# Hate the new computer controlled alternator



## XtremeRevolution (Jan 19, 2012)

Something isn't right in the way you're describing this. You shouldn't have any power issues running two weak subs into a 4 ohm load, which should be at least 75% efficient on that amp. What else are you running in there? Those batteries also shouldn't be having issues. I just don't see how you're having electrical problems on 700W @ 4 ohms. 

Did you upgrade your Big 3 wiring? What do your grounds look like? If you upgraded them, where did you run the grounds? Ask yourself why your batteries are sitting at 12.2V. The alternator automatically starts charging once it gets low, and that sounds like way too low of a voltage. 

The car keeps track of voltage and load, and adjusts alternator output accordingly. You need to run the ground wire in the engine bay through the correct sensor in order for it to read correctly. I don't believe there's any way to adjust it. 

That said, we have other members on this board who are running some decently high powered systems with zero issues, so my best guess is it has something to do with either your install, or your specific amp. Your amp shouldn't be going into protect mode at 12.2V. My MRP-M1000 has zero issues at high volumes (600W @ 4 ohms, 75% efficient) regardless of voltage. I see nothing wrong with the alternator or how it works.


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## spacedout (Dec 7, 2010)

First time I noticed the running car only showing 12.7V I came on here & read all about the computer controlled alternator. Sure enough when more power was needed(turn on fan to max or headlights) the voltage increased. 

I wondered though how well this would work for things not running through the cars computers(after market amp), but never have heard any complaints. I'm sure others have checked, but after installing your amp does the car still only put out the 12.7V at idle? does the alternator only increase charging once the battery condition goes to low? If this is the case I wonder what effect it has on battery output/life since a normal car alternator would always be charging the max 14.5V or so a large aftermarket amp would never drain the battery in such a way. 

I realize this variable alternator is made to reduce drag & increase MPG, if its always charging more with a amp installed, would this not have some negative effect on MPG?


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## obermd (Mar 3, 2012)

I have to agree with XR. I suspect your amp isn't properly grounded. The car tracks power usage and fires up the alternater as needed. If your equipment isn't grounded properly then you can't get a reliable voltage and current across the equipment which is the source of your problem. It's not the load sensing alternater.


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## GoldenCruze (Dec 18, 2011)

With a multiple battery setup, did you install an isolator in the charging circuit? An isolator is needed because each battery will not have the same current draw, which means that they will need different levels of charging input.


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## amalmer71 (Apr 5, 2012)

GoldenCruze said:


> With a multiple battery setup, did you install an isolator in the charging circuit? An isolator is needed because each battery will not have the same current draw, which means that they will need different levels of charging input.


:sigh:


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## Chevyderek72 (May 16, 2011)

I have had no issues at all running 800 Watts rms.

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## Mtopper (Mar 15, 2011)

i have the big 3 done in knu knocenptz 0 gauge ofc wiring. i have dual grounds on the rear battery directly to the frame. i drilled out the grommets in the trunk and went straight to frame which was sanded down before attaching.

i have the bc2000 on the subs that was set with an oscope, the big 4 channel running my components conservatively active which is being controlled by ms8. 


when i drive, i have the stinger meter hooked up on my rear battery. the car volt meter setup on the DIC. both were telling me 12.2 when my amp went poof. i haven't had a chance to crack it open and see whats up but i talked with crescendo and they said my voltage probably dropped low enough to mess up the power supply. All that it comes down to really is that i wanted to know if anyone had figured out a way to trick the computer into charging like alternators of last gen, 14.4 at all times (theoretically of course, it doesn't always and i know that). i'm sending the amp back friday to get looked at. until then, i'm running my old school rockford fosgate 501s bridged on the w3s and it will run from 10v up to 15v no problem.


Honestly, it could be the amp just died on itself and it just so happened to be when my meter said so low. i was frustrated and pissed but will look at it. i'm going to run the bc2000 at 1 ohm on some beefier subs sooner rather than later but won't be doing so until voltage/amp issue is figure out.


