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Thread: Issue with Alternator Noise through Car PC

  1. #11
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    When you get to your battery isolator, try a relay energised from the D+ (or L) charge lamp circuit from the alternator.

    I have posted details elsewhere....


    PS:-
    Quote Originally Posted by highamperage
    ... but since power is being drawn from the 2nd battery I figured that wouldn't be a big issue.
    Be aware that that cable carries all the load current plus 2nd battery recharge & float current.

    It also acts like an antenna for noise etc (though the battery might remove a lot of that since it's a big capacitor).

    True-sinewave converters generate more noise internally since they use PWM techniques to produce the sinewave. If insufficiently filtered & shielded, they'll probably be worse than early DC-DC converters for noise. (Sinewave users generally care about the load. Some manufacturers are yet to realise that some also want input DC filtering!)

  2. #12
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    Battery Isolator

    I have a Schottytec (however u spell it) battery isolator in my car.. 2 optimas and a hp slimline pc 14" screen upfront, and a 24" in back connected to a ps2 in my aspire.. I have a similar problem but it turns out my inverter was (it died) a modified sine wave. it is definatly a ground. Do the big 3 upgrade, and get a good isolator will solve that whine. My radio used to do that before the upgrade. Now all is fine except when using that crappy inverter.. I have 3 amps.. mono for bass, front/rear and had noise like crazy when i fist installed it... do the big 3 and get a isolator and you'll be good with that pure sine wave.. Thats next on my list


    Update: 4 amps.. did away with radio and have 7.1 from the pc.. Hella sweet.. used a 5v relay to turn the amps on and off.. new thread on this
    Last edited by Simbalage22; 08-20-2011 at 11:31 AM.

  3. #13
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    Talk about awakening of the dead.

    I presume your isolator is a diode type (Schottky)? I don't think they are too popular here except for small installations.

    And yes, a sinewave shoiuld always be quieter than a mod-sinewave; both on the output (should be zero noise) and often the input as they tend to be of higher quality (ie, design) and may spread the input over a wider pulse (though that isn't certain).


    EMI occurs with any modulating or switching electrics. It occurs in digital displays & gauges, alternator regulators, alternators, big audio amplifiers, dc-dc converters and inverters, etc. The primary solution is design (circuit, frequencies) and shielding. Then comes external suppression.

  4. #14
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    yup correct on the isolator.. 260amp from ems at bone yard...

  5. #15
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    260A diodes? Wow! What a pity the batteries can't be paralleled....

    But that whine is usually independent of battery isolators, it's just that yours blocks the noise from the inverter into the other battery & load. It won't block any alternator noise.
    And for many, diode isolators are not suitable or economical.

  6. #16
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    Battery Isolator are the way to go

    Quote Originally Posted by OldSpark View Post
    260A diodes? Wow! What a pity the batteries can't be paralleled....

    But that whine is usually independent of battery isolators, it's just that yours blocks the noise from the inverter into the other battery & load. It won't block any alternator noise.
    And for many, diode isolators are not suitable or economical.
    Isolators are economical for anyone who wants to "Isolate" 2 batteries. if you have a sound system and want the batteries separate when car is off then its the best solution, hence why ambulances use this setup. Lot of people use large relays to connect the batteries, but this is bad because once connected the full battery has to surge to bring the bead battery to same charge often shorting the life of the batteries.. I had this setup and it sucked. A good isolator will prevent the large voltage drop as with the cheaper isolators and maintains an even charge while the car is running.. and when car is off providing the batteries are deep cycle you can drain it flat and start the car without a big surge

  7. #17
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    You don't have to tell me about battery isolators.

    The thing is that I simply use a relay whereas others that also have charge lights use to these expensive (and usually flawed) voltage sensing types.
    And I won't even consider diode isolation (except for small set up of a few amps) since they do not allow paralleling of batteries, and for some systems (eg, singe-wire D+ alternators), their voltage drop cannot be compensated for.


