Alternator Paralleler Circuit

[Gibbo]

The sticking point in this auto-switchoff circuit seems to be whether the W output falls to zero or not. If it does, even for a fraction of a second, this is enough to switch off a thyristor

 

You seem to be missing the point that the signal on W is AC. So it drops to zero several times per alternator rotation. So that will continualy switch a thyristor off. So it will never stay on.

 

Gibbo

[WotEver]

The sticking point in this auto-switchoff circuit seems to be whether the W output falls to zero or not. If it does, even for a fraction of a second, this is enough to switch off a thyristor, which of course will not conduct again until "restarted". It may not be enough to delatch a relay. Can an alternator expert tell me if this happens?

 

OK, my circuit needs a diode in the W feed same as smileypete's and the thyristor may need to be biased correctly but it is still simple and positive in operation. (if it works! I'm not a circuit designer)

 

Hi Semitrad,

 

I'm loath to post another schematic which will only serve to muddy the waters but the problem with using a thyristor even if you take my modification of your circuit and then apply Gibbo's modifications onto that is that it has to end up being switched on with a toggle switch (or be left in permanent auto-on). The reason being that in order to supply the gate with a smoothed output from W (to keep it switched on) you now have a permanent connection to W, so it'll just switch itself on without the push-button start. If you don't feed the gate in this way the thyristor will switch itself straight off due to the square wave coming from W.

 

Regards,

Tony

[Sir Nibble]

I like that but there's something telling me that with some alternators there will be no quench diode across the rotor at the time of switchover between D+/B+ and vice-versa.

 

Gibbo

The quench diode is generally integral with the regulator and only the supply to the reg is switched. Upon reflection, it may be better to enslave the D+ output to energise the relay too as W would probably drop it too soon.

 

If hacking the engine alternator isn't a problem, another way is to tap into the 3 stator phase outputs, feed them into a diode trio, and connect the other side to the domestic batts.

 

If the diode trio heatsink is sized right, a 14.4V engine alt will give full output until the domestic batts reach 14v or more.

 

For the diode trio, part of a 35A bridge rectifier could be used for each phase, giving 100A rating in total. Not quite as good as a relay solution, but only £10 in parts.

 

cheers,

Pete.

This is a cute solution too and is actually built into some alternators. The reason I didn't advocate a second rectifier is that it involves serious alternator surgery wheras the reg mod is only precisely the same as loadsa people do to fit their battery boilers.

[Gibbo]

The quench diode is generally integral with the regulator and only the supply to the reg is switched. Upon reflection, it may be better to enslave the D+ output to energise the relay too as W would probably drop it too soon.

 

That's my point. The diode is in the reg, but the +VE brush doesn't always go via the reg. And on the rare units where it doesn't, when the relay switches, the rotor will have no diode across it.

 

Gibbo

[Sir Nibble]

That's my point. The diode is in the reg, but the +VE brush doesn't always go via the reg. And on the rare units where it doesn't, when the relay switches, the rotor will have no diode across it.

 

Gibbo

Any machine sensed alternator will have a connection to +ve brush, this mod is not applicable to a battery sensed jobbie. I have made the mistake of assuming this is only applicable to a pair of A127s, I do not think we could come up with anything that would be readily transferable to any and all units without using some external component such as an ACR alternator reg just to use as a voltage sensitive switch. Smileypetes second diode trio is the perfect fully automatic solution, and whilst it requires cracking the casings apart on some alternators would be a simple job on others.

[Semitrad]

Hi Semitrad,

 

I'm loath to post another schematic which will only serve to muddy the waters but the problem with using a thyristor even if you take my modification of your circuit and then apply Gibbo's modifications onto that is that it has to end up being switched on with a toggle switch (or be left in permanent auto-on). The reason being that in order to supply the gate with a smoothed output from W (to keep it switched on) you now have a permanent connection to W, so it'll just switch itself on without the push-button start. If you don't feed the gate in this way the thyristor will switch itself straight off due to the square wave coming from W.

