Battery Revisited

1994, 2.0L Nissan Primera, 130k miles

Just blew a 30AMP blade fuse on the wire from my Battery to the

4x104Watt RMS amp... though I only have essentially 200 Watt RMS around the car in speakers with about 240 Watt peak in the front and roughly the same in the back...

Rather annoyed though that the blade fuse actually melted rather than blowing and breaking. So, false sense of security.

I've just fitted a new fuse and I was reminded to get the voltmeter out and test the battery power.

With the engine off, I have 12.2 Volt at the battery. With the engine on, Im getting 14.4 volt. If I use the amp conservatively, I still get about 14 volt. But when I switch basically everything on and turn the stereo up load, I find there's about 12 volt, maybe even 11.9 volt at the battery. Perhaps that's the problem.

Now... I've heard of capacitors, batterys, and alternators, I don't know what I should be looking for. But my own opinion, capacitors are a waste of money bass hits don't really affect me, and with modern music compressed the way it is, I can't understand how there can be enough dynamic range in music in order to give the capacitor something to work with. Anyhow, I think my problem is more fundamental.

The second thing is the battery... but Im not sure what a bigger battery would do? Surely all a battery does, is provide reserve when the alternator can't cope, while also providing reserves for starting the engine or providing power when the engine is off... so I would tend to think it's the alternator, although, when the car is driven normally, and revved, I do get more voltage at the battery for me to be happy. So maybe it's a car problem in not controlling the revs to provide the extra power? I thought my car was supposed to do this??

But people do keep mentioning replacing the battery. I don't understand why. If I had a bigger battery, i still probably wouldn't be getting enough charge from the alternator???

As for the alternator, I'd like not to think of getting and fitting one of these.

Any opinions?

Thanks Simon

Reply to
Simon Dean
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Turn the music down?

Reply to
Chris Street

The wiring is of insufficient capacity or you have a short circuit.

Huw

Reply to
Huw

Your alternator has gone into warp drive.

Reply to
Paul Hubbard

Which bit of the wiring? Alternator to Battery, or Battery to AMP? Im assured 8 gauge cable is enough for my particular amp with 60 Amp fuse.

CHeers Simon

Reply to
Simon Dean

Hmmm, if the amp is truely 4 x 104W, then that's a 34.6A current drain.

Then, lets say it's a class-A amplifier, with a theoretical maximum efficiency of 50%, then that's now a 69.2A drain.

Why do you think the fuse shouldn't blow?

Oh, BTW, the speaker power rating is just that - if they are rated at

200W then that's how much power you should use to drive them without damaging them. It's not an indication of how much they draw - they can still drain every last watt out of your amp, until they themselves melt.

If you're worried about the fuse, then I think you should pay close attention to all the power cabling to the amp - make sure that's sufficiently rated, and then investigate the proper current required to feed the amp.

And if you're anywhere near the above figures, then a new alternator will be required. And a silver-oxide cell for the hearing aid that you'll soon be needing.

Reply to
Mike Dodd

Eh? Warp drive? More power? She canny handle any more captain? Is that what you're saying to me? Damn it Jim, Im a computer programmer and music enthusiast, not a mechanic.

Cheers Simon

Reply to
Simon Dean

No, I think it should blow. I just don't think all the plastic and the fuse holder should melt around it...

Even though i've adjusted the output's out of the amp accordingly which should in theory be sending out less wattage?

Well I got the amplifier and wiring from the same place, they assured me it is sufficient, though Im doubtful. It's an 8 guage cable that came fitted with a 30 amp blade fuse. I now have a 60 amp inline fuse. the amplifier instructions state maximum draw is 85A (ahem, even though the fuses on the amplifier itself consists of two 30 amp blade fuses), and according to what I can gather, I really need to be using a 4 guage cable for 85 amp. But I can't be arsed right now to rip all the cable out now. Maybe in a couple of months I'll go and shove my fist down the throats of bass-junkies who sold me an underrated cable.

It's really not that loud though. Not really as loud as the 4 x 52 Watt Clarion radio I had in there in the first place. i wouldn't mind getting a bass tube though just for those rare occasions I drive through the middle of town playing such classics as Orpheus of the Underworld.

Cheers Simon

Reply to
Simon Dean

"WHAT - I CAN'T HEAR YOU"

Reply to
Tim S Kemp

Music Enthusiast?

