Never ending voltage issue I can't figure out!

[shepherd92683]

No the battery is a little over a year old. Xs power d3400. Maybe I should ground the amps to a different location?? I don't know. I'm out of ideas.

 

[IllogicTC]

Here's what I don't understand about the system as a whole. Increasing the voltage reduces the amperage, so how does it save fuel to drop the voltage? It seems to me that it would just increase the amperage which would actually put more load on the alternator. Either way mine does the same thing. Also are you reading the "idiot" gauge on the dash for the voltage or are you monitoring the system with an external meter? Because if your using the cluster gauge, that would be a fatal flaw on your part. It could be that the stepper motor is wearing out.

While we know the amperage capacity, I think the real figure is in terms of wattage. At first it would seem silly to rate alternators in terms of amps when you don't see powerplants bragging about being "20,000 A!," it's all about their KW/MW/GW rating. But since we're working in a known voltage here (rather than having loads applied at various voltages depending on the requirement), we could just figure that if the 150A rating is at 12V, the alternator puts out 1800 watts and that's why they give amp ratings. The duty cycle would affect overall wattage I would imagine (and therefore power input).

I figure rather than adjusting to exactly the level needed for whatever thing was turned on, it goes either to the next step above it (as it can't adjust exactly to that level, just to certain presets) or maybe one or two levels higher. Since the load does not meet the increase in overall production, there is a rise in voltage.

Frankly I wish ammeters were still an option. So much easier to see exactly what kind of draw/charge you were getting.

 

[bobdec]

Blazing Trails, In addition to above.. The ECM and GBCM reduce voltage to 12.5 V and lower the alternator duty cycle (save fuel) after they determine there is a LOW LOAD condition on the system. I believe this is sheperd's problem. The setup is drawing a load to the amp that is NOT being monitored by the ECM/GBCM . The negative wire is not going through the GBCM inductive current monitor. Therefore the system is confused and is lowering the voltage in ERROR. I do agree with the voltage at 12.5 and a high audio load the system is not at an ideal situation for the amp and the alternator. The alt is probably providing 16% more current at 12.5 volts than it would if at 14.5 volts. And the amp drawing 16% more current would probably like a higher voltage. But the ECM & GBCM are erroneously holding it at 12.5. Was thinking dummying up a load (rear defoggers) to the ECM pin may or may not work all the time and it adds software variables to a jury-rigged off the wall fix.
I would first test incorporating the audio amp load into GBCM current monitoring inductance loop -or- it that does not work ,install an external regulated controller to the alternator. External regulators are normally the fix when the stock intelligent regulation can not manage multiple batteries, multiple alternators or altered power systems. It's done all the time on emergency vehicles. However the regulation has to be customized specifically for each vehicle/model and the charging system tests and DTCs would have to be turned off in the tune. If the OP can not find a Kit that fits the vehicle, designing a customized setup it is not what I would call typical DIY procedure.

 

[shepherd92683]

So if I make a run to my rear battery from the ground connection that connects to the engine block (pic below), would that read as part of the current still since that ground that it will attach to does go through the sensor?

 

[shepherd92683]

I also had the voltage stay steady again a couple days ago at 14.2. The only time it dropped was when I parked and it went to 13.8 for a minute or two then right back over 14. The next day, back to the 12's... I am not changing anything through this process yet but only looking for consistencies.

 

[bobdec]

Yes you're correct, I screwed up and overlooked that you're setup is " Battery negative terminal -----> through GBCM current monitor loop --------> engine block stud ----> engine block stud ------> AMP negative terminal " If set that way 1- the GBCM should be seeing the amp current and that blows my theory out of the water and something else is effecting the voltage. By the way can't see it clearly but is the wire from battery neg to block still a smaller gauge than the wire to the amp ? If so it's a weak link. Should not cause what we are seeing, but it may cause a voltage drop or a current draw from another ground (ground loop) . With amp on put a volt meter at a low voltage setting (millivolts) black lead on battery negative and positive on the ground wire to the amp at the block stud. Power up the amp and draw some wattage. Then see what (if any) the voltage drop is between the battery negative and the ground to the amp. An analog meter would be better if you have one as the needle will move under fast load changes, digitals are slow to react. . Sorry but I'm running out of ideas on this... We are sure all is normal when the amp is turned off and it only occurs with amp on. Also don't forget the amp may draw more power with base than higher frequencies and the load fluctuates up and down. Maybe someone on the audio forums has seen something like this..

