Power Issues


I was wondering about power for my car. I own a 2003 Honda Civic and have a 375 watt Orion amp, and plan to get a 500-700 watt amp to power my subwoofer, possibly 2 12" subs of some sort, havent decided yet. Basically my question is would that drain my car battery too fast, and if the answer is a resounding no, here is why i asked it. My friend owns a 75 gold duster, and he powered a 15" punch speaker with a 1100 watt amp. Everytime he would really turn the volume up and we went cruising, his car would be difficult to start up after the engine was turned off. I know his car is an old peice of junk, but he just installed a new alternator, and his car battery was pretty new as well. Should i get one of those giant sub batteries? How long would one of those things last with my setup? p.s. sorry, im a newb at this sort of thing :)

well first of all, never bump your system when your car is off. that's a good way to kill your battery. it only takes 5 minutes to drain a lot out of it if your system is more than 500 watts. you don't need a giant battery for your car. i have a 2002 honda civic and i'll tell you exactly what upgrades i did. for the battery, i got an optima yellow top which is the best if you have big bass. i upgraded the weak 60 ampere alternator to 100 amperes. finally, i upgraded all the battery cables to 2 gauge wires. my car is fine now and can handle the 1500 watts my amps put out. in your case since you're system is around 1000 watts, all you need is an optima yellow top and 2 gauge wire for the battery cables. your stock alternator could handle it if you upgrade your battery cables. upgrading those cables is probably the most important thing you need to do so get that done first.

Your Civic probably has an alternator that can give about 60amps for charging (but could be as high as 150.) This means that with your engine running above idle, your car is PRODUCING about 60amps for use. Anything beyond 60amps of demand is going to have to come out of the reserves (the battery.)

Figure in the air conditioner, the headlights, and other power consuming electronic devices and you don't have all that much left. If you have a 60-amp alternator you could have as little as 25-30 amps free for everything else like the radio.

It would be a good idea to figure out the rating on your alternator. You may have to ask a dealer to look it up as high-current alternators are typically options and not marked where you or I could tell with a glance. Hopefully you have a higher-output alternator.

Then figure out what is the MAX current draw of your amps. This is in the brochures or available online for current models. You won't be operating at full power all the time, probably nowhere near, so figure on 50% - 60% of the MAX current draw for each amp you plan on using. Example, my Linear Power 5002 pulls 80 amps at power with an 8-ohm load. I would figure this amp as needing 40-50 amps of alternator power.

You just have to figure out what you have available (from the alternator) and what your equipment will demand (all amps added up and leave about 30 amps for the car itself) and make sure you have more available than you will need. If you do this, you'll be fine.

If your system pulls more power than your alternator produces...well you see what happens in your friends Duster.

More batteries are not the answer, those are in demo vehicles which operate for extended periods of time without the engine running. This will only delay the dead battery problem. If upgraded alternators are not available, contact a local electric motor repair shop and ask them if they can re-wind your alternator to produce more output. This service typically costs in the neighborhood of $100 - $200 but you CAN have your alternator produce upwards of 200 amps (which will cook the factory wiring so don't do it!)

Of course, if you spend 99% of your time just listening to the radio normally and on occasion crank it up for giggles the stock setup should be fine. Just watch the battery gauge and don't let it drop. Also, your Civic should have that theft deterrence system on the stereo so if your battery goes dead (it thinks it was removed) your radio won't work until you have it turned back on by the dealer. Letting your battery go dead can be a real bummer in newer cars.

Thanks guys, that helps me out a great deal. I might look into a new alternator if i find mine is around the 60 amperes you guys said. You never know if ill want to get another amp on top my current setup, im like that.

Teflon had an excellent point about cable size. Make darn sure you have adequate power flow potential on your power and ground cables going to your amps. I rarely see use for the wimpy 8-ga power cable that comes in the amp install 'kits.' That 8-ga cable has to carry the power from the front of the vehicle to the back (usually there is about 15' of cable length if you straighten it out) and 8-ga just doesn't cut it. You'll waste a lot of power just trying to overcome the parasatic losses within the cable.

For the power you are looking at now (and in the future) I'd suggest running 2-ga power cable from the batter straight to the amp rack and don't forget to put a fuse as close to the battery as possible (to protect the cable from shorting, not the amps.) You can spend upwards of $5/foot for exotic brand-name cable, and there are benefits to it, but welding cable is much cheaper and works fine. See if there is a welding supply shop near you and ask them if they sell 2-ga cable by the foot. It's plain-old ugly cable but inside it's the same fine-braid copper cable that has the flexibility we need.

what about the 1g install kit on this site, is 1g too stiff and difficult to move? http://www.justamps.com/Accessories/Fusion_Amp_Kits.htm

in most cases you won't need 1 gauge cable unless you're running over 1,200 watts rms in your system. i've installed 1 gauge and i think it's a pain because it's just not as flexible as 2 gauge. stick with 2 gauge, it's good enough.

Good call Teflondog

1ga is overkill
2ga is perfect
4ga is adequate (or perfect if you don't expect much system growth later)
8ga is asking for trouble.
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