Suggestions for reducing vd

2023 LTZ

CarAudio.com Recruit
51
21
USA
I’ve been experiencing what I’ll call voltage drop. I have 0ga from the alternator to battery then from battery to a 150a fuse then the same 0ga back to an inline fuse of 100 and 200 for a fosgate t400 and t1500. The door components are focal and take 75w some hertz tweets and 6x9 focals take maybe 90-100w and kept the oe 3.5” bose on back deck. This is in an impala limited v6. I’ve had several new interstate batteries replaced on warranty bc it seems my car kills them. I have a 240 alternator and a substantial ground in the trunk of 0ga to the chassis behind the backseat. It is sanded to bare metal and bolted, 0ga from alternator to battery and oe ground from battery to chassis behind headlight which was 4 aught but since reduced to 4ga. The charge system has a sensor of sorts on the negative wire that goes to to battery. This is from alternator to battery. I believe having that 4 aught or 0000ga allowed too much ground that was undetected by this sensor thing which caused over charging. Changing back to 4ga and the original design of 0ga seemed to correct this. I’m able to play heavy bass stuff that while driving will drop voltage to the 11s or 12.1 but briefly. It usually hangs at 13.8-14 or so.

I have something called maestro which has cool features one of which is a voltometer which I consider very helpful.
A previous and very similar setup but a bit less power hungry seemed to do the same thing. Sitting w vehicle running I played some tunes for a friend and fried a cell in the interstate agm group 34. Those guys won’t honor anymore warranty returns.
Is it possible this system is killing these batteries and is it also possible the alternator or alternators in general aren’t capable of keeping up w the varying demands of a high output setup such as this? Am I missing something obvious?
Any questions welcomed.
 

Water Bear

Senior VIP Member
265
33
Atlanta, GA
11.9 is something like 40% battery charge for a 12V battery. That's pretty hard on them. If you drop there gradually over a song then you need an extra battery. If you drop there in a sudden spike then you need an ultracap. In both cases, get something good like XS or Ioxus. That's my guess.

240A alt is probably good enough for 2k watts or so. It's possible those Rockfords are underrated and you're actually getting much more than that wattage.
 

winkychevelle

CarAudio.com Veteran
10+ year member
4,542
473
Ponchatoula, La
First off if you are running real 1/0 wire replace the under hood fuse with a 300amp

Second throw a headway or any other lifepo4 bank in the trunk at least 32ah worth. It may be possible to bypass the oem voltage regulation. Diy you can build a 32ah bank for fairly cheap.

If you are using flooded cells and not agm that's a problem.
 
OP
2

2023 LTZ

CarAudio.com Recruit
51
21
USA
The bit I’ve been finding online seems to center around the idea that a second battery is no more than extra load on the alternator. I was hoping that it’d act more like a cushion or buffer in those dropping points. What I’m hearing from y’all is that would be the case?

I did go backwards from agm to flooded.
So 2 high capacity or ah agms could reduce this drop and flatten the load for that alternator?
It is ofc 0ga. That 150 fuse is just inline I have fused distribution right before the amps one 0 to two 4ga and the recommended 100a to the 400w and a 200 to the 1500. They’re at 2ohm.

what’s an ultracap?
I’ll look it up.

I appreciate the quick thoughts on my issue.
 

winkychevelle

CarAudio.com Veteran
10+ year member
4,542
473
Ponchatoula, La
The bit I’ve been finding online seems to center around the idea that a second battery is no more than extra load on the alternator. I was hoping that it’d act more like a cushion or buffer in those dropping points. What I’m hearing from y’all is that would be the case?

I did go backwards from agm to flooded.
So 2 high capacity or ah agms could reduce this drop and flatten the load for that alternator?
It is ofc 0ga. That 150 fuse is just inline I have fused distribution right before the amps one 0 to two 4ga and the recommended 100a to the 400w and a 200 to the 1500. They’re at 2ohm.

what’s an ultracap?
I’ll look it up.

I appreciate the quick thoughts on my issue.

Batteries to act like a buffer with transient music. After long bass lines year they are just another load on an alt but most music is not really long bass lines.

Again whatever the fuse is under the hood from the front to rear it should be 300amp for the 1/0 wire. You fuse for the wire. You have a potential amp draw over 150amps on that wire. This wire result in 1 blown fuse or 2 a melted fuse holder if not fixed.


The fused distribution block should be fused for the amplifier amp draw.

Ultracaps/supercaps are just stupid powerful capacitors and are a good addition but until you get you alt to continuously charge at 14.4 your pissing in the wind. It needs to bypass the pcm control unless the alt is charging your just running off of battery power.

unplugging the sensor on the ground lead will default it to 13.8v but it will set a battery light on the dash

Flooded cells are terrible for anything nowadays and agms should be the standard unless you really can't afford anything else.
 

Water Bear

Senior VIP Member
265
33
Atlanta, GA
The bit I’ve been finding online seems to center around the idea that a second battery is no more than extra load on the alternator. I was hoping that it’d act more like a cushion or buffer in those dropping points. What I’m hearing from y’all is that would be the case?