 

[BlazingTrails]

I'm going to start working on bypassing this system. I'm sure it can be done, I'm going to do some testing and let you guys know what I come up with.

 

[IllogicTC]

I'm going to start working on bypassing this system. I'm sure it can be done, I'm going to do some testing and let you guys know what I come up with.

I think it'd be simple, depending on how the duty cycle is commanded higher. If it's a PWM signal or something, I'm sure a dupe signal could be rigged up with a little know-how.

 

[coolasice]

I think it'd be simple, depending on how the duty cycle is commanded higher. If it's a PWM signal or something, I'm sure a dupe signal could be rigged up with a little know-how.

it communicates via class II serial data.

 

[coolasice]

schematic

 

[shepherd92683]

I guess my other question would be, if efforts to save $50+ on 1/0 ground wire, grounding my rear amp to the same ground as my front battery should be on the same circuit... I can ground my amps to the rear battery and it should all be in harmony theoretically right? I guess try and find out is next. Thanks for all the help here guys, I did find a great read on the system as a whole earlier too.
http://www.archivedsites.com/TECH_CONNECT_new/English/2005/TechConnect03%20MayJune05%20Final.pdf

Also yes the chassis to block is 4ga. That was the stock size. I can always upgrade to 1/0 if it's a deal breaker lol.

 

[06TrailblazerLSS]

Sheperd what kind of audio are you running? Where in IL ya from? Sold my 15" L7s, got 2 American Bass HD 15s and a custom box just today- hitting 146.4 db sealed and 147.5 in the kick, is that any good? Dont even know what my L7s were hitting at, wish i did- they hit somewhat similar but HDs much cleaner and can throw far more power at them. HDs are brand new and stiff as sh*t still.

 

[coolasice]

I think your problem is not that the rear amp is grounded incorrectly, but that you have an additional battery in the rear that is not grounded through the gbcm. The gbcm only measures amperage in/out of the battery, not the alternator. If your second battery is not grounded through the gbcm it is not being monitored for amperage in/out of it. The system is working as it was intended to by design. You could TRY to route the Secondary battery ground through the gbcm, but it may not make a difference. The only way to bypass this system is to Unplug the gbcm and allow the system to default to 13.8v constant, this will illuminate the battery light and if you have the dic will say "Service Charging System" everytime the vehicle is started. I do not understand why 12.6v is such a problem?

 

[shepherd92683]

12.6 is a problem because I need audio power. The difference is 12.6 putting out 1900w and 14.4 doing 2200. That's almost a 14% power loss. Also equipment is happier with higher voltage

 

[coolasice]

Have 4 options here.
1) move ground from second battery through gbcm and hope it recognizes the drain
2) swap to a manual style alternator and have the dash lights.warnings on
3) turn on lights and or extras all the time.
4) induce a 98% Pwm signal into the alternator to increase output, which will cause dash lights/warnings

You could also contact someone with a tuner to see if the software can be altered, not sure there

Have you tried running without the gbcm plugged in yet?

 

[shepherd92683]

No I haven't ran with it unplugged. The best solution I have so far since it's summer is having the air on. It seems when that system runs I stay over 14. Even when I turn it off it stays that high. I need to tinker more with the wiring of the rear battery and go from there. More copper lugs need to be ordered and soldered first then testing will take place. I really would've rather ran an extra 14v alternator/system for the stereo but that is a whole other expense far out of the budget.

 

[06TrailblazerLSS]

No I haven't ran with it unplugged. The best solution I have so far since it's summer is having the air on. It seems when that system runs I stay over 14. Even when I turn it off it stays that high. I need to tinker more with the wiring of the rear battery and go from there. More copper lugs need to be ordered and soldered first then testing will take place. I really would've rather ran an extra 14v alternator/system for the stereo but that is a whole other expense far out of the budget.

