Charging systems questions on driving performance...
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Bronze Member Username: AuroradrvrFt. Lauderdale, Florida Post Number: 13 Registered: Jul-06 | Just a couple of quick questions. My brother has a decent radio system in his car, a 2003 GTI VR6. The system amps are a KX1200.1 sub amp, and Infinity REF7541 speaker amp, so its pulling about 1700 watts rms. The problem is that his stock charging system just isn't up to it. It dims pretty bad and you can hear the subs weakening. He added a 3 farad capacitor to help resolve this, it helped, but its not all gone. My questions are that what are the best options for upgrading? The two mains options we've heard/looked into are upgrading the alternator to something with more amps or adding a second battery. The hitch is that he has a fair bit of performance mods done to it as well, and really doesn't want to scariface too much peformance. He heard that a more powerful alt really puts a drag on the motor. Can anyone vouche for/against this? He's leaning towards adding a second battery because his logic is that the second battery would be in the back, be really close to the amps and therefore be able to provide more juice. He would plan on removing the spare and jack and putting the battery there, to keep the weight down. I believe that I recently read on here, that all adding a second battery does is put more of a strain on your alt. True? It seems it me that a second battery wouldn't do anything till the amps pull all of the juice until they start going into the juice from the batteries? I really wish I knew more, just never had to play with my mine (fine stock). |
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Gold Member Username: CtmikeCt. Post Number: 1297 Registered: Feb-06 | get a ho alt., upgrade the big 3, and new battery. he shouldn't need a second battery. and adding a cap. didn't help any problems he had, it just masks the problem. lights dimming is a sign you need a new alt. cause the stock can't keep up and provide the power everything demands. if i was you i'd take the cap. off, at least until you upgrade the charging system. maybe even unhook the system entirely until everything gets fixed, you don't need your car dieing on you. |
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Gold Member Username: IlluminatorUSA Post Number: 3882 Registered: Apr-05 | Yeah, you might as well get a new high output alt anyway since the one in there is going to die soon. Second battery is only for if the system is run most of the time with the car off, and it still adds stress to the alt. You'll lose 2hp MAX(and even that much is unlikely) by adding a high output alt, and if you want to prevent electrical system damage (thousands of dollars for wiring harness replacements etc.) and/or alt replacement every oil change, I suggest he gets a high output alt. |
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Platinum Member Username: GlasswolfWisteria, Lane USA Post Number: 11510 Registered: Dec-03 | http://www.betteraudio.com/geolemon/newmain/battcapalt/ one horsepower = 746 watts, so even with a 200A alternator, you're not going to notice much of a loss or drag on the engine unless you're driving some 3 cylinder econobox that has about 50HP to start with. capacitors won't do jack for a lack of current but additional batteries (over the drive tires if you want good weight over them) and a bigger alternator will help. |
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Gold Member Username: Safe_crackerChicago, IL US Post Number: 1291 Registered: Jan-06 | I tend to disagree, my 300A alt pulls an extra 1.5mpg off my drive to/from work, lol. I can litterally use my ho alt as a brake! The drag of an alt increases with rpm and load, due to the needs of the cars ignition/fuel system, especially if modded. a water pump itself can kill up to 15hp just from cavitation, an ac compressor, 15-20hp. There is a little trick you can do is put a larger battery under the hood, get a HO alt, 200A should be fine, do the big three and put a toggle switch on the field wire for the alt for racing situations. The toggle switch will turn off the field winding and will not allow charging unless turned back on this will eliminate the drag associated with an active alt. Keep the cap it will smooth out the electrical system, you may look into replacing the stock battery with a yellow top. Just be sure when he is done racing to flip the charge switch back on, lol. Polo...  PS-Adding an extra battery will only add extra weight and slow th car down. On average every 100lbs you lose, you gain 1/10th of a sec on the 1/4 mile. So maybe he might look into a lighter enclosure too. |
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Bronze Member Username: AuroradrvrFt. Lauderdale, Florida Post Number: 14 Registered: Jul-06 | Thanks a lot for all the input, definitely some stuff to check out. I think we're leaning to a HO alt upgrade, which would be around 200A from the stock 120A, and a new battery. (Anyone have some favorite places for alts?) I have question though on the Optimas, what's the deal with the yellow tops? I know they're for 'deep-cycle' but he hardly ever uses it with the car off, and looking at Opitma's website, the best Red Top puts out more power then the best Yellow Top. So why does everyone run yellows? |
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Gold Member Username: Safe_crackerChicago, IL US Post Number: 1301 Registered: Jan-06 | I was always pushed to deep cycle but after reading an article that GalssWolf posted it opened a new light about them so I guess you should go with a strong starting battery(non deep cycle), doesn't have to be an optima if going under the hood! Polo.. |
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Gold Member Username: IlluminatorUSA Post Number: 3922 Registered: Apr-05 | Here's a pretty sweet article I found about types of batteries: Battery technology is continually changing. To completely discharge, or "flatten," a battery will cause permanent damage. This is the reason modern vehicles have chimes to tell if headlamps have been left on and why dome lights will automatically shut off after a few minutes. While charging or jump-starting a battery that has been completely discharged will seemingly revive it, permanent damage has been done. A battery subjected to this abuse may load-test satisfactorily; however, much of its original capacity is lost forever. Repeated episodes of this nature will result in a battery which will start the engine, once jump-started, but will fail to hold a charge after even a few minutes of nominal drain. Additionally, overcharging, excessive heat and vibration are also battery killers. Numerous makes and types of batteries exist; some good and some