Toyota Yaris Forums - Ultimate Yaris Enthusiast Site


Go Back   Toyota Yaris Forums - Ultimate Yaris Enthusiast Site > Technical Forums > In Car Entertainment + Electronics (audio / video / alarm)
  The Tire Rack

Thread Tools Display Modes
Old 02-28-2009, 09:51 AM   #1
Roadrunner Jr.
sqcomp's Avatar
Drives: 2007 Yaris S
Join Date: Jan 2007
Location: Back at home
Posts: 2,614
Send a message via AIM to sqcomp
Electrical System Upgrade Advice

This topic was brought over to this forum from Sounddomain. I know many of the moderators on the site, having been one myself. There is a LOT of good advice over on that forum if you'd like some reference. Thanks go to xTHANATOPSISx for the write up:

"At-A-Glance" Guide To Electrical System Upgrades

If you're interested in making some upgrades to your car's charging or electrical system, but want some advice, you've come to the right place. I hope to make this clear and simple, to use as baseline information on what you need and why. If you are still confused, by all means, ask a direct and clear question and tell us what you don't understand. This SHOULD cover what you need to know, and give the next step.

"How do I know I need to upgrade?"

Many times, people ask what upgrades to make before they even buy their system, let alone install it. While in cases of very high power systems, it's a given, some systems may require remarkably little reinforcement. If you can save money without cutting corners, you will certainly benefit. So here's the first tip:

If you are installing less than 1000 watts in a car with a 90+ amp alternator, install your system FIRST!

In many cases, with moderate power, up to 1kw, you will not need to make significant upgrades to support a daily driver system. Music is dynamic and average listening levels are not sufficient to tax a decent charging system. Rushing out to buy an expensive high output alternator may be a waste of money. It takes a fairly harsh current draw to really push the limits of reliability on a system with 90+ amps supply and in many cases you won't even have significant voltage drop. By installing the system first, you can gauge how much the voltage drops, decide what is the best, and the most cost-effective way to solve the problem. So if your system is still at the manufacturer's warehouse, WAIT! Read the rest of this later. It will be here.

"My system makes my lights dim! What should I do?"

Dimming lights aren't actually the problem. They are a symptom of a problem. When your stereo amplifier tries to produce a lot of power for a loud bass note, it uses a relatively large amount of current to do so. If this current isn't available, it causes the voltage of the charging system to drop lower than the constant. When the voltage drops, it causes things like lights to dim and makes electric motors slow down. This is because lower current requires higher voltage and vice versa to do the same work. If the current is being used, and is insufficient, voltage will drop. This is the problem. You don't have a sufficient supply of current to keep the voltage up all the time.

So you've identified the problem. Now let's look at the severity of it. How badly do the lights dim? If you played a LONG loud bass note, would the lights dim and remain dim the whole duration of the note? Would your lights only dim for moment at the start of the note? Go check. This is important. I'll wait.


Ok, so if your lights only dim for a moment, you're probably only dealing with a minimal voltage drop caused by "regulator lag". This is the condition where the regulator that "tells" the alternator when and how much current to make can't recognize the demand quickly enough. This causes the voltage to drop for a split second until the regulator tells the alternator to make full output and then the system recovers. This is easy. If you have regulator lag, skip ahead to your section below.

If your lights stay dim the whole time, you've got a bigger issue. You simply do not have an adequate charging system. It's time for another test. This time, get out your voltage meter or watch the horridly inaccurate gauge in your dash, if so equipped. Now play the same long bass note and see how much the voltage drops by the end of the note. If you see it drop from say, 14.4 to 13.1, you've got a strong voltage drop. If you get less than a full volt drop, you've got a minimal or moderate voltage drop.

If you drop 1.x volts, you're dropping nearly 10% or more of your voltage and that translates directly into amplifier power output. You'll need to consider some more extensive charging system upgrades than others with lesser draws. This should be obvious, but many people want a massive, $500 H.O. Alt to rectify a .7v drop. Go on ahead to the part about moderate voltage drops for more information.

