12v 200amp relay wanted

Discussion in 'Tech/Mech General' started by olley, Apr 28, 2009.

  1. olley

    olley Funster

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    Hi I need a 12v 200amp relay with normally closed contacts, plenty about with normally open, but not closed. Anybody help; pretty please?? :BigGrin:

    Olley
     
  2. pappajohn

    pappajohn Funster Life Member

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    hi Olley,

    might be worth a look at this type of thing. 12v SOLENOID

    its for a 9000lb winch so will easily be in excess of 200amp.
    these are normally open/open until powered then one (pair) contact/post will be closed while the other remains open.....switch the other way and the other is closed while the first is open.

    edit.....Ooops....just re-read your post re: normally closed..:Doh:
     
    Last edited: Apr 28, 2009
  3. Thepips

    Thepips Trade Member

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    Hi Olley,

    You need a double throw double pole relay. Terminal 87 is normally open and 87A is normally closed. Terminal 30 is common. Terminals 85 and 86 are the energising coil. When the coil isn't powered 87A is live and 87 is dead, power up the energising coil and 87 becomes live while 87A is dead.

    Hope that helps

    Regards
    Doug
     
  4. pappajohn

    pappajohn Funster Life Member

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    but does all that relate to a 200amp+ relay doug,

    i know these numbers apply to a normal auto type relay's (20/30amp) but the only ones i know at that ampage are the ones i mentioned.

    never had need for anything else so i dont know.:Doh:
     
  5. olley

    olley Funster

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    Hi guys, I know what I need but I can't get it. :cry: ordinary auto relays don't come that big.

    It needs to be big enough to pass sufficient current to start the RV. :Eeek: Long story but my alternator is designed to produce 14.95volts It was designed that way by delco-remy to allow for the voltage drop when a solid-state isolator was used, unfortunately GM didn't fit one. :Doh:

    Now on my 3rd set of batteries and enough's enough; I have fitted a 160amp split charge diode in the house batteries and they are now being charged at 14.15, the only way I can see of using it on the chassis battery is with a N/C relay, as soon as I turn the ignition on, the relay energises and disconects the direct connection to the charging sys, leaving the feed from the diode only, turn to start and the relay lose's its feed, and we have lift off. :BigGrin:

    I did fit the diode directly after the alternator but its voltage sensing, so that was a waste of time.:cry:

    Olley
     
    Last edited: Apr 28, 2009
  6. Wildman

    Wildman Read Only Funster

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    I think we have a problem Houston
     
    Last edited: Apr 28, 2009
  7. PeteH

    PeteH Funster

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    Charge Voltage?

    Hi

    Shurely the problem lies with the alternator? It should produce high voltage/charge with low batteries and reduced charging as the Battery condition comes UP? this would normally be the function of the regulator/diode unit in the back of the alternator? Have you had it checked out on the test bench?.

    Or have I got the wrong end of your problem?

    Pete
     
  8. olley

    olley Funster

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    Hi Pete alternators regulators are set by the manufacturer, most around 13.8 to 14.2, mine is unusual in that its set for 14.8 to allow for the voltage drop caused by a solid state isolator. GM didn't fit a solid state isolator, they used a standard mechanical relay instead. :Doh:

    If I knew what I was doing I might be able to strip the regulator and alter it, unfortunately I don't. :Rofl1:

    Olley
     
  9. davida

    davida Read Only Funster

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    Hi olley
    google albright winch relays.
    Rated I think 600 amps completly watertight. Dogs dooglies as a winch solonoid/relay. Used them in extreme 4x4 winch challenges putting 1200 amp hr batteries through an I/8t hP electric winch motor and never had a problem. Should turn over the Rv let alone its engine LOL.

    Dave
     
  10. davida

    davida Read Only Funster

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    Hi olley
    When all else fails read the instructions, Sorry I didnt read your problem correctly first time. Still worth a google on albrights as they do a few different type of relays contactors and solonoids.
    Alternatly could you not use a 5 pin relay to activate a solonoid or in your case deactivate a solonoid

    Dave
     
  11. SIFTA SAM

    SIFTA SAM Read Only Funster

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    Would a ballast resistor not be worth considering?
     
