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running an amp off the alternator?

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Re: running an amp off the alternator?

Post by MECHMAN » Monday, 13 July 2009, 11:04 AM

manonegra wrote:dont know if i have the right way, but this is how i have it the field from the alt to the regulator the alt output direct to the battery 12v in the back and only went im goin to key i may ajust the regulater a lit as may be 16v and wend key it my drop to 15v wont try it any higher so i wont burn somethings up so far has work for me but this is a temporary set up.


16V will overheat the batteries in short order. Flooded style batteries can charge at 15.2 volts for quite a while without damage, AGM batteries no more than 14.9 volts. If you want more voltage than that, you can always switch to 16 volt batteries, which will run charge at 19.2 volts continuous.
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Re: running an amp off the alternator?

Post by manonegra » Tuesday, 14 July 2009, 6:16 AM

thanks for the post mech 73s
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at 15v on 12v batt set up for now
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Re: running an amp off the alternator?

Post by manonegra » Friday, 21 August 2009, 5:33 AM

OK IM DONE WITH MY SUBERBAVAN MY ALT IS ON,NO LUCK AT 18V BURN WRITE AWAY SO I WENT DOWN TO 16V BUT FOR SOME REASON ONE BATTERY WASNT CHARCHING LIKE IT SUPOST TO SO I WANT DO GOING BACK TO 12V CHARGING TO 14.7 AND WEND I KEY UP TO 16V WORK GOOD,
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Re: running an amp off the alternator?

Post by madsage » Friday, 21 August 2009, 7:00 AM

Somebody said large caps dont work with CB?

Why would you say this, i am currious. A cap doesnt care what kind of component is behind it, if it draws a voltage, a cap will help keep that voltage constant, it will oppose a change in voltage. It also fills any gaps that could be related to noise or ripple from the alternator.

A big power cap like 1-3farad can store a **Censored** load of energy as well, helping an under powered alternator, if you are running a setup that when you key your alt pulls down and your lights dim, seriously try a big power cap. It will help smooth the load recharging between keys. unless i key down long enough to drain the cap fully, all of my alt pulldown and light dimming effect went away, I also boosted my pep as i was dropping voltage previously. I run a constant 14.5volt to my 5pill in the jeep from it, otherwise it would drop to 11.2volt. Yes i should problably upgrade the alt and this maybe a better solution, except for the cap was $50 and a 250amp alt almost $300, and its working!

anyways sorry to change the subject i know this has been discussed before,

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Re: running an amp off the alternator?

Post by 'Doc » Friday, 21 August 2009, 10:33 AM

A capacitor no matter what it's size is not going to relieve any stress on an under powered alternator. That alternator is having to recharge that capacitor all the time. In effect, it's putting a larger 'stress' on an alternator. On the radio side, you may not notice any 'dips', but there certainly will be some on the alternator/battery side of that capacitor.
What it amounts to is that you can never get more out of something than what you put into it, plus a little bit more because nothing is 100% efficient. If you start with an under powered alternator, add a capacitor, you still have an under powered alternator that is going to have to work just as hard to keep the system charged as if that capacitor wasn't there. Actually, it's going to have to work a little bit harder because that cap is there. Gotta keep it charged just like the battery. Oh it's certainly quicker, but that just means that the whole thing is cycling more often.
Any time you 'push' something harder than it was designed to be used, you will loose something some where else. If that 'price' is worth it to you, then knock yourself out with it! If you want to keep things efficient (sort of) then you have one of two choices. Larger alternator, or less current draw (or power). That's it. If you can really think of some way of doing that thing, you better patent it!!
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Re: running an amp off the alternator?

Post by Capndave » Friday, 21 August 2009, 11:48 AM

Ive been always under the impression that the CB be connected to the battery,which is connected to the block and frame for positive ground.for good transfer you might want to run a second battery in the trunk(Depending on what vehicle you own)So you would run the amp off of the second cell running a 120 amp alternator and filters (if needs be)as you accelerate the noise would increase if you are connected to the alternator.

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Re: running an amp off the alternator?

Post by Century21 » Friday, 21 August 2009, 13:23 PM

Doc is good on that one..
Caps aint all that, while ill never doubt the filtering and stuff they can do. But storing massive amounts of power, no. Hook your biggest cap up to your battery to give it a charge. Then hook you radio or amp up to it, see how long that cap powers it..........better off with a battery.
And your alternator is putting out 13.8 to 14.8 volts normally. And it charges your cap, And as soon as you key that mic, in the matter of milliseconds its pullin the alternator. They use caps in car stereo setups normally to help with punch for the quick hitting base.
The only job a battery has to a car, besides giving the alternator the voltage needed to start charging, is to start the vehicle. After that, its all on the alternator. No im not saying your battery is no longer any benefit. But thats the main purpose of the battery.
To keep from burning up alternators, install a second one, be a little creative, there is always room. OR make it. And isolate it from the cars electrical system.
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Re: running an amp off the alternator?

