Very Important Alternator Information!

[shizzzon 461]

I just had a fun time fixing my charging system today so i thought i spill some info out there for ya.

When you look at an alternator, you must understand it's purpose and how it will safely work.

An alternator basically keeps your battery(ies) charged.

In car audio, we usually tend to buy a H.O. alt because it will help run the system and\or keep the battery(ies) charged but it's not that easy!

There are things you must know or damage can occur to your alt or batt(s)!

1 - If purchasing a H.O. alt, do NOT purchase only based upon what size you need to run your car audio install! BIG NO NO!

Why?

Alternator's charge batteries, not just run stereo equipment! If you have a lot of aH worth of batteries in a vehicle, and they drop to 12.0v or less, you run the risk of overheating your alternator to charge them back up. How? The alt will be at maximum output all the time until the batts are charged which is bad for prolonged periods.

Solution-

If you only have 1 starting battery and\or one other battery in the rear... do NOT buy yourself a 200+ alternator as it's not a good idea! The reason is if at a certain time one of the batts is fully charged whereas the other one isn't and is considerably low, ALL the alternator current WILL be sent to that one battery. NO BATTERY CAN ACCEPT 200A+ AT THE TERMINALS! It will immediately become damaged and could boil the battery, swell the battery, overheat the terminals, etc...

If you need a 200A+ alternator, you must have enough batts in the vehicle to prevent excessive current to be sent to one battery in any given situation!

1 starting battery and at least 2 auxiliary batteries in the rear is recommended to prevent excessive current from damaging a single battery. This way the charging current is divided evenly.

If you are not going to use that many batts, then downgrade your alt output capability to prevent this scenario from happening.

2- Adding more and more batteries to your electrical system can be good or EXTREMELY bad if no maintenance or safety devices are installed!

Why?

If you are adding batteries to a stock alternator, this isn't good as it will now take the stock alt LONGER to ensure that all batteries in the system ar charged 100%. This will open the alt up full blast constantly for a LONG time, especially if you have more than 1 auxiliary battery in the vehicle to charge. This "CAN" inadvertently overheat the alt if proper cooling is not available to prevent the alt from failing.

IF you have a H.O. alt and have, for example, 50 batteries, hehe, you can still be safe as long as the alt can keep these batts charged all the time.

The problem isn't one or the other, but BOTH!

Too many batts undercharged will KILL any alternator, stock or H.O., due to overheating if required to run for extended periods of time.

Too much alternator and not enough batteries that need charging will provide too much current at the terminals and immediately lower it's life or cause damage at the spot with swelling, boiling, etc...

So, just because you have a H.O. alt doesnt mean your safe, I'm not kidding either!

Proper maintenance and proper safety equipment should be used and installed at all times.

I use a SMART fuse block which immediately shuts amplifiers down if they experience voltage below 11.5v, 12.0v or 12.5v. I keep mine set to 12.5v for utmost safety.

You can also use a remote voltage meter to monitor the realtime voltage. If you choose to do so, do NOT buy a cheap one. Make sure it can be calibrated to properly match your DMM for visual accuracy.

IF you have a problem with your alternator and it dies for instance, you will need to charge ALL batts with a charger suited specifically for your batteries.

If your starter battery is different then the auxiliary batteries and you only have a charger for the rear... and you charged them up but not the starter battery.. and it's low... and you have a H.O. alt, and you turn the car on and drive it... you will KILL or DAMAGE your starting battery immediately due to overexcessive current. In this situation, it would be best to run at idle or at 700-750rpm for several minutes if batt is really low and that's it! Any higher on 200A+ will usually cause excessive current being sent directly to it.

3- If your alternator no longer comes on all of a sudden, that does not mean it died so don't go crazy because so and so brand said they were the best.

So what do i do?

In a lot of newer cars today such as Toyota, has a specific fuse in the fuse box to protect against a signal sent from the computer to the alternator to tell the alt to "come on" by spinning the rotor.

In stock alts, the signal may only be about 4A but in H.O. alts, they are closer to 10-15A! My fuse for this is rated 7.5A.

So... in my car, the fuse is called ALT-8 7.5A.

So, if your alt ever quits workin, check this as it's common for this to happen.

Now, i've had mine on there for almost a year on the 7.5A fuse and it just popped sending 12A of current through it. Now, i'm not saying to increase the fuse rating because of the facts, BUT, i would suggest increasing the fuse rating ONLY if you are popping this fuse more and more consistently.

