Amplifier installation question..

Yes, yes you are lol ..BUT it's a cool idea.

Can you provide some detail around the statement "I want to keep my current draw on my 12v system under 40a"? How was this determined and what "system" are you referring to? The radio circuit or the entire Prius electrical system?

I ask because like you I am looking at upgrading by adding a subwoofer and I keep seeing "Don't use more than 30A for a subwoofer. " In fact most recommended amps in the size and power i am looking at come with a 30A or smaller fuse. So this would be a "Don't exceed 30A additional draw on the cars electrical system and not a TOTAL car system power use.

 

The OEM JBL upgrade (which AFAIK makes no changes to the power delivery) is rated for 800W (66A on 12v) peak output so that's what your peak output ceiling is.

I'm running gear that has peak output of 100A but I obviously don't hit that level because I'm not blasting music at 50+ volume. I'd be doing severe damage to my hearing if I was getting anywhere near peak output. If I had to guess I'd say I'm probably more in the ballpark of like 50A max (and that's peak, not sustained) with how I listen and it still gets loud. My system can do 75W max to each speaker (2 dash, 2 front door, 2 rear door), and 760W max to sub.

But I'm not just sitting there playing 40hz sine wave tones to my subwoofer. I have it dialed in for sound quality, not rattling my doors off their hinges.

I also only have base trim level of the car so no heated seats or heated steering or whatever other notable draws could be put on the 12v system. Freeing up more headroom.

And in case you go searching my post history, while my OEM battery did show signs of unhappiness, that was before my final iteration of two amplifiers was installed. So that was a separate issue from my audio upgrade journey. The AGM battery I've replaced it with has been holding up just fine. And prior to me disconnecting the BMS, it easily handled my amps, spending plenty of time in the 12.7 resting voltage while driving as I played music.

 

Now, I know next to nothing about this stuff, but I've been reading up some on BMS. Did your BMS 'see' the draw of the amps, as in, were they connected directly to the negative battery terminal, bypassing the BMS?

 

Before I go on I do want to say what I've said before to others... your best bang for the buck upgrade with minimal hassle is replacing your dash speakers with some nice tweeters or widebands that have good OFF-AXIS RESPONSE (because they're not facing directly at you and you're getting reflected audio off the windshield), crossover frequency around 2-2.5k (so make sure the tweeters you get cleanly handle that low), and then add a subwoofer which is fed from the front dash/door speaker feed (not the rear, rear is not good signal).

That gives you the missing bass and cleans up the muddy high end. Do not use kicker tweeters. They did not sound good in this car and were very piercing sounding.

Doing those two things will be a notable jump in audio quality without worrying about breaking your wallet or worrying about power limits and for the most part both are VERY simple to do yourself.

Personally I'm now running CDT Unity 8.0 widebands in my dash and they're great. Dash speaker upgrade should be something you do yourself, before you even get into doing amps and other stuff since they'll run fine powered off the head unit. And if you get good tweeters/widebands then continue to use them as you do further upgrades.

I have no idea lol.

I monitor my charging voltage via a little accessory plugged into the cig outlet. Brought it from my last car, it's about +/- 0.02v difference from what I can read at the battery with a multimeter. And my car has operated exactly as other people have described theirs, where as long as it's not extremely cold the BMS will do either 14v, 13v, or float down to 12.7v (I assume to load test briefly). I have never had an issue running my gear while the BMS did it's thing.

After about a year of car ownership, BEFORE I had my 100A setup, my OEM lead acid battery was showing low voltage in winter at the terminals with a multimeter and I didn't like it. Since I was heading up to the mountains a lot I wanted better reliability so I swapped out to an AGM battery and it's been rock solid.

And with the recent discovery of being able to disconnect the BMS for stabilized charging, I have done that as well for additional peace of mind.

But yeah just because a system can do 1000W doesn't mean that's what it's gonna be drawing. I've had my AGM long enough now that if my system and its power draw was too much for the car the AGM would've been showing signs of that.

IMG_1190 by soft_r posted Oct 24, 2025 at 8:21 PM