truck stutters when bass hits

been in business 20+ years and have never seen this..

need help

got a 1991 Chevy truck

basically when the bass hits.. the truck stutters to the beat.. not a lil bad enough to sometimes kill the truck.

now the setup

under hood
2 Optima batteries.
stock 110amp alternator for those.

in rear
1 optima battery
hooked directly to my PB 5k amp
another 110a alternator powering it directly

now the riddle.

the system battery is not hooked to the vehicle electronics at all.
however when the truck stutters, I can see the volt gauge (aftermarket) drops volts from the vehicle batteries..
how in the hell can it do that.

secondly..

it goes from system alternator to 200amp breaker.. then to system battery.

if I pop the breaker. the truck will not stutter..
however with it popped rear battery receives no charge.



somehow its drawing from the truck electronics. and I cant figure out how where or why..

please advise.

So you are not charging the audio Optima? (It is totally separated fro, the alt & main battery(s) and non-auto electrics.)

Maybe insufficient grounding between engine-chassis-main_battery or shared audio grounding - ie- using audio sharing with main.

oldspark wrote:

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So you are not charging the audio Optima? (It is totally separated fro, the alt & main battery(s) and non-auto electrics.)

Maybe insufficient grounding between engine-chassis-main_battery or shared audio grounding - ie- using audio sharing with main.

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ok, the audio optima has its own alternator..
and is not connected to anything else.. truck will stutter, but if I break the fuse from alternator to batter the truck will run fine. however the optima then is not charging

also for grounds. not sure if that would be issue. as amp is grounded rear battery is grounded.

and I have grounded numerous places through out truck.

What have you done to add to the engine-chassis/body grounding?

Each alternator has a 4 ga ground
Each ground strap has been redone. Also added 9 new 8 ga grounds throughtout body and frame

are your alternators internally regulated or do they have external regulator packs to control them? where did you tap for the field wire of the alternator for your audio?

Also, how is the engine driving the two alternators? Same belt/pulley or completely separate setup?

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If grounds are good and since disabling the audio alternator solves the problem, I'd suspect its purely mechanical and needs to be treated as if it's an aircon.

soundnsecurity wrote:

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are your alternators internally regulated or do they have external regulator packs to control them? where did you tap for the field wire of the alternator for your audio?

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internal, stock 1 wire chevy alts

DYohn] wrote:

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Also, how is the engine driving the two alternators? Same belt/pulley or completely separate setup?

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my truck doesn't have ac, but has a spot and pully for the upgrade so I mounted it there.

soundnsecurity wrote:

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are your alternators internally regulated or do they have external regulator packs to control them? where did you tap for the field wire of the alternator for your audio?

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I used the feed wire from the stock and jumped it to the other alternator.

oldspark wrote:

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If grounds are good and since disabling the audio alternator solves the problem, I'd suspect its purely mechanical and needs to be treated as if it's an aircon.

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I don't understand

My money is on the load of the amplifier is taxing the alternator and just slowing the engine down.

When you trip the breaker, the amp is still playing off of the battery. But it being not connected to the alternator, there is no load on that alternator, hence no decrease in RPM.

What I meant was as IAAI said - the load change is slowing the engine. Mere headlights can do the same and they may only be ~200W.


But...

voltagexdt wrote:

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I used the feed wire from the stock and jumped it to the other alternator.

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What "feed" wire? They should be separated.
Each alternator should be sensing its own battery - ie, each Sense wire to battery +12V - they should nit be jumpered or shared.
However if it's a single-wire alternator (D+) then there is no separate sense wire so that's not an issue. But each D+ or L charge-Light wire should have their own lamp else resistor in lieu. Connecting two D+/L circuits together can blow the regulators (D+/L outputs are usually GND else +12V - you do not want to short one to the other!),    

i am an idiot wrote:

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My money is on the load of the amplifier is taxing the alternator and just slowing the engine down.

When you trip the breaker, the amp is still playing off of the battery. But it being not connected to the alternator, there is no load on that alternator, hence no decrease in RPM.

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ok but how would it slow the engine down.

oldspark wrote:

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What I meant was as IAAI said - the load change is slowing the engine. Mere headlights can do the same and they may only be ~200W.


But...

voltagexdt wrote:

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I used the feed wire from the stock and jumped it to the other alternator.

