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extra battery or HO alternator?


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jvc m730bt

psi platform 2 12" 1800w rms

orion xtr 1500.1dz (1750 birth sheet)

1/0 front to trunk

1/0 big 3

optoma yellow top

stock 110amp alternator (2008 focus)

boss 2 farad cap

 

on heavy load the head unit audio completely shuts off. the media player and display still works, but no music comes out, either from the door speakers running off internal head unit amp, or from the sub. rebooting the radio brings the music back.

i have an outlet volt meter up front that never dips below 13.5 and a 2 farad cap in the back that reads the same on its display.

I know this is way too much for a stock alternator but my question is do you think i could get by with putting a battery in the trunk? or  do i need to just bite the $450 bullet and get a mechman 270a? would that be enough?

wisdom on the subject would be greatly appreciated.

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Not sure why your head unit would shut off anywhere near 13.5v, that's far from normal.

You might want to check your voltage with a dmm at the head unit.

With your current system, you should be able to get away with a decent rear battery and solid connections but if you plan on future upgrades, a high output alternator will be a BIG help.

 

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Ditch the Boss "2F" Cap.  That is a glorified Boss sticker and nothing more.

Replace the Boss cap with a high quality 1F capacitor from a reputable manufacturer - like a vintage Lighting Audio, Streetwires, or RF cap off of eBay.  Ensure the cap is within 12" of the amplifiers power / ground leads.

1750 Class D watts . . .

1750 / 75% amplifier efficiency = 2333 Watts Input
2333 Watts Input / 13.8 VDC = 169A of current required (on sine waves)
169A x 50% duty cycle of heavily compressed music = 84.5A of current required on music (bass discs included)

After the cap is replaced, and connected properly, then measure voltage over time at the battery with a quality DMM (Fluke 115 / 87, etc) while playing music loudly with the engine at an idle.  If you see dips below 13.4 VDC, the alternator is simply not producing enough output current to power the accessories, your system, and keep a charge on the battery.  Only then will you know if an upgraded alternator is in order.  I predict that it will be.  The cap is still a wise investment and will allow your new alternator to work far better than without it.

As far as alternators go, Mechman is tough to beat.  Like slowfkncar (lol) says, if you have any plans to add to your system then this is a smart investment anyhow.

Tony Candela - SMD Sales & Marketing
Email me at [email protected] to learn about becoming an SMD Partner!

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oh cool, thanks for the detailed response! I think i should go with an alt for sure, i was getting down into the mid high 12's at the battery. my question now is, is that boss cap really that worthless? i get that it was only $20 when i bought it for my first system (250watt ish rockford punch). if i'm better off with it out of the system altogether should i go with a better small cap, or should I put an aux battery in the trunk? after doing some reading on caps I don't know how i feel about putting in a cap smaller than 30f. thanks again for your help!

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Snafu is a very knowledgable guy. I have no doubt the caps he recommended would help in some small way. But imo a reserve batt is way better than any cap of that style. With that voltage a nice size reserve batt would help more. But id be more concerned with the headunit shutting down. Have u tried using a different hu in there? Maybe the factory amp has a safety feature causing it to shut off due to the voltage drop your experiencing?

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Get rid of the cap all together and just get a 2ndary battery that will be alot more effective then a crappy boss cap any day, but don't skimp on the 2ndary battery a 2nd yellow top, since it is recommended to go with the same kind you already have if you have a Optima battery already.

 

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On 8/15/2018 at 1:36 PM, lightfoot said:

Sounds like you might have a speaker grounding out, either on the door panel skin or the voice coil is going out on your mids. once you turn it up the voice coil on your mids might be jumping out of the motor/magnet. 

i thought that too, but it still kicks off with speakers disconnected. my current thinking is maybe it draws from the head unit amps psu. maybe it kicks into protect if that goes dry.

 

On 8/15/2018 at 11:33 AM, AlpineNut said:

Get rid of the cap all together and just get a 2ndary battery that will be alot more effective then a crappy boss cap any day, but don't skimp on the 2ndary battery a 2nd yellow top, since it is recommended to go with the same kind you already have if you have a Optima battery already.

 

does it matter to keep them the same if i buy an isolator? so that the starting batt doesn't drain the system batt? do isolators have any negative effects anyone knows of?

 

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The batts dont have to be same brand. Its common practice to make sure they are both agm but ive had a small kinetik agm for years in a few vehicles inline with the stock batt with no issues. The few tenths of a volt youd loose from the agm draining into the stock batt will never b noticed unless competing. Ive heard it can shorten the agms life but mines runnin on five years strong. Also no isolater is needed unless playing loudly for long periods with the car off. Wich shouldnt b done anyways. Just get another small agm from a reputable company if u choose to go that route.

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Guys, you really should educate yourselves about what capacitors do and their place in high powered audio systems.  I blame it on the industry - where once quality products were the norm, they are now the exception.  I asked our admin to revive an old thread in regards.  Once that's up, you should all read it.

Science > conjecture.

Tony Candela - SMD Sales & Marketing
Email me at [email protected] to learn about becoming an SMD Partner!

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