Voltage Dropping

[rdlyn13000 10+ year member]

My buddy has a 1997 Cadillac STS, he's running 2-12" W7's on 2- JL 1000/1 amps. We upgraded the big 3 to zero gauge. We also have zero gauge running back to a battery in the back then 4 gauge to the amps. The second battery is a red top Optima, I know red top isnt meant for this but we had it laying around. As of right now the voltage is dropping to 11 when the bass hits according to the OEM volt meter on the cars cluster. We are also going to be adding a JL 450/4 soon but want to get this voltage issue figured out. If possible we would like to keep the stock alternator as its already vairly new. Is the Red top our issue? Would a good deep cycle battery do the trick for us? Any info appreciated thanks

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[timma100 10+ year member]

My buddy has a 1997 Cadillac STS, he's running 2-12" W7's on 2- JL 1000/1 amps. We upgraded the big 3 to zero gauge. We also have zero gauge running back to a battery in the back then 4 gauge to the amps. The second battery is a red top Optima, I know red top isnt meant for this but we had it laying around. As of right now the voltage is dropping to 11 when the bass hits according to the OEM volt meter on the cars cluster. We are also going to be adding a JL 450/4 soon but want to get this voltage issue figured out. If possible we would like to keep the stock alternator as its already vairly new. Is the Red top our issue? Would a good deep cycle battery do the trick for us? Any info appreciated thanks

Do you have the back and front batteries in full parallel? (2 runs of 0 to the trunk, one for neg and one for pos???)

 

[rdlyn13000 10+ year member]

no there is just 1 zero gauge wire going from the front battery to the rear then the rear battery is grounded in the trunk

 

[timma100 10+ year member]

no there is just 1 zero gauge wire going from the front battery to the rear then the rear battery is grounded in the trunk

From personal experience (not saying this is 100% the issue) but grounding a second battery to the frame is asking for voltage issues, no matter what it needs to create a full circuit with the front battery. So the voltage is using the car frame to get back to the front.. If you have the wire its the first thing I would try, it may not solve the issue but it will help.. a lot.. If that's not an option check the grounds.. I know everyone says that to every **** problem (ohh check ur grounds bro) just make sure that the rear batteries ground is well sanded and very solid, as well as the front battery frame ground. Also are the amps in full parallel with the back battery? (one for pos one for neg) or are the amps grounded to the frame as well

 

[rdlyn13000 10+ year member]

Amps are ground to the frame as well, I have some extra zero gauge I'll try running that and checking all grounds. Should I have the amps ground hooked to the negative on the battery?

 

[All_Logix 10+ year member]

It is true that you there may be some voltage drop due to the grounding of the second battery but 2 kW is pretty hefty for a stock alternator. Defently try running ground back to primary battery first but I am afraid due to the high number of electronics generally included in Cadillacs, you may just be overworking the electrical system

 

[timma100 10+ year member]

Amps are ground to the frame as well, I have some extra zero gauge I'll try running that and checking all grounds. Should I have the amps ground hooked to the negative on the battery?

It is true that you there may be some voltage drop due to the grounding of the second battery but 2 kW is pretty hefty for a stock alternator. Defently try running ground back to primary battery first but I am afraid due to the high number of electronics generally included in Cadillacs, you may just be overworking the electrical system

2K output is a lot of pull @ ~85% efficiency they are pulling 170 amps easy if your voltage could stay at 14V that is.. (not trying to talk ****, just numbers) Also definitively ground the amps to the rear battery.

Here is a ****** pic I snapped from one of my videos, the two batteries are grounded to the frame as well as being in full parallel with the front and amp

Edit, at 11 volts, if the amps are somehow still doing rated, they could pull 218 AMPs if amplifier efficiency is ~80%

Feel like I should add this, no matter how many batteries you have, if your alternator output is lower than your power draw, you will (eventually) drain the batteries

 

[bgowdy 5,000+ posts]

i was thinking the same thing. seeing that caddys have alot of electronics, plus your adding 2 jl 1000/1's thats probly why the voltage is is dipping so much

 

[rdlyn13000 10+ year member]

OK so we are going to add another strand of sero gauge from the front battery ground to the rear battery ground then gound both the amps to the rear battery negative. Hopefully this helps!! How about the Red Top Optima? Is that ok to use back there or is it not doing anything because its not a deep cycle?

 

[timma100 10+ year member]

OK so we are going to add another strand of sero gauge from the front battery ground to the rear battery ground then gound both the amps to the rear battery negative. Hopefully this helps!! How about the Red Top Optima? Is that ok to use back there or is it not doing anything because its not a deep cycle?

Having any battery will help, don't put all the blame on the red top but start looking for an upgrade, something from XS power, Kinetic, heck even some 12V UPS batteries are okay provided they are big enough.. Anyway, great plan with the wiring please update the thread and let us know how it goes!!!

 

[Chriszle 10+ year member]

Did you double check your voltage at the amp input with a DMM?

 

[rdlyn13000 10+ year member]

No I didn't double check at the amp, what's a DDM and how do I check?

 

[VisceralSound 10+ year member]

If you have not used a digital multimeter before your gains are most likely wrong.

 

[rdlyn13000 10+ year member]

Where do I hook up the multimeter? The speaker terminals or power/ground?

 

[Chriszle 10+ year member]

The power and the ground. Most likely the gains are set wrong as stated before. Listening to music, you will not ever see 1000 watts of output per amp. I would guess your amp draw right now is ~100amps for both.