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Ok, I received my fluke current clamp today - and just got back inside from doing a few tests. My system (2 orion amps, 4 JL speakers, 1 10" orion sub). I had the puppy cranked, it was loud. I was only seeing an average of 10-15 amps of current draw from the battery. There were peaks of around 30 amps or so, but nothing extremely high.

I also measured the current that the car was sucking, on average the alternator would kick out around 10-15 amps alone (at idle, with no accessories or stereo on). When I turned the stereo on, the alternator compensated for the current flow, as it doubled to around 20-30 amps.

However, good part - here is what I am getting at. I just wanted to see how well the alt would work at idle. I turned all of the accessories on (head lights, air on full blast, flashers) - and measured around 40 amps of current draw at idle. I than turned on the stereo (again at a high level). The value of 40 amps did not change.

So it appears that at idle, the alt is only able to out out around 40 amps. I don't have any tests done yet to see what the current draw is during driving when the alternator is ramped up - but 40 amps for all accessories is fairly high, considering the damn thing is rated for around 70. Tack on a decent stereo to that - and I would be around 50-60 amperes (with most of the accessories on, such as A/C and head lights, which consume the most current). Also - don't neglect the fact that the battery is still going to draw a small amount of current as well, to remained charged....

Moral of the story - if you have a large system, you may not have enough charging capacity for your car if you run the A/C and headlights a lot.....

I wish the freakin' rumor about the hundyai 100A alternator fitting was true - cheap power (vs dropping $250 freakin' dollars for a high output 150 alternator when its really not needed).

During the day, it wouldn't really be too much of a problem - unless you drive with the AC cranked all of the time. Luckily I don't.

 
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I think this is a wonderful post, providing some concrete scientific evidence to back up the real world data thats been gathered by members here to prove huge stereo's dont neccesarily need high output alternators to keep the vehicle functioning.

bravo, opto!

BTW, whats the maximum measurable current capacity of those current clamps?

 
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The one I purchased is rated to read from 1A to 400A, the fluke i410....

 
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Not bad, if you are drawing 400 amps or more, I would consider you certifiably insane

(btw, the West Coast Extreme SPL Civic draws around 1200 peak)

 
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Rabbit, what would you suggest I do to get rid of light dimming now that the alternator theory is proven..

Most Group 51 sized batteries don't really have much more capacity than the stock batteries, so where is the extra juice supposed to come from to keep the voltage level up during a heavy load?

 
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Bigger alternator

 
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exactly

 
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when a hair dryer is turned on at home, my lights flicker. can i do anything about it? not really.

a bigger alternator won't neccessarily solve temporary dimming issues by itself. the transient response will be the same. it's kinda like HP and torque the way i see it. alternator bumps up HP, but if the torque is the same you will never reach the peak HP when the amp needs it. those quick bass hits will still dim your lights. and you wasted a good chunk of money.

gearbox, do your HID's dim at all?

 
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Maybe, but your alternator will last a lot longer. The damn things almost pegged with just the accesories and system running. Granted, my system is modest - My front orion amp is only 400w, rear is 300w. Driving around at almost 70 amps all of the time isn't too healthy for its longevity.

Plus, if he did have a larger output alternator, the transients would not be as large, as the extra current capacity would be there to absorb them. I think that honda really ****ed this one up, and should have put something with at LEAST a little more reserve in - 70 amps really just doesn't cut it. Hell, I'd LOVE to see the current draw of HID lights.....

 
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One thing I've also been noticing is when the weather gets hot. Now normally when I start the car, my voltmeter shoots up to 14v fast! Now on hotter days, it would inch its way up to around 13v, and try to very slowly reach 14 (sometimes doesn't make it). Do you know what that problem is?

Here's the deal with HID. When you first turn them on, the igniters suck ALOT of juice for a couple seconds. But once they're on and running, there's no problem. With my old lights, I could hold up the front power window switches (when window is closed already) and see massive dimming while driving. I don't think the HID dims at all, or maybe not enough to notice. I'll have to try it against a wall sometime. But they only use maybe 1/2 the wattage of stock halogens.

 
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there is no problem with your battery. this is a pretty good explanation, kinda confusing:

An interesting phenomenon happens in the physical world. Many `things double every C.' Before you conclude that this is a hen without lips talking, let's elaborate. If a particular mechanism has a determined failure rate at 10C, then the failure rate will more than likely double at 20C. A transistor that has a specific leakage current at 35C will exhibit twice the leakage at 45C. A battery that forever accepts 5 Amps of charge current at 14.4 Volts and 75F, will maintain 10 Amps at the same voltage if the temperature is raised to 93F.