So, now since you see how an alt works and wont work if used improperly, you can now gauge on what makes an alt good or not. It's mostly boiled down to heat just like anything else, heat is bad. Cheaply priced alts usually have terrible cooling solutions and are not wise to be used for prolonged periods when Wide Open at any given rpm.

Read this again and again because you may not have heard this before and i dont want you losing close to or over $1,000 on your new electrical system and getting pissed for the wrong reasons.

[SilkySmoove 0]

Great write up man. This seems to put into perspective all of the varying view points I have been seeing across the net in regards to adding an additional battery vs getting a HO alternator.

In my case I have slight head light dimming running about 1300W rms. I currently have a duralast gold under the hood and a Kenetik HC600 in the rear. Would you suggest upgrading my starting batt or simply place say a HC1400 in the rear instead of the HC600????

This is all in a 2008 Altima 3.5SE with a stock "130A" alternator.

[Tirefryr 1,742]

I just had a fun time fixing my charging system today so i thought i spill some info out there for ya.

When you look at an alternator, you must understand it's purpose and how it will safely work.

An alternator basically keeps your battery(ies) charged.

In car audio, we usually tend to buy a H.O. alt because it will help run the system and\or keep the battery(ies) charged but it's not that easy!

There are things you must know or damage can occur to your alt or batt(s)!

1 - If purchasing a H.O. alt, do NOT purchase only based upon what size you need to run your car audio install! BIG NO NO!

Why?

Alternator's charge batteries, not just run stereo equipment! If you have a lot of aH worth of batteries in a vehicle, and they drop to 12.0v or less, you run the risk of overheating your alternator to charge them back up. How? The alt will be at maximum output all the time until the batts are charged which is bad for prolonged periods.

Solution-

If you only have 1 starting battery and\or one other battery in the rear... do NOT buy yourself a 200+ alternator as it's not a good idea! The reason is if at a certain time one of the batts is fully charged whereas the other one isn't and is considerably low, ALL the alternator current WILL be sent to that one battery. NO BATTERY CAN ACCEPT 200A+ AT THE TERMINALS! It will immediately become damaged and could boil the battery, swell the battery, overheat the terminals, etc...

If you need a 200A+ alternator, you must have enough batts in the vehicle to prevent excessive current to be sent to one battery in any given situation!

1 starting battery and at least 2 auxiliary batteries in the rear is recommended to prevent excessive current from damaging a single battery. This way the charging current is divided evenly.

If you are not going to use that many batts, then downgrade your alt output capability to prevent this scenario from happening.

2- Adding more and more batteries to your electrical system can be good or EXTREMELY bad if no maintenance or safety devices are installed!

Why?

If you are adding batteries to a stock alternator, this isn't good as it will now take the stock alt LONGER to ensure that all batteries in the system ar charged 100%. This will open the alt up full blast constantly for a LONG time, especially if you have more than 1 auxiliary battery in the vehicle to charge. This "CAN" inadvertently overheat the alt if proper cooling is not available to prevent the alt from failing.

IF you have a H.O. alt and have, for example, 50 batteries, hehe, you can still be safe as long as the alt can keep these batts charged all the time.

The problem isn't one or the other, but BOTH!

Too many batts undercharged will KILL any alternator, stock or H.O., due to overheating if required to run for extended periods of time.

Too much alternator and not enough batteries that need charging will provide too much current at the terminals and immediately lower it's life or cause damage at the spot with swelling, boiling, etc...

So, just because you have a H.O. alt doesnt mean your safe, I'm not kidding either!

Proper maintenance and proper safety equipment should be used and installed at all times.

I use a SMART fuse block which immediately shuts amplifiers down if they experience voltage below 11.5v, 12.0v or 12.5v. I keep mine set to 12.5v for utmost safety.

You can also use a remote voltage meter to monitor the realtime voltage. If you choose to do so, do NOT buy a cheap one. Make sure it can be calibrated to properly match your DMM for visual accuracy.

IF you have a problem with your alternator and it dies for instance, you will need to charge ALL batts with a charger suited specifically for your batteries.

If your starter battery is different then the auxiliary batteries and you only have a charger for the rear... and you charged them up but not the starter battery.. and it's low... and you have a H.O. alt, and you turn the car on and drive it... you will KILL or DAMAGE your starting battery immediately due to overexcessive current. In this situation, it would be best to run at idle or at 700-750rpm for several minutes if batt is really low and that's it! Any higher on 200A+ will usually cause excessive current being sent directly to it.

