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Discussion Starter · #1 ·
I have been reading up on adding car amps to the stock electrical systems and was wondering if this setup would be ok. <--meaning no additional battery upgrade, HO alternator, etc.

I have a 08 civic LX that I am planning on putting the following upgrades in.

Headunit: Kenwood DNX5120 touch screen DVD/Navi combo
Front/Rear Speakers: Kicker KS600
High Amp: Kicker ZX350.4
Sub: Single Kicker CVR10 DVC in a sealed enclosure
Low Amp: Kicker ZX300.1 mono

So will I have any issue with this system killing my stock alt or battery?

I don't listen to music super loud and probably will not be listening above 50% that much.

Thanks for any advice


1,616 Posts
Most stock systems can handle ~1,000rms.

It is VERY beneficial to do the big 3, the battery to ground and battery to engine block being the most important as you do not have a high output alt.

Set your gains correclty and you should be fine, setting yours gains (cranking them) can leads to problems and light dimming on even the best of set ups.

make sure to post pics of finished product :)

752 Posts
just dont blast your stereo and then turn the car off. If your going to be parking soon turn off the system and let your battery recharge before turning the car off over night. This will help extend your battery life

1,917 Posts
Your stock alternator will be fine with that load. Do the big three (always), and look into upgrading the factory battery to a larger/more powerful unit. If you have a few extra bucks, NST makes an overdrive pulley which spins the alternator faster, increasing output at low rpms.

Those are small amps, but the factory wet cell group 51 battery is marginal at best, even for just starting the car to begin with. I would definitely do the big three, and upgrade the battery. With some modifications, you can fit a group 34 optima underhood - which is pretty much the largest battery that will fit in the factory space without major work. If that's too much of a project, look into a nice AGM battery (Kinetik, Powermaster, etc.) that is close to the factory group 51 dimensions. Either will work just fine for those amps - but the group 34 would allow room to upgrade down the road, if you so desire.


538 Posts
I found this formula on Crutchfield's site which should give you a ballpark figure on what your stock system can handle in terms of power draw.

Car Amplifiers Frequently Asked Questions

Bascially it's :

Figure in the reserve ampere rating:
alternator ampere rating * 40%

calculate the average current draw of the amp/amps that you are considering.
-First you calculate output: (#of channels * RMS output of each channel) * 2 to account for amp inefficiency (probably assuming an AB amp, class D's are more efficient).
-Divide that by 13.8V average voltage
-then divide that number by 3 since a test tone is usually 3 * the power of typical music

This will give you the average current draw of the amps.

In your situation: I believe the LX has a 90 ampere alternator.
-40% is 36 amperes.

For the amps: Assuming you're running them at 4 ohms
ZX300.1 = 150 x 1 RMS = 150
ZX350.4 = 60x4 RMS = 240
total of 390 RMS total and 780 for purposes of our calculation.

780/13.8 = 56.5 peak draw.
56.5/3 = 18.9 average draw.

So by these numbers... you can support your system without straining the stock system assuming that you wire it correctly.

However, if you're running at 2ohms... the numbers are more:
300 + (90 * 4) = 660 RMS max load
double that to 1320 for amp inefficiency
divided by 13.8 V = 95.65 peak load.
divided by 3 for average load: 31.8 ampere draw

As you can see by the second example... you're way over the capacity with peak draw and dangerously near using all of the reserve capacity with average draw. You would definitely need to consider the Big 3 and a battery upgrade at this point, and would have to be rather conservative with the volume knob.

I know this formula's gonna get picked apart... but it gives you a decent rule of thumb to go by. :)
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