Hooking up aftermarket stereo to Battery

Hate to bust your bubble but most high power amps are wired directly to the battery ans have constant voltage applied. Now, when the audio system is off, there is minimal draw off the battery - say less than 0.1 amps. I'm thinking your amp may be drawing more than 0.1A static current or your normal playback is pulling the battery down faster than the inverter can keep it charged. For example, if you have a 500W amp that will draw nearly 40amps from the battery and the inverter is setup to push what the car will typically draw, say 25amps, then you're going to suck the battery down every time.

 

There are probably 3 power wires

Yellow wire (usually labeled Batt.) Is the battery wire goes directly to the + positive on the 12V Aux (starter) battery. This wire also supplies power to the radio when vehicle is off to store station presets, settings, and the clock.

Red Wire (sometimes Orange) (usually labeled as Acc.) There are several ways to hook this wire up, anyway you decide it Needs to go to a power lead that turns off when the car is turned off. I would probably connect it to one of the 12V car lighter plugs if I wasn't using the factory radio wiring.

Black wire is the Negative Ground. (usually labeled as ground or -) This wire needs to be bolted to a piece of metal attached to the chassis of the car, if you are unable to find a suitable spot run a wire of the same guage (thickness) as the power wires to the negative terminal of your battery (I prefer the spot where the battery bolts to the car usually about 6 inches or so from the battery on most cars.

The amp also has three wires
The Amp needs to be connected
12v+ directly connected to the positive on the 12v positive on the battery
Ground 12v- directly to the 12v Negative on the battery
Remote wire to the Blue remote wire on the back of the radio, (if you do not have this connect it to the same wire you used for your Accessory (red wire) when hooking up your radio

 

Yes, because the radio will turn off if the car is turned off. If the car is on and you power off the radio it would also turn off the amp.

Are you using an aftermarket in dash radio radio.

 

Not too much you can do. The typical alternator in a non-Prius has the capability to push out up to 80-100A for brief periods of time. I don't know the spec on the inverter charging the 12V battery, but I would suspect is was setup for the typical 12V load in the car - and that would be a worst-case scenario: headlights on, wipers running, A/C blower motor on high, and you're stopped at a light with your foot on the brakes. I would guess the number to be around 20-30A.

Now consider your high power amp may peak at 42-45amps at the loudest passages with the audio cranked all the way up, its average is likely pulling 20-25A continuously off the battery.

Your solution: keep the audio down to a reasonable level or parallel the Pri battery with a larger capacity one.

Footnote: constantly sucking any battery down to where you've got to put it on a charger to bring it back up will shorten its life.

 

stock radio changes quite a bit of what I posted above.
Completely ignore it, it was for a head unit and amp.

Here is what you want to do, and this is how I have my amp set up. Its a 4 channel 600W RMS amp, I transplanted it myself over a year and a half ago (about 35,000 miles ago) and have never once had to get jumped.

12v+ Needs to go directly to the 12v + Positive of the battery, (make sure you have a 30A fuse in this power line closer to the battery is preferred and a nice thick guage of wire that will match the power demands of your amp)

the Ground (Negative 12v-) I chose to connect mine right next to the small Auxillary battery where the negative cable from the battery connects to the chassis of the car.

the remote turn on (this is where you are killing your battery)
this needs to connect to something that turns off when you turn off the car. I connected mine directly to the fuse box, initially I was going to use the car lighters, but ended up choosing to connect to the fuse for the rear wiper. (they sell in autoparts stores a fuse that has a wire coming out that makes this easy)

 

The Prius 12 volt battery is charged by a dc-dc converter that takes the traction battery voltage of approximately 200 volts dc and converts it to about 14 volts dc which keeps the 12 volt battery charged and also runs all the 12 volt equipment in the car. The Prius in ready mode will keep the traction battery and 12 volt battery fully charged automatically as long as you have gas in the tank. According to this thread the dc dc converter in the Prius should be able to output about 75 amps at 12 volts for a total capacity of 12*75 = 900 watts:

http://priuschat.com/forums/prius-technical-discussion/54601-dc-dc-converter-output-limit.html

If you only run your amplifier/equipment when the car is in the ready mode and it requires less than say 50 amps, the dc-dc converter should be able to run your equipment, the car, and still charge the 12 volt battery. In the ready mode you will be running your equipment and the 12 volt equipment in the car off the power provided by the dc-dc converter.

As was stated before you will have to make sure the amplifier is really off and not drawing any current when you turn off the car and leave the ready mode. Additionally you cannot run the car in accessory or ign on mode for very long if your amplifier is on as the Prius dc dc converter doesn't operate in these modes. In these modes the Prius is running completely off the 12 volt battery which as you have discovered, has a pretty small energy capacity.

If you mean an audio capacitor is a capacitor placed across the 12 volt input to your equipment, such a capacitor will limit the current peaks drawn from your 12 volt system, but will not change the energy available from the battery. In other words your equipment will still run down the battery just as fast if you're not running in the ready mode.

And as stated above, fuse your wiring at the 12 volt source (battery) and run your power wiring directly to the battery through that fuse.

 

Try an Optima battery, which is made for deep discharges and matches the Prius charging system perfectly.

12 Volt (12v) Toyota Prius Auxilary Battery for 2004, 2005, 2006, 2007, 2008 and 2009 with free shipping

 

BubbaVO, as others have stated above, adding a cpacaitor will not change anything. The capacitor might provide for an increase in instantaneous surges but it will do nothing for the long run. Remember, those 45A you're pulling for your amp has to come from somewhere, and that is your battery.

Others above have provided some very good input. If you can get ahold of an ammeter from someone, try to measure the current draw from both of your amp inputs: 12V main and 12V remote. NOTE: If you've wired the 12 remote directly to the battery, then your amp is on all the time and don't try to measure the 12V main or you'll likely blow the ammeter. Disconnect the 12V remote BEFORE you measure the 12V main.

Good luck and keep us posted here of your findings.

 

They have given you good advice.

You shouldn't be having charging issues even with a "large" amplifier (which yours is not). I've had 2 amplifiers hooked up for some time now and never had an issue pop up althought I cannot verify the life expectancy change due to such large current draw on the 12v battery and the associated components used to keep it charged.

My amplifers have a max current draw of:

Diamond Audio D61500.1 1500w rms (160amps)
Diamond Audio D9800.2 400w rms (80amps)

It is doubtful the Prius system can supply the current I need to run these amps correctly but everything sounds great, the system runs at an appropriate temperature, the headlights don't dim (lol), and I've had no issues with the car. Does that mean I will never have a problem? Who knows.

 

Using low profile fuse splitter, can you put fuse box cap back on?

I drive a Gen 2, it doesn’t look like I can put the lid back on