    If you know of any REAL examples where the startup surge has been a problem, please provide a link - and I'm not talking about mere "stories" (they are like reading about "priority charging" by voltage sensing isolators - all it is is a delay before the 2nd battery is connected which is one of the time delays required with voltage sensing isolators which is easy to add to any relay isolator).


    What is the price of your isolator from normal outlets?

  8. #18
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    Quote Originally Posted by OldSpark View Post
    You don't have to tell me about battery isolators.

    The thing is that I simply use a relay whereas others that also have charge lights use to these expensive (and usually flawed) voltage sensing types.
    And I won't even consider diode isolation (except for small set up of a few amps) since they do not allow paralleling of batteries, and for some systems (eg, singe-wire D+ alternators), their voltage drop cannot be compensated for.


    If you know of any REAL examples where the startup surge has been a problem, please provide a link - and I'm not talking about mere "stories" (they are like reading about "priority charging" by voltage sensing isolators - all it is is a delay before the 2nd battery is connected which is one of the time delays required with voltage sensing isolators which is easy to add to any relay isolator).


    What is the price of your isolator from normal outlets?
    Cant buy it from a retail outlet... for emergency equipment only. And look it up the relay type you speak of.. work well at adding batteries together for added Ah but when used to separate the batteries its common sense that the charged battery surges current to re-supply the dead battery with current when it comes back into play. Who says you cant parallel batterys when using an isolator? As long as the end current is 12 or 24 depending on system it doesnt matter if you have 4 6v batteries or 2 12v batteries in a 12v application.. I think you have your info wrong as is it sometime wrong on the net..

    battery relay
    An electrically controlled mechanical device that opens and closes electrical contacts when a voltage (or current) is applied to a coil. A relay provides isolation of control signals from switched signals and is operated by a solenoid.

    for example like If u have dual battery through the relay (actually a starter solenoid) if the ignition was on, the relay was closed and both batteries got charged, with the switch off...(or even during the start cycle) the batteries were isolated.

    So u can run your stereo with the engine off, and which will not drain your battery.

    The isolator has no moving parts, and always keeps the batteries isolated, with the relay the batteries are tied together after the engine starts.



    lot of these so called relays are marketed as isolators are just switches which allow the current to pass.. inwhich the current flows in both directions. You wouldnt want a system demanding lot of current to be sucking juice from a dead battery while it iteself it trying to get charge from the good battery... Also relay doesnt work well with different type and size batteries.. When you parallel batteries even without a relay u want them same Ah, age ect.. I know because I used to install this stuff in recreational applications

  9. #19
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    You MUST use the continuous duty relay if you want to actually use the second battery to power the vehicle [bad alternator]. Otherwise the relay coil will overheat and fry. Either type of relay can be used to "jump" the main battery from the aux.

    HOWEVER!!!!

    To keep both batteries charged properly you MUST use a battery isolator! If you do not, one battery will discharge the other over time, or one will fail to charge, due to differences that develop in their electrochemical makeup, even if they are exactly the same to start! If you are using a deep cycle battery for the aux the problem is magnified. Or if you start out with mismatched batteries [very bad idea] the system will fail rapidly. Ford used to use the continuous duty relay setup as an OEM solution because it was cheap and it would usually last thru a 1 year warranty period with new batteries. It never did work for long, and could not work due to battery chemistry problems. If you use an isolator you can use different types of batteries in the system, or even a new and old(er) one.

    ALWAYS USE AN ISOLATOR! You can use the proper relay to bypass the isolator for those high current needs.


    Quoted from an old post here
    http://www.ford-trucks.com/forums/76...ry-system.html


    Simply put... they cost more for a reason.. If you are asking for more Ah hence power then relay is good.. but if you want 2 independent banks totally separate then go with isolator!!!

  10. #20
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    Sorry, for some reason I haven't been getting notifications.

    But Simbalage, I suspect you are not aware of my other posts on this subject - you are generally just repeating what I have said.

    The "not paralleling" refers to diode isolators (and some FET types) where you have to use a bypass (eg, relay) to bridge the semiconductors. But in that case, why bother with the isolator? (I know, your surge comment refers....)
    As to not paralleling batteries (except when in use or being charged), HERE HERE! I've had enough crap like "why not - it's done all the time!?". (Yeah, so too is lifting heavy weight, over-revving engines, exceeding inspection/service periods...)


