure to our ideal figure of 1300W RMS, and we come up with 910W RMS (1300W X 0.70 = 910W). This shows that in the real world, at 13V, an amp with 100A fuse on it will not be able to make more than around 900W RMS (regardless of what it says on the box).

Its good to know this info when looking at amplifiers... because you see these amp companies that claim their amps make 1000W RMS, and then they have 40 amp fuses on them. Regardless of what the amp company says their amp can put out, the math doesn't lie.

Now of course, you can also apply the efficiency figures the other way, and use it to figure out how much current you really will be drawing at a given wattage… which is precisely what the math in the Voltage Drop DIY does.

But no matter what is going on, efficiency always works against you. Meaning you will either make LESS power, or draw MORE current than you theoretically would.... never the other way around.

Hopefully that clears things up.


Hans

[blue07]

So that means I'm under powering my sub?!?

What amp is best to run a JL W7? I currently have a PDX1000, which claims 1000wrms, and it has some certification thing....

[HsOffRoad]

What amp you want to run depends on the enclosure you are using, and how loud you want it to play. If you are looking for maximum output (on music), you generally want to use a large, ported enclosure with a ton of port area, and an amplifier(s) rated for at least twice the RMS rating of the woofer, if not more (at whatever nominal impedance you are wired for).

That would mean that for say, a single 12W7, you would be looking for an amp in the 2000-3000 Watt RMS range. The problem is, those woofers use a goofy, single 3 ohm voice coil... which seriously limits you amplifier choices.

Now obviously, if all you are trying to do is get a little extra bass out of your system, you don't need to run an amp that large. Something rated for 1000W RMS at 3 ohms would work just fine. It will even work off of less power, if you don't expect tons of output volume. A lot comes down to what you are looking to get, output wise.


As for the PDX 1000.1 , With 80 Amps of fusing, at 13V, it will be limited to around 720 W RMS.

When you look at the CEA rating system, it assumes 14.4 Volts of input, which isn't practical in the 12V electical system in our vehicles. They also test the amps at a 4 ohm load, at which point the amp is much more efficient than it is at lower impedances. Not that the CEA system is worthless, but it doesn't necessarily express completely accurate figures, either.

But to explain where the CEA figures are coming from...

If we do the math for the amp at 14.4 Volts, and assume a higher efficiency due to the higher impedance load, you can see that you can get close to their 1000W figure. 80A X 14.4V = 1152 W RMS. Now apply a higher efficiency number, say 85%, and you come up with 979.2 Watts - pretty close to the stated 1000W RMS.

So yes, its doubtful you will be getting full power out of your amp... but that doesn't mean its the end of the world.

Without getting overly complicated, when you look at the way impedance works and the losses of the speaker itself due to heat, friction, etc... it turns out that the speaker is almost never getting anywhere NEAR the actual power the amp claims to be able to make (which is a big part of the reason why if you want the thing to play really loud, you use an amplifier rated for 2 to 4 times the RMS rating of the speaker).

For normal use, you will be fine with whatever power you wind up getting out of the PDX. It may not set any SPL records, but as long as it's loud enough for your taste, don't worry about it. As you can see from the above explanation, a speaker's RMS rating doesn't mean that much anyway. Other than going off of test figures and reputation, the only real way to know how much power a speaker can withstand or an amp is capable of making is to look at the components used in its construction and its design... which can get pretty complicated. If all you're trying to do is get a little extra bass in your car, don't sweat this kind of stuff.

But it does help explain why having a solid electrical system with heavy gauge wiring and enough battery reserve power to keep voltage up around 13V is important, and why some of the competition guys run their amplifiers off of dedicated 16V or 18V electrical systems. When you are trying to get a lot of ouptut volume from the stereo, having steady input voltage is key.

Just think of how much power you are losing now with the voltage dropping... if you were happy with how loud it is now with the headlights dimming, you'll really be stoked once you get your electrical system up to par.


Hans

[blue07]

Very good explanation....honestly, I wouldn't feel comfortable throwing 2k at a W7, I'll go big on my next setup once I get the cash together...and a few extra batterys.

So you think the yellow top up front will be up to par for my system? Or should I look into doing more upgrading?

