Do I need a Cap?

[silent_1999]

Ok. I'm on my 4th Alternator this year, getting tired of replacing them. I don't know if I'm pulling a large load on the system cus I have Hid's and indiglo gauges (which don't dim). I'm running about 700 watts rms to the subs and about 240 watts rms for the mids and highs. doesn't seem like a lot but my kicker amp is underated (zx750.1). Is a cap a necessity? And can I use something different that a car audio one maybe one from an air cond or something? I have redone all the ground wires in the engine bay. And the charging system is stable at 13.0 at 2000 rpms w/ no accessories, which isn't good anymore. What do I do to prevent another alternator going bad, is stock amperage not good enough? Thank You in advance!

[mellowness65]

do you have an alt odp?

[nvSpeed]

I thought HIDs used less power. And I would just to be safe. Only 100 bucks for a kit for it.

[Bluezx2]

what kind of battery is u using bigger batter will help alt pull for power as long as charging system becomes stable or u might just need a seconday batt but eathir way what size is the alt

[ZX2R]

Check into a Batcap. I have a Massive one that holds all my stereo load. I have two 1100d's(800 Watts a piece RMS) an 1100d5 (300 RMS) and a 4500 (300 RMS) no alt upgrade, no big three and only a 4 GA power wire. It was $300, but I think it was well worth it considering how much I saved on not buying all the other components.

Here is the one I have. There is a bigger one, but I couldn't spend that much.
http://cgi.ebay.com/Xstatic-Model-2000-Stereo-Battery-35-lb-BatCap-New-2008_W0QQitemZ130183365215QQihZ003QQcategoryZ1498Q QrdZ1QQssPageNameZWD1VQQcmdZViewItemQQ_trksidZp163 8Q2em118Q2el1247

[Midwestzx2]

I didnt really read throught your post that much, but maybe do the big 3 upgrade, and get an optima battery along with a higher output alt... caps suck imo

[xtremecaraudio]

As many of the stereo guys here have said many times. A cap is a band-aid. In all reality it will probably toast your alternator faster. There is no substitute for a proper charging system. You may want to think about upgrading your alternator, use a larger gauge wiring, get a decent battery, etc.

[silent_1999]

thanx. just replaced my alt. im not jamming too hard w the car off. voltage is above 14 w the sys on. i have 4 ga wiring right now to the amps. the alt wiring looks good enough to me.

[dragon2200]

Get an Optima yellow top and you should have no more problems.

[Fat_Dave]

yea dude do it the right way get an optima yellow top... its a deep cycle battery that can handle being drained alot and the be charged back up, get an alt odp (the stock alt pully off a zetec focus will work you can get one from a junkyard for cheap or just pocket it) or get the bigger alt off the ford e250? i believe... use the search box and youll find it, and last but not least upgrade ur grounds, switch out the negitive battery cable (from the battery to the chassis) with some zero gauge wire and then youll be set for good.

[Buster]

Get an Optima yellow top and you should have no more problems.

Actually, a LOT of people have had trouble with those batteries.

[ZX2R]

yea dude do it the right way get an optima yellow top... its a deep cycle battery that can handle being drained alot and the be charged back up, get an alt odp (the stock alt pully off a zetec focus will work you can get one from a junkyard for cheap or just pocket it) or get the bigger alt off the ford e250? i believe... use the search box and youll find it, and last but not least upgrade ur grounds, switch out the negitive battery cable (from the battery to the chassis) with some zero gauge wire and then youll be set for good.

That's what the batcap is made for. I haven't done any of the stuff you mentioned and still my alt and charging system are fine. That's alot of unnecessary stuff to do for the O.P.'s system that I'm sure isn't pushing the kind of wattage I am.

[JonsZX2SR]

Just installing a larger alternator without paying attention to the rest of the electrical system is as much a band-aid as bolting in a capacitor.

The reason voltage drops occur during peak demand by the amplifier is the battery is not providing current for peaks and the alternator cannot respond fast enough to provide extra current. Devices running at constant current draw (headlights, fan, amp running at low level) are far less of a problem than devices that require short current peaks (bass amp running at an average of 20A with short 100 A peak requirements.)