    But as to some of the differences.... Who the heck would use an isolator connected triggered by the IGN switch? (Probably those that think it is ok to keep batteries paralleled!)

    I deal with what people can readily obtain. I do not rant about battery diagnostic methods to which I am privy (ie, that the so-called "priority charging isolators" would have to use to determine the state of charge of the primary battery using only a voltage connection (ie, not current monitoring). Though if emergency equipment is readily available....


    For various reasons I am against diode-type isolators though the newer FET types can overcome the voltage drop issue and can be thought to emulate a mechanical relay. But FETs usually still have a voltage drop greater than a relay.
    Plus they are more expensive, and more prone to failure (in general).
    The diode and maybe MOSFET advantage - it can isolate a failed battery from the other (whilst charging), but most with other isolators (should!) have an voltmeter else alarm to warn of resultant voltage drops (or especially with AGMs, battery temperature monitoring). But with some solid-state isolators, a failing battery may blow that half of the isolator.


    If you argue against surges, then you are effectively arguing against the isolators that most people have - namely relays. And I won't mention jump-starting of cars! (I might write it though.)
    Not that I mind - that helps my argument against those ridiculous (and often fraudulent) "priority charging" systems. (That's in general: for undersized alternators and "priority charging" that does not assert "when the primary battery is (nearly) fully charged", (it) is IMO quite acceptable.)


    So again, I ask you, when have relay-type isolators been problematic due to surges?
    [ Imagine how often they occur for voltage sensing isolators! And what great advertising for the UIBI if you can demonstrate your case! ]

    I use different batteries in with my isolator (a UIBI - ie, an alternator-controlled relay) - different sizes, ages, and types (AGM & wet). Mind you, I only get 8 years out of my standard 2-year warranty wet-cells (that's a LOL).


    Note too that I use the term "isolator" in its common usage. It is not specific to the technology (solid state or mechanical), though in these discussions it is typically meant to infer a automated connection system and not a mere IGN or ACC or manually controlled inter-battery isolator.

    One beauty of the non-solid state isolators is that you do not have to worry about their voltage drop. Whilst this is not a problem for newer and multi-wire alternators (ie, SL, SIL etc), it can be a big problem for those with single-wire alternators (D+ only) - especially if using the traditional diode types (a 0.6V drop).

    Also, the only IMO reliable solid-state isolators I have seen are those that handle the transient currents from alternators (typically about double the alternator output - ie, sub-transient reactance). Not that that means the diode's/FET's RMS rating, but they are already expensive just handling expected currents. (Except for the FETs - $2-$3 for 100A capable MOSFETs is fine, but diodes at that rating tend to cost, especially with heatsinking.


    Anyhow it seems like this is largely academic since you are discussing something that seems too expensive or of limited availability to most [whereas the UIBI etc is essentially just any appropriately rated relay, albeit with a buffer in some cases (ie, a smaller relay else transistor/FET)], though for those that don't want to fit or use a dash voltmeter etc or not worry about battery maintenance (ie, checking) and can afford the money and space, MOSFET isolators are quite good - especially if 2-way, even IMO if not as robust as relays. And I doubt the solid-state types are big enough for big-audio needs (not that this forum get's into that).
    (I presume MOSFET isolators use a soft-start to guard against surges?)

    Besides, I swore not to respond to non-OP's arguments. The last time I argued (the merits of the UIBI approach over a voltage-sensing isolator) it turned out the arguee had a marine system which was not relevant to the OP's vehicle system!
    (Though at least he interjected into a "live" thread. This one was old and dead.)


    I'd suggest you start a new thread if you want to highlight the hazards of surges. Many hereon would be interested in that since they often use some form of switching to interconnect main and aux batteries - typically smaller batts for PCs etc. Surges are very relevant indeed!
    I find it strange that I haven't noticed others post their surge problems, but maybe that's just me.

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