Post by madsage » Saturday, 22 August 2009, 9:50 AM

my ideology wasnt that the capacitor creates power. its that it stores the power between keys, and on demand releases that stored energy when needed.
when off the key, the alt charges it at a slower rate than what would be needed to key the amp, effectivly smoothing out the load across time. now this wont work for long key down rag chews, but for calls and short responces i have noticed a significant differnce.

also, i'm running a 120amp alt with the 667v currently, so i fugure i'm not too far from sufficient power, other than i do notice without the cap much more alt pulldown and lights dimming. also i've got 6gauge cable for line. so that should also be good. been thinking about upgrading this to 4 or 0gauge.

eventually i am going to order a bigger alt from mechman, something in the 275-300amp range, definatly going to need this for some better offroad lighting and a winch, as well as a dual battery setup. need new baja claws now.. always something!

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Re: running an amp off the alternator?

Post by 'Doc » Saturday, 22 August 2009, 9:59 AM

You may not see a huge difference by going to a larger power line, but it will reduce the amount of resistance the system has to overcome to get power to where it's going. That is an improvement whether you see it or not.
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Re: running an amp off the alternator?

Post by 55builtit4me » Sunday, 23 August 2009, 9:15 AM

Sheriff Bart wrote:
okay...the original premise is "running an amp off the alternator" ...answer, how do you run it when the engine isn't running :basketball: ...now to cross you over..

73's


to cross you over, running an amplifier with the engine off is never a good idea. Why? it will introduce loads of awesome harmonicss into your amplifier because although it may be so small that it's unnoticeable, there will be voltage drop. and more voltage drop. transistors like a steady current of the same voltage, otherwise, you will have a harmonicing turd box...

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Re: running an amp off the alternator?

Post by 'Doc » Sunday, 23 August 2009, 12:56 PM

The biggest problem with running a high current draw amplifier (or anything else for that matter) with out the engine running is that you will be taking a chance of trying to start the car with a dead battery. Forget the harmonics thingy, that just doesn't happen that way. Harmonics are not caused by low voltages. They may be noticeable then, but that just means they were there to start with and you didn't notice them.
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Re: running an amp off the alternator?

Post by Foxhunter » Sunday, 23 August 2009, 21:59 PM

Well I did post in this thread once before. From experience & common sense it's easily understood that although the alternator is a source of renewable power-----more importantly it is the source of voltage fluctuation, electrical noise/trash and other maladies. The battery(s) are most often needed as a buffer/filter, with beneficial stored current reserve. Running an amp straight from the alternator would introduce all sorts of problems and negative side effects.


Mentioning using an amp from just a battery with the engine off? Running an amplifier system without a running charging engine is almost an excercise in futility. "Resting Voltage" (voltage of a battery not being charged/replenished by an alternator) for most automotive batteries is only 11.5VDC. A nominal voltage of a battery considered "dead" to electionics and other DC applications is 10.5VDC. Even with a fresh battery, that's only one volt away from being considered completely dead.


In the battery-only scenario, an amp/radio combination would be powered at 11.5VDC at the battery, then factor-in a voltage-drop along the length of the supply cables PLUS an insertion loss of any cable connections crimps connectors etc-----you would be running your amp/cb in "brown out" conditions and it would deplete the battery in short order.


Electrolytic filter capacitors, also known as car audio stiffening capacitors? Although their use is often misunderstood and at times hotly debated, I am still from the side of opinion that they can be a benefit.


Not only from a concept point-of-view, but from actually having used them. They just cannot be relied on to actually nearly "power" a system, either car audio or rf amplifier based systems. That is where many go wrong, thinking they can put one in-line and suddenly, with an otherwise stock charging system, power a 1000W amp. Critics also cite this misunderstanding and misuse in application and wrongly deem them entirely useless.


They are not a replacement for a good or extra battery and a replacement for an adequate high-output alternator. What they are however is a good accessory for bolstering a marginal charging/battery system whose maximum rating is at that point already close to actual demand. They can be useful for highlighting or functionally complimenting (if you will) an already adequate charging/battery system. The electronic noise reduction, voltage fluctuation stabilization, momentary surge capacity and other benefits can be a boon to your otherwise decent supply system. At the initial point when a heavy demand/load is placed on the system, there is a small lag time where a power supply system responds with increased output. The alternator doesn't respond in an instant. But a capacitor will. It is only in that momentary initial lag where a capacitor can be found useful. They are not to be used as a band-aid measure or crutch to a really inadequate system.


