New Battery or Capacitor

So, I replaced all my speakers and added a 12" sub , all together takes about 800w ,so whenever its playing decently loud every dims from the headlights to the gauge cluster so im wondering if i need a capacitor or a new battery(current battery is sorta old).

 

The first thing you need to look at is the current rating of your alternator. The battery stores power but the alternator charges the battery and supplies power to run everything on the truck. Next you might look at adding a capacitor to supplement your electrical system. The way these work is they react much faster than the battery is able to and can supply a large amount of current very quickly for a brief period of time.

 

How many amps is your alternator putting out? I'm not versed in aftermarket audio, but from what little I have learned a higher amperage alternator is needed for high wattage stereos. If I'm wrong, please correct my dribble.

 

The stock alternator output is pretty low from what I recall, in the neighborhood of 80 amps if I remember right. I'd recommend going with a higher output alternator if you've got lots of demand for power. Do you know which engine you've got? I've got a couple of alternators sitting in the garage from my 5vz-fe. One is stock, the other is high output. I had them tested and I think I have the result papers around. From what I remember, the stock alternator peaked at a lower pulley RPM, which equates to a lower engine RPM. The high output needed a higher RPM. I found that when cruising on the freeway with the HO alternator the engine RPM was too low get much of a charge. In town it was fine. Wound up going a different route to meet my power needs.

I'll dig around in the morning and see if I can find the test sheets.

 

Yes, get a capacitor. your amp is draining your battery/alternator. it should be drawing from a capacitor.

Also, look into the chevy alternator swap. Go from 80 amps to 140 or so.

 

Nope. Adding a cap to an already deficient system is just adding 1 more thing for your charging system to charge. If your boat is sinking you dont add an extra hole to let the water out. Alternator, then battery.

 

And make sure you have solid grounds.

 

A healthy charging system has two tasks. First, it supplies power to satisfy the electrical load. OEM charging systems are generally not sized to add power high power aftermarket appliances, for example, audio, lighting or winches. When the combined electrical load exceeds the output of the charging system, the difference is supplied by a healthy battery until the battery is drained. Secondly, it needs to replace the power in the battery that it has been consumed and to keep it fully charged. If a battery is consistently undercharged, it will loose CCA performance and amp hour capacity due to a gradual build up of lead sulfate. The charging system's ability to accomplish these tasks are based on its average current and voltage output, your driving habits (duration and RPM), and ambient temperature.

So the first step is to determine if the charging system is supplying sufficient power and sized to keep the battery fully charged based on your driving habits. If not, an alternator upgrade is in order. The second step is to deal with your immediate loss of voltage during high momentary peaks in power usage. A lead acid battery is an electrochemical device which can produce a large amount of current, but it takes several milliseconds. Large electrolytic capacitors are designed to deliver high current in microseconds and are commonly used in audio applications to eliminate voltage sags caused by heavy base.

Sizing the capacity of the charging system, battery or capacitor should be based on the worst case loads, driving habits and ambient temperature. If the charging system is undersized you will be fighting an uphill battle with the battery or capacity sizing. In the interim, you can keep your battery fully charged by using a battery charger and periodically topping it off.

 

If looking for a bigger alternator, the factory tow package alternator is 130 Amps and is definitely compatible with the mounting and pulley location on the 4.0L V6 (2nd gen). There should be a corresponding part from the 1st gen tow pkg which would fit a 1998.