not-so-good. The varieties are endless: starting, SLI, maintenance-free, marine, RV, deep cycle, lead-acid, gel and AGM, just to name a few. Each battery has a specific intended usage, and to deviate from that usage may be defeating the intended purpose. Additionally, it is not a good idea to incorporate different types of batteries within the same charging system as charging requirements differ. Lead acid batteries are considered to be the "traditional" battery, and have been for many years. The lead acid battery is supplied as Original Equipment (OE) by our automakers. This type of battery is referred to as a "starting" or SLI (Starting Lighting & Ignition) battery. This battery is designed to produce large amounts of current necessary to operate the starter. These batteries work well unless they become completely discharged. Deep cycle batteries are designed to be discharged to within 80% of their capacity; however, a deep cycle battery produces less cranking amperage, and it is not designed to provide large amounts of current for starting. If a deep cycle battery is used to start a vehicle, it is suggested that a battery with 20% additional capacity over the recommended OE battery be utilized. Another solution would be to use a marine battery as those batteries are somewhat of a hybrid between a starting battery and a deep cycle battery. Gelled electrolyte batteries, otherwise referred to as "gel-cells," contain an electrolyte that has been gelled into a solid mass similar to the consistency of Jell-O. These batteries can be mounted in any position and they won't spill acid even if broken. Disadvantages to gel-cells are they are very sensitive to overcharging. Both excessive voltage and current will permanently damage this type of battery. In automotive applications, voltages in excess of 14.0 Volts are sufficient to cause damage to this type of battery. Successful utilization of "gel-cells" requires special voltage regulation so that this voltage is not exceeded for both the vehicle's charging system, as well as the shop charger. The AGM type of battery is a relative newcomer to the industry and offers a lot of advantages. Absorbed Glass Mat batteries are marketed under the trade names of Exide Select Orbital, Concorde, Odyssey and Optima. The AGM battery construction utilizes a very fine fiber Boron-Silicate glass mat, saturated with electrolyte, between the plates. Like the gel battery, this battery can also be mounted in any position. Similar to the above batteries, the AGM battery is unforgiving if it has been "flattened," even once. |
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Gold Member Username: Safe_crackerChicago, IL US Post Number: 1302 Registered: Jan-06 | #4 would be to add a second (or third) standard battery. I avoid deep cycle types... deep cycle batteries are the slowest charging - and discharging (ie. transient response) type of battery. Ideally you might install that near the amps, minimizing the wiring between battery and amp, for those moments where you exceed your alternator's current capacity. Also, due to the relatively inferior transient response of a deep-cycle battery, I would recommend using a standard battery at least in the back by your amplifier (if adding a second battery back there), if not underhood also. Even if your average current draw exceeds your alternator's capacity for some period of time, this may provide sufficient supply to endure this abuse. Batteries are large, expensive, and heavy, and may require significant planning to properly install (most sanctioning bodies require that a secondary battery be installed in a sealed compartment vented to the outside of the vehicle). That being said, You don't need to buy anything special to add a second battery, electrically speaking. No "isolator" required. It's as easy as wiring the + pole right to your distribution block, and grounding the - to the same place as your amplifiers are grounded. The only downside to a non-isolated approach is that realistically if you ran your system with the car off, you could drain both batteries, leaving you needing a jump-start. But... you'd have two batteries, making the system run longer before that could happen, and you'd have two batteries to start your car from. And chances are, with that much power on tap - unless you have some real fundamental inefficiencies in your installation (which would imply you could get more output going on with less power) - chances are you won't be able to stand having it cranked up to that level of output for more than short periods of time at any rate... Because as soon as you do turn it down, you also inherently are turning down your current demands, of course. |
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Platinum Member Username: GlasswolfWisteria, Lane USA Post Number: 11519 Registered: Dec-03 | http://www.bcae1.com/capacitr.htm http://www.glasswolf.net/caraudio/capacitors.html http://www.glasswolf.net/caraudio/charging.html http://www.betteraudio.com/geolemon/newmain/battcapalt/ http://www.bcae1.com/charging.htm http://www.bcae1.com/chargin2.htm http://www.bcae1.com/battiso.htm http://www.glasswolf.net/caraudio/batteries.html http://www.the12volt.com/info/recwirsz.asp as for drag I doubt it's polo's alternator. I had a 150A lestech alternator out of an ambulance in a ford festiva with no noticeable difference, and my charger has a 300A alternator, and I see little difference as well. I still pull 10.20s in the quarter with it. |
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Gold Member Username: Safe_crackerChicago, IL US Post Number: 1330 Registered: Jan-06 | "as for drag I doubt it's polo's alternator." So what are you trying to say? For one you will never notice a difference in any of those cars, for one a Festiva is just plain drag to drive anyways and a charger running in the 10's would never feel it. It has been a proven fact for alts to be able to kill 15hp just from drag, that is why they do make toggle switch for winding control, call up Jegs and ask. Matter of fact if I am not mistaken (3rd gen mechanic here) an alt will come close to the amount of drag imposed by an AC compressor and according to others I have talked to that is said to pull 15-20hp and yes you would notice that off your little fetiva, lol. You have to remember these little ricers have sooo little torque compared to the muscle cars of the past so every bit counts and sorry if I lose a measured and consistant 1.5 mpg on a 30 mile 1 way trip, there is significant power loss. Polo. |
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Platinum Member Username: GlasswolfWisteria, Lane USA Post Number: 11533 Registered: Dec-03 | believe whatever you like. I'm not here to argue over the internet with you. |
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