  12. olley

    olley Funster

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    Hi guys using a split charge diode, when the engine isn't running the chassis battery is isolated and can't power anything, that's why I need a "normally closed" relay to give an alternative electrical path.

    hi sifta how would a ballast resister work?

    olley
     
    Last edited: Apr 29, 2009
  13. SIFTA SAM

    SIFTA SAM Read Only Funster

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    A ballast resistor would 'drop' the voltage from your alternator to just your charging system.
    Depending what current your charging system is taking along with the voltage drop to give you approx. 14volts, the value of the resistor can be worked out.
    My very rough calculations, and knowing nothing of RV electrical systems, would indicate something like a one ohm/50Watt value resistor. An inline rectifier diode might do.
    Just might be a cheaper and simpler way of solving your prob?
    Would appreciate any comments from anyone who has had practical experience doing things this way!
     
  14. Geoff

    Geoff Read Only Funster

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    Hi Olley.

    I think you are creating an unnecessary problem by trying to wire in your split charge diode incorrectly.

    A split charge diode input should be wired directly to the alternator only. All supplies should be wired to the output (battery) side of the split charge diode, and will therefore be "live" as normal. This also ensures that your systems are supplied with the correct (14 - 14.5) voltage not 14.95V

    I don't think a ballest resistor would work as it would need a constant resistance on the demand side, which is obviously not the case.

    As an aside I would have thought that a standard 14.4V regulator would have been readily available if not here then in the States, and if you can't change it yourself it should be well within the ability of any auto electrician.

    Regards Geoff
     
  15. olley

    olley Funster

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    Hi found some, thanks david, albrights. :BigGrin:

    However another idea occured to me, why not use another diode? only snag is it would need to be rated at perhaps 300amps, can you get them that big???

    Olley

    PS the alternator has "voltage sensing" if it detects the system voltage has been lowered by a split charge diode wired directly after the alternator, it simply boosts it's output voltage to compensate. Been there, done that, got the tee shirt.
     
    Last edited: Apr 29, 2009
  16. Geoff

    Geoff Read Only Funster

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    All alternators are voltage sensing, and are either machine sensed, sense voltage at alternator output or battery sensed, sense voltage at the battery.

    Battery sensing is used to compensate for voltage drop through the split charge diode.

    Because your alternator has a high voltage output it has already compensated for the voltage drop and therefore must be configured as machine sensed. From your above symptoms I can only assume that when this high output alternator was fitted the wiring was not changed and you are still configured for battery sensing. I can't see that this will ever work with this alternator. I would suspect that if you reconfigure to machine sensing and wire the split charge diode as I previously suggested this should sort your problem.

    Regards Geoff.
     
  17. olley

    olley Funster

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    Hi Geof the alternator has a main positive terminal and a 4 pin plug which gives, turn on signal, field duty, ignition feed and relay, this goes into the PCM (Power Train Control module) it senses the voltage from the PCM but it also provides the PCM with data, voltage low and high, and load factor, high and low voltages 19 and 11v respectively will trigger limp mode, it uses the load factor to adjust the tick over speed.

    I think it uses the ignition feed to sense the voltage, it might be possible to reconnect it before the split charge diode and run a feed after the diode back to the PCM, but I am very wary of interfering in anything to do with the PCM. I have the phone number of a company who can supply a 500amp diode, so depending on price my problems could be solved. :Smile:

    Thanks for your comments. :thumb:

    Olley
     
  18. Jim

    Jim Ringleader

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    I can honestly say that I have hardly understood a single sentence in this thread:Blush:
     
  19. 45eEver

    45eEver Read Only Funster

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  20. olley

    olley Funster

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    Hi 45 thanks for the link but I am going to try a diode first, RS are flogging a 600amp one for £33 plus post. Not sure what effect the lower voltage will have on the old girls starting ability; hopefully not much.

    Olley
     
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