Now consider this. Power is equal to Volts times Amps. For 14.4 Volts and 5 Amps, power is equal to 72 Watts. If we double the current to 10 Amps, power is equal to 144 Watts. Have you ever noticed the difference in the heat generated by a 75 Watt light bulb versus one of 150 Watts?

Prevention of thermal run away is easy. As the battery begins to heat, reduce its terminal voltage. This defeats the doubling effect of charge current. As the voltage goes down, the battery will accept less current. That means less heat buildup. It also means longer battery life and less electrolyte loss.

 
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Okay great, but how can I put this to use? Just turn off all the accessories when it's hot outside?

 
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not much you can do. higher temps means higher current levels inside the battery, unless you lower the temp, or lower the voltage of the battery.

 
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screw a group 51 size... i posted on here before that a big *** battery CAN fit under the hood with only 20 minutes of work

 
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i forgot the exact group number of the battery, but its the biggest one sears sells

 
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a cap can help your dimming, too, mega

 
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i think a 34/78 is the biggest, if not it's close enough.

 
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our alternators suck, end of story. and to make things worst, alot of the 01,02 s are faulty, mine died recently and in turn ruined my battery. the alternator was replaced under waranty.

i have aroung 350w system. on my stock battery and alternator, the dimming was incredible, almost to the point were pople would think i was flashing them on stop lights. now i just changed my battery, i got a ORBITAL EXTEME deep cylc ebattery. its bigger then stock, but i got it to fit after some work. Now there is almost NO DIMMING, there is a little at extremly high bass, but almost unnoticble. i was surprised that a battery alone would do this, but i think the math makes sence.

350 wats = v *a.
v is say at 13, so A has to be at 27A for the system to run no problems and without sucking to much from the electric system, and considering 26Amperes is less then what opto just found the alternator produces at idle, it keeps the battery fully ready for the rest of the electrical components in the car.

so i guess my conclusion is that our Batteries really suck. because for a small system upto 500 watts, theoritically our alternators should be able to handel the power at idle, so why all the dimming/

Excellent thread BTW

 
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I have a Group 51 yellow top, and a cap and my interior lights still dim. My HIDs never do though

 
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your alternator died, so all honda alternators suck? I think there is more of a story here....

your alternator died, then I presume you ran the car until the battery was fully drained. The battery was ruined due to improper use, and the conclusion you draw is that all honda batteries really suck as well?

 
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no no i didnt mean they suck in general, i meant they suck in terms of providing enough power for our sound systems. Mine dying is another story, it has nothing to do with the alternator being good or bad, it was just a faulty one from Honda, which is very commen with the 2001's and 2002's

 
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I just installed the same battery. Group 34/78 size and it BARELY fit. There is like no clearance anywhere now, but what a difference, it's like night and day. I have a very good voltage display in my car so I try and watch what my voltage is doing as much as possible, and with the new battery now, there is virtually no dip when I turn it up, unless I REALLY turn it up obnoxiously loud, but for a regular listening volume it's fine.

Okay that's about it, I just thought I would rant about how awesome this battery is

 
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Now that those issues are dealt with we need to move onto caps.

My question is this:

Do you think capacitors help alleviate dimming by discharging to avoid voltage drop when there is a high demand for current, or do they make dimming WORSE by placing an extra load on the battery casued by the cap being charged and causing voltage drop and therefore dimming.

My thought is that if you had no capacitor in your system it wouldn't dim as much because your electrical system would be more consistent, by which I mean you wouldn't have the capacitor slowly charging while trying to play music still....... in other words, once the cap is discharged, the power is still being sucked up by the amplifier causing the cap to take forever to charge.

I don't know if that made sense. I have something in my head but its hard to explain in words, but hopefully I was successful at bringing this new issue up now.

 
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there is nothing slow about the way a capacitor charges or discharges. A deep cycle battery... now THERE is a device that charges AND discharges relatively slowly!

you can debate reasons all you want, but capacitors can definitely potentially cure light dimming. we can talk about why that is till the cows come home, but does it really matter? They still have that ability.

Do they make it worse? maybe, I dont know. Maybe if you messed up installing it or bought a $5 one from an electronics surplus that has a massive ESR. That might do it....

I reccommend reading http://www.betteraudio.com/geolemon/newmain/battcapalt/ written by chris evert. its well written, and even talks about differences between starting batteries and deep cycles.

It should put to bed any budding debate about the function of batteries, capacitors, and alternators. What each does, and why we would be motivated to upgrade, from a desired performance benefit.