Hey guys I have a demanding stereo setup and I've already added a second batt. but my stock alt can't keep up. I was looking at a 240 amp alt and was wondering if anyone has had any issues with the added amps screwing up any of the stock operating systems/wiring of the car?

98 SLE

Have you upgraded the Big 3 yet? Added capacitors yet?

These are two things you can do that help tremendously before cranking out a ton of amps.

as long as you do i right it shouldnt be a problem. you need to greatly upsize the wires, you have twice the current you need twice the path. ground too. also all alts are not created equal, most people who have systems spend alot of time at idle showing off or whatever check out the alt performance specs at idle and compare that way. some people just upgrade to the cs144 because of the regulator being better at idle

If the wiring is upgraded then you could go with a higher amp alternator, but if the wiring is not upgraded, and you do not have any capacitors I'd start there first before upgrading the alternator, I had an above average system and I ran a 10 farad capacitor.
Around 1 farad per 500W of RMS power would make a big difference.

If you have done everything else already then there are some CS144 200 A Dual Rectifier alternators, also 250, and 350A ones available, but they are $$$
Here is the 200A one.
CS144 Series Self Exciting (One-Wire) 200 Amp Extreme Duty Dual Rectifier Alternator

Thanks for the replies. I did the big three upgrade, and I even ran an extra ground from the Alt bracket to the passenger side shock tower. I have a 2 gauge wire running from the Alt to battery and I have 1/0 gauge running from my front batt. to my rear batt. I already have a cs144 Alt in the car, I get 14.5 volts at idle. The problem is when the bass hits the voltage drop is about 1 volt at first, then after about a half hour of play the voltage drop is about 2 volts(and this is while I'm driving). So the only part of the charging system I haven't touched is the Alt that'* why I'm assuming the Alt can't keep up with the demand of the stereo system, Oh and I have a 2 farad cap already.

i would agree you need a bigger alt, so your question was more about the other stuff in the car? i would say the problem would be not adding the bigger alt as the voltage drops it takes power away from other things not working as efficiently as they would

Yeah I think I'm going to upgrade the Alt and go with the 1/0 gauge from the alt to the front batt just to keep the wiring consistent. Also I grounded the whole system to the rear cross brace under the rear dash can you guys think of a better spot to ground in the trunk? I know the brace is welded to the shock towers.

98 SLE

Directly to the battery.

So you think I should ground the Cap and and amps directly to the battery and then run one ground cable to the chassis?

Everyone I have ever talked to (some of the highest ranked installers in the USA, top ten actually) have said capacitors are a band-aid/garbage. I also have a high demand system running off my factory alt with no problem. The key is appropriate sized wiring as everyone has already suggested, as well as audio batteries. Regular batteries are not capable of putting out the power needed for those heavy bass hits. An audio battery (such as those manufactured by stinger) can keep up. I replaced the main battery with a full size stinger battery, and tucked a smaller stinger battery behind the back seat.