Zepo.

I have a problem with my battery draining. I have a power wire coming directly from the battery to a 1600 watt amp that probably only does 400 watts most of the time. The remote wire is connected to the + wire on the cigarette lighter. It's all grounded to the rear seat. Every time i start the car it seems to be mroe and more sluggish untill it fails, and when i turn the steering wheel or do anything else the lights seem to dimm even when not playing music. I've purchased a capacitor and am waiting for it to arrive. What could be causing this to happen? The amp does turn off when the cars off and none of these problems occured untill the amp was installed.

Jedi54

iTrader: (7)

I have a similar setup with my 1400 watt amp, only I grounded mine back to the battery and have a capacitor.
You're certain the amp is turning off?

are you running the stock battery? Are you sure your trunk is closing properly? That damn light can drain a battery quickly.

Zepo.

Yea its a stock battery. Light and amp are off for sure. Would not grounding it back to the battery be the problem?

Georgia8er

Sounds like you might just have a bad battery. The tiny stock battery didn't last long for me.

forbidden

I agree, the battery is 3 years old and has had lots of hard use on it, time for a new one.

arrexate

Not the best idea to run the ground wire back to the battery...the conductivity of the chassis of the vehicle is absolutely higher than that of a 14-20ft wire running all the way back under the hood.

Before you go purchasing new parts do a little basic troubleshooting...

Do you have access to a meter with an amperage setting? If so, remove the amp power fuse. Place the positive lead on the battery side and the negative on the terminal going toward the amp. If the meter reads any more than 150ma you have a current draw issue.

Also check the voltage across the battery with the vehicle running. At 2k rpms the voltage should read at least 14.0 volts...If not you might have a bad alternator.

If it does read at least 14v, check the ac voltage across the battery terminals...anything more than 300mv, would indicate a failing rectifier bridge.

Short of having a meter...I would say to isolate the amplifier as the offending component. To do so...pull out the fuse overnight. Does your issue continue? If yes its time to delve into your electrical system a bit further.

Any further questions feel free to axxxxxxxxxxe

Identify Isolate Elimate ftw!

beahs!

Zepo.

Well the capacitor reads 13.6 and then to 13.7 then to 13.6 with the music off. With the music on low on low it goes to 13.4 then back up then down and up. This leads me to believe that the voltage going there is correct right? Across the battery terminals on 1000v setting it reads 14-15 with the car idling and 12-14 with it off.

arrexate

sounds like a good alternator...check the current draw

Zepo.

Sorry to be a noob but how do you do that?

Silver06

The easiest way to check for current draw with all power off is to disconnect the positive battery terminal and hook up a multimeter:

1. switch meter to dc amps.

2. Place one lead on the + battery terminal

3. Place the other lead on the battery cable you disconnected.

4. As long as the meter doesn't read off-scale, switch the range to DC mili-amps and read.

If you are seeing a draw in the AMPS range, then don't switch to the mili-amps range, or you will fry your meter!

Note that there is always some draw: the clock, radio pre-sets, ecu memory, etc. I've never tested a RX-8, but usually these total less than about 200 mili-amps.

Now, if there is significant draw, go next to your CAP and remove the positive wire. Bridge the connection between the wire going to the cap and the input for the amp (ie, taking the cap out of the circuit).

Your amp manual should tell you what the amp should draw while it's 'off'. check this against your values. Then, check the cap, then check anything else.


arrexate has great advice: Identify Isolate Elimate ftw!


Good luck!

Zepo.

Hah thanks checking now.
Well between the two it slowly raises until about 10.9 volts, but could the capacitor filling right?

Zepo.

Ok heres another analysis i did.
I charged the battery until the capacitor shows 13.7 started the car played some music whatever for 5 mins the capacitor showed a constant 13.7. Once i turned the car off it dropped to 12.3. Bad battery?

Georgia8er

You should be measuring current draw in mA (milliamps), if that is what you are trying to test.

arrexate

not at all...the alternator has to maintain a voltage higher than the battery while the vehicle is running in order to to charge it. when the alternator is no longer running (when the vehicle is off) the battery will show approx 12v

Zepo.

Well i replaced the battery because it was old anyways. We'll see if it goes dead now.