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## Mtopper (Mar 15, 2011)

i did not install an isolator, i have one run of ofc from alternator to rear battery, one ofc from front batt to rear batt and the big 3 fused from front batt to alt. both are agm same maker and what not. i work at a battery store and do wiring jobs everyday from golf carts to big ford f-650. i know how to wire things up guys. i'm not trying to get smart or anything with you, i'm grateful for any help, its just one of those things. the isolator from my experience is used more so to keep the two separated and let the rear drain to nothing if told to while the front stays separated so that if rear is dead, i can still start my car and drive home. both batteries are hooked together in a large circuit in theory making them act as one big battery. i'm then hooking up from rear battery positive and negative and running amps off of that. 

i've also had to swap out a lot of batteries in gm vehicles from 09-now with the new voltage regulated alternator. i can't run half my tests to see it the alt is working properly since it will only be charging at something like 12.9 my reader says it fails.


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## tecollins1 (Nov 6, 2011)

Can u upload some photos of your set up. Would like to see what you did with the big three and batteries


Sent from iPhone 4


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## XtremeRevolution (Jan 19, 2012)

Mtopper said:


> i have the big 3 done in knu knocenptz 0 gauge ofc wiring. i have dual grounds on the rear battery directly to the frame. i drilled out the grommets in the trunk and went straight to frame which was sanded down before attaching.
> 
> i have the bc2000 on the subs that was set with an oscope, the big 4 channel running my components conservatively active which is being controlled by ms8.
> 
> ...


Where exactly did you run the ground wire in the engine bay? Did you run the ground from the battery through the same loop sensor that the original wire went through?

I simply don't know of any way to keep voltage consistent. With a good set of amplifiers that are stable at 10-15V, this shouldn't even be a problem. You're the first one I've heard of to complain of an amplifier failure and attribute it to under-voltage. 

I have a pair of Coustic Power Logic amps (u160 and u460, Class AB) running my active sound stage with a miniDSP, and an MRP-M1000 (Class D) running at 4 ohms into an IDQ15, and I haven't had a single issue. I bought the two Coustic Power Logic amps for $80 *shipped* since they're 20 or so years old. If the Crescendo amp truly failed due to a 12.2V "under-voltage" at 4 ohms, I'd swear to never use a crescendo product again in my life. That's just pathetic. 



> Uncorrect....lot of misinformation ITT.....I will just say this.....Crescendo,DD,AQ, and AB are all close buds......to add to this i have a bud running 2 BC2k's @ .5ohm each....*has dropped below 12v @ comps on a few occasions no prob*......****....*my teammate ran 2 BC3500's down to 8v accidentally before the amps went into protect!* lol


Crescendo bc2000 vs dd m2a wtf??? - Page 2 

Call up crescendo and ask them exactly how it is possible that a voltage of 12.2V is able to send an amplifier of that caliber into protect mode. I'd love to hear the explanation, and a reason as to why so many amplifiers out there can do it and their amplifier can't.


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## amalmer71 (Apr 5, 2012)

Mtopper said:


> i did not install an isolator, i have one run of ofc from alternator to rear battery, one ofc from front batt to rear batt and the big 3 fused from front batt to alt. both are agm same maker and what not. i work at a battery store and do wiring jobs everyday from golf carts to big ford f-650. i know how to wire things up guys. i'm not trying to get smart or anything with you, i'm grateful for any help, its just one of those things. the isolator from my experience is used more so to keep the two separated and let the rear drain to nothing if told to while the front stays separated so that if rear is dead, i can still start my car and drive home. both batteries are hooked together in a large circuit in theory making them act as one big battery. i'm then hooking up from rear battery positive and negative and running amps off of that.
> 
> i've also had to swap out a lot of batteries in gm vehicles from 09-now with the new voltage regulated alternator. i can't run half my tests to see it the alt is working properly since it will only be charging at something like 12.9 my reader says it fails.


The alternator is the reason to use an isolator. The benefit of having one battery drain (the auxiliary battery) is a perk, but it's not the primary reason to use an isolator. The reason is to separate the batteries to keep them from draining each other. If you still need more amperes than one auxiliary battery can provide, then add another auxiliary battery and those are the ones you want to wire in parallel if necessary.

It's like anything in life. You have to prioritize. One battery has to be higher on the food chain than the other, otherwise the alternator doesn't know which to feed first and will go crazy trying to figure it out. Add in the complication of a computer trying to tell the alternator it isn't supplying enough voltage and things will start to get all out of whack.

There are different types of isolators. There are the common diode-type isolator used for RV, such as campers, motor homes, etc. Those work well for what they are, but they're often bulky and they literally isolate the batteries from each other. Two batteries can't be charged simultaneously. Those are probably the type you're familiar with.