3- If your alternator no longer comes on all of a sudden, that does not mean it died so don't go crazy because so and so brand said they were the best.

So what do i do?

In a lot of newer cars today such as Toyota, has a specific fuse in the fuse box to protect against a signal sent from the computer to the alternator to tell the alt to "come on" by spinning the rotor.

In stock alts, the signal may only be about 4A but in H.O. alts, they are closer to 10-15A! My fuse for this is rated 7.5A.

So... in my car, the fuse is called ALT-8 7.5A.

So, if your alt ever quits workin, check this as it's common for this to happen.

Now, i've had mine on there for almost a year on the 7.5A fuse and it just popped sending 12A of current through it. Now, i'm not saying to increase the fuse rating because of the facts, BUT, i would suggest increasing the fuse rating ONLY if you are popping this fuse more and more consistently.

So, now since you see how an alt works and wont work if used improperly, you can now gauge on what makes an alt good or not. It's mostly boiled down to heat just like anything else, heat is bad. Cheaply priced alts usually have terrible cooling solutions and are not wise to be used for prolonged periods when Wide Open at any given rpm.

Read this again and again because you may not have heard this before and i dont want you losing close to or over $1,000 on your new electrical system and getting pissed for the wrong reasons.

Where did you get your information from?

Lot's of misinformation here.

1. First off, the alt's main job is to power the vehicle, then charge the battery.

2. It will NEVER output full current to just one component such as the battery, in fact, the electronics will limit it to supplying only what it needs.

If running multiple batteries and one is fully charged, the alt will simply not charge anymore. No risk of damaging the other battery aside from the main leaking into it. That's where you'll have problems.

3. You can buy as large of an alt as you want without fear of overcharging, unless there is an internal problem with the unit itself.

I could pick apart the rest too, but the my previous statements pretty much sum it up.

[shizzzon 461]

What size alternator or battery should i get?

For battery sake- you should match the aH rating to half that of your amplifier's recommended fuse rating.

For example - if you have 640A worth of fusing for amps, you will need approximately 320aH worth of batteries.

Now, you can get away with this rule of thumb by having a large H.O. alternator.

Alternator rule of thumb works in about the same manor, you just gotta take the car into consideration as well.

If you had 640A worth of fusing, for example, half that is 320. They make 300A alts but some are impractical for car use due to size and most vehicles do not have the room for DUAL alternators. If alt size was always custom, you would want to reserve about 60A for the car and the rest for the stereo.

So, 60+320 = 380A alternator unrealistically. Now, if you have an alt that can supply power to the car AND the entire stereo system like this, I have some good news for you. The rule of thumb for batts in the back decreases. You still need batts in the back but not as strong, you need something just to keep the voltage up in the rear. In my opinion, you would only need 25% of the fuse rating of all your amps for batts IF AND ONLY IF you have an alt strong enough to run everything on it's own... so in this example, it would be a 380A alt and 160aH worth of BATTS, not batt, but BATTS. Remember, when using a H.O. alt, you must use multiple batts to prevent over excessive current from being sent to one battery. 3 60aH batts, 2 80aH, 4 40aH and so on...

Now, if you do not have enough alt which realistically you wouldnt in that scenario since there is no such thing as a380A alt, you need to follow the rule of thumb for the batts. So, for 640A of fuse rating, you would need 320aH worth of batts. Now, this is where things get reversed... If you are using the stock alt, you can use large batts or multiple smaller batts. Multiple smaller batts wired in parallel exhibit lower resistance allowing slightly faster charging. However less larger batts will allow the alt to send higher current loads to these types of batts allowing faster charging so you see when it comes to stock alt, the preventive rules are not as strict.

Now, if you have a H.O. alt but it's not large enough so u have to go with 50% worth of aH for batts, tend to stick with smaller batts if possible, or at least 3 batts total in the system PER alternator (if using multi alt setup) to prevent over excessive current charging to a single battery accidentally.

In your situation- 1,300w = ~120A fuse rating if really is a truly rated amp.

You need at least 60A + 60A worth of alternator... You PASSED with 130A.

Now, you only need 25% of 120 in the rear(never count the starting battery into the rule of thumb equation).

25% of 120 is 40A.

You have only a 20aH battery in the rear.

I would suggest either replacing or adding enough battery capacitance to equal at least 40aH in the rear alone.

with your electrical system, you say lights dim, this should only be happening because the regulator cannot keep up with the rapid current changes that car audio pulls. A battery can so it will pull from it first. 20aH batt is so small that it is probably pulling that baby down so low it's causing dimming or a quick low voltage scenario.

