12v Amp on Aux

Discussion in 'Tech/Mech General' started by RS_rob, May 24, 2014.

  1. RS_rob

    RS_rob Funster

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    So the intention is to beef up the sounds, I dont need to buy anything as I have all the equipment from previous builds however none of them ever had been set up from 2 batteries ie main & aux.

    So the question here is.............

    If I power my Radio from the Vehicle Battery & Connect my Amplifier to the Auxiliary Battery will this cause any problems/interference with the original wiring circuits.

    The reason I ask is that the remote power lead is not totally separated from the main power inside the head unit.

    or perhaps could a simple manual operated switch be the answer.... ? i.e turn on the power from the aux when i want it............
     
  2. RS_rob

    RS_rob Funster

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    So I take it nobody on here has any experience installing ICE in a motorhome & using the leisure battery as the main mode of power then!

    I guess Im on my own then.............

    Uncharted Territory just how I like it :Rofl1:

    Bring on the bass.................
     
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  3. dave newell lvs

    dave newell lvs Trader-Vehicle Services

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    Just spotted this thread, yes I have installed ICE kit into motorhomes before. I would power everything from the leisure batteries (you will need more than one if you plan on using it while off grid) as when the engine is running the split charge will simply pass the current required (assuming it is properly set up of course, you may need to install a B2B system to cope depending on how powerful your amp is). More detailed info on the kit in question is required if a more detailed answer is wanted.

    D.
     
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  4. cmcardle75

    cmcardle75 Read Only Funster

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    You could have some problems if you split the head unit and the amplifier from different batteries, but the problems are likely to be very slight. Although technically you could get get ground loop effects, these aren't significant as the system is DC.

    However, there are many very good reasons to run the sound system entirely from the leisure batteries. Basically, you want to run it without the keys in the ignition, take advantage of your mains/solar chargers, use it for many hours and still be able to start the engine in the morning. This is a job for the leisure battery, not the engine battery.

    So I would personally rewire the stereo to be leisure battery only. I'd put in a switch to ensure that it is entirely disconnected when stored (it's worth doing this whatever battery it is powered from to prevent battery discharge/damage after a couple of weeks).
     
    Last edited: May 25, 2014
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  5. ivorantony

    ivorantony Funster

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    Hi I have run my radio off the leisure battery to improve the radio reception with good results, but since fitting a quality roof aerial I no longer need too,

    I also fitted a separate switch to power the radio so not relying on the ignition switch, it all works well including using the aux to power the Avtex TV to give good 4 speaker sounds,

    the Avtex picks it's power from the main battery and so far no problem with ground loops or background hum,
     
    Last edited: May 25, 2014
  6. RS_rob

    RS_rob Funster

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    Thanks for the replies.....

    1st up the bit that is bugging me is seperate power.

    I would really like to power the head unit of the main batterie & the amp from the leisure battery, yes I know I could just power the whole lot from the leisure or main & yes the main does need replacing.
    & it wont take much rewiring as its only live & earth as due to some dodgy owners ive ripped out the crappy radio they put in & installed mine fresh direct to the battery.

    As for the amp & leisure battery... I know the switching wire has a small amound of power 5amps i think & this can be gotten round by simply not using it & wiring in a switch to the amp.
    Will the pre-outs cause any problems as again a small amount of current is passed down these.

    Here is what I intend to do for know & then I may build on it later.

    Head unit connected to 4 speakers & powering them
    Amp to power bass speakers mounted centrally & probably switched seperatly so I can still have radio on without bass & not annoy neighbors - this i would power from the Leisure Batter.
    The amp will be a good ol Alpine mrv from the 90s either a 300 or my 1000watt connected to 2 1000w 10" bass speakers in a push n pull set up.

    if it works & sounds nice I may then build on it as I have a stack of amps in the spare room :BigGrin:
     
  7. RS_rob

    RS_rob Funster

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    Please excuse my stupidity

    a what :Eeek:
     
  8. dave newell lvs

    dave newell lvs Trader-Vehicle Services

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    A Battery to Battery charger. Standard split charge will pass limited current to leisure batteries but a B2B fools the alternator into producing more current than it would normally do and passes it to the leisure batteries. Two main manufacturers are Sterling whose most popular unit can run at 45 Amps or CTEK whose most popular can do 25 Amps.

    I see no good reason to power the head unit from your engine battery, run the lot off the leisures but be prepared for the amps to flatten your batteries quite rapidly, you will need an alternative means of charging the leisures, either solar or via hookup.

    As for upsetting the neighbours I think you will unless you do a fair bit of lone wild camping, 2X 1000W subs make a fair bit of noise (even if they're driven by a 300W amp) and as its low frequency noise it travels easily.

    The "switching wire" you mention is I presume the trigger to switch the amp on when the head unit is switched on, if so it will take 5/8 of sod all current, its simply a signal telling the amp to power up when it goes to +12V.
    D.
     
    Last edited: May 28, 2014
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  9. RS_rob

    RS_rob Funster

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    Currently the van has a single 80ah leisure battery new in feb & a solar panel on the roof but I have no idea of its output.
    I have eyed up a space next to the current battery for a second already.
    I will look into this b2b charger...

    Ill gather my gear & run a test rig to see how it will sound before I make it permenant.

    Thanks Dave.
     
  10. jockaneezer

    jockaneezer Funster

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  11. Reallyretired

    Reallyretired Funster

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    This subwoofer amplifiers take a lot of current, which is why vehicles that have it built in, like my Discovery, have a circuit that limits the volume severely if the engine is not running. They use in the region of hundreds of amps which could flatten your leisure battery very quickly.

    Unless you park on your own you will be unpopular with your neighbours who will only hear a dull thumping sound.
     
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  12. G8WVW

    G8WVW Read Only Funster

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    It is grounding/earthing that's likely to cause you problems if any exist. When the leisure battery is charging/discharging, there will be a small potential difference between the two battery negative terminals due to wiring resistances in the earthing system. With the head unit connected to one battery and amplifier to the other, the screen of the interconnecting audio cable will be at slightly different potentials so a small current will flow in the screen. This difference may only be a few tens of millivolts however the audio signal in the cable inner is not that much greater so changes in the battery current flows caused by for instance, voltage ripple from the alternator may be induced onto the audio signal as a tone that changes frequency with the engine revolutions. You may also hear a 'pop' each time something switches on/off.

    The answer has been given already, ideally both units should be fed from the same battery, positive and negative. If you really cannot achieve this then feed both units should share the same earth connection point, wherever that may be.

    Good Luck.

    Ian

    (25-years with BBC Engineering)
     
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  13. RS_rob

    RS_rob Funster

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    Thanks Ian

    :thumb:
     
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