The reason for this problem is inductance in the system inhibits change in current flow and inductance generates out of phase voltage spikes that cause local heating and damage components.

This happens because the battery is undersized or losing capacity or the battery is poorly connected to the system. The alternator tries to make up the difference by providing short term current peaks and short term voltage spikjes also occurs.

Batteries can provide current faster than alternators while capacitors can provide current faster than batteries for a short term.

Probably the best solution is to install a large capacity high current primary battery with larger guage wiring with upgraded connections. These can be augmented with a small second battery and capacitor near the amplifiers. The net result will have the batteries providing peak current and the alternator only needs to provide continuous current with smaller fluctuations.

In many cases, with upgraded batteries and wiring, the 95A alternator would be adequate and a 130-135A alternator more than sufficient.

[Fat_Dave]

yea but the batcap is just a crutch, a temporary fix... i always say if ur gonna do it, do it the right way

[Midwestzx2]

I would upgrade the big 3 definatly to 4 gauge wiring, install a higher output alt, shorten your ground cables to the absolute shortest they can be (mine are both under 1 foot) clean all your ground connections and positive connections, and if you like sitting with the car idling and bumping, an alt overdrive pulley.

[ZX2R]

yea but the batcap is just a crutch, a temporary fix... i always say if ur gonna do it, do it the right way

So getting another battery for the car stereo setup is a crutch as well?

[xtremecaraudio]

What's the point if you don't have the alternator or wiring to power it properly?

[Fat_Dave]

So getting another battery for the car stereo setup is a crutch as well?

no i diddnt say that and if you need another battery for your stereo setup you should already have thoe upgrades done

[JonsZX2SR]

yea but the batcap is just a crutch, a temporary fix... i always say if ur gonna do it, do it the right way

Why do people keep saying a capacitor or a battery located near the amps is a crutch. Neither is a substitute for an upgraded electrical system, but they provide a useful function, to supply current during peak demand and maintain voltage at the amp when a rapid demand for peak current happens.

The concept is called 'peak shaving' and it is well understand for electric power applications. Rather than sizing electrical components for peak current demand, such as when a motor starts up or a sudden large load is applied, a secondary source of current satisfies the short term demand, so the primary system can be sized for slightly more then the greatest expected average demand (typically 300%) rather than the peak which might be 300% or more.

If you think capacitors don't work or are just a buch of hand waving, I can show you elevator systems where capacitors and batteries are used, allowing the input converter and feed lines to be decreased by 1/2 to 1/3 in size than without the source of peak current.

There are two problems in an auto electrical system that are caused by bass peaks and large amps. First, due to large inductance, the alternator cannot respond fast enough. So just bolting in a huge alternator without other changes (large primray battery, upgraded wiring, etc.) Second, due to V = I*R losses along the power cabe to the amps, large current draw results in significant voltage dropped along the power cable.

You can fix the problem with a very large and high quality primary battery, a very large power cable from the battery to the amps and very low resistance connectors. As long as the battery provides most of the peak current and the alternators runs at more or less constant load everything will be fine. However, the V= I*R loss along the power cable will be greater than if you provide a current source in the trunk with the current in the feeder cable more or less constant.

Adding both a secondary battery and a capacitor in the trunk will reduce the peak draw from the primary battery and peak current down the feeder cable. The capacitor will provide current for the first 200-300 ms with the secondary battery responding within 300 ms. The primary battery and alternators will hardly see any peak demands at all, with the alternator running a steady 10% or so higher than if the audio were shut off to recharge the battery and capacitors in the intervals between the peaks.

This isn't rocket science, but well understood 50-60 year old technology applied to things such as elevators, diesel electric subs, etc. I'm not sure why kids today need to reinvent problems when solutions are well understood. Just upgrading wiring and bolting in a larger alternator is more of a crutch vs. installing a system level approach which would include a local battery-capacitor pair, better wiring and connections, bigger primary battery and if needed a larger alternator.