# a question about computer regulated alternators!



## lasmujercitas (Feb 17, 2008)

I have a 2005 silverado, has a stock 145 amp alternator!

I have added a deka battery, the stock was showing its age.

big 3 has not been done

I noticed how the voltage starts out high, upper 14, then drops off as i cruise around, lower 13(nothing is installed right now as far as amps)

then i find out that the alty is controlled through the computer, it drops voltage when not needed to add to fuel economy(yikes, like that really helps)

my question is, is there a way to bypass this? i plan to add a aftermarket HO alty sometime in the future, this will no doubt effect this, or am i wrong?


thanks for the time
mike


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## guitarsail (Oct 12, 2007)

lasmujercitas said:


> I have a 2005 silverado, has a stock 145 amp alternator!
> 
> I have added a deka battery, the stock was showing its age.
> 
> ...


It only drops voltage when its not needed...if you put a load on it and start taxing the system the computer will let the alt. know to start putting out more So yeah it drops when you're cruising, but you're also not tasking it with anything.


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## chad (Jun 30, 2005)

guitarsail said:


> It only drops voltage when its not needed...if you put a load on it and start taxing the system the computer will let the alt. know to start putting out more So yeah it drops when you're cruising, but you're also not tasking it with anything.


the Honda ELD is in the fuse box, it does not detect charging load or any load on the battery not gong thru the stock underhood fuse panel. Therefore audio or after market winches/lights AND their dis-charging effects are not noticed  DUMB, DUMB, DUMB!

But turn on the headlights, rear defog, AC compressor/fan, or operate a window and she charges!

I'm working on a fix this winter I hope to detect auxiliary loads.

For others with this, I own a Honda, got that one pegged, where is YOUR load detection located in the stock electrical stream?


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## lasmujercitas (Feb 17, 2008)

thanks for the replies, it just seems weird, it seems only certain models under different makes have this "feature", i wounder what the reasoning is?


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## chad (Jun 30, 2005)

lasmujercitas said:


> thanks for the replies, it just seems weird, it seems only certain models under different makes have this "feature", i wounder what the reasoning is?


Gas mileage seems to be the common reasoning.

Where is the load detected?


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## Hillbilly SQ (Jan 26, 2007)

chad said:


> Gas mileage seems to be the common reasoning.
> 
> Where is the load detected?


If I crank my system hard enough with my engine running the alty will kick in with a vengence. If I listen for extended periods of time with the engine off the alty tends to stay kicked in forever it seems like but once it drops back down to around 13v I know it's charged back to normal.


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## chad (Jun 30, 2005)

Hillbilly SQ said:


> If I crank my system hard enough with my engine running the alty will kick in with a vengence. If I listen for extended periods of time with the engine off the alty tends to stay kicked in forever it seems like but once it drops back down to around 13v I know it's charged back to normal.


Which normally means that you have standard regulation.


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## ErinH (Feb 14, 2007)

chad said:


> the Honda ELD is in the fuse box, it does not detect charging load or any load on the battery not gong thru the stock underhood fuse panel. Therefore audio or after market winches/lights AND their dis-charging effects are not noticed  DUMB, DUMB, DUMB!
> 
> But turn on the headlights, rear defog, AC compressor/fan, or operate a window and she charges!
> 
> ...


let me know what you come up with in the end. I'd be interested.

I don't really have any issues that warrant drastic changes, but it'd be good food for thought.


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## chad (Jun 30, 2005)

bikinpunk said:


> let me know what you come up with in the end. I'd be interested.
> 
> I don't really have any issues that warrant drastic changes, but it'd be good food for thought.


I'm looking to keep it really simple and find a way to grab another stock ELD sensor, couple that to at least the load on the battery and leave charging load alone, find a way to isolate/voltage divide&amplify and make the input see both senses. Honda is VERY elusive as to how the sensing works, as in the service manual won't even tell you theory/operation but will be more than happy to give you logic/pulse counts on every damn thing else. So far it appears to be a coil around a shunt for the most part, since it's DC that means it's only looking for a pulse  Problem is what is the delay/hold of the charge ramp up? I don't want that alternator commutating the charge current for every kick drum beat by any means!


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## ErinH (Feb 14, 2007)

^ dude, I have no idea what you're talking about. You said you were going to keep it really simple, but your dang paragraph confused the crap out of me by itself.


