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Did the big 3 but still getting light dimming issues

8K views 18 replies 4 participants last post by  d0ugmac1 
#1 ·
hey guys its been a while since I have been here, but have recently gotten back into the game again. So I finally got the time to to do the big 3 on my 2005 Altima SE-R in order to get rid of the light dimming issue. The wiring did improve the voltage drops but I am still getting what I think is a big voltage drop when my Subs hit hard. My alternator at idle puts out around 14.14 volts. I run a parrot asteroid head unit with stock factory bose speakers and 2 8" JL W3 powered by a JL 500/1 amplifier. I decided to check how much power my subs are using when my alternator is at idle and I saw a drop to around 13.4 volts . I used a digital multi meter and clamp meter for my test. I also used a 40 hz test tone off of youtube and got around 500 - 503 watts. Anyone think its normal for my voltage to drop that much while using 500 watts?

Thanks
 
#2 ·
It's all about charge storage and delivery and really good grounds.

500W @ 13V is 40A give or take, well within your 110A/130A alternator's capability. However that is average power, not instantaneous.

To ensure you have fast acting reservoirs of charge, you typically upsize your main battery (total stored charge pool) and add large 1+ Farad capacitor(s) at (each) consumption point(s) (right close to amp power terminals). The capacitors can provide large surges of charge very quickly.

the upshot of all this is that you provide for more available power delivered more closely to the use point. Any remaining voltage drops will primarily occur between the cap and the amp, and any other small variations will be smoothed out by the RC time constant used to recharge the caps safely. End result, less voltage swing at the IPDM and less if any visible light flicker.
 
#3 ·
d0ugmac1 so basically my charging system isnt fast enough to provide the sudden surge of power required by the amp. Am I getting that correctly? Also if I were to switch my battery for a kinetic or yellow top would really make a difference with a car on? I ask because my voltage never dropped below 13 volts or so when the car was idle, so even with a good battery providing lets 12.7 volts, the voltage from the alternator never dropped far enough for the battery to pick up the slack. Well that's my understanding of a car's electrical system, please correct me if I am wrong. Also I have a 5 farad cap sitting around, would that be safe enough to use?

Thanks
 
#4 ·
Think of your alternator and battery as being similar to the water main and toilet tank (it's early, good analogies come later in the day)

Your battery stores enough charge (even when the 'water' is off) to do things like power the starter motor to start the engine (flush). The drained battery is slowly and steadily replenished by the alternator (refill cycle). You can flush again at half full, but it's not as effective as waiting for it to fill completely.

You will notice when you start your car, that so much power is drained by the starter that your lights will dim, possibly to the point of seeming to go off. This is exactly what is going on with the sound system, albeit at a lesser draw but much higher rate of repetition.

Now measuring voltage (or current for that matter) is tricky because it's an average at best (whether the sampling period of a digital meter, or the mechanical hysteresis of an analogue needle). The only way to truly measure what's happening, would be to use a sampling oscilloscope, or some other kind of fast sample and record mechanism (at least twice your highest audio frequency...so about 40,000 times per second).

A larger battery is akin to a bigger tank, one that doesn't completely drain on the first flush, and so recovers more quickly (at a fixed rate of water input) for the next flush. As long as you don't exceed the maximum input flow on average, you can sustain flushing, with faster response times in general. Electrically speaking what you want is a bigger 'tank size' and battery capacities are measured in Ampere/hours, the more the merrier (and heavier)...so long as it still fits in your car.

Now the other problem with filling tanks is the length of the piping. The more piping, the more pressure (voltage in our analogy) drop you get at the use point. You can reduce this by using bigger pipe (fatter wire). You can also provide local pressure storage (imagine a big balloon on the water main right at the tank) which provides on demand water at full pressure...this is your capacitor. The more Farads of capacity, the bigger the 'balloon'. It's also a way to build up a reservoir of easily and quickly deliverable 'water' at the point of use, which is then replenished over time using a smaller pipe. This could be used to ensure that our toilet tank always refills in say 10s, rather than the 40s required by using the water pipe alone...which is exactly what we want to do for your audio power. Go ahead and install that cap as close to the amp as you can. It should come with a charge limiting resistor that goes in series between the battery and the cap, make sure that goes in the right place!

The last point not to neglect is the 'drain'...it needs to be at least as good as all the supply system...so if you can deliver 100 gallons per minute at 50 PSI...your drain better be able to handle the efflux :) In our analogy the drain is the negative/ground system. It is particularly important to ensure your battery is very solidly grounded to the chassis, and that all your high power equipment also has a solid and robust ground. Keep in mind that steel isn't the best of conductors, and that even a few tens of milliohms of extra resistance can result in a voltage drop in the order of 1/2 volt or more at high power. For instance, assume 0.02 ohms extra resistance (versus copper #2 cable) to battery via steel chassis and chassis to battery strap. (This is probably conservative and it completely ignores how that resistance chances with frequency)...but at 40A, using Ohm's law...your voltage drop (or in this case rise) from battery -ve to amplifier -ve is V=IR, or in other words Vdrop = 40 A * 0.02 ohms or 0.8V

Hope I didn't lose you in all that, but if you tell me which model of battery you have and which one you are looking at I can help you understand if the new one is significantly increased in capacity.
 
