Is it normal for amp to cut out at higher volumes when engine is off?

[rbtrucking 10+ year member]

Well today I installed a new headunit and just decided to further investigate something that has been an issue for years now but I never really addressed it as I am not quite sure if its an issue. I noticed that my subwoofer amp (memphis mcd1000) cuts out at higher volumes when the engine is off and I can see there are severe voltage drops because all the lights in the car dim like crazy but when the engine is running everything is fine. I am also running an amp for the comps which is a JD audio slash 300/2. The car is a Hyundai sonata 06 running an Optima Red Top battery but otherwise stock electrical. Stock alt and no big 3 done.

What are your thoughts, normal or should I be concerned?

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[n2audio 5,000+ posts]

It's not a surprise.

A typical alternator will generate 75-100A at around 14v at idle. Enough to keep your amps generally happy with a little voltage drop in response to high demand moments in the music at high volume.

With the engine off you're at 12.6v w/no load. Start to load the battery down and voltage will quickly drop below 12v, probably ~11 at higher volumes. At that point, one surge in current demand and voltage will drop even lower and the amp's low voltage protection will/should kick in.

I wouldn't call it a problem, but I would keep the volume down (better yet, powered off) with the engine off.

 

[rbtrucking 10+ year member]

It's not a surprise.A typical alternator will generate 75-100A at around 14v at idle. Enough to keep your amps generally happy with at little voltage drop in response to high demand moments in the music at high volume.

With the engine off you're at 12.6v w/no load. Start to load the battery down and voltage will quickly drop below 12v, probably ~11 at higher volumes. At that point, one surge in current demand and voltage will drop even lower and the low voltage protection will kick in.

I wouldn't call it a problem, but I would keep the volume down (better yet, powered off) with the engine off.

Thank you, I figured it was something like that.

 

[adulbrich 5,000+ posts]

Yeah, I don't play my system with my truck off. That's an easy way to damage things from low voltage

 

[Boomin_tahoe 5,000+ posts]

And kill your battery too.

Jumpstart ftl...

I wouldn't play the radio any more than 10-15 mins at best. Otherwise, you will need a jumpstart. I calculated mine to be 30 mins max before I needed to jump mine. Just keep your eye on the voltmeter on your instrument cluster.

 

[adulbrich 5,000+ posts]

Still, I don't recommend playing your system with the car off, especially if your amp is protecting from low voltage

 

[Boomin_tahoe 5,000+ posts]

If it was a must, that's what I would suggest, my last reply.

Otherwise, agreed. Don't do the car off thing.