[HsOffRoad]

Like I said, I'd start with a single group 34 or 34/78 yellow top under the hood, along with running a main 1/0 AWG ground wire, and if you haven't already done so, picking up some mil-spec battery terminals. That will definitely be a huge improvement, and may be enough, depending on the way you use the stereo.

If after that you are still getting dimming, you will need a second battery to mount in the trunk, and wire it into the audio circuit by running 1/0 AWG from its positive and negative terminals into your existing distribution blocks for your main power & ground wiring (this is a lot easier than trying to run 1/0 AWG all the way from the front battery to the trunk, and serves the same purpose). Mounting wise, many different companies offer mounts for holding group 34 and 34/78 size Optimas (like this one from Billet Specialties):



Obviously, you can go with a different size or make of battery in the trunk, it doesn't have to be a group 34 Optima. But the group 34 Optimas do tend to simplfy things somewhat, because they are very common and widely supported. If your battery fails, you can get a replacement relatively easily, and there are tons of companies out there making mounts and such for the group 34 size units. Most of the other brands/sizes are going to be less supported, meaning that you'll have fewer choices for replacement and may need to fabricate your own mount(s).

Two group 34 size yellow tops would definitley be sufficient power for what you are running now, and give you a little room to upgrade to slightly larger amps in the future, should you ever decide to do so. If you do get two batteries, make sure they are compatible charging types and both deep cycle design. For instance, you wouldn't want to mix yellow and red top optimas, since one is a conventional starting battery and the other is a deep cycle type unit.

No matter what you wind up with battery wise, I would definitely recommend running a main ground wire the way I have been mentioning.


Hans

[blue07]

will i need a mount for a yellow top G34 under the hood or is the stock one okay?

[HsOffRoad]

Nope, the mounts are used for safely mounting a battery elsewhere in the vehicle (the trunk, rear floor area, etc.). For replacing the underhood battery, you can just modify the stock battery mount a little bit.

To get the group 34 to fit, first you will need to either modify the plastic base on the factory mount by cutting it down and making some sort of spacer to fit in the recessed area, or you can just remove the whole plastic base completely and not use it (in this case you would rest the battery directly on the metal bottom of the tray, with no plastic). Either way, you will want to bend the J-hook tabs on the base out out some (to accommodate the wider battery), which can easily be done with a pair of pliers, or even your bare hands. Finally, you will need to go to a Pep Boys, Autozone, Etc. and get a new, wider battery hold down crossbar (they sell adjustable ones that work with different width batteries, or if you prefer you can measure and make one yourself out of a piece of flat stock or angle iron) and a new set of J-hooks, washers, & wing nuts, all of which are available at pretty much any auto parts store for a few bucks each.

You will also need to modify the factory positive battery cable to fit with the new battery terminals, which will require removing the red plastic cover on the factory cable, unbolting the factory end, and then trimming down the metal so that it can connect to the military style terminals (This will all make perfect sense when you have it apart and are looking at it). You will also need to unhook a few of the clips holding the factory wiring in place, and re-route them with some zip ties. Since you have already upgraded your big three wiring with 1/0 AWG, you can just get rid of the factory ground wires completely.

Thats pretty much it, all in all, not very complicated.


Hans

[Debo]

this is good info... Hans you are the man...

[blue07]

Originally Posted by Debo

this is good info... Hans you are the man...

+1


Put in the yellow top, now dimming is minimal and I think I can live with that, it's only as much as when I had my 500 watt amp for my first system, hardly noticeable.


Thanks for all the help Hans, and others. I will be making a thread with the pics later for you guys to check out.


EDIT: here ya go

small system in FA5, JL W7, Alpine Head unit, MB Quart components! Check it out!

[rEdLiNe]

Im also having dimming issues. I shoe horned a Kinetik HC1800 rated at 81 Ah. I will be doing the big 3. Any suggestions? My story is: Im currently running a PDX 2.150 & 1.600. pushing a set of of Alpine Type X components & a DC Audio 12" Level 4. Im unhappy with the turn out and will be going with a DLS A5 pushing a set of DLS UP6i components (maybe upgrading the midbass with Iridiums) and a 10" Nobelium. Eventually I want to go active and a second amp (A2 or A4 if I upgrade to 3-way).
Sorry for the winded post & hijacking.