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Discussion Starter #1
A friend of mine gave me a digital voltmeter today, I went to my truck battery and did a test. The reading came out to 12.99/13.04V with my truck turned off. I turned my truck on, it read out to about 13.40/50 or so.

Additions I have done:
- Hifonics 4 ch. amp (set to 2 ch), bridged ch. sets to a pair of Zeus HZ 10"
4ohm svc subs.

- Big 3 upgrade using 4g wiring only

did I do something wrong? why is my battery reading that output? do I need to put in a better battery/alt? Both battery and alt. are stock (right off the dealership lot parts).
 

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battery voltage with engine off should be 12.5 - 13 volts, so nothing wrong there.

alot of alternators dont put out full current or voltage at idle. increase the idle to 2000rpm and test again, I bet it is higher.

if your battery is not going dead and you dont put it on a charger to keep it running, then everything is fine.
 

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Discussion Starter #3
oh, damn lol don't I feel dumb. Follow up question:
My lights are dimming, should I upgrade from 4g to 0g for the big three or will that still be the same outcome? I can see all my instrument lights flickering here and there when the bass hits, but it's only certain bass.
 

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Your 4 gauge wire should be fine for your setup. Upgrading a battery will not help with dimming lights either. Does your battery have a good clean ground to the chassis? Where is your amp grounded at? How old is your alternator?
 

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"Upgrading a battery will not help with dimming lights either." THAT IS FALSE! AGM battery would make a HUGE difference, hell even a new battery would be better then a used one that is ready for the pile!

First we need to know the size of alternator, power wire size and company, and the amps your running.
 

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Discussion Starter #6
For my alternator, it is stock (2007 tacoma base model 2.7l). I have 4g wiring for the big three upgrade (I grounded the engine and the battery to the side of the fender where the OE ground was close to, got a bolt to fit into the fender and engine block). For my amp wiring I am using also 4g wiring for power/grnd (ground for this is the side of the door sill, under the panel that has some wire through it, don't know the name). My amplifier is a Hifonics ZXi 6410 set to 2 channel mode. I plan on running another amp for the mids/highs but not happening anytime soon.
 

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I'll just check the wirings first, before I do something more stupid later on.... Sometimes upgrading the power cables for amps may affect the connection to the lights...
That's why the original wirings on power and ground I won't touch but I lay another run of power cable from amp's -ve to battery... Some extra cost maybe, but then I don't have lights dimming issue....
 

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"Upgrading a battery will not help with dimming lights either." THAT IS FALSE! AGM battery would make a HUGE difference, hell even a new battery would be better then a used one that is ready for the pile!

First we need to know the size of alternator, power wire size and company, and the amps your running.
You are wrong. With a functional alternator charging at anything above +13v a battery sitting at 12v is doing nothing but charging. If the engine was off then the battery will be powering the electrical demands of the vehicle and accessories. When the engine is on an alternator powers the vehicle's electrical demands and accessories. Unless the alternator can not supply those electrical demands and once voltage drops to the resting voltage of the battery, then the battery supplies those electrical demands.

Case in point. I have a 90amp stock alt. XS Power D3400 as a factory battery replacement. 1/0 electrical wires throughout. I have a 1000wrms system. My headlights always dim during high electrical demands. The puny 90amp alt isnt enough.

 

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"Upgrading a battery will not help with dimming lights either." THAT IS FALSE! AGM battery would make a HUGE difference, hell even a new battery would be better then a used one that is ready for the pile!

First we need to know the size of alternator, power wire size and company, and the amps your running.
no it is not false, to a point. if your alternator is not producing enough current, then it will pull alternator voltage (13.8-14.4V) down to battery voltage(12.volts). if the battery is in good shape, then that is as far as your voltage will dip for the whole electrical system. if the battery is not so good, it may pull down more.

long story short. if you are seeing dimming lights, then you have 2 choices.
1) fix it right with an alternator that can keep up.
2) add a 1 farad cap to bridge the gap between bass hits. this will dampen the light flicker effect but will in NO WAY, fix the problem. you are still not producing enough current and you will do damage to the alternator eventually.
 

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Discussion Starter #11
You are wrong. With a functional alternator charging at anything above +13v a battery sitting at 12v is doing nothing but charging. If the engine was off then the battery will be powering the electrical demands of the vehicle and accessories. When the engine is on an alternator powers the vehicle's electrical demands and accessories. Unless the alternator can not supply those electrical demands and once voltage drops to the resting voltage of the battery, then the battery supplies those electrical demands.

Case in point. I have a 90amp stock alt. XS Power D3400 as a factory battery replacement. 1/0 electrical wires throughout. I have a 1000wrms system. My headlights always dim during high electrical demands. The puny 90amp alt isnt enough.


damn that math part is gets kind of confusing after a while. :confused: I do get what the guy in the video is saying though. will have to figured out all the math to determine what I need to upgrade as far as my system requirements.

on the math part I got as far as finding out what the amp needs - 74a
after that I got confused on what to do.

