bigger alternator?

FG!! · Post by **FG!!** » Wed Jun 25, 2003 2:28 am

all that is listed at napa for our cars is the 70amp hitachi, any other ones fit?

Post by **Legacy777** » Wed Jun 25, 2003 3:10 am

I'm looking into an upgraded one. There's a guy on nasioc in texas that has a shop that's doin them. I'm probably going to get one.

what they found is the casing is too small, so they have a completely different housing and such. You just need to solder on the different connectors. At idle his puts out 110 amps. Full power will generate 160+ amps.

Cost is around $275, which is a little steep, but for the kind of power that it's putting out, it's pretty good. I'm checking on fitment and a couple other things first, but I'll let ya know if I decide to do it.

evolutionmovement · Post by **evolutionmovement** » Wed Jun 25, 2003 11:26 pm

What kind of accessories are everyone running? I've got 220K+ on my original alternator with no light dimming or engine hesitation as discussd elsewhere and I've got some big Hella fog lamps on top of the bumper.

Redline Dreamz · Post by **Redline Dreamz** » Tue Jul 01, 2003 10:56 am

you can get them rewound for as much power as you want but too much will burn up your electronics.

Post by **Legacy777** » Tue Jul 01, 2003 2:02 pm

The stock casing will limit how much you can have it rewound.

Voltage is still limited by a voltage regulator, and amperage is a function of the device that's being powered, so how would you burn up the electronics?

magicmike · Post by **magicmike** » Tue Jul 01, 2003 5:03 pm

Redline Dreamz wrote:you can get them rewound for as much power as you want but too much will burn up your electronics.

Just not true.

Alternators create voltage which can be drawn from them in the form of amps. It doesn't matter what they put out. What ever is drawing from them is what that unit gets. It's like the alternator is a bucket of water and a radio for example is connected to the bucket. The radio will only take as much water from the bucket as it needs. if you have too many components drawing from that bucket the water drains faster than it can be filled up and thats when you have problems. thus needing a bigger alt that either has a bigger resovoire or that fills up quicker. I hope my anology makes sence.

Mike

eastbaysubaru · Post by **eastbaysubaru** » Tue Jul 01, 2003 6:55 pm

That's a great analogy Mike! I couldn't have said it better myself. I've got a few stereo items as well and would like to know about beefier alternators. Unfortunately, it seems like it'd be really expensive

-Brian

Redline Dreamz · Post by **Redline Dreamz** » Wed Jul 02, 2003 7:53 am

magicmike wrote:
Redline Dreamz wrote:you can get them rewound for as much power as you want but too much will burn up your electronics.
Just not true.

Alternators create voltage which can be drawn from them in the form of amps. It doesn't matter what they put out. What ever is drawing from them is what that unit gets. It's like the alternator is a bucket of water and a radio for example is connected to the bucket. The radio will only take as much water from the bucket as it needs. if you have too many components drawing from that bucket the water drains faster than it can be filled up and thats when you have problems. thus needing a bigger alt that either has a bigger resovoire or that fills up quicker. I hope my anology makes sence.

Mike

My lord... ok, if you have a 170amp alterantor on anything other than a red/yellow top battery, your going to destroy the battery. This inturn means the battery has the ability to ground the plates inside of it. When those bad boys touch together, ground themselves, and surge, YOU WILL HAVE 170AMPS@14.4V OF POWER RUNNING THROUGH YOUR CHASSIS. Anything grounded w/o a fuse or regulator on the ground circuit will be toasted. i dont know too many cars that can support that kind of power so chances are you dont have the circuitry to support that either.

Ever have your battery go to shit, your guages flicker and you turn your headlights on and the car just shuts off? Usually the fuse for your all your acc blows and the car is completly dead. Thats grounding the plates... now triple the current and imagine the problems that could cause. Do some homework there guy before throwing a flamefest this way

morgie · Post by **morgie** » Wed Jul 02, 2003 2:03 pm

Humm, you guys just made me realyse something...

since about a month, my headlights seems to have lost a lot of "power" (they light up more yellowish that white, and they are realy not strong)

Could that be related to Alternator / Voltage regulator ?

thanx

Post by **Legacy777** » Wed Jul 02, 2003 2:31 pm

Good thing I have an Optima yellow top battery then

Morgie,

Yeah it's very well possible the alternator could be not putting out all the juice you need. Might be battery as well. I'd have the electrical system checked. Not sure you have autozone or not, but most chain automotive stores will do this test for free.