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## chad (Jun 30, 2005)

bikinpunk said:


> ^ dude, I have no idea what you're talking about. You said you were going to keep it really simple, but your dang paragraph confused the crap out of me by itself.


Damn Rocket Scientists


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## Calum (Aug 13, 2008)

I had a similar problem with a car, the PCM controled the alternator output based on BATTERY TEMPERATURE! of all things.

I picked up a voltage regulator & harness plug and sliced it in. 

It's pretty simply, the case of the regulator is it's ground so it needs to be bolted to the chassis of the car. Next there are two wires, one is essencially a voltage sensing wire so the regulator knows the alternator output/power for the regualtor. The other wire goes to the alternator for field control. To find the wires in your car, remove the small plug form the alternator (not the B+ wire) grab a volt meter and check to see which wire is switched 12v. Tap into this wire and run that to the middle pin on the regulator. Cut the other wire from the alternator plug and run that to the other pin on the regulator.

http://www.dieseltruckresource.com/pics/data/500/17307regulator2.jpg
http://www.rockauto.com/catalog/x,carcode,1094273,parttype,4884

These regulators will work with MOST alternators. Obviously if you don't have two wires going to your alternator (such as the GM one wire's) this wont work for you.

After I installed one of these the car ran at a constant 14.4 volts, even at idle.

oh yeah, and a small resistor would probably allow you to run the alternator at a higher voltage. I know the car I put this on, the first regulator I bought was a dud. The car ran at 19 volts at idle with that one...!


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## lasmujercitas (Feb 17, 2008)

sweet, i have options now


i guess its not to big a deal because i'm not looking at spl burps and annoying neighborhoods for extended periods of time!


because of the regulations i have been eyeing jl amps


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## baggedbirds (Sep 21, 2008)

contact missing link audio . they make modules that tie into the factory harness and change the charging curve of the car. I have one in my older ford car. i am not sure how they work, some military guy builds them. neat unit. after the module you will charge about 15V which was great for me. they also make modules so that you can run multiple alts and not goof up the computer and cars charging.
http://www.missinglinkaudio.com

heres mine -yout hook up would be different.


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## chrisw85 (Apr 24, 2008)

I too have a honda civic ('94) and would love to find a way to make the voltage run higher at all times. But I always drive with my headlights on so I think I'm good for now?


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## chad (Jun 30, 2005)

15+V is a bit hot for a charge voltage, I would bo concerned with battery longevity.

Chris, as for the civic issue, that's what I'm working on this winter hopefully but the ELD will work as designed, it will sense charge state and a load on the battery with the revision.


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## Bluto Blutarsky (Apr 1, 2007)

chad said:


> 15+V is a bit hot for a charge voltage, I would be concerned with the battery exploding.


 fixed


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## chad (Jun 30, 2005)

Many chargers pulse in the 15V range, but by no means float the battery at 15V! that's cwayzee mang!


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## baggedbirds (Sep 21, 2008)

that 15V is with the car running.

Everyone says the same thing when they first hear about them. I don't know the science behind them, but the ex military guy that builds them knows his stuff. His lead acid battery is going on 8 years old.


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## chad (Jun 30, 2005)

is that initial charge voltage or constant charge voltage?


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## baggedbirds (Sep 21, 2008)

that was the very cold number. It will vary from 14.8V - 15.2V . MLA says that after the battery gets some charge time on it with this system it should stabilze right around 15.1V. I have yet to drive the car since i have gotten the module. I have started it a few times. The battery rests at 11.4V last i looked. MLA knows a ton more than i do. they are smart guys.


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## chad (Jun 30, 2005)

That's waytoofukenmuch for a constant charge voltage.


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## baggedbirds (Sep 21, 2008)

here is a snipet of what missing link says about their modules. It took me a little bit to get it over here. Chad your inital reaction is common, but take a peak below and see what you think. It may or may not change your mind. I'm easy. I just want to provide all the info.

( this is copy and pasted from MLA )

The MLA voltage control module

I will try to answer all of the voltage and battery questions in the other threads relating to this unit here. Here are the basics:

What it does:

1) Modify the charging curve
By reshaping the charging curve, it raises the voltage seen on your gage or meter at some parts of the operational curve. You may see nearly the same voltage as before install at some times. This is normal operation.

2) Temperature compensation
Our module includes temperature compensation. Because the internally regulated alternator can only sense it's own temperature, it reduces charge voltage quickly when heavily loaded. Batteries change temperature much slower than the alternator. Our temperature sensor is inside the module, surrounded with epoxy. It more closely follows the battery internal temperature changes from engine compartment heating or cooling.


