How much watts for stock battery to handle

[Kspec01]

Anyone know how much watts can an amp be before the stock battery starts to give out? :confused: I'm asking this cause I just slapped a 420 RMS watts amp in the car and now at night everytime the bass hit the whole car dims out. :( My guess is that I prob gotta upgrade the battery now due to me putting such a good amp. Maybe somebody has some sort of calcuations that can be done to make sure everything gets it juice, if so please post it so that I can see it. Thanks

[only1db]

its not the battery your going to kill...it will be the altenator....you would have to measure how many amps you are pulling with everything going at once...windows a/c windshield wiper ect....and if you are over the 75 amps then you need to do something about it....i put one cap in but my lights are still going so i need two caps...i have an 800 watt amp and a 620 watt amp. you best bet is to get a cap

[Rdubois]

Get a cap. It's normal for your lights to dim when the bass hits if you don't have one. Cap first and battery second but that's more if you play your music with your car off a lot

[NHElantraGT]

The optima yellow top battery is nice, but may seem expensive if you've never shopped for a performance battery before.

The cap is the way to go. If you have the cash, may I suggest...

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=1498&item=3094809558&rd=1&ssPageName=WDVW

[Rdubois]

Wow that's pretty nice looking. I would buy it if I didn't already have a couple caps.

[Kspec01]

does anyone know how much amps are alternators do? Isnt it soppose to be 90amps or so?

[Rdubois]

If you have a 2003 and before it an 80 amp. The 04 and maybe the late model 03 have the 90 amp. Believe me you are fine with the stock alternators. I have a max amperage of 180 from my two amps and with the cap and the optium yellow top I'm fine. You are fine if you get a cap. You don't even need the 5 farad if you don't want to spend that much a single 1 farad will do.

[Kspec01]

thanks for the info !!

[Elantra2.001]

I had a 1500 watt amp and a 500 watt amp running together and two caps and my yellow top never dimmed.

[Rdubois]

How many amps are you pulling on those Elantra?

[CarbonGT]

same problem with my 800 W monoblock amp. I am going to get a cap and then put everthing back in to see how it is. Then depending i may buy the yellow top.

[Kspec01]

I also have a monoblock amp, wonder if those mono amps suck more current then your reg ones?

[Rdubois]

All you have to do to find the amp pull is add up the amount on the fuses on the amp. Ex. An amp with 4 25 amp fuses has a total max amp of 100.

[CarbonGT]

The amp is also set to run at 14.4 V, so i just thought that a more powerfull bat might help.

[Havro]

i would hate to rain on everyones parade and piss people off...
but getting a CAP will do nothing for you!
yes your lights wont dim (if thats the only problem you want to fix then a cap is good)
but ur problem is with a cap u are working ur alternator twice as hard!
with a cap ur battery is shooting power to the cap when it drains and ur alternator has to dish out even more power because its charging the battery and the cap!
the WORST thing would be to get a 5 farad cap!
all a cap is, is an extra battery, and would anyone here hook up 2 batterys for ur one alternator to charge???
i know a very lot about stereo systems, kinda weird this is the first time posting in the car audio section! (never even posted on the old forums)

this is weird that your lights are dimming!
im running a solid 7-800 watts no cap, stock batt and alt and no lights dimming!
i also have a digital fuse block that reads the car voltage and i have not ever dropped lower than 13.8 volts!

i would understand with the people running 2-3 amps and anything over 1000 watts would dim the lights!

also whoever said, you add up the numbers on the fuses on the amp to find out the amps is wrong!
there is a formula to convert watts to amps! i will get that for you guys!
i know just to run the car you are pulling between 25-30 amps constantly!
so all i need to do is find the formula and it will tell you how many watts you can run safely! with the 45-55 amps that are free!

on saturday im going to get my system tested for spl
because i know someone is thinking (he only has a 700 watt amp thats why hes not dimming his lights)
just by ear i think i might hit between 150-160 DB....not bad for 1 sub!



heres the formula!

volts x amps = watts

so if volts x amps = watts than ...

watts divides by volts = amps!

so if u have a 420 watt amp running at about 14 volts ur pulling...30 amps!
which means you are very safe!

i remember there being things about the very ****ty batteries put into the hyundais.....might wanna check into that!

my 700 watts is pulling 50 amps!
so im running the alternator at the max 80 amps with car running

(and by the way....not to be a smart *** but my amp isnt running a 50fuse..)

that info should help

[NHElantraGT]

the WORST thing would be to get a 5 farad cap!
Just to be clear, I only suggested the 5 farad cap to solve the dimming issue, nothing else. If you were definitely planning on buying a single 1 farad cap, you can get the 5 farad for just a bit more $$$. That's all. :)

Havro is correct about the strain on the alternator.



I had a 1500 watt amp and a 500 watt amp running together and two caps and my yellow top never dimmed.
I also had (at one point), close to 2000 watts (max) from 3 amps running and only dimmed at stop lights at high volume.