What kind of audio you running?

 

[IllogicTC]

it communicates via class II serial data.

The wire running TO the alternator is not a part of the serial bus. This would be the wire to intercept to take deliberate control.

 

[coolasice]

Removing or altering that wire will result in a DTC thrown and the service charge system light illuminated as the gbcm monitors the alternator output wire (not the 12v out) it then compares input to alternator and output to verify it is working properly

 

[coolasice]

I think it would be easier to modify the auto-headlamp sensor to turn the headlamps on whenever the vehicle is on thus forcing the gbcm to command a 14.5v charge whenever the vehicle is running.

 

[IllogicTC]

A PCMofNC tune can remove a lot of trouble codes from tripping. If he hasn't gotten a tune yet, then it's a 2-for-1.

 

[shepherd92683]

What kind of audio you running?

2 AQ HDC3 18's, AQ 2200, Boston 4100, 2 sets of Boston Pro 60SE...

 

[bobdec]

coolasice, Been paying a lot of attention to my voltage as a result of this thread. Other day after 30 mins of H'way driving voltage was at 13 volts and we hit stop go traffic in Atlanta. Sitting there stopped w/headlights (DLR's), brake lights, radio, AC front and rear blowers going the darn PCM kept the voltage at 13 no matter what the engine RPM. I then turned on rear defogger and put front blower up all the way to load the system up fully, and it still stayed at 13. Traffic cleared we started moving again and the voltage stayed that way for 10 mins till we go home. I shut it down a restarted and the voltage went to 14.5 for a bit and settled at about 14. Bottom line I'm totally confused on how the PCM makes he duty cycle decision. According to books the headlights and rear defroster should have upped the voltage, but that did not happen.. There is more to this picture than we are seeing..

 

[06TrailblazerLSS]

2 AQ HDC3 18's, AQ 2200, Boston 4100, 2 sets of Boston Pro 60SE...

Do you know what decibels youre hitting? Probably sounds great huh?

My truck, as with yours, hits great when voltage is up- and mediocre when not.

 

[coolasice]

DRLs are not considered headlights, the auto headlights must be on or the switch on for it to consider headlamps on.

 

[bobdec]

Another tidbit to store away, DLR' are not considered headlights, probably because running, dash and tails are not on w/them

As far as the OP's problem, trying to remember DC power theory is hurting my head. I we have a dual parallel battery setup. Batteries are not the same size and capacity. The battery negative sides are tied together at the engine block albeit via different gauge wires from the batteries. There is a GBCM current monitor that monitors negative side current between front battery #1 and the block feeding the PCM. After reading this thread and the link thread I was not able to see how the two battery positive sides are linked together. No mention of a battery isolator, if there is none, then the audio will draw current from both batteries almost equally except for wiring gauge and resistance in the positive and negative connections. Question to sheperd.. how is the amp positive wired up to the stock positive system, is it a heavy gauge wire under the hood to the #1 battery. rember as the #2 battery starts drawing down the audio will be pulling current from the amp to #1 positive terminal. That wiring is an unknown to us..

 

[meerschm]

Here's what I don't understand about the system as a whole. Increasing the voltage reduces the amperage, so how does it save fuel to drop the voltage? It seems to me that it would just increase the amperage which would actually put more load on the alternator. Either way mine does the same thing. Also are you reading the "idiot" gauge on the dash for the voltage or are you monitoring the system with an external meter? Because if your using the cluster gauge, that would be a fatal flaw on your part. It could be that the stepper motor is wearing out.

http://www.motor.com/article.asp?article_ID=1606%C2 for some discussion

increasing voltage does not reduce amperage.

higher voltage from the alternator will push current into the battery, causing chemical changes, and charging the battery. past a certain point, will cause trouble. the battery chemestry depends on temperature, (higher voltage required to charge at lower temps)

higher voltage also increases current for most loads. (headlights, seat heaters, defrosters...) this is for the most part waste heat, which does take energy from what you put in the tank.

regulated power supplies will take more current as source voltage is reduced, but there are plenty of resistive loads on the system, and these are the primary loads.