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What "feed" wire? They should be separated.
Each alternator should be sensing its own battery - ie, each Sense wire to battery +12V - they should nit be jumpered or shared.
However if it's a single-wire alternator (D+) then there is no separate sense wire so that's not an issue. But each D+ or L charge-Light wire should have their own lamp else resistor in lieu. Connecting two D+/L circuits together can blow the regulators (D+/L outputs are usually GND else +12V - you do not want to short one to the other!),    

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the sense wire is a single wire that basically turns the alternator on I believe..

I contacted stinger on this and was instructed to simply jump from one sence of stock to the next.

I ask about the slowing the engine down because I thought of this, but then realized the engine spins the alt.. not visa versa.

but I did question this.

I doubt very much that the 2 alternator wires should be shared UNLESS it is the IGN +12V feed, but few have that - especially these days.

If it's the "battery sense" (S) or the charge lamp (D+ or L), they should definitely NOT be connected together. And obviously the main output (B/B+) isn't being shared.
Only the GND is shared between separate alternator/battery circuits (plus IGN +12V if that is also required).

If Stinger told you that - especially if they also told you the BC12 was suitable as a "dual battery isolator" - I'd be very wary, though maybe they do know what they are talking about in this case (it depends what that wire/circuit is).   


As to slowing the engine down - electrical current is a load. A 110A alternator may take 2HP from the engine. At half output which is quite feasible at idle speeds, it's 1HP (~745W).
As I said, if headlights under 200W (less than 1/4 HP) can dip an engine, then certainly so can a >1HP alternator.

oldspark wrote:

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I doubt very much that the 2 alternator wires should be shared UNLESS it is the IGN +12V feed, but few have that - especially these days.

If it's the "battery sense" (S) or the charge lamp (D+ or L), they should definitely NOT be connected together. And obviously the main output (B/B+) isn't being shared.
Only the GND is shared between separate alternator/battery circuits (plus IGN +12V if that is also required).

If Stinger told you that - especially if they also told you the BC12 was suitable as a "dual battery isolator" - I'd be very wary, though maybe they do know what they are talking about in this case (it depends what that wire/circuit is).   


As to slowing the engine down - electrical current is a load. A 110A alternator may take 2HP from the engine. At half output which is quite feasible at idle speeds, it's 1HP (~745W).
As I said, if headlights under 200W (less than 1/4 HP) can dip an engine, then certainly so can a >1HP alternator.

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Ok I did some research and numerous forums show that the field or excite wire needs to be connected to 12v switched. So I assume that's why stinger said to link between them

It does take horsepower in order to turn an alternator. With no load on the system, the alternator turns freely. With a load, it takes more power from the engine in order to turn it.

So what do I do?

Try using one battery for the truck, and 2 for the amplifier.

i am an idiot wrote:

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Try using one battery for the truck, and 2 for the amplifier.

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I have. Nothing has changed anything.

Gone from stock to now 3 batts 2 alts and frustration.

voltagexdt wrote:

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So what do I do?

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Get a bigger engine.
Disable the 2nd alternator when idling (that means (say) 12.5V battery voltage for the amps instead of the higher alternator/charging voltage).
Increase idle speed (when the amp is on - ie, an air-con idle speed booster {enable in ECU if appropriate and connect SCU sensor}).
Various solutions.

voltagexdt wrote:

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I did some research and numerous forums show that the field or excite wire needs to be connected to 12v switched. So I assume that's why stinger said to link between them

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That Field has nothing to do with connecting their regulators - you'd have to have a very old vehicle (like mine) or a non-OEM alternator for that to have any relevance. (The regulator looks after the field winding.)

Modern alternators with integral voltage regulators - excluding ECU-interacting DP etc alternators - are usually single-wire - ie, a charge Light circuit called D+ on most single wire alternators or L on 2- or more-wire alternators. (We don't count the heavy +12V often B or B+ to battery +12V nor the alternator GND as wires.)
A second wire is usually a Sense (S) wire that goes straight to the battery +12V terminal (maybe via a fuse or resistor) - eg, common "SL" type regulators/alternators.
Rarely is a third "I" for IGN +12V/on used, but they do exist - eg, SIL type alternators (Nippon Denso, some Hitachi etc).

Hence maybe your 3rd wire can be commoned, but NOT the other 2.
If one the other two, either you are commoning the D+/L circuit which risks a +12V to GND short that may ruin both alternators (or rather, their voltage regulators), or you are commoning both Sense circuits to one battery which means eventual death to the 2nd battery(s), and maybe a fire or explosion seeing as it's an Optima. (And with TWO "permanently" paralleled Optimas on that #2 alternator output - man, you don't even need the alternator for the fire from 2 of those in thermal runaway...)