"Case in point. I have a 90amp stock alt. XS Power D3400 as a factory battery replacement. 1/0 electrical wires throughout. I have a 1000wrms system. My headlights always dim during high electrical demands. The puny 90amp alt isnt enough."

That kind of sucks, all that and your lights are still dimming.
 

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Discussion Starter #12
no it is not false, to a point. if your alternator is not producing enough current, then it will pull alternator voltage (13.8-14.4V) down to battery voltage(12.volts). if the battery is in good shape, then that is as far as your voltage will dip for the whole electrical system. if the battery is not so good, it may pull down more.

long story short. if you are seeing dimming lights, then you have 2 choices.
1) fix it right with an alternator that can keep up.
2) add a 1 farad cap to bridge the gap between bass hits. this will dampen the light flicker effect but will in NO WAY, fix the problem. you are still not producing enough current and you will do damage to the alternator eventually.
so my best bet would be to upgrade my OE alternator to one that can do higher ratings (or at least enough for the amp(s) I am putting in)?
 

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Discussion Starter #13
also, did the big 3 upgrade I do even work? I'm supposed to be getting close to 14.4v right? Is it the grounding on the fender? The shock tower is close enough for me to get to with the wires, would it be better if I used that for the big 3 grnd? I am also thinking of taking off my grnd wire that I have on now and making it longer so that I grnd straight to the frame. - would any of this benefit or be a downfall? I don't think I will be getting a new alt./batt any time soon :(
 

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so my best bet would be to upgrade my OE alternator to one that can do higher ratings (or at least enough for the amp(s) I am putting in)?
short anwser, "yes" :D

long answer:

good basic rule of thumb. take your stock alternator and multiply by 75%, that is how much current your vehicle needs to operate (worst case)

so if you have 100 amp alternator then you will need 75 amps just for the vehicle. this leaves 25 amps for other stuff. of course this will not be the case all the time. if your headlights are not on and the blower fan is not on high, etc ,etc. you will pull less. but always best to err on the side of safety.

for amplifiers, take the rated wattage output and multiply by the system voltage, then multiply that by efficiency.

EX: 1000 watt amplifier in a 14.4V car. 1000watts @ 14.4V is 69amps. take into account that most class "D" are about 85% efficient and it will pull 81 amps. if it is a class "A/B" then it will be closer to 65% efficient and you will pull 106amps. will it pull that much all the time? of course not. you can divide that by 10 for most music listening, but you have to consider that it could pull that much.
 

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also, did the big 3 upgrade I do even work? I'm supposed to be getting close to 14.4v right? Is it the grounding on the fender? The shock tower is close enough for me to get to with the wires, would it be better if I used that for the big 3 grnd? I am also thinking of taking off my grnd wire that I have on now and making it longer so that I grnd straight to the frame. - would any of this benefit or be a downfall? I don't think I will be getting a new alt./batt any time soon :(
maybe, if your alternator is regulated to 13.8V, then no. you wont ;)
 

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Discussion Starter #17
short anwser, "yes" :D

long answer:

good basic rule of thumb. take your stock alternator and multiply by 75%, that is how much current your vehicle needs to operate (worst case)

so if you have 100 amp alternator then you will need 75 amps just for the vehicle. this leaves 25 amps for other stuff. of course this will not be the case all the time. if your headlights are not on and the blower fan is not on high, etc ,etc. you will pull less. but always best to err on the side of safety.

for amplifiers, take the rated wattage output and multiply by the system voltage, then multiply that by efficiency.

EX: 1000 watt amplifier in a 14.4V car. 1000watts @ 14.4V is 69amps. take into account that most class "D" are about 85% efficient and it will pull 81 amps. if it is a class "A/B" then it will be closer to 65% efficient and you will pull 106amps. will it pull that much all the time? of course not. you can divide that by 10 for most music listening, but you have to consider that it could pull that much.
I know the amp is an A/B type. that's for sure, GAH!! :mean: I really suck at math. going to give it a go and see what I come up with, if it's completely off ... I'm going to have to do a spec run and see if anyone can do the math for me lol

maybe, if your alternator is regulated to 13.8V, then no. you wont ;)
lol damn going to have to run some tests again.
 

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I know what I'm talking about.

Say you have a 90 amp alt and a 80 amp CONSTANT load. Bass hits, needs 120 amps, were will it get it from? Battery. Oh your battery is $#*!. Touch luck, your lights dime and your car hates you. See, that is why a battery is just as important as your alternator. But it will never replace it.

Note: you need a reserve, ANY electrical power system does. Hell go get one and be amazed what it will do for your car and how it will save your alt! NOTHING in your car can handle any upgraded audio that we want and ALL of it must be addressed, even the battery!
 

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that is my point.......if you have a 120 amp draw and 90 amp alternator. your battery will go dead. dosent matter what battery you have. your alternator has to be up the task.
 

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Indeed and most are within reason.
 
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