I am willing to bet that if you went out there and played a constant test tone real loud that your lights would only dim at the beginning of the tone then return to it's brightness orat least a lot brighter then when they first dimmed until the tone was over then it may just slightly get brighter again.

Of course this is rule of thumb. there may be some instances where u may still need slightly more batt capacitance and\or alternator but this rule of thumb is based on music output and how it varies.

If you are goin down the road playin test tones and bass tracks non-stop, then the requirements will go UP.

[shizzzon 461]

1. First off, the alt's main job is to power the vehicle, then charge the battery.

2. It will NEVER output full current to just one component such as the battery, in fact, the electronics will limit it to supplying only what it needs.

If running multiple batteries and one is fully charged, the alt will simply not charge anymore. No risk of damaging the other battery aside from the main leaking into it. That's where you'll have problems.

3. You can buy as large of an alt as you want without fear of overcharging, unless there is an internal problem with the unit itself.

I could pick apart the rest too, but the my previous statements pretty much sum it up.

1- Understood. Simple.

2-3 - The electronics will receive what they need and only what they need.

The response to outputting all to one battery is true and i'll give you an example.

Lets say you have your batts isolated from one another and you drained your rear batt down to 50% but your starter battery is fully charged. you have a 200A+ alt.

You start the car and hit constant engine rpms that make the alt put out the highest possible load it can do... All the remaining power, because i assume approx 60A give or take is being used by the car, will be sent to that batt to charge because... it's low. If it receives too much current at once, it will damage it no questions asked.

I've had 2 alt companies tell me this. Excessive current sent to a battery will damage it.

Another scenario- Your starter battery dies. You get a jump from somebody but you have a 200A+ H.O. alt. NEVER rev your car up once it's started. Doing so, again, will send excessive current to that battery and can damage it.

If all batts are wired in parallel, then yes, sometimes all batts may not be 100% charged but that's not what i'm trying to say. It involves them being isolated as well which makes this scenario happen. I didn't mention isolation before but it's possible.

3- not overcharging, but receiving too much current at once. This is a difference.

[shizzzon 461]

Tirefryr, you do make a point about electronics still getting what they need.

It gave me an idea. If your alt is too powerful for charging just one battery, create a load that will divert some of the current from the alt to other devices to lower the charging current to the battery.

[Quentin Jarrell 671]

This is a quote off powermaster website.

Will a higher amp alternator hurt my battery or charging system?

No. A good rule of thumb is that more amps are not harmful, but more voltage is. If you look at electrical power like water, amperage is equivalent to the volume of water, and voltage is equivalent to water pressure. More amperage is like having a larger pool of water to draw from.

[shizzzon 461]

i dont want to drown....

Of course, i'm not the engineer telling you this first hand, but it makes sense.

I'll contact Powermaster and ask them if i can send 200A or more to a single battery and see what they say and bring up what you said as i can't argue with it.

[rumproast789 0]

so, assuming all of what you said is right, could a battery isolator help? Maybe I am thinking that it does something else, not quite sure what it does.

Edited April 7, 2009 by rumproast789

[Quentin Jarrell 671]

What they might have meant was you could get a voltage spike that could damage your battery and electronics. That's why they tell you don't start a vehicle (jump off) that doesn't have a battery installed. The battery helps level voltage spikes coming from the alternator

[Tirefryr 1,742]

1. First off, the alt's main job is to power the vehicle, then charge the battery.

2. It will NEVER output full current to just one component such as the battery, in fact, the electronics will limit it to supplying only what it needs.

If running multiple batteries and one is fully charged, the alt will simply not charge anymore. No risk of damaging the other battery aside from the main leaking into it. That's where you'll have problems.

3. You can buy as large of an alt as you want without fear of overcharging, unless there is an internal problem with the unit itself.

I could pick apart the rest too, but the my previous statements pretty much sum it up.

1- Understood. Simple.

2-3 - The electronics will receive what they need and only what they need.

The response to outputting all to one battery is true and i'll give you an example.

Lets say you have your batts isolated from one another and you drained your rear batt down to 50% but your starter battery is fully charged. you have a 200A+ alt.

You start the car and hit constant engine rpms that make the alt put out the highest possible load it can do... All the remaining power, because i assume approx 60A give or take is being used by the car, will be sent to that batt to charge because... it's low. If it receives too much current at once, it will damage it no questions asked.