I did go backwards from agm to flooded.
So 2 high capacity or ah agms could reduce this drop and flatten the load for that alternator?
It is ofc 0ga. That 150 fuse is just inline I have fused distribution right before the amps one 0 to two 4ga and the recommended 100a to the 400w and a 200 to the 1500. They’re at 2ohm.

what’s an ultracap?
I’ll look it up.

I appreciate the quick thoughts on my issue.

The rough idea: batteries add capacity (so after a song you'll be at, say, 13v instead of 11.9) but they aren't great at delivering high amperage current. Capacitors are the other way around. They don't have much reserve but they can deliver very high current without being damaged.

You do need to fix your fuses. If both amps draw just below their max rates capacity then all that current has to come through one wire at the battery and that fuse will pop.

Is your alternator not charging properly? I missed that.
 

winkychevelle

CarAudio.com Veteran
10+ year member
4,542
473
Ponchatoula, La
The rough idea: batteries add capacity (so after a song you'll be at, say, 13v instead of 11.9) but they aren't great at delivering high amperage current. Capacitors are the other way around. They don't have much reserve but they can deliver very high current without being damaged.

You do need to fix your fuses. If both amps draw just below their max rates capacity then all that current has to come through one wire at the battery and that fuse will pop.

Is your alternator not charging properly? I missed that.

His alt shuts off to save fuel. Most cars these days do that to some extent. Gm and Honda are probably the worse offenders though.

And agm and flooded cells are low c rate batts but you can get lifepo4 and lto with anywhere from 1c -75c discharge and charge rates which are leaps and bounds faster than agm and flooded cells.

Ultracaps are still faster but even at there immense size dont have much internal reserve and should be combined with a battery system preferably lto
 

audiobaun

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Change that 150 amp fuse to a 300 as stated. Have you done the Big3? Not clear on that. Get the largest AGM to fit under the hood
 

winkychevelle

CarAudio.com Veteran
10+ year member
4,542
473
Ponchatoula, La
Change that 150 amp fuse to a 300 as stated. Have you done the Big3? Not clear on that. Get the largest AGM to fit under the hood

From what I've read he said the big 3 ground run was messing with the factory alts voltage regulation. The shunt on the ground wasn't reading right or something.

Other than that he appears to have the batt to alt run and tried the batt to frame. No batt to engine though
 
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some dude

CarAudio.com Regular
242
131
Virginia
I have a 2500w and a 300w amp and I've been running them with a 60 amp fuse for over a year. I'm kinda surprised it hasn't popped yet. I guess I'm not really using their potential?
 
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audiobaun

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I have a 2500w and a 300w amp and I've been running them with a 60 amp fuse for over a year. I'm kinda surprised it hasn't popped yet. I guess I'm not really using their potential?
LOL...Dayuuum!!!
 
OP
2

2023 LTZ

CarAudio.com Recruit
51
21
USA
I have added a ground as per alternator manufacturer instructions. This goes from battery to alternator bolt which secures it to engine. I also added a custom fitted piece from an empty threaded hole on the bottom of the block to its aluminum engine cradle. I had disconnected that at one point to rule it out as my problem. I have done big 7 but dialed that back to 5 as feeding my under hood fuse block w 0ga was part of the things I eliminated to reduce the wild sporadic charging.
Deleted 4/0 from alt to battery and 4/0 from battery to chassis. Then back to 0 from alternator and regular 4ga to original ground on chassis and 4 ga feeding fuse block. Those were considerably smaller than 4ga originally. The ground that’s measured by the sensor is from alternator bolt to battery along w original ground from starter.
Ive found that having the fan on high seems to ask for more power from alternator which definitely reduces the dips below 13v
I’ll get a 300 coming for the first fuse. The 100 abd 200 are what rf states are needed. a small oversight on my part is the subs each take 800w and are wired to 2ohm this is almost a perfect match for the amp which was rated at 1760 @2 ohms.

I know there’s a lot going on in those pics but if looked at closely, it’s a solid upgrade.
13C43DBE-9988-4F9A-9019-C663153D7A5F.jpeg
41DB6F1A-6517-4DE9-9C02-63E744888044.jpeg
 
OP
2

2023 LTZ

CarAudio.com Recruit
51
21
USA
Another question; if on that splitter/ distribution fuse block consisting of a 100 and a 200 amp fuse will one 300 upstream be well enough or should I get a 350?
 

Water Bear

Senior VIP Member
265
33
Atlanta, GA
Another question; if on that splitter/ distribution fuse block consisting of a 100 and a 200 amp fuse will one 300 upstream be well enough or should I get a 350?

You don't really need the upstream 300 honestly but if you're going to fuse it 300 is the right number. The upstream protects you in the instance that the cable pops out of your distribution block and touches metal.

If turning the fan off helps, your electrical is definitely overloaded. For the wattage you have more battery and more alt is called for. Assuming your car won't agree with us about a new alt, more battery is the way to go here. Lithium is the best solution but is the most expensive (assuming you want a COTS solution) and you need to ensure that your voltage is within spec at all times.
 

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