I have a 95 Es300, i just installed my stereo "JL Audio 700Watt monoblock amp, 2 JL 12's". My headlights are dimming when its loud and when rolling up my windows. The reason im confused is because Car Toys told me they dont sell capacitor because its a bad idea and not reliable. Then with the 2nd battery the guy told me that my alternator will try to charge both batteries which thats not good. I hope someone can help me.

 

I think you need a stronger alternator.

 

you have signs of a weak battery first off, and you need a stronger alternator if your going to run 2 batteries..
yeah capacitors may not be needed..

 

Car pretty well runs on the batteries which are constantly being recharged with the engine running.
Amp at max. output puts another 58A (700W/12V) load on the system, lower out put will draw less.
You need some serious upgrades to the electrical system on the car or make sure you have a couple good fire extinguishers on board!
Capacitors "used" to be installed for radio noise suppression from the engine electrical components. Not sure what the purpose is in a modern car, could be similar.

Get the battery out & to a battery retailer. have a load test done on it to see the true condition of the cells.

 

Get an Optima battery before you do anything else and see if that solves the problem. If not then I *think* it's the RAV4 alternator that fits our engine but bumps output from 80 amps to 120 amps.

 

With the addition of the new, more power-hungry stereo, you have fundamentally changed the power demands of your cars electrical system. Demands that it was never designed to meet.

As pointed out in a previous post, the extra demand on the system would be 58 more amps. It sounds to me like that extra current is going thru the same path that is feeding your fuse box, and hence, the lights, windows, etc.

It also appears like the fundamental problem is one of internal resistance in the wires from the battery to the rest of the system (ie: the battery cables). You could also have marginal connections to the battery in the clamps. Those need to be very clean.

If it were mine, I would buy new "beefier" battery cables (lower gauge number) to handle the extra current draw. Of course your battery needs to be big enough and capable of supplying the instantaneous current demands of the stereo. But better cables for sure.

 

Aftermarket alternator - try Ohio Generator.
Better battery - you won't need an additional battery for what you described.
Upgraded battery cables (3) - positive, ground, & power to the starter.

A good capacitor could help (maybe enough for you by itself).
Capacitors obtain and release a lot of power very quickly.
MJ

 

You only need new larger cables for + and - and not the starter. The starter works fine as is and would not contribute to voltage drop due to IR loses except during the brief starting period.

At this point, I am wondering how your "second battery" is actually wired in?