Finally, if your voltage is hitting 13.0 or lower, you've got a high to severe voltage drop. You're getting dangerously close to the static charged voltage of the battery and that's no good. First of all, you're cutting a LOT of power away from most amplifiers. Second, your battery may be fighting for a charge and you may eventually damage it and end up stranded, needing a jumpstart. Find your section below.

Regulator Lag

While many people think capacitors are "evil" or "junk" or even "voodoo", regulator lag is the only thing I'll recommend them for. When you have a small and momentary voltage drop lasting less than a second, you can get the intended benefit from a quality capacitor. With a small, short "twitch" in the voltage, you may not face any real ill effect, but have an annoying blink to your lights. For many people, that's enough cause for alarm. So you want to relieve some or the entire lag? Check out the capacitor section and take the action you feel appropriate. Regulator lag is unlikely to cause any damage to your car's electrical system and its not long enough to noticeably reduce the power output of your stereo system. If you can live with the brief twinkle of your lights, don't bother spending money if you don't want to.

Minimal & Moderate Dimming

With moderate dimming, you can typically reduce or eliminate the problem with the Big 3. It's a cost effective way to, if nothing else, make your charging system as efficient as possible and if not cure the voltage drop, reduce it to something lesser, like regulator lag. You can get more info on the Big 3 below, or view the sticky on the main page for in-depth info and some good How-To and pictures.

High & Severe Dimming

With high to severe dimming, you're likely overtaxing the stock alternator and charging system. When you reach this point, you're adding a significant, unintended current draw on the alternator and can potentially shorten its lifespan. You can also starve the battery, causing drain and damage. None of this is a good thing. You're most likely to need a higher output alternator. This will supply you with abundant current to power the system AND the car that carries it around. Once again, head down for more info.

"But won't a fancy, popular, expensive battery fix all this?"

If that question sounds ridiculous, just search and see how many times people ask if they should buy a nearly $200 battery to solve a problem that's 99% to be in no way related to the battery's type or condition. First of all, the battery's voltage is only 12.2-12.8 depending on condition and charge state. That's well below charging voltage of the alternator and below the optimum voltage for your amplifiers.

Batteries are for starting cars and providing power when the engine is OFF. If the car is on, your battery is charging for the next time you need to start the car. That's all it's really there for. Starting the car. Unless you drive a hybrid, I'm not even STARTING to address that in here. Just go ask your question now.

What you need to do when it comes to batteries is ask ONE question of yourself:

"Will I ever listen to my stereo with the car's engine OFF?"

If not, then you don't need anything more than the battery that the parts store recommends for stock replacement. You're not asking anything extra of the battery, so you need nothing extra from it. Don't waste your money where its poorly spent.

If yes, then consider how LONG you'll listen with the car off. If you will only listen until your favorite song on the radio is over or long enough to show your friends your system, but rarely if ever more than 10 to 15 minutes, you need only a deep cycle battery to provide durability and sufficient key-off time to prevent dead batteries.

If you are the guy who brings the music to the beach or park, then you need a second battery and ISOLATOR. The isolator is important here because without it, you'll still drain you main battery and need a jump. If you drain a regular battery to nothing, it'll never be right again, so use an isolator so you can start your car off a standard OEM-type battery. Then install a second, DEEP CYCLE battery that is isolated when the car is off so you can safely take the deep cycle to nearly dead and recharge it after you easily start your car. This is what deep cycle batteries are for. They can be taken to that dead or near it state and recharge and HOLD that charge MANY more times than any standard automotive starting battery.

For information on batteries and isolators, please go "BACK" and check out the sticky below this one about them.

And now a little information on what each upgrade does for you and what to do with them.


Capacitors are, in a way, like a battery. They simply release current faster and store less of it. A capacitor is intended to provide a resistance to a change in system voltage. They store energy and, when voltage drops, release it to try and maintain the voltage to which they were charged. They also store energy at the voltage of the system, rather than 12.x volts like a battery. So for brief voltage drops, they can be beneficial. They won't fix anything more than small dips caused by regulator lag, but they can do that.

