Since upgrading to 2 amp-powered Polks (200W RMS) my alternator can't keep the battery charged. When I go for long drives (blasting the stereo the whole way) and then park the car for more than 2 days, the battery will be dead. Is this normal?

At first I thought the battery was weak so I bought a new one. Same problem. Now I drive the car for at least 30 minutes with the stereo off before parking it. This keeps the battery alive.

 

sounds like something else. there are plenty of others in s2000's as well as other cars with smaller alternators running more than 200w. you might want to put a meter on the battery, check voltage. then see what it is when the car is running.

 

Do you have your amp remote hooked up properly?

 

I measured the voltages and they seem normal (13.4 at idle). The remote is fine.

 

you might have a parasitic drain some where, may not even be related to the sound system. you can do a simple test by placing a test light between the battery and ground cable.

 

I've got, just found out about this POS from the PO, an Xterminator XT1600.4 which claims to run 450Wx2 @4ohm and I have no battery issues. Then again, this AMP totally sucks and I can't vouch for the claimed RMS. Might be more like 20W

 

The problem only started after I installed the system. I do need to re-measure the ground though; IIRC it's almost 1 ohm. Could that cause the amp to work harder than it's supposed to? It does run rather hot.

My amp is a Kenwood KAC-7205 (170x2 @4) but my speakers only draw 100W each. Does that mean I have a 200W system or a 340W system? Either way I don't think I should have a problem.

 

your speakers are rated for 100w. that's not a measurement of what they draw.

if the amp is 170 rms@ 4ohms then it's putting out 170 watts. the only way you change that is either by changing the resistance or voltage.

pull the fuse up front and drive normally. see if it still happens. maybe it's just your battery's time to go.

 

On second thought you may be right. I discovered tonight that my map light was actually in the ON position, it just isn't emitting light for some reason. I'm not sure how long it's been that way. The lights work in DOOR and individual modes though, why is that?

Thanks for the knowledge, makes sense. The battery is brand new.

 

if you really think that the sound system is causing it i would disconnect the system to see if it has any effect. you can also try to diagnose the problem with a multimeter(if the drain isnt strong enough to light a test light) to measure amperage draw between the battery negative and ground like with test light. if you do see an amperage draw then 1 by 1 pull fuses from the fuse box til you the amperage draw disappear then youve pin pointed battery drain is coming from.