 

[BlazingTrails]

I respectfully disagree with everything you just said.

 

[shepherd92683]

coolasice, Been paying a lot of attention to my voltage as a result of this thread. Other day after 30 mins of H'way driving voltage was at 13 volts and we hit stop go traffic in Atlanta. Sitting there stopped w/headlights (DLR's), brake lights, radio, AC front and rear blowers going the darn PCM kept the voltage at 13 no matter what the engine RPM. I then turned on rear defogger and put front blower up all the way to load the system up fully, and it still stayed at 13. Traffic cleared we started moving again and the voltage stayed that way for 10 mins till we go home. I shut it down a restarted and the voltage went to 14.5 for a bit and settled at about 14. Bottom line I'm totally confused on how the PCM makes he duty cycle decision. According to books the headlights and rear defroster should have upped the voltage, but that did not happen.. There is more to this picture than we are seeing..

Yes!!! It makes no sense!!!

Another tidbit to store away, DLR' are not considered headlights, probably because running, dash and tails are not on w/them

As far as the OP's problem, trying to remember DC power theory is hurting my head. I we have a dual parallel battery setup. Batteries are not the same size and capacity. The battery negative sides are tied together at the engine block albeit via different gauge wires from the batteries. There is a GBCM current monitor that monitors negative side current between front battery #1 and the block feeding the PCM. After reading this thread and the link thread I was not able to see how the two battery positive sides are linked together. No mention of a battery isolator, if there is none, then the audio will draw current from both batteries almost equally except for wiring gauge and resistance in the positive and negative connections. Question to sheperd.. how is the amp positive wired up to the stock positive system, is it a heavy gauge wire under the hood to the #1 battery. rember as the #2 battery starts drawing down the audio will be pulling current from the amp to #1 positive terminal. That wiring is an unknown to us..

There is a 1/0 run from the front battery to the rear battery. There is also a 1/0 run to the alt post. There is a run to a distribution block on the rear to allow for 2 1/0 runs, one to each amp. The Boston amp takes 2 4ga inputs so I have reducers to make that work.

 

[shepherd92683]

Do you know what decibels youre hitting? Probably sounds great huh?

My truck, as with yours, hits great when voltage is up- and mediocre when not.

Yes I do like it but would like more power. Never had it on a term lab but to guess I'd say mid to upper 40's.

 

[meerschm]

http://www.motor.com/article.asp?article_ID=1606

Thought I posted this for reference.

more here:

http://www.metroplexalternator.com/uploads/1/5/2/8/15280940/delco_remy_remote_voltage_control.pdf

sent BlazingTrails a pm to clarify/resolve differences of understanding and assumptions.

 

[meerschm]

Here's what I don't understand about the system as a whole. Increasing the voltage reduces the amperage, so how does it save fuel to drop the voltage? It seems to me that it would just increase the amperage which would actually put more load on the alternator. Either way mine does the same thing. Also are you reading the "idiot" gauge on the dash for the voltage or are you monitoring the system with an external meter? Because if your using the cluster gauge, that would be a fatal flaw on your part. It could be that the stepper motor is wearing out.

for some discussion

increasing voltage does not reduce amperage.

higher voltage from the alternator will push current into the battery, causing chemical changes, and charging the battery. past a certain point, will cause trouble. the battery chemestry depends on temperature, (higher voltage required to charge at lower temps)

higher voltage also increases current for most loads. (headlights, seat heaters, defrosters...) this is for the most part waste heat, which does take energy from what you put in the tank.

regulated power supplies will take more current as source voltage is reduced, but there are plenty of resistive loads on the system, and these are the primary loads.

I respectfully disagree with everything you just said.