What it does NOT do:

1) Constant voltage charge
While it may seem that after install you have a constant charge voltage, this is not true. Many times your batteries are not fully charged, and the module is trying to correct that. With modern vehicle loads a stock 140 amp alternator is using half of it's output just to run the vehicle. Add thousands of watts of audio equipment, and it may never fully charge the battery. The module will cause the voltage to rise if the total power use exceeds the alternator capacity. 

Fix bad parts
If you have a faulty alternator with a failed diode, you lose 30% of your output. The module can't compensate for that damage, but it will try. You will see higher voltage when unloaded, and poor performance under load.

A failing battery with a weak cell will have low voltage after standing overnight. The module will see this and raise charging voltage on startup. It may compensate for this enough to hide the condition for several months (or longer). A battery that is out of equalization (more on that later) will show similar symptoms, but will recover with the module in use.


Now it gets more technical.

There have been questions about higher voltages and the effect on batteries & vehicle systems.

For any given manufacturer, there are many voltage regulators. The GM AD244 series alternator has 14 different voltage regulator part numbers, each with a different curve. Add to that mix aftermarket alternators & regulators, and you can see why there is no carved in stone voltage number. To add to the confusion, GM began using a parameter called RVC, or Reduced Voltage Control. This parameter reduces the charging voltage when the battery reaches 80% state of charge – your battery may never be fully charged.

Spread out across the GM line there are 6 alternators we cover, which means about 60 regulators we must function with. The ford line is smaller, 4 alternators & about 24 regulators. Without custom trimming a unit to an exact alternator / regulator / battery combination, we must settle for a safe operation zone for all systems. This has been carefully considered.

Vehicle manufacturers state that voltages as high as 19 volts are acceptable during operation. Newer cars electronics are tested at 24 to 36 volts and safe with levels above 20 volts. We never go that high. Our module is ultimately controlled by the vehicle computer, and can be shut down by it. The original voltage regulator is still doing it's job monitoring the alternator temperature, and may reduce charge if it is running too hot.

A word about voltage measurements. Accuracy varies wildly in voltmeters, and the OEM in-dash unit is rarely correct. We have seen some more than 1 volt off form actual battery voltage. Inexpensive digital units as built in to items like amplifiers & capacitors may be off as much as .6 volts. It is common to see 2 amplifiers & 2 capacitors connected to the same battery – showing 4 different voltages. We use calibrated test equipment that is regularly checked against a voltage standard in the shop. It is best to use the same meter for all of your measurements, so that at least any error is constant.

Finally, you must take into account that the original charging system was designed around the normal intended use of the vehicle. Little or no allowance was made for aftermarket equipment like lighting, audio equipment, winches, snowplows... A good factory alternator is rated at 2,000 watts continous, so adding a 3,000 watt amplifier was not on the designer's list at all.



Batteries and Chemistry

There are many different battery chemistries and types on the market today. Each one has a slightly different charge / discharge cycle and requirements.

Lead / Acid batteries have changed over the decades, with various alloying elements added to the lead. Each of those elements changes the battery charge response and self discharge rate. Some of the elements are:

Antimony. Raises the mechanical strength of the plates, but raises the self discharge rate as well. It also is somewhat catalytic, and causes the battery to use a bit more water. Makes a great long life battery. Lead/ Antimony deep cycles very well.

Arsenic. Usually used in small amounts as a doping compound to change the battery's discharge character.

Calcium. Used in place of Antimony for strength, it improves the self discharge rate a lot. The original "Maintenance Free" batteries used lots of calcium. It raises the charging voltage significantly, and installing those batteries in older cars resulted in lots of undercharged systems. Lead / Calcium batteries do NOT like deep cycling, and will fail early.

Nickel. Used to improve strength, and raise corrosion resistance of flooded batteries. Usually found with Silver in a battery – one brand was marketed as "Nickel-Silver" at one time. 

Selenium. Another doping compound.

Silver. Added to improve conductivity of the lead, and add strength. It does affect the charging voltage, and allows higher rate discharge.

Tin. Used for strength, and as a doping compound. The effect varies by quantity & other alloying elements.


Now you must consider the battery type. Predominately vehicles are shipped with flooded type batteries. Many maintenance free batteries are of the flooded type, and still have cell caps (hidden below a cosmetic cover). If it "sloshes" when you move it, it is a flooded battery.