Find out what wire you have paralleled before you wreck your alternators, or - maybe later - allow your vehicle to burn to the gnd.

i believe each field wire needs to go from each alternator to whatever batteries that alternator is trying to charge. as it stands now, both alternators are only charging when they sense your main battery voltage dip, which is almost never because the amp is not hooked to it. so this is probably causing a bad voltage drop at the amp's batteries, i dont know what else you have connected or how, but maybe your rear audio batteries are finding a way to pull power from the main when they drop voltage. and since one alternator would have trouble charging all those batteries it might cause your trucks voltage to drop enough to make the truck run badly(weak spark plugs). thats my theory...

solution, make sure every piece of audio equipment is getting power from your extra batteries so that there is no possible path for the two systems to bleed into each other. this means the radio, any eq's, line drivers, crossovers, capacitors, etc all need to get their power from your audio batteries.

you need to run a fresh field wire from your audio alternator to the audio batteries and it needs to be ran through a relay that is switched from the ignition, this way there is only a connection when the truck is running.

Thanks for the advise but so far no one is really paying attention.

It's a 91 chevy k1500. The alternator has a plug with 1 wire in it. It is the excite wire. Nothing more. It's not a sense wire. Furthuremore I'm getting 14.8 volts from both alternators.

You say you mounted the second alt on the A/C mounting studs. I assume it's being driven by the same serpentine belt as the OEM alt? If so, then a big load on the audio alt WILL put load on your engine, cause it to slow momentarily and could cause other issues with the OEM alt. Or the belt could be slipping. In any case, the issue is your system is placing a large load on the alt. That's all. The only way to "fix" this assuming it's all hooked up correctly is to live with it. It's one of the down sides of trying to run a large audio system. Set the engine to a higher idle RPM and make sure all your belts are 100% properly installed.

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voltagexdt wrote:

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...a plug with 1 wire in it. It is the excite wire.

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That excite wire is what many call D+ or L - the charge light circuit - often called 'I' in chevy etc sources.
Chevy's 'A' or 'A+' is akin to S = Sense;
Chevy 'S' is the Stator's star centrepoint which is an indication of the alternator charging - ie, it turns on the Field Relay hence turning off the charge-Lamp (I);
And F = F = rotor field - its current varies in order to maintain the required (say) +14.2V at the battery.

But with modern integrated or internally regulated alternators you don't normally have access to the Field nor Stator.

However I was even more confused than those that wrote the web refs I saw. Many contradict, and others were ambiguous enough to be inconclusive (ie, whether charge-Light I output can be connected to the Ignition, though older external electromechanical regulators often could be without direct damage)...
I'd have to work out what's what from appropriate wiring diagrams...

But normally a single extra wire means it's a D+ aka L.
For some alternators, there must be a resistive connection to IGN +12V to guarantee rotor excitation (whether directly or via intermediate regulator circuitry) and that tickle or trickle current is supplied through the charge light or resistor or other bulbs connected to IGN +12V.
But many L/D+ terminals supply +12V when charging (and thence turn on {electric...} chokes or fuel stops or fuel pumps or battery isolators).
Some D+/L terminals are merely the centre (30) of a 2-way or SPDT relay with 87 to GND and 87a to Alternator +12V output terminal (aka our B/B+). You do not want to connect those D+ outputs together!   
But unlike integral regulators, many externally mounted electro-mechanical voltage regulators could tolerate that - but who'd use an e-mag vreg these days? Even if external, it could be electronic. But for modern vehicles with ECUs and user-added PCs & big audio, internally regulated is the way to go.

I would connect the 2nd alternator's wire thru a 12V 2W or 3W bulb to IGN +12V, else see if it already has a ~15 Ohm to IGN +12V.
If it extinguishes once the engine is running, then the alternator is charging. (Or rather, when it is lit, it is not charging {sufficiently}.)
And if it is a Sense wire, the above will not do any harm.

But you should always check each battery's 'rested' voltage (to preempt failure) and each batt's charging voltage (eg, normally not above 14.4VDC long term, and usually above (say; preferably) 14.0V - 14.2V under any load and any speed.
However Optima specify different voltages and charging regimes (below whatever max temperature) so you can align your voltages to them.

And hence the advantage of the S = Sense circuit (ie, typical 2-wire S & L alternator) so that even with the alternator up the front and battery down the back, the alternator can regulate its output to provide the proper voltage across the battery terminals (ie, 14.2-14.4V). But a Sense wire almost always be connected to the battery else over-voltage can occur (typically limited to ~15.5V on Jap SL & SIL type alternators).