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Author How do you run an amp at 14.4v?
beatsri
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Registered: 16th Jan 03
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19th Feb 03 at 15:08   View User's Profile U2U Member Reply With Quote

I am wondering how to run an amp at 14.4v. I have 2 different power ratings for my amp (alpine t757)
1x300RMS @ 4ohms - 12v or
1x400RMS @ 4ohms - 14.4v
Would I need to install a power cap to sustain voltage or does it depend on what type of wire I'm using (currently 8awg).
The sub I'm running is a JBL power 1220e rated at 400rms @ 4ohms.
jjcymru
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Registered: 28th May 02
Location: ammanford,south wales
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19th Feb 03 at 16:12   View User's Profile U2U Member Reply With Quote

you get 14.4 volts with the engine running

12v when the batterys providing the power with the engine off
beatsri
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Registered: 16th Jan 03
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19th Feb 03 at 16:17   View User's Profile U2U Member Reply With Quote

Cheers thats a great help!
Daimo B
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Registered: 20th Mar 00
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19th Feb 03 at 16:35   View User's Profile U2U Member Reply With Quote

I doubt u will need a power cap no.
Mikorsa16v
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Registered: 2nd Sep 02
Location: Burgess Hill, West Sussex
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19th Feb 03 at 18:43   View User's Profile U2U Member Reply With Quote

quote:
Originally posted by jjcymru
you get 14.4 volts with the engine running

12v when the batterys providing the power with the engine off


are you sure? i didnt think so! try it with a meter matey to test this theory
corb
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Registered: 24th Apr 02
Location: Calgary, Alberta, Canada
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19th Feb 03 at 19:20   View User's Profile U2U Member Reply With Quote

well thats an estimate, but most cars are 12v when engine not running, then the battery charges at around 14.4v.
Kris TD
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Registered: 25th Mar 02
Location: Ware, Hertfordshire
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19th Feb 03 at 20:33   View User's Profile U2U Member Reply With Quote

i agree with corb
corb
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Registered: 24th Apr 02
Location: Calgary, Alberta, Canada
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19th Feb 03 at 20:40   View User's Profile U2U Member Reply With Quote

quote:
Originally posted by Kris TD
i agree with corb


cant blame you, most people uasually do!
sxi16vjoe
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Registered: 16th Dec 02
Location: Kent
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   19th Feb 03 at 21:14   View User's Profile U2U Member Reply With Quote

i had an alpine amp til monday nite. some fcukers played smash and grab on my car. cunts
dig dave2811
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Registered: 6th Jan 03
Location: newport sout wales WCM
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19th Feb 03 at 23:02   View User's Profile U2U Member Reply With Quote

YEAH IT IS 14.4 OR AROUND THAT WHEN ENGIN IS ON HAVE CHECKED IT WITH A METRE AND ABOUT 12 WHEN ENGN IS NOT ON
Kris TD
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Registered: 25th Mar 02
Location: Ware, Hertfordshire
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20th Feb 03 at 18:02   View User's Profile U2U Member Reply With Quote

quote:
Originally posted by sxi16vjoe
i had an alpine amp til monday nite. some fcukers played smash and grab on my car. cunts


pete-w had an alpine amp nicked monday too
TOMAS
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Registered: 7th Aug 02
Location: Nottinghamshire
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21st Feb 03 at 00:36   View User's Profile U2U Member Reply With Quote

Feck me if they are going for alpine better change to 100% tints all around
ultim8DTM5
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Registered: 18th Jun 02
Location: Sydney, Oz
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21st Feb 03 at 07:38   View User's Profile U2U Member Reply With Quote

Incorrect, unless you get a multimeter and test the voltage of the battery both when the car is running and when it is turned off, that is too large a generalisation to assume the voltage from the battery is always 12V with the car off, and 14.4V with the car running and the battery recharging.

Basically, most car electrics are given in 12/14V because that is what the electrical system is, just like a powerpoint is 240V.

Given a new car, the voltage given from the battery (when the car is off) would normally be the average of the two, or 13.8V which is the normal guide for operation.

For voltage to reach 14.4V, the alternator would have to be in excellent condition, with no other in-car electrics in operation (such as headlights, air conditioning, fan etc.) This would be 14V.

However, in normal conditions and depending on how much current all the car's electrical system draws from the source equates to how much power your amplifiers will output. For example, after a series of burps (loud bass notes) it is quite typical on a stock electrical system for voltage to drop below 11V. And this will be visible if your car has a voltmeter guage or a capacitor with a status display.

Unless your alternator is upgraded, the best your system can achieve on normal day-to-day driving with normal music will be around 13.8V with the electrics in use. This is why cars with large systems and multiple amps drawing large current from the althernator often complain of dimming headlights and stalling.

