Car Audio Capacitors & Batteries

Often times when people experience headlight flashing on big bass hits, they'll be told by their local audio shop or friends to install a capacitor. The capacitor is a bandaid to the real problem, the cars electrical system is being taxed beyond what the factory wiring can handle! Dont believe me, read on for real world testing of power capacitors in a car audio system..

The Test System:

JBL W15GTi subwoofer
JBL A1201GTi 1200WRMS Monoblock
2x 900CCA batteries
0g wiring harness
Lightening Audio Competition Series 1.0 Farad Cap

Test Equipment:
Digital Multimeter
Goldline DSP-30 RTA

Test Method:
Amp hooked up to CRO, gains adjusted @ 60 Hz until clipping, and then backed off. LP Xovers set to 80 Hz using CRO & DMM.
Engine idling @ 800RPM. Tests run with voltage on amp terminals showing @ 14.1V idle. 15 minutes cool down between runs.
Run some tones, find the "mad note" @ 51 Hz and commence testing.

No Rear Battery, No Capacitor.
Voltage on Burp: 12.8V (1.3V Drop)
Output: 140.7dB, 140.7dB, 140.6dB

No Rear Battery, 1 Capacitor.
Voltage on Burp: 12.6V (1.5V Drop)
Output: 140.5dB, 140.4dB, 140.3dB

Both Batteries, No Capacitor.
Voltage on Burp: 13.8V (0.3V Drop)
Output: 141.0dB, 141.0dB, 140.9dB

Both Batteries, 1 Capacitor.
Voltage on Burp: 13.2V (1.2V Drop)
Output: 141.0dB, 141.0dB, 140.9dB

Conclusion:
The installation of a capacitor in a weak audio system leads to a LOSS of SPL. This is due to the capacitors nature of draining very quickly then increasing the electrical load on the system as it attempts to recharge. Hopefully these results will inspire you to avoid a capacitor and spend the money on a proper battery & large gauge cabling system .

From http://decibelcar.com

Ever wondered the benefits of running a "Specialist Audio Battery" against a normal, everyday battery ? For todays comparison we see the following go head to head:

Odyssey 1500 12V: Considered to be THE deep cycle cell. Capable of providing 1500 amps for 2 seconds before the battery drops to 10.2V, its deep cycle and built basically specifically for car audio applications. All the top guys in dB Drag used them for many years.
950 CCA, 12.5V stable, 13.1V float

2x 720CCA standard lead acid:
720 CCA, 12.7V stable, 13.1V float

Test System:
JBL Crown 2200 amp
JBL W15GTi subwoofer

Test Equipment:
TermLAB USB Sensor

Seeings as how this system was already calibrated for SPL purposes, there was no need to set it up again.
Engine off.

2x SuperCharge Gold MF = 145.2dB
1x SuperCharge Gold MF = 145.2dB
1x Odyssey 1500 = 145.4dB

From http://decibelcar.com

Back to back tests of the previous Odyssey champion versus the new.

1500: Renamed the 1700 for2005 & onwards, and re-badged by Stinger as the Stinger 1700. 1700 Peak Cranking amps.. 950CCA. A battery with a long and respected history. G31 size and suits most cars. SAE binding posts, sealed, AGM.

2150: The successor to the 1500's heritage. Rebadged by Stinger as the Stinger 2150 (funnily enough). 2150 Peak Cranking amps.. 1200CCA. Just inside the dB Drag 800 inch^2 limit, its an N87 truck size battery and will be a very tight squeeze in any car. Threaded rod screwdowns, sealed, AGM.

Test System:
JBL Crown 2200 amp
JBL W15GTi subwoofer

Test Equipment:
TermLAB USB Sensor

The amp is calibrated to make max power when the HU's on V34.

So, results:

V28:
1500 = 148.8dB & 9.5V (2 second burp & protect)
2150 = 149.3dB & 12.1V (3 second burp)

V29:
1500 = 0dB & 9.5V (Less than 1 second burp & protect, so no reading)
2150 = 149.8dB & 11.9V (3 second burp)

Thats it. Couldn't test any higher 'cos the 1500 isn't delivering the juice to drive the amp!

From http://decibelcar.com

This gets asked a lot, so here's a basic guide..

1. Get a better battery. It doesn't need to be a $$$ Optima or Odyssey, just a nice Exide with 500+CCA & 120+ minutes reserve...

2. Upgrade the earths. Buy 4 gauge cable. Replace the battery -ve to chassis earth and engine block to chassis earth straps with the 4g. While your at it, run another 4g from the battery -ve to the firewall.

3. Upgrade the earth cables on your amps to 4g. The +ve should also be 4g.

4. Get an auto-electrician to check out the alternator and see how healthy it. You can also ask them to upgrade the alternator to battery charge wire to something bigger while you're at it.

5. Clean your battery terminals & clamps with steel wool or sand paper for a good clean connection.

In 99% of cases these simple steps will solve any problems you have with lights dimming, etc. Caps are worthless, spend the money on cable or battery upgrades.

From http://decibelcar.com