I started a new thread to follow up.

http://gmtnation.com/forums/topic/11028-electrical-system-discussion/

 

[coolasice]

Here's what I don't understand about the system as a whole. Increasing the voltage reduces the amperage, so how does it save fuel to drop the voltage? It seems to me that it would just increase the amperage which would actually put more load on the alternator. Either way mine does the same thing. Also are you reading the "idiot" gauge on the dash for the voltage or are you monitoring the system with an external meter? Because if your using the cluster gauge, that would be a fatal flaw on your part. It could be that the stepper motor is wearing out.

This is true for POWER transmission applications. the power company uses a very high voltage to pass a lower amperage so that the size of the wire can be smaller which costs less. But for DC theory where the resistance is constant (seat heaters, lights, rear defroster) the amperage will increase as voltage increases.

 

[shepherd92683]

Update... Reinstalled rear battery and nothing changed...which is somewhat good. No voltage drop like before (going down to 12.6 and staying there) but the same drop I had without it in at full tilt so it's done nothing for a gain.

 

[stvrob]

I'm curious what the function of the second battery is in your application. Is it to extend the period that you can run the stereo system with the engine not running? Or is the charge from the second battery to be "held back" to start the vehicle if you were to accidently drain the first battery? Does the second battery serve any useful purpose while the engine is running?

It seems to me the only purpose of a second battery would be to start the engine should the first battery become drawn down, but this is not possible without isolation of the second battery. If they are simply in parallel, they need to be virtually identical with respect to internal resistance and amp-hours, otherwise it seems to me you are just dragging around extra weight.

 

[Mounce]

Stereo systems that are designed for high performance require large amplifiers which draw large currents. The second battery is for the stereo (maybe I should call it radio?). The need for the second battery is for extra amperage/power to the amplifiers so that they can run at their max potential and in turn, put out better power to drive the speakers. Some people also add more alternators to produce the power and/or keep the extra battery(s) at full charge or to recharge them in a more timely manor.

 

[stvrob]

Stereo systems that are designed for high performance require large amplifiers which draw large currents. The second battery is for the stereo (maybe I should call it radio?). The need for the second battery is for extra amperage/power to the amplifiers so that they can run at their max potential and in turn, put out better power to drive the speakers. Some people also add more alternators to produce the power and/or keep the extra battery(s) at full charge or to recharge them in a more timely manor.

Yes, but the current is supplied by the alternator, if the engine is running, the battery is just behaving as a big capacitor in the circuit, I don't see how a second battery adds any value. I guess it could be benificial at idle, but I thought a modern RVC alternator would ramp up the idle speed or dump other loads to strive to keep the battery at a high state of charge.
If this thread really about suppling a higher voltage to the amplifier to boost its performance? If so, that is contrary to the task of the alternator, whose sole task is to keep the battery at a high state of charge. A goal of 14+ volts at all times is contrary to the task of the alternator. If one wants a higher voltage to increase the performance of the amplifier maybe there is a boost converter that is up to the task. Just how much power are we talking about anyway? like 200W?

 

[Mounce]

That's not the task of this thread. The task of the thread is finding a voltage loss within his electrical systems. I read this thread at one point but I can't remember the exact issue now, I just wanted to answer your question. And I'm unsure of the dynamics of how adding batteries helps but it does. Some guys run many batteries. And with the wattage his amps are putting out, probably more than 500 Watts (just a guess). But I don't know anything about the OP's system. Could be 1000w or more but I have no idea. Maybe the OP or someone with more knowledge than I will comment when they wake up tomorrow and clear things up.

 

[stvrob]

Well i don't know much about stereo systems, but I am familiar with dual battery marine systems. But the goal there is different I guess.... to make sure you can start up and get back to shore after partying or fishing with your stereo blasting and other electronic loads. A lot of people misunderstand how there system is set up and get stranded anyway.

 

[Mounce]

Yeah, I understand what you mean, but think of it this way. A 24 volt trolling motor runs on two 12v batteries, they're just wired up in such a way to put out 24v which let's the trolling motor create more thrust than if it was running on 12v. but on a car with two batteries it has the batteries wired to put out 12v but it will put out more amps. Sorry, I'm horrible at explaining things.