Just a note though. A bad alternator may not always show up with an on-the-car test. It may only show bad with it on a stand-alone tester.

morgie · Post by **morgie** » Wed Jul 02, 2003 3:14 pm

Ok thanx, i'll sure go check that, cuz since that month, the car runs strangely too...

it's like if my hesitations that i've been hunting for months and tougth were solved, have came back

soon i'll get tired of all that and install an SDS or Haltec or something like that... stupid ECU

hehe

magicmike · Post by **magicmike** » Wed Jul 02, 2003 4:59 pm

Redline,

I'm not getting into a pissing match with you about this. I know you think you are right so lets just leave it at that. When I come accross some documentation that supports what I'm talking about I'll post it.

Mike

Post by **Legacy777** » Wed Jul 02, 2003 8:21 pm

Ok, it's time to put an end to the false info.

I decided to do some more research and get some more definitive answers. I didn't necessarily find one particular article that answered all the questions, but I feel pretty confident on the diagnosis.

The first thing I found was about testing charging systems. One of the things they mentioned was about disconnecting the cables while the engine is running. This is a big no-no, and will fry things.

The reason why it fries stuff is because of amperage. Voltage should not come into play assuming the internal regulator is working properly.

The reason why amperage fries stuff is because the battery itself acts like a regulator/filter for current. When you suddenly remove it from the electrical system, you have excess amperage that the alternator produced and is fed through the other electronics and can fry them.

Let's look at Ohm's law, V=IR.

In an automotive electrical system voltage is for the most part constant, so current and resitance are the only things that can change and are indirectly proportional. If you look at the entire electrical system using the V=IR, V will be roughly the same all over. The battery acts like a resistor (for explanation purposes). If you look only at current I=V/R when you remove the battery, R becomes zero, and I will momentarily spike to infinity....or so that's how you'd theoretically do the math.

I have found zero information about high output alternators killing automotive electrical systems that are working correctly.

What I did find though is a general rule of thumb for sizing alternators. You want an alternator with an output that does not exceed 40% of batteries out for liquid batteries, and 50% for gel batteries.

So let's use my optima for example purposes. It's lowest CCA's is 650 amps @ 0 degree F. So using the lowest possible number and the lower sizing factor that would mean it could take an alternator with an output of 260 amps. Now there'd be no way I'd put that on, but considering the fact even the high output ones are less then half that or around there. I think they would be fine.

A good intuitive example of amps is water flowing through a pipe. Voltage is related to water pressure. If you think of the alternator as a pump or pressure vessel header, and all your wiring is like different water lines leaving the header. larger lines will flow more. If pressure remains constant, everything is fine. If you were to have a pressure spike, pressure in the lines will increase and surge, and you could damage things.

Yes an electrical circuit is a little more complex, but it explains the idea behind it.

If anyone can explain to me contrary to what I have posted, I'm all ears.

mTk · Post by **mTk** » Wed Jul 02, 2003 9:08 pm

Yay!

MK

morgie · Post by **morgie** » Wed Jul 02, 2003 10:28 pm

Ok for the higher output Alternator,

But does changing the battery for a higher Amp battery (let's say a 750amp instead of a 650amps) could cause damages or influence the alternator, be less effective, reduce the overall output of the alternator/ the electrical system ?

(my point is, knowing that the alternator provides power for the spark-plugs, Does a Normal Alt. + 650amp battery will have a more powerfull spark on the sparkplugs than a Normal Alt. + 750amp battery ? )

Post by **Legacy777** » Thu Jul 03, 2003 12:25 am

mk750 wrote:Yay!

MK

what was that for?

Post by **Legacy777** » Thu Jul 03, 2003 12:29 am

morgie wrote:Ok for the higher output Alternator,

But does changing the battery for a higher Amp battery (let's say a 750amp instead of a 650amps) could cause damages or influence the alternator, be less effective, reduce the overall output of the alternator/ the electrical system ?

(my point is, knowing that the alternator provides power for the spark-plugs, Does a Normal Alt. + 650amp battery will have a more powerfull spark on the sparkplugs than a Normal Alt. + 750amp battery ? )

higher CCA battery just really helps in starting. I don't think it'll help much in normal day-to-day driving unless your current battery is weak.

The electrical system all works together, so if you have one bad thing, it could hurt the other.

The alternator is designed to maintain the battery's voltage, if your amperage draw is more then what the alternator can put back in the battery then your battery will slowly drain down.

mTk · Post by **mTk** » Thu Jul 03, 2003 4:37 am

The post reminded me of someone on an irc channel i'm in.. too long of a story to go any further

MK

vrg3 · Post by **vrg3** » Thu Jul 03, 2003 5:29 am

Legacy777 wrote:In an automotive electrical system voltage is for the most part constant, so current and resitance are the only things that can change and are indirectly proportional. If you look at the entire electrical system using the V=IR, V will be roughly the same all over. The battery acts like a resistor (for explanation purposes). If you look only at current I=V/R when you remove the battery, R becomes zero, and I will momentarily spike to infinity....or so that's how you'd theoretically do the math.

