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I want to run an Alpine mrp-m500 amp (500w @ 2ohms). Do you think it would be a good idea to get a capacitor? If so, which capacitors have the smallest charging times?

as for the future, I'm planning on also hooking up my speakers to an amp as well, but I don't know which one yet. I also know I can buy a dedicated audio battery for my amps.

How do I know if my alternator can handle the load? I'm not sure if the alternator was ever replaced, and I certainly don't trust Autozone's fixed machines to tell me my alternator is bad. I'm also very careful of where I spend my money. A battery or capacitor may be nice, but it might make more sense to upgrade my alternator for a few bucks more.

let me know what you guys think

 
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all a cap does is take power away from the alternator. the actual solution is to upgrade the alternator to something more than the stock 60 amps, which can barely run the basic car systems. the problem is its not so easy on these cars. they have an ELD (electronic load detector) which under certain conditions will cycle between 11.5v-13.5v in the summer and 12.0v-14.0v in the winter. in other words, the alternator could be shutting down while driving and you could only be getting barely 12v to your stereo equipment. the ELD will not "sense" any aftermarket hardware you hook to the battery like it will with stock parts like the heater and lights. so even if you add a big alternator, the ELD will still be turning it off under these conditions which will cause audio to suffer and also drain your battery very quickly to the point where the car may not start.

- Load below 10A
- Speed below 40 MPH
- Engine speed below 3600 RPM
- Coolant temp above 140 F
- A/C off
- Intake air temp above 65 F
- Brake switch off
- Fuel cut-off not active

basically the alt turns off when you are coasting with foot off the gas and turns on when you are pressing the gas, depending on speed and air temp. you could try to bypass the eld by removing it (located in the under hood fuse box) and jumpering the two wires together. this should in theory allow the alt to stay at 14v all the time. but you will also have the check engine light stay on and i dont know of a fix for that. you should only do this mod if you need the extra amps for aftermarket equipment. otherwise you can risk overcharging the battery. it makes even more sense to put a heavy duty switch on the ELD circuit, or even better a relay controled harness switch, so you can turn the alt on or off as you need it. but with a big stereo, you will probably be safe leaving the alt on all the time so it has enough left to charge the battery and power the system and other car functions. be sure to install a dash mounted volt gauge so you can monitor the power output.

 
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I've noticed that sometimes my car cranks a little too much before it starts, or it starts up very weak. Sometimes when I accelerate in the first and second gears the AC goes from cold to outside air temp for a moment as well. Would you then recommend I get a battery for my amp? There's a good probability I'll get another amp (4 channel) for speakers, and maybe further upgrade my subwoofers and sub amp in the next few months. I was looking at this one for now though:

http://www.onlinecarstereo.com/CarAu...ik_KHC600.aspx

 
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a larger battery will always help, but if you are using more power than the alternator can provide, you can kill ANY size battery eventually. to save yourself the trouble, i would just go with a larger battery with a long reserve time and invest in a battery tender plus charger that you can hook up to charge the battery to full every so often when it gets below 12.4v charge (assuming you have access to a power plug, otherwise you may have to go with the battery tender solar version). ideal charge is between 12.6 and 13.2 under normal conditions. stick with a good conventional lead acid battery like interstate for the best power and reliability. AC going hot to cold is normal due to the compressor cycling on and off. it cannot stay on constantly without blowing up. older r12 freon systems did not have this problem because they were so efficient, the air would stay cold for a minute even after the compressor shut down. new r134a systems like in the civic are far less efficient and even with a huge condensor, its harder to cool the air.

 
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Thanks for your advice. If I hook up the amp, subs, speakers, and head unit, and I'm sure to keep the subs hitting just enough to hear them, do you think that doing so would have any adverse effects on the battery/alternator (the stock battery/alternator)? At least until I can upgrade the battery?

 
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its hard to say, you would have to monitor the battery voltage daily (after the car has been sitting at least 4 hrs, but preferably 24 hrs) and see how much its dropping. if it stays close to 12.6v every time, then you are fine with the oem alt/battery. just grab a cheap multimeter and set it for 12v and touch the probes to the + and - battery terminals to get a reading. as for adverse effects, the alt will not really be affected since it will turn on and shut off normally as if you didnt have any system. its the battery that will suffer if it drains below 12.4v and is not able to receive a high enough charge voltage. in which case you need to grab a battery tender plus and recharge by plugging into a wall outlet when needed. as a bandaid and temp solution, you can turn on some of the car's accessories (a/c, blower, lights, etc) to increase load and force the alt to run at 14v all the time. but again you will need a voltmeter to monitor all this as it happens.

and actually i may be wrong about the alt being fine. i havent encountered this situation before, but if you drain the battery enough, the alt may start working full time to recharge it and die trying. primary cause of alt failure is overheating due to constant running, usually from trying to charge a bad or low battery. alts were never meant to be a battery charger, only to top off the battery and replace what was used to start the car. and a voltmeter will show you this also. its one of the most important gauges you should have in the car. i mounted mine in a custom pod. the gauge is isspro analog EV voltmeter.

 
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yeah, if you run with a bad battery the alternator is strained more. Anyway, you mentioned that I should try upgrading the battery (which I should be doing soon anyway). Could you point me in the right direction as to which batteries I should look at? Links would be much appreciated!

I found a DIY for how to bypass the ELD. Although I'm not an expert with cars, I can probably do this right the first time.

http://www.stevemeadedesigns.com/boa...ivicaccordfit/

Do you think it's worth it to do so (and does it come with any risk), or is it better to invest in a battery

 
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the only negative i can see with ELD bypass is more alternator wear (it should still last a good while tho) and worse gas mileage and possibly worse acceleration. the ELD is setup so that the alternator only charges during times when it wont be noticed (like at a stop or while coasting). i would prolly do the bypass, get a bigger battery, a voltmeter, and call it a day. monitor how the battery is doing over the long term and if it sits near 12.65v, you are good to go. stick with a flooded lead acid battery, the biggest you can fit, and stick with the best brands like interstate. autocraft gold from advance auto is really good, so are some versions of honda brand (interstate) battery. the more reserve time the better. if the battery starts to drop below 12.6v, you may want to invest in a battery tender pro and use that every couple weeks to fully charge the battery.

 
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eh I don't know what I want to do yet. As much as I want to put the system in, I don't want to mess around with the car and do anything that even might slightly hurt it (because it's a commuter car). I've been considering just putting in speakers and a head unit, selling the sub (Rockford fosgate punch :[ ) and amp, and investing in things that might help the car run better like a CAI and exhaust.

I want to do all this stuff to the car, but I have to be practical in how I spend my money on a 131,000 mile commuter car.

 
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i was in a similar situation when i first got the car. ended up buying lots of stuff for it that ironically is mostly gone now. i dont even have a radio or speakers.

 
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I can see that happening to me. I'll only be driving the car for commuting purposes on the weekends, so putting that money and time in the car feels unnecessary.