Caps are pretty easily installed and typically cost less than $100 for a good, basic 1Farad electrolytic (cylinder typically) type cap. The "rule" has been to use 1F for over 1000 watts of amp power, but I do it a bit different. First of all, many will tell you that you should put the cap nearest to the sub amp so the sub amp gets the power, not the rest of the system where it's "less needed". The fact of the matter is that if the voltage drops because of any draw on the electrical system, the voltage drops at the cap, and the cap discharges a bit. Even if you hit your power windows or turn the AC on, the voltage can drop and the cap will dump power. This is because the voltage in the positive side of the charging system is common throughout the system. You can't have more power at the amps, without the same voltage being available elsewhere, without some rather pointless filters and diodes. One point on a positive wire is the same as any other. The connection at the end of your power wire is electrically the same as the connection AT the battery. Voltage is common to the system.

So by that nature, even if you put the cap directly next to the amp in the wire, the voltage will be transferred throughout. This means that connecting it in the main power wire or to an empty power input on a distribution block is fine. Do whatever the installation requires so you can keep the power and ground wires short to reduce any line loss. This is why I deviate from the 1f/kw "rule".

I prefer to use no less than 1Farad on any system needing a cap. This is in part because it rarely makes a noticeable difference in cost and the extra capacity is never a bad thing...unless you're already overtaxing your alternator. Then, if I need more than 1Farad, I add another full farad. So for 1001 watts and up, I'd recommend having 2F of capacitance available. This ensures you get the desired performance from the cap without stressing them. Additionally, many amps are under-rated and make more power than the spec sheet says. This can easily be enough to take you beyond 1kw with an amp rated at 900+ watts. Always consider the real world, not just the papers.

Also, I believe that having the cap before the split to the amps is beneficial because it typically puts the cap before the fusing and this prevents any accidental shorts that could cause more damage if the cap were allowed to discharge fully rather than blowing the fuse and cutting off all power. Adding extra fuses is impractical, but putting the cap before them only requires a couple ring terminals and you are already going to break the wire for the cap anyway, might as well protect your investments.

The Big 3

The Big 3 is a charging wire upgrade that allows your alternator to get the best connection to the battery and charging system. It also makes certain your chassis is the best ground it can be. This is done by supplementing the stock wires from the alternator positive to the battery positive, engine block/alternator case to battery negative and battery negative to chassis ground.

You use a larger wire, preferably the same size as that wire which feeds the amplifier(s) but not less than 4ga for any practical gain. You also place a fuse in the wire between the alt positive and battery positive to prevent a short causing a fire.

By making these connections better, many people see as much as a full volt of increase in charging voltage. Also, many times you'll recover from a hard discharge more quickly than before because current can flow more freely into the electrical system. You also remove strain from the stock wiring when powering a high wattage system.

For more info on the Big 3, once again go "BACK" and look in the sticky covering this upgrade.

High Output Alternators

A high output alternator is one that provides more current than the factory available unit for your car. Most H.O. Alts are rated from 140 amps on up to as much as 300+ amps or competition use. You will typically want to locate a shop or dealer that offers a custom built unit that features parts that are heavier duty and designed for higher output rather than a basic rewind that may use mostly stock parts. This will ensure you get a reliable unit that will make the power claimed.

You also need to consider where you need the higher current, idle or cruise. You can then tell the builder if you want to be able to feed your system at idle to show off, or while driving when you're just out listening. Just remember than many cheap or very high output alternators will lack idle current output that's superior to stock, so make sure the builder knows what you want to do with your system.

Also, you'll need to go ahead and do the Big 3 when installing a H.O. Alt because the stock wiring isn't sufficient to carry the extra current provided. You won't get any benefit form your H.O. Alt if the wiring is choking it. So remember to do the Big 3 with a gauge of wire that is large enough for the current of your alternator. 4g will once again be a MINIMUM and typically 2ga or more easily, 1/0 is used with these alts.

Final Thoughts

I certainly hope this has answered many of your questions. If not, once again, feel free to ask. Just be clear about what you don't understand and mention that you've read this so no one attacks you for not doing so. Remember to read the sticky sections on each upgrade to gain more in-depth information on each section,

Additionally, you may find yourself needing to do a couple of these upgrades. For instance, you may remove your voltage drops with the Big 3, but still have regulator lag that requires a capacitor. So do the most extensive upgrade you need to first, then, if you still have problems, go back and see what's left. This way you can spend the most money where its most needed and not start at the bottom.

