12v 200amp relay wanted (1 Viewer)

[olley]

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

Olley

 

[pappajohn]

hi Olley,

might be worth a look at this type of thing. Link Removed

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..oh:

 

[Thepips]

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

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[pappajohn]

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

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.oh:

 

[olley]

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

It needs to be big enough to pass sufficient current to start the RV. 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. oh:

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.

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

Olley

 

[Wildman]

I think we have a problem Houston

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[PeteH]

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

 

[olley]

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. oh:

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

Olley

 

[davida]

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

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[davida]

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

 

[SIFTA SAM]

Would a ballast resistor not be worth considering?

 

[olley]

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

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[SIFTA SAM]

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!

 

[Geoff]

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

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

 

[olley]

Hi found some, thanks david, albrights.

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.

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[Geoff]

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.

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.

 

[olley]

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.

Thanks for your comments. :thumb:

Olley

 

[Jim]

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

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[45eEver]

This any good to you?

Link Removed

From what I know of them, not definitive, you can mount the pull in relay either way.

Ie, it can be normally closed, or normally open.

 

[olley]

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

 

[45eEver]

Olly, the battery voltage will be just the same.

Around 12.6 before you start it, and about 9 or 10 when you are actually starting it.

The charge voltage can't alter the storage voltage, as long as it's over 13.5v.

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[45eEver]

Diodes are complicated little devils Olley.

The amount they drop the voltage varies with the current.
I'm not quite sure where you intend to use a diode, but if I had your what I understand as your problem, problem, I'd simply disconnect the lead from the alternator to the start battery.
And connect the start battery to the storage batteries with a decent bit of cable.
Say small starter cable.

Wired that way, your storage batteries get first bite at the charge from the alternator, and they are the ones that are usually flattest.

Starting doesn't take much out of a battery, so unless you leave the lights on, or something like that, it never gets very discharged.
Storage batteries on the other hand, can get pretty flat.

 

[olley]

Hi 45 the starter will be getting its feed through the diode so their will be a voltage drop of maybe 1 volt straight off. If as you say starting voltages can drop to as low as 8v then I should be ok.

I want to keep the house and chassis batteries separate incase I flattern the house batteries, connecting them together as you suggest could mean I flatten all the batteries, not likely; but possible.

Like most RV's I have an emergency start relay to enable the house batteries to start the engine in the event the chassis battery is flat.

Just ordered the diode will let you know how I get on.

Olley

 

[45eEver]

I'm not sure why you want a diode in your starter circuit Olley.

I seems like you want to drop the battery voltage to the starter motor.

I've run a 6v starter motor off a 12v battery for yonks.
The motor hardly gets warm, even though my motor takes a fair time to start if I don't prime the carb.
I reckon you could safely use 24v on your starter motor for cold weather staring.

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[45eEver]

To prevent a flat starter battery, fit an ignition operated solenoid in the cable from the storage batteries to the starter battery.

When you switch on, the solenoid pulls in, when you switch off, the solenoid drops out.

You need a big solenoid though, because the storage batteries will bung a chunk of current the starter's way.

 

[olley]

I'm not sure why you want a diode in your starter circuit Olley.
.

To prevent the alternator feeding the batteries with 14.9 volts. The alternator is connected directly to the starter motor, as are one or two other wires, without a fair bit of rewiring I can't change this.

Olley

 

[45eEver]

I don't know about your particular diode Olly, but most diodes drop the voltage a lot at their maximum current.

But there's very little drop when they are passing a low current.

You need to it the other way round.

A low drop at high charge rates, and a hight drop at low charge rates.

As someone's already advised, your best bet is to fit a different regualtor to your alternator.
Or top your batteries up more frequently.

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[olley]

Hi the high voltage doesn't just mean you have to top up more often, it destroyed the batteries, I have just replaced 3x185amp at £100 a piece, bought two years ago at the PB show, the chassis battery is also U/S and I will replace that at the Stratford show.

It is possible to change the regulator according to a yank poster on IRV2.com but they are difficult to source, and the price?? Their are undoubtabley better ways to do this, but after my initial idea of buying (£90) and putting a split charge diode directly after the alternator failed because of the voltage sensing from the PCM I want to use it if possible.

Fitting large diodes and the like is more engineering than electronics, unlike stripping an alternator and replacing the regulator, engineering is my field, electronics??

Olley

 

[45eEver]

Fitting a new regulator to an alternator is Meccano stuff Olley.

Two screws on this one and it's off.
Alternator Fundamentals - Alternator and Voltage Regulator Operation

Anyhow, what's the make and model number for your alternator Olley?

 

[45eEver]

If you charge the average 12 lead acid abttery at above say 14.5 volts, the water in the acid turns to hydrogen and oxygen, and floats away.

If you charge at 14.0 volts, you need to top the battery up with distilled water very frequently.
There's nothing like a water shortage inside your battery for ruining it Olley.

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