#5 ·
d0ugmac1 thanks for the explanation. I just went ahead and put the capacitor in the car to test it out and I have to say it is a definite improvement. Doing the 40 hz test tone again I could definitely hear that the bass was louder at a lower volume. Also my voltage with the car idling was around 14.2 volts which is a definite improvement over 13.4 volts when I did the test without the cap. Also dimming was almost non existent, but there was just a hint of it. My battery is almost five years old and I would like to replace it soon with either a yellow top or a Kinetic HC BLUE 1200. I live in Toronto, Canada and the yellow top is more readily available so I am kinda of leaning more towards the yellow top.

Thanks
 
#6 ·
The following are equivalents:

YellowTop D31A is equivalent to a Kinetik HC Blu 1800 with 75A/hr (gi-normous!)
D34A to Blu 1400 with 55A/hr
D25 is superior to Blu 1200 with 48 vs 40 A/hr or capacity.

Apparently the D35 fits our cars...so the Yellowtop is superior to KBlu 1200 with 48A/hr vs 40A/hr (a 20% increase)
 
#8 ·
Discharge rate is related to the internal resistance of the battery, which goes back to chemistry and structure. A battery that has been optimized for faster delivery rate at the expense of storage capacity will therefore have lower internal resistance and thus higher CCA scores. For a given instant large draw of power, the terminal voltage of the optimized battery would drop slightly less than another battery of similar size.

That said the Kinetic Blu's are their entry level batteries, with only a 1 yr warranty (vs 3yr for their Pro cells). The Blu's come with this disclaimer: "Designed for storage and able to take moderate abuse. Tailored for the casual user." I don't think that's you. On top of that they play games with their numbers...anyone with a real battery will spec it's capacity, internal resistance and CCA. Kinetic gives you maximum Watts...but they don't tell you what voltage that is delivered at. The Blu 1200 weighs 28 pounds, the Yellowtop D35 weighs 36 pounds. My money is on the Yellowtop both for performance (at -20'C) and longevity.

Keep in mind there have been some recent unfavourable reviews on Optima batteries. But in general a well designed, well built sealed AGM battery will do you proud. Use the D35 specs as a benchmark (0.003 ohm internal resistance, 48A/hr, 770 max CCA).
 
#9 ·
Have a look at this review article Might wan't to consider the XS 3400D.

Try these Canadian dealers

XcentricK Autosports Inc. (Canada)
Phone: 519-737-6080

Karbelt Speed and Custom (Canada)
Phone: 905-619-6660

Gem-Sen is our Distributor for Canada. Just give them a call and see how they can help you out.

Gem-Sen
266 Applewood Cres.,
Concord, ON
L4K 4B4
Telephone: (905) 660-3110
Fax: (905) 660-3108
Email: sales@gemsen.com

But I'd be buying it off Amazon.com and picking it up at UPS store in Buffalo... $260 USD.
 
#10 ·
Good analogy doug. I haven't heard one like it since my first class in DC electronics waaaay back in the rocking 80's. Of course our teacher used the water reservoir , and creek analogy, but I like yours better.

Question, could you used a cap to help out with the factory Bose amp, and how would you wire it?
 
#11 ·
d0ugmac1 thanks for the link. I saw that review a few days and might act on it depending how things go when I get to Toronto next week. I was busy last night and this morning changing the power and ground wires for the amp to OFC from CCA. I feel and hear a definite improvement from the subs now. Cannot believe the guy who installed my system years ago used some cheap scoch wiring. Also found that the ground my amp was connected to under the seat had rusted so I cleaned it up and put some WD-40 on it. I am going to be getting a Type-R 12" and 1200 watt RMS MB Quart amp, so I will definitely be needing a good battery.
 
#15 · (Edited)
Is that a self-tapping screw--like not even a bolt?!? Looks like it goes through to the salty underbelly of your car..that's a shockingly ignorant install.

There's a perfectly good 3/8"? chassis stud 4" over to the right in the picture. I would enlarge the internal opening of the O-lug on your ground wire (file or drill) and move it onto that black stud and crank it down.

If you don't, then all that lovely and expensive OFC cable will be for not..kinda like hooking a fire hose to a garden faucet. Rule of thumb, the cross section of your grounding lug should greater than the cross section of the wire attached to it. That little screw was causing problems and will again soon...think about how much of that screw is actual in contact with the sheet metal, then look again at the size of the cable attached to it. Not much of a fight...
 
#14 ·
Yes, a cap will help the stock Bose amp. All amplifiers love having near infinite power available, stock are no exception. You should notice the improvement in the low end like @Ramin did. Improvement is will likely be proportional to max amplifier wattage.
 
#16 ·
Use some kind of anti-oxidant...I have some high-temp anti-seize (copper particles suspended in heavy oil) but would also use something like NOALOX (zinc dust in grease), or even just axle grease...anything to keep air and water away from key electrical junctions.

If you keep any of the CCA (copper clad aluminum) wiring, then you ABSOLUTELY need to use the NOALOX (Anti-OX in Canada) type compounds available at Home Depot and others to ensure that any exposed aluminum doesn't become an insulator over time. Anti-OX should be applied before crimping connectors, especially for hand crimpers or crimpers with less that say 6 tons of pressure--because you won't get a gas-free crimp otherwise and it is thus susceptible to oxidation.

I use it even on copper connections, again to displace gas, but it also helps to prevent wicking of moisture up the strands of wire under the jacketing causing hidden corrosion.

Heatshrink over top of all crimp connectors to further improve resistance to corrosion from moisture wicking.
 
#19 ·
He's just trying to steer you away from Optimas (yellow top or otherwise) as they have had reliability issues in recent times.

A more equitable price comparison for the XS line would be the Kinetic Pros. Maybe the 3100 is more palatable?
 
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