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voltage drop problem, what battery to buy?


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michigan_tech 
Member - Posts: 32
Member spacespace
Joined: September 16, 2008
Location: Michigan, United States
Posted: November 18, 2009 at 8:40 PM / IP Logged  
I would like to thank the previous two men for their sarcasm, it hasn't benefited me.
Anyways, I ran a 4 gauge wire from the battery to the grounding point in the back (negative terminal on the battery) where the two amps are grounded too. It was somewhat more stable, but still chilling at 10.5 Volts measured at the sub amp. The guy i'm working with insists a bigger battery will surely help me here, and he's not a salesman, he's just saying it would. My battery light came on too, and after 10 minutes of charging with the system off it stayed on, but turned off when I restarted the vehicle. What gives?
i am an idiot 
Platinum - Posts: 13,609
Platinum spaceThis member consistently provides reliable informationspace
Joined: September 21, 2006
Location: Louisiana, United States
Posted: November 18, 2009 at 9:39 PM / IP Logged  

Did you crimp and solder all conections?   When the voltage is dropping down to 10.5 volts, is that at the amp or at the battery?  If at the amp, what is the voltage dropping to at the battery?   Did you ground the amp to a seat or a seat belt bolt?

oldspark 
Gold - Posts: 4,913
Gold spacespace
Joined: November 03, 2008
Location: Australia
Posted: November 18, 2009 at 10:05 PM / IP Logged  
Again, what can I say?
I bigger battery WILL NOT reduce your voltage drops.
It will provide a higher source voltage for a longer period of time.   
If his solution solves your problem, do it.
If you still want to reduce those losses later, hopefully all that I have said other than my last compliments to Rockwell have been beneficial.
If not, let me know so I can delete my posts to save space, boredom & confusion.
ADDENDUM re charging:
Your system probably dropped below some threshold voltage.
Some charging systems need a higher voltage or a re-start to initiate charging again (ie, ignition off-on).
Whilst your charge light is on, your system is not charging, hence no higher voltages etc.
(Charging systems vary. For most you must have a charge lamp (or similar trickle path) to ensure charging is initiated. For some you can disconnect the charge lamp once charging is initiated, etc etc...)
A bigger battery will last longer, but it too will discharge if the alternator isn't big enough.
bigtime_077 
Member - Posts: 20
Member spacespace
Joined: December 01, 2009
Posted: December 03, 2009 at 6:41 PM / IP Logged  

i'm new to the forum but if i may say i would take the car to a local auto shop or like an autozone to have the alternator checked to be sure it isn't defective because to me it sounds like you have a weak alternator.  a new bigger battery will not "give" you a higher voltage it will only hold the higher voltage for longer.  if you can't replenish that power in the battery it will cause a voltage drop.  now in my experience with both car audio and with automobiles i have also had this problem and found that the problem for the voltage drop was due to a failed voltage regulator in the alternator itself.  this will allow sometimes allow the alternator to still charge the battery for starting purposes but as soon as a load from like an amplifier is put on it,  it can not keep up with the current demands.

all in all remember that the alternator is what makes this higher voltage so therefore it is the brain of the charging system.

oldspark 
Gold - Posts: 4,913
Gold spacespace
Joined: November 03, 2008
Location: Australia
Posted: December 03, 2009 at 7:28 PM / IP Logged  
Hey BigTime - you may be new but what you said is something others often do not seem to grasp.
An alternator that cannot keep up with demand typically means a 1.5V system drop which is at least a 20% drop in audio output and spark power (assuming non-SMPS nor CDI etc).
A voltage drop due to inadequate cabling (from the battery/alternator) has the same effect. And the battery/alternator will not change the cable's drops & losses.
At least the cabling is cheap & easy to solve.   
I this case, it seems cheapness is a priority and no extra equipment can be fitted.
But unless the battery is faulty, there is little point upgrading it.
If the regulator is faulty, it needs to be repaired anyhow. And that probably means replacing the alt/reg, so why not with a larger unit? These days many vehicles have 120A and larger alts.
I know I am just expanding what you said, but some readers are like old keyboards - you have to punch the information in.
Welcome to the site!
bigtime_077 
Member - Posts: 20
Member spacespace
Joined: December 01, 2009
Posted: December 03, 2009 at 8:39 PM / IP Logged  

