Alternator/ battery/ cap issue?

[BigDaddy13440 3]

I've got a question for all of you in-the-know......

Running a couple of old-school Celestion AD15H's in my Tahoe, 'glassed in the rear corners after cutting out the inner rocker panels. Approximately 2.4cu ft each, with a 3"x8 1/2" port. I know these are rated at 600w RMS, but I'm pushing them with a Lightning Audio S4.500.1 at 2 ohms - supposedly putting out 250 watts to each sub, but sounds like it's making way more power than that - I'd guess closer to 400 watts to each sub, if not more.

I'm using 4ga wiring from the battery to the amp rack under the Powerbass S-10's firing down betwen the front seats (nice midbass staging! LOL!). Have an old Kenwood KAC744 (40wx4@4ohm) pushing the components, and a Kenwood KAC714 (140x1@2ohm) pushing the 10's - with the LA amp, it's only 900 watts RMS (supposedly), and I've got a 1 Farad cap.

My problem is that my voltage is constantly fluctuating, even w/o having the subwoofer amp on. Hell, I can have the stereo off, and my voltage ranges from approximately 12 volts to 14 volts. Sometimes I can watch the voltage drop when turning on the heater fan and the wipers, other times it's completely unaffected. Sometimes, I can crank the volume up to 30 with the two Kenwood amps, and the voltage may flicker a little, and when I hit the button for the LA amp, it may or may not drop (depending on the tunes I'm playing)

What do you think? Do I simply need a larger cap? Do I need to upgrade my alternator (stock 105 amp now in the '96 Tahoe)? The battery is less than 4 months old, and it's a 825CCA with the largest reserve I could get.

Any help would be appreciated!

Chuck

[Cheesemind 0]

I think an additional battery would probably help you the most.

[akjay907 0]

ditch the cap. see what happens. Capacitors are useless and just add another strain to the alternator while you might as well have another battery IMO. How many whats(rms) total are you running? i had the same alternator and a similar battery on my silverado and ran 1kW no problem.

[///M5 2,833]

Curious as to how you are measuring the voltage as well.

[BigDaddy13440 3]

ditch the cap. see what happens. Capacitors are useless and just add another strain to the alternator while you might as well have another battery IMO. How many whats(rms) total are you running? i had the same alternator and a similar battery on my silverado and ran 1kW no problem.

IF the ratings are correct, I'm running the Kenwood amps at 160 watts (40x4) and at 140 watts. Add that to the "supposed" 500 watts from the S4.500.1, and it's only 800 watts RMS. That's why I thought one 1-farad cap would be more than sufficient. And, I don't push them at anywhere near maximum, the gains are maybe 40%.

My only other thought is to upgrade the charging wire from the alternator to the battery to 4ga, and run 4ga from the battery to the underhood fuse panel as well. I'm only using about 8 ft of 4ga from the battery through the firewall, and to the amp rack under the center console, so I know I'm not getting any current loss there. I don't need any more power than what I've already got, my head hurts after listening for more than 10-15 minutes to anything really bass-heavy - I don't know how you guys running 5000 watts plus can deal with it, I'd be rocking myself in a dark corner saying "Mommy, please make all the light and noise go away!" from the headaches I'd get.

All I want is consistent voltage, so I don't have to worry about my vehicle stalling at a stoplight (yes, it has.....).

[akjay907 0]

i would get a different amp...lightning audio isnt known for a being real efficient and draws more current for less power.

[KU40 173]

i would get a different amp...lightning audio isnt known for a being real efficient and draws more current for less power.

that's not the problem. Especially since he noted that the voltage fluctuates even without that amp on.

You mention running 4 gauge to the fuse panel? What fuse panel? I assume the one for your vehicle, but why does your power wire run through there?

And what are these switches you are talking about for the amps? What are they hooked up to?

Is your alternator the same stock one from the factory 12 years ago? If so.......it may be on its way out. Stop by an auto parts store and ask them to do a check on it.

[BigDaddy13440 3]

i would get a different amp...lightning audio isnt known for a being real efficient and draws more current for less power.

that's not the problem. Especially since he noted that the voltage fluctuates even without that amp on.

You mention running 4 gauge to the fuse panel? What fuse panel? I assume the one for your vehicle, but why does your power wire run through there? The stock setup uses an 8-gauge wire to supply power from the battery terminal to the underhood fuses/relays. No, my power wire doesn't go to the fuse panel, but directly from the battery (w/ a 200amp fuse).

And what are these switches you are talking about for the amps? What are they hooked up to? Not necessarily a switch, but the Kenwood EQ has a subwoofer defeat button. The Lightning Audio amplifier can still draw power, but it doesn't (draw much) without an input signal. The same goes for the Kenwood mono amp pushing the two Powerbass 10's - I can use the JVC head unit's subwoofer output to effectively turn off the signal to the amp, even though it is still able to draw power. Basically, they are both in "standby mode".

Is your alternator the same stock one from the factory 12 years ago? If so.......it may be on its way out. Stop by an auto parts store and ask them to do a check on it. Yes, it's the stock one, a 105 amp version. I know there was a higher output 140 amp one, and I can get that relatively cheap - I just don't want to waste $125 on a 140 amp one and not have it be sufficient, when I should have gotten a 200amp model. And I have stopped by 2 or 3 auto parts stores, they've put my vehicle on the charging system monitor, and everything "reads fine", according to them......

[BigDaddy13440 3]

Little update - cleaned my garage yesterday, found some 1/0 wire that already had terminal ends crimped on (from a prior vehicle). Upgraded the Alternator wire from the stock 8ga to the 1/0, and added a 1/0 ground directly to the framerail - didn't change the ground to the block, as it was a 4ga already. Let it sit overnight (was exhausted, went to bed right after I finished), couldn't wait to get out this morning to see what difference it made.

Nothing.

Voltage still down to about 12 volts on even semi-demanding tunes, running just the 10's. When I hit the SUB button on the EQ, the Lightning amp cranks up, and I can watch the voltage drop down to under 11 volts, even at 1400-1500rpm.

Put in some old-school DJ Magic Mike, and it dropped way down into the orange, or about 10volts.

Second battery time? Swap it out for a new one? Upgrade the alternator? Ditch the cap? Add a bigger cap?

[fritosaregood 0]

have you checked the voltage coming out of the alternator

[KU40 173]

did the voltage drop at all when the auto parts stores were testing it?

Simplify this thing down a little and go step-by-step. Turn off the radio so that none of the amps are on. Sit there idly and see if the voltage fluctuates. Then turn the A/C on and see if it fluctuates. Then add headlights and other systems to put more of a strain on and see. Then go back and disconnect the remotes on all of the amps so that they won't turn on when you turn the radio on. Only the head unit and EQ should turn on then. See how the voltage reacts. Then add the remote wire back into one amp at a time and see how the voltage reacts. Between adding each amp, start with the volume all the way down, and then raise it up to maximum listening level. That way you can see if one individual amp is causing something or if it's just overall load.

Also disconnect the cap for this test, and add it back in at the very end after everything else has been tested. Are you reading the voltage from the cap or from your vehicle's voltmeter when you notice these problems? If reading it from the cap, don't trust it.

[johnecon2001 82]

I'm going to go with bad battery. How old is your stock one? Have you gotten it tested?

[BigDaddy13440 3]

Stopped by the local Advanced Auto on the way home, had them run the tester on my charging system. At idle, all accessories off, my voltage was approximately 14 volts - I did have the system on, but the volume was set at Zero. Next, ramped the rpm's up to 2100 - voltage increased to 14.3 - 14.4. Stayed constant, the "tech" said the diodes in the alternator were fine, it was working as intended.

Then, I asked him to watch the meter as I turned the system on - at "normal" volume, the voltage stayed from 13.8 - 14 volts, a slight drop, but I'd expected that. Turned the volume up, and watched the voltage drop on the tester to 12.5 - 12.7 volts. Should I be concerned? My lights still dim, as much as they did before I did the 1/0 wiring.

At least now I know my factory voltage gauge is off by about 1.5 volts. It was reading about 12-12.5, while the tester was reading 14.2+ - anybody have a suggestion for a cheap (accurate!!) voltage meter I can drop in a small place in my dash?

[RobClay 20]

stinger volt meter, goes right in your dash.

http://www.darvex.com/miva/merchant.mvc?Sc...Product_Count=1

[dbjunior 0]

if there is not a loose connection somewhere id say you need a new alt or rebuild.

[KU40 173]

dropping to 12.7 on a big bass hit isn't too bad. It's probably fine.

[akjay907 0]

I agree...