Adding an amp on a Prius: must it have voltage regulation?

Re: Adding an amp on a Prius: must it have voltage regulatio

Gary,

When I have a chance (if someone doesn't post it first), I'll check out the voltage readings over the course of the ICE turning on and off.

I know nill about this stuff but isn't the draw that the amp imparts on the battery fairly low unless the stereo is really cranked up loud? I can do a test on my newly installed amp and see.

Also, just to throw this out, when in the store purchasing my new speakers and amp, I noticed that Monster sells a capacitor to put in line between the battery and the amp to assist when the amp requires peak power. Would this help?

To answer your question in bold at the beginning of your post, I haven't noticed any change in sound level in my system but I'll listen closer to it in over the next couple of days. I do play my system relatively low on the volume scale. BTW, my amp is hooked up directly to the battery...

Cheers,
-bob

 

Re: Adding an amp on a Prius: must it have voltage regulatio

Following is the spec about DC-DC converter from Toyota Tech Manual.

input voltage: 168-300V
output voltage: 14V
output amp.: 100A max

The output voltage is very consistent and no relation with ICE running in READY mode.
In ACC or IG-ON mode, the voltage is raw 12V and battery never been charged.

Regards,
Ken@Japan

 

Re: Adding an amp on a Prius: must it have voltage regulatio

Hi again Gary,

I installed the system myself.

The remote turn on for the amp comes from tying into the wire that supplies power to the OEM head unit when the power button is pressed on(ACC mode). I was following your thread earlier about tying into the antenna amp and from that, this seemed to be the best solution.

Yes, my beep volume did increase. There was an earlier post in this forum about that happening. One poster sugggested that the owner go back to the installer and they could easily remedy this by altering the freq. cutoff (I think) on the amp. No specifics were given, tho. The person did this and it took care of the loud beeps. I'll have to post this question so someone can fill me in on what I need to tweak.

-bob

 

You would have more power fluctuations caused by too much resistance in the feed wires from your power source to your amp, than at the power source itself. The capacitors or secondary batteries are usually to accomodate the amp's large but fluctuating draws than the power source fluctuation.

Ken, I'd like to know where you got your info. The DC/DC output is fused at 100A, and it seems Toyota providea aprox. 20% margin between max draw and fuse value. For example, outlet is rated 120 watts or 10A, yet it has a 15A fuse. Typically alternators output 80A, and I have seen that figure someplaces, though I can't remember where.

ICE wouldn't be a factor, as it is started using the HV battery, as the other motor is. There is no alternator providing 12V charge current like conventional cars, it is done in the inverter using the HV battery coverted down to 12V using a switching power supply cirucuit.

 

Re: Adding an amp on a Prius: must it have voltage regulatio

READY: 14V
ACC: 12V
IG-ON: 12V

Regards,
Ken@Japan

 

The spec is came from Toyota Tech Manual CDROM for NHW-20 Prius (P/N 7A04700).
It contains Theory of Operation, Service info and wiring. It's all written in Japanese.

Again, the output spec of the DC-DC converter is 100A max. no matter how much rated fuse is installed.

Regards,
Ken@Japan

 

Re: Adding an amp on a Prius: must it have voltage regulatio

Gary,

Here's my voltage numbers which equate to Ken's. These are from putting the meter right on the battery:

Car is off: 12.4v
in ACC mode: 12.4v
Ig-on: 12.4v
Ready mode, ICE off: 14.0v
ICE on: 14.0v

These are one time readings, so who knows what happens over the course of a daily drive but as per Danman's comments, I would suspect that the voltage is pretty well regulated and maintained. I've intently listened to the stereo system that last couple of days and there's no fluctuations/degradation from potential voltage fluctuations, which was your initial concern.

Also, with regards to draw on the battery from the amp, I cranked my stereo up to 65 and the voltage reading didn't budge From an electrical engineering friend, he said that car amps really don't draw much unless one is playing at ear splitting levels or driving huge subwoofers. He went on to admonish me about getting sucked into the marketing scheme that one has to upgrade the OEM speaker wire because they can't handle the load and using 8 gauge wire for the amp... Something about Ohm's law and how little wattage is really going through these wires...

As for your other questions, the power for the amp is coming directly from the battery. As Danman and my friend stated, this provides for clean power to the amp and is not affected by other loads turning on and off if the amp was powered from elsewhere in the car.

The turn on for the amp comes from the ACC ON wire heading into the OEM head. Yes, the radio really does have to be taken out, as per Jon at PriusXM's instructions, to get to this wire. I'm sure someone else could easily find this wire elsewhere inside the car (OK, it's at Junction Connector J19) but since I had the radio out, it was already accessible. It's the only Gray wire coming out of the OEM radio (Standard radio)...

As for the louder beeps, again from my friend, any tweaking of the frequencies at the amplifier will degrade the sounds coming from the speakers. More on that later....

Hope this helps!

Cheers,

-bob

 

I think one has to go as crazy as 8 guage wire, but wire guage needed is not a direct function of watts, but of amps. Watts is a function of amps*Volts. Amps is also a function of volts/ohms. So if you have low ohm speakers, you just might need thicker wires for higher wattage output so that you don't lose all your power in the natural resistance of the wire.