That's not to say that this information applies 100% of the time to 100% of situations, but this is a good starting point and it will give you better questions to ask if you're unsure.

Thanks for reading this far and also, thanks to the other members for bouncing ideas around and allowing us all the gain information over the past days/months/years.
To argue with a person who has renounced the use of reason is like administering medicine to the dead.
― Thomas Paine
sqcomp is offline   Reply With Quote
Old 02-28-2009, 10:42 PM   #2
FEINT's Avatar
Drives: Vitz RS 1.5
Join Date: Feb 2009
Location: Japan
Posts: 67
Excellent read. I think it should be a sticky!
FEINT is offline   Reply With Quote
Old 02-28-2009, 11:51 PM   #3
Alien Mantis
Secret Agent
Alien Mantis's Avatar
Drives: 2008 Yaris Hatch
Join Date: Feb 2009
Location: Arizona
Posts: 350
GOOD information.

Hopefully this post will help people who still don't understand how this stuff works.

__________________ for all your mobile audio needs!
Alien Mantis is offline   Reply With Quote
Old 08-09-2011, 12:54 PM   #4
I've made a post!
Drives: 2000 Monte Carlo
Join Date: Aug 2011
Location: Chesterfield, Michigan
Posts: 1
Multiple Alternator Modules

I removed my factory alternator and replaced with three 390 amp alternators in my 2000 monte carlo. This site has Multiple Alternator Modules. I talked to the guy and he gave me technical info on his product, but had a southern accent and I heard a baby crying in the background, so I don't know if this guy is selling junk or these modules actually make any difference. The guy has these modules for all American and Import vehicles including toyota. The place I bought my alternators from says to use my factory voltage regulator on my primary alternator as normal, but use relays to turn on the other two alternators. They are for 9 batteries in my trunk for my SPL stereo system. So my question is, are these multiple alternator voltage modules really needed or is the factory good enough? and why from your view.
ladybridgeport is offline   Reply With Quote
Old 08-09-2011, 01:07 PM   #5
bx in the house
Drives: toyota yaris sedan
Join Date: Oct 2008
Location: N.Y.
Posts: 113
bxrich is offline   Reply With Quote
Old 03-11-2016, 02:20 PM   #6
Drives: 2007 yaris 2 door hatchback
Join Date: Aug 2014
Location: B.C. Canada
Posts: 5
Thank you for this info......a great help
Flamethrower is offline   Reply With Quote
Old 03-23-2016, 01:15 AM   #7
Roadrunner Jr.
sqcomp's Avatar
Drives: 2007 Yaris S
Join Date: Jan 2007
Location: Back at home
Posts: 2,614
Send a message via AIM to sqcomp
I'm really glad to see that this thread is still giving people insight into charging systems 7 years after it's posting.

I can say with confidence that I personally still use the advice
In this post. As a matter of fact, my latest project (a 1978 Cressida resto mod) has a nice 1/0 gauge big 3 upgrade on a sweet Stinger battery and remanufactured alty.
To argue with a person who has renounced the use of reason is like administering medicine to the dead.
― Thomas Paine
sqcomp is offline   Reply With Quote

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
My car's electrical system just stopped working today..? jamhot18 DIY / Maintenance / Service 14 11-04-2018 01:40 AM
ACRONYM thread Shroomster Off-topic / Other Cars / Everything else Discussions 44 08-23-2014 03:55 PM
Disconnecting battery to work on electrical system goku87 In Car Entertainment + Electronics (audio / video / alarm) 8 03-28-2009 11:56 PM
The Advantages of Nitrous on an Engine KCALB SIRAY Performance Modifications 7 01-02-2009 10:53 AM
Intake Systems Decision Maker.. Blenjar Performance Modifications 25 09-15-2007 10:07 PM

All times are GMT -4. The time now is 01:55 AM.

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, vBulletin Solutions Inc.