Results 1 to 5 of 5

Thread: Why is my voltage dropping?

  1. #1
    Low Bitrate
    Join Date
    Nov 2008
    Posts
    60

    Why is my voltage dropping?

    I noticed my voltage was dropping on heavy bass hits and I was wondering if it was something to worry about. At full volume while idle my voltage can drop as low as 10.5 volts on big bass hits. With my sound system off my voltage stays about 13 to 13.5. A friend gave me a capacitor for free so I decided to install it because it has a voltage meter on it which I thought would be more useful than the actual capacitor. The cap matches what my volt meter says so I am assuming its fairly accurate.

    Here are some specs about my car...
    Stock alt @ 105 amps

    sub amp @ 500 watts rms
    Component speaker amp @ 200 watts rms
    car computer @ 250 watts(dont know if its rms)
    Total watts 950 watts rms.

    I upgraded "the big 3", and I am running a 4 gauge wire from the positive battery terminal to the amps. I am also using a 12" 4 gauge ground wire to the body of the car. No connections are getting hot, and my positive battery terminal is clean.

    So what I want to know is should I worry about the voltage?

  2. #2
    FLAC
    Join Date
    Jan 2008
    Location
    Dartmouth, MA
    Posts
    914
    Get a bigger or "faster" battery. AGM batteries like kinetik are designed for audio systems. You could always get a bigger alternator too. You can probably get away with just some big deep-cycle battery though (I do just fine with a sears die-hard battery for audio).

    It may not be a problem that the voltage is dropping like this though. 10.5 isn't THAT bad. Though 10.5 is considered a flat-dead battery. Check your batterie's voltage with nothing on. Try charging it to full capacity before doing anything and see what happens.
    My Nearly Complete Car:
    http://www.mp3car.com/vbulletin/show...ed-car-pc.html

    Micro Control Center... Control Your Car Across the Internet
    http://www.mp3car.com/fusion-brain/1...-internet.html

    Website: (It's a work in progress, really. All my projects have taken me from ever really developing it.)
    http://paulfurtado.com/

  3. #3
    Low Bitrate
    Join Date
    Nov 2008
    Posts
    60
    Quote Originally Posted by PaulF View Post
    Get a bigger or "faster" battery. AGM batteries like kinetik are designed for audio systems. You could always get a bigger alternator too. You can probably get away with just some big deep-cycle battery though (I do just fine with a sears die-hard battery for audio).

    It may not be a problem that the voltage is dropping like this though. 10.5 isn't THAT bad. Though 10.5 is considered a flat-dead battery. Check your batterie's voltage with nothing on. Try charging it to full capacity before doing anything and see what happens.
    The battery is a little above 12v when the car is not running, plus its only a year old at this point and it has not been drained completely. How big should I go for with a new battery? The battery I have now has 690 cold cranking amps and 820 cranking amps. It is a superstart 75EXT. I am too low on money right now because things came up recently and I am broke so I dont want to buy anything that wont help. I would also like to avoid buying an alternator if a better battery will solve the problem.

    I posted another thread about my amp clipping at low volumes, could this be part of the problem?

  4. #4
    FLAC
    Join Date
    Jan 2008
    Location
    Dartmouth, MA
    Posts
    914
    Define clipping. Also where is your gain/sensitivity at?

    If you buy a battery locally, get one with some sort of return policy.

    If you're in the US, I bet the sears batteries would be your best bet since they are cheaper than all batteries branded for car audio. I believe that they have something around the $120 price point that is massive. Get something with a reasonably high capacity ex. a reserve capacity of 80+, and the cranking amps to match your starter's needs.
    My Nearly Complete Car:
    http://www.mp3car.com/vbulletin/show...ed-car-pc.html

    Micro Control Center... Control Your Car Across the Internet
    http://www.mp3car.com/fusion-brain/1...-internet.html

    Website: (It's a work in progress, really. All my projects have taken me from ever really developing it.)
    http://paulfurtado.com/

  5. #5
    Raw Wave
    Join Date
    Nov 2009
    Posts
    2,118
    950W means about 100A so your alt won't handle the peaks.
    That will cause the alternator voltage (up to 14.4V) to drop to the battery voltage which should be ~12.7V fully charged (ignoring surface charge) less its {current x internal resistance} voltage drop .

    But 12V on a good battery means it's discharged - certainly way bellow recommendations for a cranking battery (no less than ~12.4V) and borderline for deep cycle batteries (12.1-12.2V). That's rested and unloaded. A battery just off charge should be above 12.7V - up to ~13.6V (surface charge).
    Otherwise 12V means a stuffed battery - collapsed or compromised cells etc


    I'd say your battery is stuffed, though the alternator may be undercharging (ie, under 13.6V; they are usually set for ~14.2V and shouldn't exceed 14.4V long-term).


    The cap would have been useless. In fact caps are generally useless - their main use being to protect AGM batteries in BIG systems - but yours is far from big.


    I'd suggest replacing the battery with another cranking battery, and not AGM. You might however consider a second battery (AGM) next to or near the amp. You could try charging the battery separately to see if it's voltage does come up.
    But have your alternator output checked. (Get a voltmeter for the dash, else a DMM.)

    Flooded/wet batteries are just as fast as AGMs, but AGMs have a lower resistance - typically half that of wets. Hence AGMs have typically double the short circuit current of wets and can supply higher currents to loads. But they don't always like that - hence why caps are used, else cable resistance is enough to protect the AGM (ie - when it is up front as the cranking battery - assuming it tolerates the cranking current).

Similar Threads

  1. power dropping out
    By kristianvanek in forum Power Supplies
    Replies: 2
    Last Post: 05-10-2011, 07:42 AM
  2. Usplash dropping to shell!
    By locs4dayz in forum LinuxICE
    Replies: 6
    Last Post: 01-13-2010, 07:17 AM
  3. Noob dropping by for a beer
    By tywebb in forum Newbie
    Replies: 1
    Last Post: 06-07-2007, 11:11 AM
  4. GPS dropping in and out
    By DK888 in forum GPS
    Replies: 35
    Last Post: 06-24-2005, 03:33 AM
  5. PSU dropping out at 10V
    By apparatus in forum Power Supplies
    Replies: 3
    Last Post: 01-15-2002, 11:11 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •