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# Car audio power

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#### mistermatrix24

##### New Member
okay so i recently installed a 1700 watt lightning audio system into my car. ever since then i keep having power problems. i recently had to replace my battery because i just couldn't jump it again. (7th time) my question is, if i install a second battery say, in the trunk, and route all the add-ons to that battery and leave the other one to just power stock parts like lights and starting the car, will that take away the risk of the amps draining the starter battery because i do blame them for the battery dieing even tho i make sure the switch for them is off.

then if so. do i need to match the battery to the starter battery as in like 500cca. am i wrong in thinking that the allternator powers the whole system anyway. does it really matter the size of the battery that acts as the pass-through?

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#### tcmtech

##### Banned
Your sound system is way to big for the size and type of battery you are using.
For something that large I would recommend getting the two largest marine type storage batteries you can fit in your vehicle and the biggest amperage capacity alternator you can find.

A typical automotive alternator has at best around 200 watts of reserve above what your vehicles electrical system normally uses. Once you go past that reserve your on all battery for the power.

The standard automotive starting batteries are purpose built for short duration high amperage loads like starting the car and then immediately being fully recharged when the vehicle is running. What your doing is running them flat which kills them fast as you have found out.
Deep cycle and marine type batteries are built to take being drained down with less damage and will last much longer Than what your using now. But still they need to be recharged and the only way to do that is with the alternator which has to power every thing first before the batteries get any charge put in them at all.

For a 1700 watt sound system I would recommend having around 300 amps of alternator capacity or more. That may very well require dual alternators as well.

#### ke5frf

##### New Member
okay so i recently installed a 1700 watt lightning audio system into my car. ever since then i keep having power problems. i recently had to replace my battery because i just couldn't jump it again. (7th time) my question is, if i install a second battery say, in the trunk, and route all the add-ons to that battery and leave the other one to just power stock parts like lights and starting the car, will that take away the risk of the amps draining the starter battery because i do blame them for the battery dieing even tho i make sure the switch for them is off.

then if so. do i need to match the battery to the starter battery as in like 500cca. am i wrong in thinking that the allternator powers the whole system anyway. does it really matter the size of the battery that acts as the pass-through?

They both matter.

Your battery is a storage tank, so to speak, for instantaneous demand.

Think about it this way, if you have a bathtub filled to the top with water, and you have a fire in the living room, which would you rather do...run back and forth with a five gallon bucket and dip it in the full tub to quickly get your water supply, or go to the faucet and wait for the spigot to fill the bucket up each time?

You'd probably be more efficient if you had a full tub of water waiting on you, right? And the bigger the tub, the better. Same with your battery. You have an amplifier and speakers that are power hungry and will drain your battery very fast. Better to have a battery than can deliver the power.

But I said you need both, a high capacity battery and a better alternator. Think about your bathtub. If you have a big fire and you keep running back and forth to the tub, eventually the tub will be empty and the fire will still be burning. You need a spigot that replenishes the water as fast as you take it out. So, you'd prefer to have the spigot delivering high water pressure and flow, refilling the tub each time you run back and forth with the bucket, right? If the water pressure is too low, it might take longer but eventually you will be faster with your bucket and the tub will be empty and you will be having to wait each time with the bucket to let the tap fill it up.

Same thing with your alternator (the spigot, metaphorically)...If your stereo amplifier and speakers are demanding power, even from your big battery system, it might take a long time, but eventually the alternator won't be able to keep up and the battery power will not replenish quickly enough to maintain your demand.

Replace both, and on a side note, you can't have a special battery JUST for your starter and another one JUST for your stereo. By the nature of the beast they must be in parallel and be recharged by your alternator, unless you are willing to recharge the stereo battery with an AC powered battery charger in your garage, and then you would only be able to listen to your stereo for an hour or so tops before the battery died on you and needed another charge.

BTW, as an old coot, not that old but old enough, I suggest you quit dumping your hard earned money, (or your parent's money) into $2000 stereo systems that will do nothing in the long run other than ruin your hearing and get you citations from the police, not to mention rattle and vibrate all the interior moulding and fasteners in your vehicle to the point it is worthless. If I had one dollar of every ten I wasted as a teenager and 20something I might actually be debt free today and have a lot less stress. Hard to see that right now, believe me I know. Take my advice for what its worth. #### lamnak ##### New Member I had the same problem, what i did was have my altinator rebuilt to produce more power. #### mistermatrix24 ##### New Member wow. thank you both soo much. now how can i find out how much amps my current alternator is producing and (side note, is an alternator an easy replace or will i need a mechanic?) thank you for your advice ke5frf, i assure you i have thought about the costs. the system didnt cost anywhere close to$2000, im a deal hunter lol. i found it on ebay for \$150 all brand new. two amps 960 and 750, 4 x 6.5" speakers, 2 x 4" speakers, and a 10" sub.

would a 120 amp alternator suffice for the power needs? i think i have a 70 amp now?

and so your saying no matter what the battery thats not connected to the system will still die? even if i connect the other one directly to the alternator?