Capacitors are only a band-aid solution, they only store charge temporarily between bass-notes so the current to the amps is not interrupted as much as it could be.

d0gz_bollox
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Registered: 8th Apr 02
Location: Walsall
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21st Feb 03 at 16:13   View User's Profile U2U Member Reply With Quote

a better battery and bigger alternator is better then a cap. there was a big post about this somewher eon here do a search
GAZ914
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Registered: 28th Oct 02
Location: Sydney, Australia Drives:Corsa C SRi 1.8
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21st Feb 03 at 23:33   View User's Profile U2U Member Reply With Quote

Time for some electrical theory methinks (This is going to be Loooong)

There are many types of battery (duh) and cars use the LEAD/ACID variety.
If you get a couple of bits of LEAD and stick them in a bath of SULPHURIC acid, you can create electricity. A voltmeter would read 2.1 VOLTS, which is the electrical pressure. Now depending on how BIG the lead bits and acid bath were determines how MUCH electricity you could get. The rate of flow of the electricity out of the battery is determined by the size of the pipes and the requirements of the device you trying to run. This is measured in AMPS. We call this device a CELL (like a AA battery is a cell, but 1.5 volts). A BATTERY is made up of CELLs to make different voltages.

As you all probably realise, a car battery has 6 cells to make suit the "12 VOLT" system. In reality the car battery is really a 12.6 volt electricity storage container. The manufacturer of the battery packs in a lot of PLATES (bits of lead) into each cell and makes a pretty case so you will spend big bucks on you new flash battery

Now for the bad news. As soon as you start to use the electricity out of the battery, the voltage gets lower, until we say the battery is FLAT (I've seen real flat ones and they DON'T work at all!) when the CELL voltage is 1.75 VOLTS (10.5 volts for a 12 volt battery). It gets WORSE, as the faster you use the electricity (more AMPS) the lower the voltage that the battery supplies

Thats why the amplifier manufacturer rates the amplifier at 12 volts, that is the likely voltage that the battery is supplying with the engine OFF. The bad part is that the voltage drops reasonably rapidly from there and it is not unusual to see 11.5 volts after a while. Thats a 1.1 volt drop from the original 12.6 volts (almost 10%) so you can see that it is going to make a BIG difference to the power out of the speakers.

Just when you thought that it was looking grim, we have to factor in the wiring/connections from the battery to the amplifier. Everything has a RESISTANCE to the flow of electricity. We choose copper for our wire 'cause the resistance vs cost is acceptable. What does this resistance do? Well it means we get LESS voltage (read power) at the amplifier. Thats why putting a voltmeter on the battery is pretty meaningless, when you REALLY want to measure the voltage at the amplifier.
The BEST wire to use for performance is a single SOLID strand, look at house wiring and it is normally single strand. Solid copper is NOT flexible and would break when subjected to the normal vibrations in a car, so we have to use multi-strand. The faster you pull the electricity through the wire (more AMPS) the more you lose due to RESISTANCE.

Are we all lost yet (I am!)

OK, so we know that using batteries to power amplifiers and using wires to hook them up is like flogging a dead horse, 'cause the MORE performance I WANT, the LESS performance I GET.

What about alternators. Well when the first cars were built, there were no electrical things to run. The cars didn't even have dashboards! The self starter made a battery compulsory (to power the starter) and so a GENERATOR was added to recharge the battery while you were driving.
Fast forward 75 years and cars have all sorts of electrical bits that must be run while the cars is in operation. The battery cannot perform this function, as we have already seen that it does a POOR job of running electrical accessories 'cause the voltage drops off too quickly.

Contrary to popular belief, the alternator is fitted to the car - NOT to charge the battery - but to supply electricity to all the electrical accessories. The fact that the battery gets charged is a bonus!
If we set the alternator voltage to 12 volts, all the electrical accessories would run fine and everyone would be happy - except the battery.
Lead/acid batteries need to be charged at maximum of 2.4 volts per cell (14.4 volts for a 12 volt system) and so that is what the alternator is limited to - to make sure the battery isn't damaged.

Now the cool part is that the alternator voltage output is much more linear than the battery under load, and so you can get 14.4 volts right up to the rated output of the alternator. Alternators can be rated at 30 to 100+ AMPS (Corsa C is 100 amp).

There is a catch (isn't there always). Alternators like STEADY load. So when you turn the headlights on or a big bass note plays, the alternator CANNOT supply the power fast enough. Our good friend the battery does this for the split second the alternator takes to "catch up".

How does all this affect your ICE?
Make sure you have the biggest/best battery you can fit.
Make the amplifier power cables as short and as thick as you can.
Wire a BIG capacitor right at the amplifier to make sure the amplifier gets the electricity it requires for the music "burps".
Make sure the alternator is charging at 14.4 (14.0 is probably close enough for most) with headlights, stereo, etc switched ON.
Opel did not engineer the car electricals for big ICE.
Like mechanical mods, think about the weak links in the system (like the earth connection between the battery and the chassis and the wire from the alternator to the battery) since your putting more strain on these bits.

There are probably a million more questions and answers, but I hope that gives everybody an idea of how the car electrical system "works".

GAZ

 
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