severe voltage drop, bad alternator?

I would recommend that you replace the alternator with a high output unit. Adding batteries will only create more of a load on the already stressed alt. The main purpose for a battery is to supply enough current to the starter motor to start the car. Once this is done, the battery has finished its job and depends on the alt to recharge it. All the accessories in the car (radio, ignition, heater, etc.) run off the alternator's output. The only other thing the battery does is to help filter the DC output from the alternator and help with any serious current draw from the car when the engine idle is low. Your alternator was never designed to power the car and a huge stereo system even when the car was new. You need to upgrade your power supply system to the stereo and car. This should have been done first. You should also in the mean time check the ground cable from the battery to the body. They are know to corrode at the body connection.sparky

ya the battery is an interstate direct replacement....its nothing special. Actually the z34 is a lumina,youre thinking of a z24 cavaleir(its little bit bigger)thats all. The zapco amp is just 50wrms per channel. Theres like no room under the hood to put a big battery the one thats in there is buried as it is.This ncar is not stereo friendly at all! I think im gonna rewire my subs to load the amp to 4 ohms instead of the 1 0hm ive got it at now. Im not gonna get 1200rms out of it but im sure as doodie not getting it right now anyways. Last thing i wanna do is break down in the winter.... I will go by the shop and get my voltage output checked mad scientist,..i understood what youre sayin.

mad scientist....the ac readings i got,what do they mean?

sparky wrote: Adding batteries will only create more of a load on the already stressed alt.

WHERE does this come from? The BATTERY runs your car, the alternator charges the battery. Give yourself huge batteries and you 'filter' the huge grabs for power that a NAPA battery cannot handle when it's supplied by a stock alternator.

sparky wrote: The only other thing the battery does is to help filter the DC output from the alternator and help with any serious current draw from the car when the engine idle is low.

Help with serious current draw? Like running a stereo? So a larger battery would help?

astro88 wrote: I think im gonna rewire my subs to load the amp to 4 ohms instead of the 1 0hm ive got it at now.

That ought do it.. "I'm finished!" - Daniel Plainview

I'm sorry Sedate, but the battery does not run the car. If that were true you wouldn't be able to disconnect the battery while a vehicle was running. The cars electrical system is powered by the alternator. You may want to research this a little more to learn how a vehicles electrical system works. sparky

Okay I'm seriously not trying to pick a fight but ppl giving advice like yours cost me like a year and $500 screwing with my electrical system when I was wayy to poor to do it.

sparkie wrote: If that were true you wouldn't be able to disconnect the battery while a vehicle was running.

WHAT CAR do you drive?! I've NEVER heard of this; disconnecting the battery in ANY car I've ever had will shut it off immediately. I'm not even kidding.. I got a huge settlement from Firestone when they didn't reconnect a battery cable and my car shuttoff on the highway. I guess.. the circuit isn't exactly cut when you disconnect the battery.. but you remove all capacitance from the thing and alternators are so squirrly you'd fry your car out *easy*... I couldn't imagine a car's ecu letting the thing run w/o a battery. Maybe its an import thing.. I dunno. But I've NEVER heard of a car running w/o the battery connected... and I can assure you Toyota's, Mitsubishi's, and Subaru's (made in the last 10 years) do NOT run like that.

sparkie wrote: The cars electrical system is powered by the alternator.

I think the more pragmatic statement would be "The car's electrical system is run by the battery, which is charged by the alternator." I would argue either is accurate. Again, which is why I come back to a paralleled, dual battery setup. It is what I've had the *best* results installing in several applications with symptoms very similer to the original posters'. "I'm finished!" - Daniel Plainview

Actually on older model vehicles (domestic and import) without computers you could start the vehicle and remove the battery and the vehicle would continue to run. Sparkie is correct when he says the primary purpose of a battery is to start the vehicle. And no, the vehicle does not run off the battery, however todays vehicles (with computers) do require the battery to be connected to run. ~wirewise~

Thank you wirewise. Please understand Sedate that I don't want any fights or arguements either. I hope there are no hard feelings. Ideally Astro88 you need to consult an installer in your area that has the tools and knowledge to properly check out your whole system. That way they can make sure that your system is wired properly and safely. It's no good to have great stereo and not be able to enjoy it. There are many different factors that play into your senario as most members have mentioned. Trying to solve all of them without the car present is beyond anyones ability. sparky

*Deep Sigh* Okay.

wirewise wrote: Sparkie is correct when he says the primary purpose of a battery is to start the vehicle.

Right.. NOT with a HUGE stereo installed. The idea of a car coming out the factory with a nice shiny SLI battery under the hood is exactly that.. the primary purpose of the battery is to light the dome and make the car start. Installing a pair of giant amplifiers changes the .. 'design goals' of the electrical system.. now the battery needs to not only start the car, but the far more demanding task of keeping up with a giant monoblock. So.. in effect, the primary purpose of the battery(ies) is no longer "starting the car" and keeping in line with that thinking, we can look at other solutions that, as the original poster implied as desirable, would not involve replacing the alternator.

wirewise wrote: And no, the vehicle does not run off the battery

..I really could argue the semantics of this *all* day.. "I'm finished!" - Daniel Plainview

Adding amplifiers does not change the design of the electrical system and only changes the users "goals of the design" rather than the "design goal" of the electrical system. Adding amplifiers or any other accessories adds an additional load to the existing electrical system. To maintain the intergirty of the electrical system, the alternator should be upgraded if it no longer meets or exceeds the demands of the entire load placed on the system. Adding more or larger batteries is really only a band-aid for the additional load placed on the existing electrical system once it has exceeded the output of the alternator. Yes, it will appear to solve the problem at first, but eventually the system will fail. Feel free to argue all you like, but it will not change this fact. ~wirewise~