I've had 2 alt companies tell me this. Excessive current sent to a battery will damage it.

Another scenario- Your starter battery dies. You get a jump from somebody but you have a 200A+ H.O. alt. NEVER rev your car up once it's started. Doing so, again, will send excessive current to that battery and can damage it.

If all batts are wired in parallel, then yes, sometimes all batts may not be 100% charged but that's not what i'm trying to say. It involves them being isolated as well which makes this scenario happen. I didn't mention isolation before but it's possible.

3- not overcharging, but receiving too much current at once. This is a difference.

Just because the alt has the capability to produce X amount of amperage, doesn't mean it's producing that whether it's spinning full bore or not. They do not just instantly go into full output if functioning properly.. The voltage regulator will control all this and excite the field as it sees fit. Whether isolated or not, the battery in need of a charge will not see an inrush of current, nor will anything else in the circuit.

[Tirefryr 1,742]

What they might have meant was you could get a voltage spike that could damage your battery and electronics. That's why they tell you don't start a vehicle (jump off) that doesn't have a battery installed. The battery helps level voltage spikes coming from the alternator

Precisely. The battery will never see a full load from an alternator that is functioning correctly.

Your battery could be the loan load on the alt and it would still never receive the full output of the alternator no matter it's state of charge.

[djjdnap 78]

regulator...

and on newer cars pcm controlled...

[Tirefryr 1,742]

regulator...

and on newer cars pcm controlled...

Not all of them. There are plenty of brand new vehicles that are not controlled by the computer, but it is becoming commonplace. It's cheaper, more effective, AND more reliable.

[Quentin Jarrell 671]

Call powermaster for us tomarrow and lets us know what there input is. This could be very usefull information.

[Dutchie. 10]

Don't alts have a voltage regulator, so they won't ever overpower your stuff?

[Quentin Jarrell 671]

yea but they still fluctuate

[Tirefryr 1,742]

And fail. . . And are affected by heat. .

For the most part, they work exactly as intended especially with quality components.

The problems arise when you buy an HO alt with sub-par regulation and rectification.

[Dutchie. 10]

And fail. . . And are affected by heat. .

For the most part, they work exactly as intended especially with quality components.

The problems arise when you buy an HO alt with sub-par regulation and rectification.

No reason to say fail. There is a question mark at the end. Settle down.

[Tirefryr 1,742]

And fail. . . And are affected by heat. .

For the most part, they work exactly as intended especially with quality components.

The problems arise when you buy an HO alt with sub-par regulation and rectification.

No reason to say fail. There is a question mark at the end. Settle down.

You misread my post. I was furthering the previous post.

[Bobaflob 0]

And fail. . . And are affected by heat. .

For the most part, they work exactly as intended especially with quality components.

The problems arise when you buy an HO alt with sub-par regulation and rectification.

No reason to say fail. There is a question mark at the end. Settle down.

I think he was stating that regulators fail. Not your post was fail.

[Quentin Jarrell 671]

Unhook all your batteries in your car put a DMM on your alt lead and rev the engine. I bet it doesn't stay exaclty the same. I'm not saying it'll spike to 2000 volts but it can cause enough spike to damage electronics. Call Poowermaster tomorrow and ask them. I didn't say you were 100% incorrect in your thread just some of it. If your theory is correct then all the batteries this vehicle would blow up upon starting.

[Tirefryr 1,742]

Unhook all your batteries in your car put a DMM on your alt lead and rev the engine. I bet it doesn't stay exaclty the same. I'm not saying it'll spike to 2000 volts but it can cause enough spike to damage electronics. Call Poowermaster tomorrow and ask them. I didn't say you were 100% incorrect in your thread just some of it. If your theory is correct then all the batteries this vehicle would blow up upon starting.

DON'T do this! The battery is a necessity! Never run an alt without a battery as a load on it.

[Dutchie. 10]

And fail. . . And are affected by heat. .

For the most part, they work exactly as intended especially with quality components.

The problems arise when you buy an HO alt with sub-par regulation and rectification.

No reason to say fail. There is a question mark at the end. Settle down.

You misread my post. I was furthering the previous post.

Good Day.

[Quentin Jarrell 671]

I agree 1000% But for arguments sake why not? If every accessory in the vehicle along with your system is tuned on drawing 100 amps of current and you have a 120 amp alt what will it hurt?

Edited April 7, 2009 by Audibel Customs