I believe another misconception is that they somehow "rob" your alternator of power. A capacitor only takes power from the charging system during lulls where demand is at a low and energy is at a surplus. In situations of peak demand they simply continue to allow current to pass through, waiting to recharge when demand is minimized. For me it's hard to justify the cost of capacitors as an accessory, but if they are readily available I wouldn't hesitate to use them. A stiffening capacitor is not a "critically necessary" item, but then again much of what is contained in the radio hobbies really isn't absolutely necessary. IMHO it would be for the premium-install crowd, where in addition to a proper charging/supply installation, expensive accessories are considered reasonable and affordable.

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Re: running an amp off the alternator?

Post by 49 » Wednesday, 26 August 2009, 23:44 PM

Intresting thread..

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Re: running an amp off the alternator?

Post by Sheriff Bart » Thursday, 27 August 2009, 2:57 AM

I had a mobile..had three alternators...one alt was the stock one which powered the car . alt number 2 was connected to a bank of three 6V batts and drove the 3 or 5 pill driver with a regulator I could dial up from inside the mobile. alt number 3 was connected to a bank of 3 6V batts and drove the 8 or 12 pill also with a regulator inside the car I could dial up. When I wanted to however I could turn the motor off and intermittantly run my 3 or 5 pill but not rachet jawing. Just to bump it down quickly, bam, bam, bam then off the key. Now if there was room for me to have another 2 18V systems added with my 2 18V systems I could bump it twice as long, bam, bam, bam, bam, bam, bam..but not have long qso's on the driver or pump without the engine running.
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Re:

Post by -=PEAKABOO=- » Saturday, 19 December 2009, 20:45 PM

ringer wrote:the alterator isn't a power source


What is it then?
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Re:

Post by -=PEAKABOO=- » Saturday, 19 December 2009, 20:48 PM

jessejamesdallas wrote:
rotts4u wrote:Since the alternator is connected directly to the battery usually with a nice large diameter cable isnt hooking it to the "alternator" the same as hooking it to the battery except with the longer cable? Because the alternator is infact connected to the alternator anyway right?

The battery is going to buffer the charge coming from the alternator, and give you a more constant current flow. (no Up & Down spikes in current)

In junkies "Buddies" case, he stated that this guy had a farad cap inline...OK, even though these are not recommended for use in CB installs, in this case, the Cap is acting as the battery, and giving some buffering probably to his set-up. But I would be willing to bet this guy also has allot more noise in his radio, than he would if he had a battery in line rather than that Cap.


A 1 farad cap will filter all of the noise produced by an alternator. It does not even take that much.
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Re:

Post by -=PEAKABOO=- » Saturday, 19 December 2009, 20:50 PM

coondog wrote:no way would i ever think of running a setup like that,imagine how hot the alt. would get and i guess he dosen"t even use his amp at night because he"d be driving in the dark.

if he"s using the mobiles main alt.for this i feel sorry for his mobiles computer.

there has to be a battery somewhere in the mix or he"d be dead in the water in no time.

The alternator would probably run cooler because it does not have to charge batteries and supply current to the amplifier
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Re:

Post by -=PEAKABOO=- » Saturday, 19 December 2009, 20:54 PM

Crusher wrote:I ran a 6 pill in my 2000suv. It hurt the computer system. luckily the dealer was able to rest/reprogram the computer. I also smoked a sensor. I ended up using a motormaul and now am running an 8 pill. The only thing affected is that i get the voltage light to come on around 600-800 Bird watts. I am only saying this as i thought originally I had upgraded to a drop in replacement alternator that was rated at 220A verses the factory 100A. I thought I had amps to spare, but I was wrong. Upgraded alternator cable from 4 gauge to 2 gauge. I have killed several alternators in many of my vehicles. It becomes an expensive lesson.


A lot of the so called high current drop in alternators are not up to the task. I have an active load I have built that allows you to put up to a 400 amp short on items, you can dial it to whatever you want. The bolt on upgrade alternators will usually only do the rated current (if that) for a few seconds and then they sag drastically.
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Re: running an amp off the alternator?

Post by -=PEAKABOO=- » Saturday, 19 December 2009, 20:57 PM

MECHMAN wrote:An alternator HAS to have a battery in order to produce current. It needs the initial current from the battery to fire up the field for the first time, as well as supply current tothe regulator.

Even if that weren't the case, all regulators have a delay built into them, and amperage output would be all over the pplace with RPM changes. You pretty much have to have a battery in parralel with the alternator to power anything. (not just a radio) He more than likely was just running his power cable from the radio to the alternator stud, but he had to have a batter in the circuit somewhere.

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If you have a large cap in line and the cap is charged, the alternator will charge like normal. The cap has to be charged for this to work and it takes quite a bit of capacitance to do this.
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