So called "sealed" batteries are usually VRLA types. This stands for Valve Regulated Lead Acid, and as you can see above this takes in a lot of different chemistries. Gassing of a VRLA battery is generally discouraged, but some may occur safely. Some VRLA batteries include a catalyst to condense the hydrogen & oxygen back into water & return it to the cell. 

Among the VLRA types construction varies, but most are AGM or Absorbed Glass Mat type units. This means that the acid is absorbed in a fiberglass mat that separates the lead alloy plates. These are also called "starved electrolyte" batteries because they do not have a surplus of acid like a flooded battery.

Some are conventional flat plates in a square case like Kinetik or Odyssey brand units, others are wrapped into spiral cells like Hawker & Optima batteries. The style of construction can affect things like internal resistance & maximum discharge current.


You will hear terms like "Surface Charge", "Absorption Charge", "Equalization Charge" and others.

Without going into great detail, the absorption charge is what does the bulk of the work charging the battery. The surface charge is the result of a short charge & measurement immediately after charge. It can give you a reading of a fully charged battery, but will dissipate in a few hours. The equalization charge is a process of raising the cell voltage high enough to charge the weakest cell fully. It is done when the battery is made, and may need to be done again if the battery has been badly discharged repeatedly. It can also reduce the formation of sulphates in the battery.

The equalization charge is important in multiple battery banks. By raising the charging voltage high enough to equalize the cells in all of the batteries you will get better performance.

The charge to discharge rate for the Lead / Acid battery family is about 5:1. That means that it takes about five times as long to charge a battery as it did to discharge it at it's maximum rate.

All of those different battery chemistry & constructions have various charging voltage requirements. A plain old flooded battery will tolerate more overvoltage than a VRLA will. Lead/Calcium batteries need to see .8 volts more than Lead/Antimony batteries for full charge.

Batteries like the Optima incorporate some silver, as well as some sodium sulphate in the electrolyte. The Optima can be charged rapidly at 15.6 volts without damage, and can see 15.0 volts on a long term charge safely. In fact, it needs this higher voltage to stay properly maintained.

In our discussions with Kinetik, they see no issues with our charging cycle for their batteries. 

It can take days to fully charge a vehicle battery with the stock alternator if it has become discharged. The vehicle load may be more that 50% of the alternator's capacity to begin with, and short trips with multiple cranking cycles reduces the net charge even more.

Battery charging voltage is also affected by temperature. When it is cold, it takes more voltage to get the job done. In a Chicago winter, the battery may never get to +50f, but the alternator will be 150f trying to keep the lights / wipers / defroster going full blast. The alternator may reduce the voltage below proper charging voltage for the battery temperature.


Let me close this with a section about battery isolators.

There is a small niche for the isolator in today's vehicles. Ambulances and other emergency vehicles that need a separate battery for emergency use. Alarm batteries that will still function if the main cable is cut & grounded. Multiple engines & batteries in marine applications. Probably a few other very special cases I can't even imagine. 

For high power audio, there is simply no reason to use an isolator – and plenty of reasons not to. There is a voltage drop across the diode in the isolator, and it depends on the load across it what the voltage drop is. A drop of more than 1.0 volt is possible. One volt at 100 amps is 100 watts. This means the diode gets hot, and is eating your charging current. The worst part is your alternator "sees" a charging voltage of 14.7 volts, but the battery is undercharged, and may never reach full charge.

For users that need isolated batteries, we make a module with a remote voltage sensing circuit that is connected directly to the isolated batteries. This means that the alternator will charge to the battery's actual voltage needs. All vehicle connections should be made to a battery, because the voltage between the alternator and isolator can be significantly higher than 15 volts at times.

Thanks for reading my long winded post.


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## chad (Jun 30, 2005)

Have not read it but THANK YOU for that info, I'll get thru it tonight/tomorrow as time permits.


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## baggedbirds (Sep 21, 2008)

cajunner- I sent you a pm.


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## baggedbirds (Sep 21, 2008)

here is a little more they sent me - soory for the long posts


(from MLA )


_Ok, the short answer is that 15 volts will not harm any vehicle with a 12 volt system. Vehicle manufacturers offer testing instructions in the factory service manual that often go past 18 volts.