#### tcmtech

##### Banned
As far as I know its a free country to spend your money on what ever you want regardless of what others want or think. So be loud, get tickets, shake the car apart, spend your money any way you want, and if someones dumb enough to let you spend their money on your stuff by all means let them!

Part of the fun of growing up is doing stupid stuff that really bugs the old farts who think they know better because they either never lived it or where just to afraid to do it when they had the chance!

#### mistermatrix24

##### New Member
lamnak was that a costly job and how much more power were you able to get out of it. like would i be better off getting a 120 amp alternator and rebuilding it to be more powerful or would it not matter if i started with a 70amp or 120amp?

#### tcmtech

##### Banned
Deal shopping even better!

The alternator has a direct feed to the cars battery but as I stated before your cars normal operations already use up most of it. If its a 70 amp rated alternator its likely that its already putting 50 amps of it to the cars systems any only has 20 left over for battery charging.

A 1700 watt sound system if its an honest rated will have a power draw around 2300 watts which is just under 200 amps at 12 volts.
Realistically that would mean you would need 180 more than what you have now for reserve.
That means you need around 250+ amps of alternator capacity to handle your sound system and not do damage to the batteries.

Changing an alternator is not all that hard if you have reasonable mechanical skills. However with a higher output alternator you will need to put a larger power line from the alternator to the battery being the stock one is only rated to handle the factory alternators output.

#### PatM

##### Member
Trouble is that running 1700 watts is going to damage his hearing so badly that even that power will not sound loud enough in the near future and he will be looking for even more power.
Maybe that is what is happening now.
Once your hearing is impaired it won't come back.

#### mistermatrix24

##### New Member
you mean like a lower gauge wire? like 0 or 2?

#### lamnak

##### New Member
It wasnt at all costly, tcmtech did a great breakdown of what you need to do. There are companies that rewould these alinators for a reasonable price. The wiring to the batteries woould deffinately have to be changed, but this will do the trick.

If you play only when your parked then you might also consider getting one of those small generators, honda has one that is super quiet that cranks oout 2000 watts. This is a nice alternative when your playing at a park.

#### tcmtech

##### Banned
0 gauge stranded copper will support 250+ amps in an automotive application just fine being the runs from one point to another are relatively short.

Finding a good aftermarket alternator or rebuild kit is probably going to be your best bet for getting closer to the power level you need.

What type of vehicle is it?

#### mistermatrix24

##### New Member
a 1997 jetta 2.0L 4cyl

#### audioguru

##### Well-Known Member
The tiny speakers are too small for 1700 Watts. Maybe the system is rated for 1700 Whats which is 150 Watts or less.
Old batteries die soon.

#### mistermatrix24

##### New Member
what do you mean guru?

#### audioguru

##### Well-Known Member
Car audio system manufacturers lie about output power. When the output is 150 Watts at low distortion then they say 1700 Whats for a moment at a very high distortion just before the system blows up.

Manufacturers say PEAK power or MAXIMUM power which is simply double the real amount of power (at very high distortion that is not revealed). Some say PMPO which is the phoney amount of power multiplied by the age of the salesman's grandmother.

.

##### Banned
This is why it's good to live in the US sometimes, federal law requires RMS power to be listed, on home and car audio or you can't list anything, and the RMS power measurement has some standardss based on a 1khz waveform or something at leats, haven't studied it much, I just know NOT to purchase anything without an RMS power rating on it. Even chinese crap has to conform to this, so they just stop listing it.

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#### audioguru

##### Well-Known Member
Most of the American importers list lies for amplifier power. The government has nothing to do with it.

A tiny amplifier operates from 12VDC and has a 1A fuse but is listed at 1000 Whats! It is lucky if it produces 6 Watts.

#### Ross Craney

##### New Member
It's probably the same amp as in my computor's 3" 150W speakers. I think there are those who have no idea what 100W RMS sounds like let alone 1700 Watts

#### Nigel Goodwin

##### Super Moderator
This is why it's good to live in the US sometimes, federal law requires RMS power to be listed, on home and car audio or you can't list anything, and the RMS power measurement has some standardss based on a 1khz waveform or something at leats, haven't studied it much, I just know NOT to purchase anything without an RMS power rating on it. Even chinese crap has to conform to this, so they just stop listing it.

Quite the opposite, it was the USA who started listing highly imaginary power outputs, back in the early 70's or so - normal USA advertising agency practice

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