The other type, which I use, is a proprietary system. It hooks to the charging system and allows constant charge to the primary battery, but only charges the auxiliary battery when it needs to be charged, and only if the primary voltage is up to ~14.4VDC.

Sunforce Solar Battery Isolator 150 AMP (60113)

Here is the operation/installation manual.
http://lib.store.yahoo.net/lib/theshorelinemarket/60113-Manual.pdf

One huge benefit of using this type of isolator is it can easily be added to an existing system, as long as the existing wire is adequate gauge. It can be installed near the rear/auxiliary battery, which is a very uncommon option with isolators.

If you had this installed along with two voltage gauges, you'd have known right away what was going on, and where the problem developed. If it was your auxiliary battery, then that gauge would have read low, but the primary battery's gauge would have shown good voltage. If the primary battery, or the alternator would have been the problem, then both gauges would have shown lower voltage.

The only recommendation I have is to have both batteries load tested. I have a feeling one may have a bad cell.


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## XtremeRevolution (Jan 19, 2012)

The only times that one battery will drain another is if 

A. you have short circuited both batteries
B. one battery is installed with a higher charge than the other
C. one battery has a bad cell

If all batteries are charged fully, their charge will level out and the "system" will see them as one battery, providing twice the amount of amperage when run in parallel. They will hold the same charge and will act as one large battery. There is no reason to believe that they will drain each other. The alternator will charge both of them simultaneously, not one or the other, because two batteries in parallel will act as one larger battery bank; not two separate batteries. 

BatteryStuff Articles | Understanding Series and Parallel Battery Configurations

The primary purpose for a battery isolator is to separate the front battery from the rear battery, but this is not to prevent the batteries from draining each other. They will both drain at the same rate. 

Assuming they are wired correctly in parallel, this is not the reason why his amp died or why his voltage dropped down to 12.2V. The alternator should have more than enough power (IIRC, it's a 130amp) to charge both batteries and supply the car with enough current to run. Reading a 12.2V total system voltage would indicate that the alternator is not running, as the voltage will instantly shoot up to 14.4-14.6V as soon as the alternator fires back up. 

There is a loop sensor through which the stock battery ground wire goes through that I believe serves the purpose of sensing the voltage in the system so it knows when to start the alternator back up to charge the system. If that wire was removed, or if a larger wire was used in its place, that could have thrown off the reading and allowed the system to discharge more than it normally would have. 

I'm not entirely sure why there's so much talk about battery isolators here. Even if two batteries were discharging each other as a result of unequal load, the system would still show a 14.X volt load if the alternator was running.


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## amalmer71 (Apr 5, 2012)

XtremeRevolution said:


> I'm not entirely sure why there's so much talk about battery isolators here. Even if two batteries were discharging each other as a result of unequal load, the system would still show a 14.X volt load if the alternator was running.


I already explained. The benefits. 

Is an isolator "necessary"? No.

I pointed out the benefits of having one.

Read. Benefits. Isolation. Easier to monitor and diagnose. Keeps the problems isolated.

While, theoretically, the batteries "should" drain at the same rate, they don't. When the batteries in the remote for my Yamaha receiver go dead, I take them out (4 AA batteries) and measure the voltage output of each one. There is always one that is .3-.4 volts lower than the others. AAMOF, none of them are ever equal.

Isolators are beneficial to have. There's nothing wrong with having one. They don't create problems over not having one. They isolate the problems. 

It's like insurance. We hope we never need to use it, but it's sure nice to have when we do.


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## XtremeRevolution (Jan 19, 2012)

amalmer71 said:


> I already explained. The benefits.
> 
> Is an isolator "necessary"? No.
> 
> ...


I didn't quote you in my response, as I was responding generally to all participants of this thread. My post was intended to point out that the lack of an isolator is not what's causing his low voltage, and installing one would not help resolve his particular problem. 

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## amalmer71 (Apr 5, 2012)

The obvious solution is to find the source of the problem. Either the alternator went bad, the computer is over riding any demands the battery(s) have, or there's a bad cell. Those should be obvious. I'm just giving recommendations on how to prevent the problem from growing larger, next time.

Installing more than one battery in a charging system is not as easy as hooking them up in parallel and calling it good. There's more to it than that, to which I've pointed out.

If I need to explain in more elaborate detail, I guess that's what I'll do.

Electricity takes the path of least resistance. I'd say it seems most people who have posted in this thread know that. Since the aux battery is closer to the amplifier, it draws a majority of the power from that battery. That battery, in turn, draws power from the other battery and the alternator. If the alternator can't supply enough current to both batteries, they continue to power the amp by using the energy stored in reserve.

