Jump to content

2nd alternator wiring


JST

Recommended Posts

i think i know how to do it but would like some confirmation please.

sense wire through a relay then to a dash wng light then earth

relay above switched by ignition in position II.

i run two batteries in parallel therefore intend to switch the relay straight off the ign rather than going to Bat 2 as its not on a 2nd circuit.

so is this right?

secondly could i wire the charge wire to the 1st alternator? the starter or the battery?

lastly - from the above i would understand the dash light to come on when the relay is switched when the ign is in pos II. so when the alt is charging does it use this signal and therefore the light goes out? in other words i dont understand how the dash light goes out once the alt/engine is running!

any help greatly appreciated.

Link to comment
Share on other sites

yep that makes sense, following Jamies post, so questions are:

is their a suitable similar light (24v battery?) on a td5 dash?

i am correct i that i wire the wng light through a relay to the exciter on the alt, and the other end of the wng light can go to the ign as its only running one battery?

with a td5 dash i believe you only get to see one side of the bulbs - ie only a flying wire for one side the other is already earthed or 12v ign depending if it is -ve or -ve feed - so how do i wire both sides of a bulb?

can i work off pos II on the ignition as it goes to one battery for both the relay energiser and the other side of the bulb.

Link to comment
Share on other sites

more thinking

if i take a bulb that needs a -ve for the light to go on (ABS for example) and connect that to a relay (pin 87) then take relay pin 30 to the alternator. if i am right in thinking the light will come on when the ign is on and when the relay is energised as it allows the wire to earth through the alternator, ie 12v being passed to the alternator, this also excites the alt.

when the engine is started and the alternator chucks out 12v it will feed this back through and the light will go out as the earth is lost?

Link to comment
Share on other sites

My plan (not tried yet - follow at your own risk) is to have a single battery with a twin alternator setup. The reason for this is that I have 2 alternators available (one 80amp and one 65amp) and I will be using separate v-belts for them as I don't fancy putting the load of a more powerful alternator through one belt. Also I will not be winching or using a 'leisure' battery so I feel that I don't need the expense of a split charge system. I just fancy a bit more reserve than the standard 80 amp unit gives.

I intend to feed separate warning lights from a common source. No relays.

My reasoning - derived from reading around rather than experience - is this:

The alternators are internally voltage sensing and current limiting. The internally set voltage is somewhere between 13.6v and 14.4v. It is likely that any two alternators will have different 'target' voltages and hence one will always work more than the other, this I would regard as the primary unit. Now, if the primary unit can't cope (tickover, heated screen, lights, maybe other things) then the voltage will fall low enough so that the secondary alternator will join the fray. I do believe that a matched pair of alternators would be better, but this uses what I have available.

My 2p's worth..

Roger

p.s. I think that Lucas ACR alternators can be switched from one 'hand' to the other by unscrewing the front plate (three bolts) and rotating it 120 degrees. Again - not tested - but it seems to work from the diagrams, and anyway - I read it on the internet so it must be right! :lol:

Link to comment
Share on other sites

ive done more or less what three sheds sugests except using 2 bateries [12 volt] wired in parallel making them effectivly one big battery the two alternators are different and are fed power direct from ign switch via a fuze through 2 astra wing reapeater lamps mounted on the dash ,all seems to work well with no probs so far.

Link to comment
Share on other sites

i think i know how to do it but would like some confirmation please.

sense wire through a relay then to a dash wng light then earth

relay above switched by ignition in position II.

i run two batteries in parallel therefore intend to switch the relay straight off the ign rather than going to Bat 2 as its not on a 2nd circuit.

so is this right?

secondly could i wire the charge wire to the 1st alternator? the starter or the battery?

lastly - from the above i would understand the dash light to come on when the relay is switched when the ign is in pos II. so when the alt is charging does it use this signal and therefore the light goes out? in other words i dont understand how the dash light goes out once the alt/engine is running!

any help greatly appreciated.

D+ on the alternator is connected to the charge warning light. The other terminal of the charge warning light is connected to battery positive. On startup the regulator tries to produce maximum current - in effect D+ is shorted to the field windings, thereby creating a passage to vehicle earth (negative). Thus a current flows trough the charge warning lamp and the field windings and energizing the alternator. When the alternator starts producing current B+ and D+ is equalled, therefore the charge warning lamp receives positive feed on both therminals and goes out.

Not many modern alternators are equipped with remote sense these days. Either way - the above setup for remote sensing would not work. Remote sense should be conncted directly to battery positive. (Or maybe I have misunderstood your explanation)

Easyiest way to connect a supplemental alternator would be to take the battery positive feed to the charge warning lamp and connect to another 2 watt lamp working as a charge warning lamp for the second alternator. This other terminal of this charge warning lamp should be connected to D+ on the alternator. B+ on the alternator should be connected to battery postive.

Link to comment
Share on other sites

On mine I simply took the warning wire from the alternator to the spare light on the dash . and then the other terminal of the lamp to the 2nd position on the back of the ignition switch. Didnt find the need for a relay , Its nice and simple and works .