If you're blowing a 30A fuse to an in car amp it would appear that you're more of a booooom-booooom merchant. However....

30A is not enough for a 12V fed 400W amplifier. If all the loads drop your voltage with the engine running below 12V you need a bigger alternator.

And you'll soon stop being a music enthusiast when your hearing's gone.

Reply to
Tim S Kemp

Pff. Tish posh. While I enjoy my music loud, it's definitely not boom boom, with the likes of Rush, it's more like boom da da da boom crash splash waahh, screech boom. Then of course you have all the classical music, like Orpheus of the Underworld, Toccata and Fugue in D Minor, Dance of the Knights, Carmen Suite No 1, those things HAVE to be played loud.

Even if I don't use all 400 Watts of those? It just seems strange how I've managed with it all this time, for the past six months. Only since I got Rush's new DVD/CD, R30, have I had problems. The sounds been too clear so I've been able to turn it up to remind me of three hours of ear bleeding 104 Decibals that I experienced in concert at Wembley and the NEC...

Still... I guess the principal note here, is that if I go under 12v, I need a bigger alternator. The fact that revving the engine and getting

13 to 14v, means that the alternator is fine and doing it's job with the voltage regulator, but it's just not powerful enough? In that instance, do I like for one to output more watts, amps, or ??? I dunno.

Good point though. I don't intend on getting any more speakers to be honest... I only really got the Amplifier too because the internal radio one threw a hissy fit and kept crackling when it got hot.

Reply to
Simon Dean

I'm running a big old amp in the Alfa, and it's not even slightly bothering a 25A fuse.

System, for anyone who's even slightly interested, is as follows;

Nakamichi CD300 head unit Ground Zero GZNA4350X amplifier Ground Zero GZUF 65C rear speakers Alpine 12" Bass engine sub in ported box

It's pretty bloody loud, very very clear (ex sound off gear) and as I say, it doesn't bother a 25A fuse unless I go apeshit with the volume control.

Reply to
Pete M

The message from Simon Dean contains these words:

That's down to a poor contact between the blade and the socket. Proper bolt-down fuses wouldn't do that.

You also need to ask why you're using a 30A fuse in a circuit which at first glance will draw way more than 30 amps on full load.

However, I prefer the suggestion of "TURN THE THING DOWN!"

Reply to
Guy King

The message from Simon Dean contains these words:

Ah, that's 'cos the power rating of speakers has little to do with their efficiency. Some are way way better at turning current into sound. I wanted a cheap pair of 4" speakers to replace a dead pair in a tailgate of an estate car a while ago. The first pair I tried worked OK but were inaudible. The second pair were deafening at the same setting on the radio.

Reply to
Guy King

Ahh. Apeshit. 25/33 here... but then, you don't know what the adjustable gain controls on the AMP are set to...

Cya Simon

Reply to
Simon Dean

Ooh - just to finish our conversation from three months ago.

Ended up Alpine 9812RB head unit (30A fuse...) Alpine S series components front and rear (often carry rear passengers) Sony 8" sub.

Works well. Gonna change the sub for something that goes deeper in the new year I think - it's loud enough but not nice enough. Maybe fit an Alpine 10 or 12.

Reply to
Tim S Kemp

Um, Motor World, of all people, do a rather nice Alpine 12" sub and box combo for around £100. I know, that's the one I've got.

Reply to
Pete M

That's the cable they sold me with the amplifier. And not wanting to do too much tweaking I kind of left it. Plus I think I had some strange ideas..

I think I was thinking that I probably wouldn't be using anywhere near

75 Watt's a channel on these tiny speakers, only 50 watt RMS, so I figured that a 30 amp fuse should be sufficient.

Also hearing horror stories of cars being engulfed in electrical fires, I figured sticking with the 30 amp blade fuse on the power wire just after the battery, should help protect things if anything went wrong.

I don't want to stick too large a fuse in there and have everything go wrong. I figured the cheap ass 30 Amp fuse would blow...

I also figured, that as that's the fuse that's installed, that's the most that can be got out of the wire...

If I increased the gain on the inputs, I could turn it down ;-)

Reply to
Simon Dean

The message from Simon Dean contains these words:

But you said yourself that the fuse didn't blow. The connection to it melted - that can happen at quite low currents if there's a poor connection.

Reply to
Guy King

A Runrig CD finished of my Armstrong 521 amplifier. Halfway through the second track a curl of smoke was seen to issue from the top.

Reply to
Malc

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