Now the alternator is trying to charge both batteries and supply the rest of the car (headlights, blower motor, radio, etc.) with electricity. It's probably being over worked. The computer senses this, and in an attempt to save the alternator, it lowers the voltage to a "safe" level to help prevent the alternator from overheating and destroying itself.

With a diode-type isolator, the alternator only has to charge one battery and supply the rest of the car at once. The exception would be the type of isolator I suggested earlier. It doesn't per-say, isolate the primary battery from the auxiliary battery. It simply prevents the primary battery from being drained by keeping the alternator from concentrating on only charging the auxiliary battery. Even using that type of isolator, though, the aux battery will only receive current when the isolator sees that the primary battery (primary circuit to be more specific) is adequate, usually +13.6 VDC. This will keep the alternator from being over taxed, and help it run cooler.

An alternator will have a much easier time charging one battery rather than two. It's like hooking two batteries to an external battery charger, simultaneously. It's going to take a lot longer and will be a lot harder on the charger. As I mentioned, if the one auxiliary battery isn't enough to supply the amplifier with enough current to keep it putting out the rated power, then two auxiliary batteries can be used. That's probably a good time to upgrade the charging system, too (higher output alternator).


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## XtremeRevolution (Jan 19, 2012)

amalmer71 said:


> The obvious solution is to find the source of the problem. Either the alternator went bad, the computer is over riding any demands the battery(s) have, or there's a bad cell. Those should be obvious. I'm just giving recommendations on how to prevent the problem from growing larger, next time.
> 
> Installing more than one battery in a charging system is not as easy as hooking them up in parallel and calling it good. There's more to it than that, to which I've pointed out.
> 
> ...


There's only one fundamental thing that I disagree about your analysis here. The guy is using a pair of JL W3 series wired to 4 ohms, for a maximum of ~600WRMS @ 75% efficiency (about what that amplifier will deliver based on the 1 ohm and 2 ohm ratings). At 4 ohms, his efficiency is somewhere around 75%, and I can almost guarantee you that he's not actually giving each subwoofer more than 250W RMS each. Figure 500W RMS at the point of high distortion, with a 75% efficiency, and he's pulling a total of 750W RMS. Even at 12.2V, that's 61 amps. The rest of the car's electrical components don't require a very high load. Now, I can drive my IDQ15 to its mechanical limits with much less than 600W RMS, and I barely have a few slight dips in voltage during the hardest bass beats. I'm at 75% efficiency at my impedance and no electrical system upgrades. 

My point in saying all this is that his batteries aren't being drained by his amplifier. He's simply not drawing enough power from his electrical system as an average to start draining the batteries to the point where his alternator will become overwhelmed unless he's running sine waves through his amplifier to purposely draw as much power as possible. In order to recharge batteries, you need to deplete them. I don't see any evidence of him actually depleting these batteries with the kind of electrical load he's presenting this car with. 

Your recommendation is based entirely on the assumption that his batteries are being depleted, which also assumes that his alternator is being maxed out by his amplifiers and the batteries are being drained. On two JL 12W3s at 4 ohms? I doubt it. 

What you said would be absolutely applicable, if he was perhaps running a 1 ohm load on two massive subwoofers, but he's running a very easy 4 ohm load, with a high efficiency, on subwoofers that have have a relatively low power handling capacity, and his amplifier is going into protect mode. In fact, he drove around with this exact setup for a week and had no issues, indicating that his electrical system was more than capable of supporting the load I've just described. 



> short and sweet, drove around for a week enjoying my system. never going below 14.3 so i'm excited because i don't have any type of drop.


I'd be more inclined to believe that one of his batteries may have failed than that his alternator cannot support the load of charging both batteries.


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## amalmer71 (Apr 5, 2012)

My "recommendation" is to always use a battery isolator, to everyone, anytime an aux battery is installed.

I'm not trying to diagnose his problem over the internet. That'd be frivolous. I already suggested (more than once) what the possibilities can be. It's up to him to do whatever he wants with the information or suggestions he is given.

Each item needs to be isolated to determine the problem. Each battery needs to be tested, isolated from the other. The alternator needs to be tested, isolated from the battery(s). The amplifier needs to be bench tested while being isolated from the original electrical supply it was hooked to. 

See a pattern?


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