[Kspec01]

Havro, are you still using the stock battery in your car? :confused:

[Havro]

yes!
thats why i dont understand your dimming issue!

i have a 4 gauge wire comming from the stock battery directly into my amp!
no bigger alt. no caps no nothing!

my amp is 700 rms at 2 ohms
my sub is wired down to 2 ohms
its a class D amp which means i should be pulling 85-90 percent at 14.4 volts
so i should be pulling at least 600 watts all the time!

if i was you, if there are any Autozones near you, they can check ur battery/alt while its on your car
get ur stuff checked out!

what kind of amp is the 420 watter?

[Kspec01]

yes!

what kind of amp is the 420 watter?

Its a Profile monoblock. the 420 is rated RMS, its 600W total output. I to have the 4 gauge wire runing from the battery, one Punch HE2 wired to 2ohms. but as soon as that bass hit in my car, its makes the RPM drop and the lights go dim with each bump.the temp cure I have done for now is not to bump it at night, especially when Iam stopped, only on the highway. :rolleyes:

[Hyundia_90250]

O.k. been hopin my internet is working for me to find an answer for this and from what I read its pretty much my prob......I don't have a stock batt(was dead when I cam back from Iraq)....I'm running a Kenwood 8401 4ch Amp(bridged for the sub which is a 10" Lightining Audio) and 4 speakers on the other 2 ch.'s(5.25 & 6x9)...the problem is dimming(slightly, as in you have to look at it for a few seconds to see)..there is no distortion or anything else....the amp's fuse is 40.....RMS is 60 per ch. and 180 bridged.....would a "cap" help me out...also I have reverse indglo gaudge's..would that cause it too? :confused:

[southpawboston]

havro, what is the fuse rating on your amp? judging what size cap or battery is needed to optimally power a system depends more on the current draw than the stated watts output of the amp. most amps are overrated these days and if you go by what the watts say, you're overestimating the actual current draw on your system.

[Havro]

my amp is not overrated....
when u buy cheap bestbuy/circuitcity/fleamarket amps are overrated!
im pushing 750 watts at 2 ohms

i really dont understand this FUSE on the amp deal....
the amp has a 80 maxi-fuse!
one of them fuses that the cars use in the fuse box under the hood...the big fat ones

the fuse rating doesnt have anything to do with current draw!
didnt i post the formula on how to calculate how much the alt can handle?

southpaw....i understand ur a electric genius and all but i know ALOT about car stereo equipment, ive been doing this **** for a long time.
i may not understand all the crazy stuff you know but i know what i know!

and south....u knowing so much about all this....why would you suggest a cap???
save the money and get ur alternator beefed up if u are that worried!
in most big cities there are shops that re wind alternators to make them bigger amps

[southpawboston]

woah, no offense intended havro. not claiming that your equipment is overrated or that you don't know what you're talking about-- i agree with you on the alternator issue (see bottom of this msg). but my point is this: a lot of people do have cheap equipment that is for sure overrated, and they may think they are overburdening their alternators when they really aren't. for example, lots of amps generate a huge amount of heat, sometimes over half of the power they consume is converted to heat and not speaker current!!! for example, i have an old a/d/s pq10 amp that churns out a meager 50Wx4. it also has a tendency to run hot. if i used the calculation W=V*A, (or A=W/V), i would calculate a maximum load of 14 amps on my battery. but the fact is, the amp draws up to twice that current, because it also produces heat. that's something most people forget. that's also why it has a 30A fuse and not a 15A fuse. lots of energy is wasted in heat production.

let's take another example to further the point. i also have an old soundstream amp that puts out 35x4 watts + 100x1. total rated power is 240W. it is also one of the most efficiently designed amps out there, whereby virtually all the power consumed is converted to speaker power, not heat. it puts out more power than my a/d/s amp (240W versus 200W) yet it draws less current from the battery. it has 4 3A fuses + 1 5A fuse, for a total of 17A.

so in the end, if you are concerned about the load on your battery/alternator, it is more important to know how much current your amp(s) pull rather than how much power is going to the speakers, which doesn't take into account the efficiency of the amp, how much is being lost as heat.

you are right that the cap works essentially as a spare battery, but the difference is that it can get repeatedly charged/discharged for thousands of cycles as opposed to a battery, which can only survive a couple of charges/discharges. they are designed to be discharged and charged rapidly also. caps WORK BEST WHEN your system DOES NOT routinely draw more current than your alternator can supply but is capable of drawing much more under sudden peak conditions such as heavy bass hits. these are very short and transient, and that's where a cap really shines. but if you are consistently pulling more than your alternator can supply then you are right, you should upgrade your alternator.

[cclngthr]

I would also take account of the total amperage output from the battery when making calculations in this issue. A weak or small battery will drain easier (which also charges the cap) than a heavy duty one. Our batteries are rated at 550 CA and might not be heavy enough to run everything plus the sound equipment. A higher CA would keep up with the demands of the equipment draw without draining to much so the alternator would have to work as hard.

My friend has an old school American Pro 600 watt amp (probably peak power) and has no problem with his charging system which currently has a 40 amp alternator and a 800 CA battery (however, I recommended he put the 63 amp alt in).