Battery voltages vary widely depending on temperature and chemistry. Many batteries actually need more than 14.8 volts to properly charge. Below is a link to a government study, done at the NREL where they actually extended the life of Optima Yellow Top batteries by charging as high as 17 volts:

NREL Battery Study http://www.nrel.gov/vehiclesandfuels/energystorage/pdfs/evs_17paper.pdf_

the link seems to be down right now.





since its a GM vehicle in question here is a TSB they provided me






_And finally, here is the GM TSB regarding the low voltage complaints on 2005 & up GM trucks:

QUOTE 
Document ID# 2042756 


Subject: Information on Voltmeter Gauge Fluctuation Due to Regulated Voltage Control System and Concerns About Camper/Trailer Battery Charging #07-06-03-009 - (12/05/2007) 


Models: 2005-2008 Cadillac Escalade Models 

2005-2008 Chevrolet Avalanche, Silverado, Silverado Classic, Suburban, Tahoe 

2005-2008 GMC Sierra, Sierra Classic, Yukon Models 


Voltmeter Fluctuation Condition
Some customers may comment that the voltmeter is fluctuating between 12 and 14 volts on their full size pickup or utility vehicle. Starting with the 2005 model year, light duty full size pickups and utilities are equipped with a new Regulated Voltage Control (RVC) system. This system reduces the targeted output of the generator to 12.6-13.1 volts when in "Fuel Economy Mode" to improve fuel economy. The generator may exit "Fuel Economy Mode" if additional voltage is required. This will cause the voltmeter to fluctuate between 12 and 14 volts as opposed to non-regulated systems that usually maintain a more consistent reading of 14 volts. This fluctuation with the RVC system is normal system operation and NO repairs should be attempted. 

Camper/Trailer Battery Charging Concerns
Some customers may comment that when towing or hauling a camper/trailer, the auxiliary battery for the camper/trailer will not stay charged. In most cases, this concern is blamed on the new RVC system. While the RVC system does reduce the generator's targeted output voltage to 12.6-13.1 volts when in "Fuel Economy Mode", this feature is bypassed if the tow/haul feature is enabled. With the tow/haul feature enabled, the RVC system will stay in "Charge Mode" and the targeted generator output voltage will be 13.9-15.5 volts, depending on the battery state of charge and the estimated battery temperature. To keep the generator in the "Charge Mode", use either of the following two methods.

• The first method is to use the tow/haul mode when towing or hauling a camper or trailer. 

• The second method is to turn on the headlights, which will increase the generator's targeted output voltage to 13.9-14.5 volts. 



GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION


© Copyright General Motors Corporation. All Rights Reserved



Note that even in that TSB, GM says charging voltages as high as 15.5 volts are NORMAL OPERATION_


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## baggedbirds (Sep 21, 2008)

chad said:


> Have not read it but THANK YOU for that info, I'll get thru it tonight/tomorrow as time permits.



your welcome.

I wasn't sure how well this module would be recieved here, i heard about it from basicly an SPL forum i go to also. i thought it would be a neat toy to have. so i picked one up and i wanted to avoid voltage drops.
I hope you guys will see that I'm not one to talk out my butt I know little about, so I'll try to provide the facts from MLA and you guys are smart people and can make up your own mind. It seemed to fit my needs.

i just want to tell a fair story and if it works out cool.

the guys at MLA are really cool to work with and i met Chris from MLA at SEMA last year along with Scott from FI. ( there with the FI hummer ) Chris from MLA use to assemble @ FI from my understanding.


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## 6spdcoupe (Jan 12, 2006)

Interesting piece of equipment there from MLA. However I would absolutely love for someone to explain or better yet change the issue with my truck ('08 TrailBlazer SS) charging only at 85% ECU controlled. 

I was informed of this info when I called Gus at OG for an alternator. Apparently alot of the newer GMs have all kinds of different issues with their charging systems ...


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## 6spdcoupe (Jan 12, 2006)

Interesting piece of equipment there from MLA. However I would absolutely love for someone to explain or better yet change the issue with my truck ('08 TrailBlazer SS) charging only at 85% ECU controlled. 

I was informed of this info when I called Gus at OG for an alternator. Apparently alot of the newer GMs have all kinds of different issues with their charging systems ...


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## Oliver (Jun 25, 2007)

........


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## matdotcom2000 (Aug 16, 2005)

It my have something todo with the pcm resistance ohm rating. read here post 43 07 Tundra Alternator, 13.8 and less ? - Page 3 - Tundra Solutions Forum


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