thanks for the welcome.  on what you replied i could not agree more.  i have installed quite a few car audio systems with good luck and you would not believe how many people would want to run the biggest baddest system and completely neglect the fact that the stock charging system of almost any vehicle is only about big enough to run what comes standard on that vehicle let alone a subsonic bass producing power hungry amp.  i always tell people the same thing.  you are only as strong as your weakest component.  you wouldn't build a mansion on a crumbled foundation would you

j.reed 
Copper - Posts: 716
Copper spacespace
Joined: January 05, 2009
Location: Arkansas, United States
Posted: December 03, 2009 at 9:19 PM / IP Logged  
The problem is not a weak alt(well it is but not because it is defective). The problem is, that it is the new BS type wind with onstar running through it. It sucks so much life out of the power it is making. You would be lucky to be able to run a 500rms mono block off it let alone the load you are trying to run. Getting a rewind is not going to get you much more output if any. the onstar regulates it output and a new alt is not possible to get unless from the factory. Even then there so called "OPTIONAL" H/O alt is the exact same part number as the none H/O. About the only thing that can be done is add an alt for a dedicated audio charging system. Simply removing the old one and replacing it with a regular style wind is not possible either. The onstar runs trough everything and is and regulates the alt. With out it able to pass through the alt it wont work. At least to my knowledge and the last time i talked to Dominic Iaggi. So other then adding an alt you are SOL at the moment.
voltage drop problem, what battery to buy? - Page 3 -- posted image.
still_walkin 
Silver - Posts: 644
Silver spacespace
Joined: April 18, 2007
Location: California, United States
Posted: December 04, 2009 at 7:59 AM / IP Logged  
M tech . I would listen to these guys they know what they are talking about trust me a bigger battery is gonna leave you stuck somewhere on the curb.I had a factory alt. 140a on a bigger the recommend battery 800/1000 and after having 3 amps and other junk wired to it the alt left me stuck and the car shut off. They do sell. Ho alts that fit your factory specs. Highoutputalternatorscom sells them they aren't cheap but they look like thwe orginal . You can also find a local shop in your area and they will make a custom oem fitted alt. no brackets or special belts. You can go on and on and not listen but doubling your big3 and swapping batteries is not going to solve your problem. The alt keeps the car running after the battery starts it.
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j.reed 
Copper - Posts: 716
Copper spacespace
Joined: January 05, 2009
Location: Arkansas, United States
Posted: December 04, 2009 at 3:13 PM / IP Logged  
Looks like Iraggi now has them as well In 3 flavors for a for a direct bolt up for a commander. 220A, 260A and 300A he has a store on the bay and and he is who I use for all my alts. Guess i need to call him about my 300c again.
voltage drop problem, what battery to buy? - Page 3 -- posted image.
michigan_tech 
Member - Posts: 32
Member spacespace
Joined: September 16, 2008
Location: Michigan, United States
Posted: December 04, 2009 at 3:52 PM / IP Logged  
So what is general consensus here? I got one guy saying that my car has something to do with OnStar and all the alternators in the world won't make a different. Then another guy says that the alternator will make the world of difference.
Which is the right answer?
Also for Dominick, how do I get ahold of him? Can someone PM me his information? Which other HO alternators can I get for this thing that are direct bolt ins? I haven't had any luck and the ones I have found have very low idle output.
Here is the lone exception (EXCEPT its for the Grand Cherokee, but I think that works for Commanders too):
http://www.dcpowerinc.com/alternators/jeep/2007-2010-jeep-grand-cherokee-4-7v8-260-amp-high-output-alternator.html
Its still extremely expensive though. I'd like to hear what Iraggi has available though.
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