Link to comment
Share on other sites

D+ on the alternator is connected to the charge warning light. The other terminal of the charge warning light is connected to battery positive. On startup the regulator tries to produce maximum current - in effect D+ is shorted to the field windings, thereby creating a passage to vehicle earth (negative). Thus a current flows trough the charge warning lamp and the field windings and energizing the alternator. When the alternator starts producing current B+ and D+ is equalled, therefore the charge warning lamp receives positive feed on both therminals and goes out.

Not many modern alternators are equipped with remote sense these days. Either way - the above setup for remote sensing would not work. Remote sense should be conncted directly to battery positive. (Or maybe I have misunderstood your explanation)

Easyiest way to connect a supplemental alternator would be to take the battery positive feed to the charge warning lamp and connect to another 2 watt lamp working as a charge warning lamp for the second alternator. This other terminal of this charge warning lamp should be connected to D+ on the alternator. B+ on the alternator should be connected to battery postive.

On mine I simply took the warning wire from the alternator to the spare light on the dash . and then the other terminal of the lamp to the 2nd position on the back of the ignition switch. Didnt find the need for a relay , Its nice and simple and works .

Cheers guys, thats what i will do then.

Twin alternator rather than larger, td5 disco alternator?

i would happily fit a td5 disco one, can you send it on?

Link to comment
Share on other sites

Twin alternator rather than larger, td5 disco alternator?

Two alternators for me - yes. Reasons being that the two I have are free and are V-Belt (TD5 would be - what £70 2nd hand? and would require a poly-v belt which I don't have) and if one fails (mud springs to mind) the other will seamlessly take over the full load and get me home :)

That's the plan anyway ;)

edited to add: Actually I have just checked and there is a TD5 alternator assembly on eBay for £45!

Link to comment
Share on other sites

No need for a relay James. Just find an ignition concious feed, There will be plenty behind the dash, pinch one off the other dash lights is easiest. Hook it up to a spare warning light then from the other side of the bulb to the warning light terminal on the alt'.

Link to comment
Share on other sites

I have a 100 amp disco one , It still didnt put enough punch back in , so a second 120amp P38 unit added made all the difference when under constant winching .

i interested as i've been told a td5 disco ALT will be sufficient for 1 winch with two batteries.

Link to comment
Share on other sites

i interested as i've been told a td5 disco ALT will be sufficient for 1 winch with two batteries.

A 15 amp dynamo is sufficient for 2 winches, one battery. It just depends how much winching you do. I know that Jase often uses two winches together for extended periods so I guess that two alternators are a necessity in that situation.

Chris

Link to comment
Share on other sites

Two alternators for me - yes... ....if one fails (mud springs to mind) the other will seamlessly take over the full load and get me home :)

That's the plan anyway ;)

How will you know when one alternator has failed - and which one?

Chris

Link to comment
Share on other sites

separate warning lights... (If I understand the situation correctly :rolleyes: )

Aha, got you! :P You mention mud as being the demise of alternators. I am no stranger to this happening, in my case each time due to the brushes getting stuck and failing to make contact with the slip-ring. This does not cause the dash light to glow at all, the only way to tell the alternator was US was that the volt meter read low. It took a few flat batteries before I worked out just how much lower than normal the meter would read in this circumstance. Thinking about it, I think that the alternator light may not have lit when on ignition either, which would give a clue - it had been some years since it last happened.

I hope my experience can save you a flat battery. :)

Personally, in your circumstances, I would rather fit one alternator with a removable brush pack, a volt meter and carry one spare belt and one spare brushpack. The brushpack takes minutes to change and the brushes can be freed with a little water which resumes normal service.

Chris

Link to comment
Share on other sites

Aha, got you! :P You mention mud as being the demise of alternators. I am no stranger to this happening, in my case each time due to the brushes getting stuck and failing to make contact with the slip-ring. This does not cause the dash light to glow at all, the only way to tell the alternator was US was that the volt meter read low. It took a few flat batteries before I worked out just how much lower than normal the meter would read in this circumstance. Thinking about it, I think that the alternator light may not have lit when on ignition either, which would give a clue - it had been some years since it last happened.

I hope my experience can save you a flat battery. :)

Personally, in your circumstances, I would rather fit one alternator with a removable brush pack, a volt meter and carry one spare belt and one spare brushpack. The brushpack takes minutes to change and the brushes can be freed with a little water which resumes normal service.

Chris

Thanks for that - a good point about mud which I hadn't considered, and good advice too!

Link to comment
Share on other sites

  • 2 years later...

can someone please help as wireing isnt my strong point,im wireing up a twin alternator (300tdi 100amp magneti marreli),theres 3 contacts on the back D+,B+ and W

correct me if im wrong but the B+ goes to battery positive,D+ is the warning lamp/chargelight,but what is the W for?

forgive me if ive missed the answer in one of the above posts

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

We use cookies to ensure you get the best experience. By using our website you agree to our Cookie Policy