Did Big 3, still dimming. HO alt or second battery?

[skogie1 10+ year member]

So I replaced the starter battery and did the big three and I still get voltage drops down to 12.5 when the bass hits hard. Current alt puts out 80a. Wire in a second deep cycle battery or upgrade to a HO alternator? I'm confident I can wire in another battery but replacing the alternator will be a learning curve I'm sure. Pros and cons? Thanks.

I drive a piece of crap Nissan Sentra 2004 that I have every intention of trading in as soon as I pay off the SUV my wife just absconded with. No idea what a HO alt costs for this car cuz I doubt many people have ever asked for one. I'm sure it's a lot more than a deep cycle battery.

Kenwood deck

Infinity 60w rms front

JL 60w rms rear

2 10" Kicker cvr comp subs

Kicker zx350.4 (rated at 453 according to the cert) for the speakers

Alpine mrp-m1000.1 for the subs. 2 ohms.

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[mylows10 5,000+ posts]

try an extra battery first

 

[skogie1 10+ year member]

Any thoughts on what I should look for in a second battery?

As far as I can tell....

Alpine amp is rated at 80% efficiency which means to run it at 1000w rms I need 1250w supplied.

Kicker is probably 70% efficient (can't find info) which means to run it at 240w rms I need 343w supplied.

Using 12v as a low output voltage and 14.4 as high that means I need a total amperage of 111-133.

My alternator is 80a. From what I can find, about 40% of the alternator's output goes to normal car needs leaving 60% for the stereo, or 48a.

This means that I need my battery system to supply 63-85 amps on demand. I'll up this requirement to an even 100 amps to give myself lots of room.

I have no idea what my starter battery supplies so I just want to make sure that my deep cycle battery covers this on it's own, or at least close to covers it alone.

Any thoughts, opinions, feedback, concerns??

 

[sexy 10+ year member]

Instead of guessing at what you need why not just check your voltage out and see what is going on. This way you can get exactly what you need without wasting money.

Get a digital voltmeter and watch it while you are listening to some music that you know will cause diming. If the voltage drops just a little and comes right back to normal you may add a second battery as kind of a band aid. What you really want is to have an alternator big enough to handle the load and not be trying to keep up with everything plus a second battery.

Ideally you should have one strong battery under the hood, have done the big three, and have an alternator that meets all the demands. If not then you will eventually destroy the alternator and will have to buy one anyways.

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