Not quite... If you have a resistive load in a circuit and you remove it, R jumps to infinity and I drops to zero. Think of it this way -- if you remove the resistor, you've replaced that portion of the circuit with air, and air is almost completely insulating.

The battery actually works kind of as a voltage smoother-outer, to use a technical term. It works with the voltage regulator to keep the voltage under control (the voltage regulator was designed for a system that also had a battery). Also, when the alternator cannot supply enough voltage for the car's electrical system, the battery picks up the slack. It damps the AC component of the alternator's output, essentially acting like a huge capacitor across the terminals of the alternator. Without a battery, you'll basically have large voltage fluctuations, so you risk having voltages much higher than your car's electronics are meant to deal with. Spikes can reach 40 volts with some car's regulators. 40 volts into your ECU's internal power supply will easily kill it. Ditto for your stereo and most other electronics.

So you could use Ohm's law to examine it but you'd have to look at the battery as having the complex impedance of a capacitor rather than the real resistance of a resistor. But it's best not to try to think too hard about that.

There is an issue with high powered alternators, and that is having too high a charging current for the battery. At any given rotational speed, an alternator produces a certain amount of current (measured in amps). This current is available to all circuits which are wired in parallel to the alternator. Basically, the ignition, fuel injection, stereo, headlights, and other electrical devices in your car draw however much current they use, and the remainder is used to charge the battery.

The best way to charge a battery is with a trickle charge, providing a small current for a long period of time. The more current you use to charge a battery, the more stressful it is for the battery. Also, due to internal resistance, charging at too high a current for too long can cause a battery to overheat to the point where it will boil off its electrolyte.

A battery without electrolyte in it is... an open circuit. See above for info on why that's bad.

So this is where this comes in:

What I did find though is a general rule of thumb for sizing alternators. You want an alternator with an output that does not exceed 40% of batteries out for liquid batteries, and 50% for gel batteries.

But the rule as I understood it is a bit different...

So let's use my optima for example purposes. It's lowest CCA's is 650 amps @ 0 degree F. So using the lowest possible number and the lower sizing factor that would mean it could take an alternator with an output of 260 amps. Now there'd be no way I'd put that on, but considering the fact even the high output ones are less then half that or around there. I think they would be fine.

I believe the usual rule of thumb is that your charging current (in amperes) should be no more than about half of your battery's capacity (in amp-hours). This isn't a mathematically derived rule; it's just a rule of thumb, since the units don't have anything to do with each other.

So your Optima battery's capacity is probably somewhere around 55 amp-hours. That means you wouldn't want your alternator's spare capacity to be much more than 25 amps. Adding up all the current your car's electrical accessories draw, you might come to the conclusion that you don't really need much more than the 70 amps our stock alternators are supposed to put out, especially if your accessories aren't running at full blast all the time.

But, you do need to keep in mind that at cruising engine speeds most alternators don't really produce their rated current.

There's one other little issue -- if you do install a 600-watt stereo, put in 100-watt headlight bulbs with 100-watt driving lights, and whatever else, so you decide to put in a higher capacity alternator, please upgrade your alternator's wiring. The stock alternator cable is sized decently for carrying 70 amps but won't do so great at much higher currents.

A good intuitive example of amps is water flowing through a pipe.

The water analogy is often used when talking about electricity, but it is kind of limited and it's easy to get stuck... If you're just talking about DC, visualizing electricity as water is okay, but once any AC gets involved it becomes trickier. I don't mean to pick on anyone but just try not to get too caught up in making analogies. It is possible to understand this stuff just for what it is.

Post by **Legacy777** » Thu Jul 03, 2003 1:37 pm

vrg3,

Thanks for the clarifications.

You're right my battery is a 55Ah capacity.

I do have 80/100w headlights, 70w driving lights, and a little over 500w for stereo amp output.

With what you said about the charging and such. Optima specifically states in their FAQ that HO alternators are ok. http://optimabatteries.com/faq.asp#q7

You brought up a very good point about the amp rating of the alternators. Their actual output is less then what they are rated, and their rated is usually with engine speed at 6000 rpm. I could look in the fsm books if anyone wants specifics.

mTk · Post by **mTk** » Thu Jul 03, 2003 2:24 pm

Bahah, so did that (vrg3)

MK

mTk · Post by **mTk** » Thu Jul 03, 2003 2:53 pm

OK i'll stop.

MK

paf · Post by **paf** » Mon Jul 07, 2003 4:03 am

where can you get these 80/100w headlights
I cant find them anywheres...

Post by **Legacy777** » Mon Jul 07, 2003 2:34 pm

Try some of the ricer speed shops or magazines.

I've had mine since 96-97, and the import market had not floaded out to the point it has today, nor was it cracked down upon by law enforcement.

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bigger alternator?

bigger alternator?