 

Regards,

Tony

 

Hi Tony,

 

thanks for your help in posting my diagram. You are probably right about the thyristor, my understanding was that a thyristor needs a trigger to start conducting, it would then remain in a conductive state until the applied voltage dropped beyon a certain level or went negative upon which it would switch off and remain so until triggered again.

 

The thinking behind this is to end up with a contactor, a small box, a switch and a lead to connect to the W terminal of the spare alternator so that almost anyone could fit it to their boat and it would work immediately and reliably.

[WotEver]

my understanding was that a thyristor needs a trigger to start conducting, it would then remain in a conductive state until the applied voltage dropped beyon a certain level or went negative upon which it would switch off and remain so until triggered again.

 

Indeed - but the voltage dropping to zero is exactly what the W output does several times per second.

 

The thinking behind this is to end up with a contactor, a small box, a switch and a lead to connect to the W terminal of the spare alternator so that almost anyone could fit it to their boat and it would work immediately and reliably.

 

I believe that's exactly what Pete's circuit will do. Depending on how high the 'warm' resistance of the lamp gets it might require a 2W to keep the relay latched, but once he's tested it to prove the theory it becomes quite a small and simple little package

 

Regards,

Tony

[Smelly]

An engine service and my hunting issues have managed to inspire me to pick up my multimeter again...

 

As some will know, although not yet following Pete's circuit my relay is powered solely from W, a circuit diagram is below somewhere.

 

The voltage is getting up to 14.6 to 14.8 at this minute but the relay hasn't dropped out. It seems that my DAR is correctly set up now (it wasn't before due to conflicting instructions between the case and the book) and it's not spiking according to my cheapy meter, however it's definitely getting up to at least 14.6V accepting .2v accuracy, (it's flickering between .6 and .8 at the minute) and furthermore we've run until the bulk phase on the sterling has ended on several occasions but the relay has never dropped out.

 

There were comments that the residual magnetism in the rotor would give this effect and having done the tests it seems they may have been right, assuming I've been following this correctly.

 

Further testing, should it be suggested, will need to wait til next weekend as we're cruising tomorrow, but feel free to suggest them.

 

Dan

 

edit... for fullness, the tacho is still connected to the same w we would expect to shut down but it's still counting.

 

edit again... terminal voltage of the engine alt after I'd switched the rely off has dropped to 14.37 give or take .2

Edited July 11, 2009 by Smelly

[pistnbroke]

Ive come on this at the end and have not read all the posts but would not an off the shelf Voltage Sensative relay join the battery banks and hence the alternators once tthe starting battery comes up to full volts .??

 

you must get your batteries up to 14.4v and even at that they will only be 80% charged...there seems to be a lot of wooly references to voltage in this ...

Edited August 1, 2009 by pistnbroke

[Smelly]

Ive come on this at the end and have not read all the posts but would not an off the shelf Voltage Sensative relay join the battery banks and hence the alternators once tthe starting battery comes up to full volts .??

 

you must get your batteries up to 14.4v and even at that they will only be 80% charged...there seems to be a lot of wooly references to voltage in this ...

 

The thing is, it's not so much the engaging as the disenaging (although i suppose a double pole relay might do). The plan was to disengage the engine battery once the voltage gets above the engine alt' regulator voltage. ChrisW did it but did some serious doctoring to his alternator to achieve it, however that wasn't very end used friendly hence trying to use the W connection, but certainly in my experience Sir Nibble was right a there seems to be enough energy left in the system once the engine alt is doing nothing to keep the contactor closed.

 

I must say, with an un-approved version I've cut my diesel bill down significantly for the sake of pushing more amps into the battery, and it's only down to the fact that I can't find the socket that I ground down to fit the alt's that I've not gone down the reg doctoring route but having measured enough to satisfy my head; the W connection route doesn't shut down; at least on my installation.

[pistnbroke]

dont see the piont in diconnnecting engine battery once it is fully charged ..the current taken will be very small and if the battery is nearing the end of its life you are risking a non start.

 

the output from W is high frequency half wave rectified AC and it will not be affected by the action of the voltage regulator ......if you want to disconnect the starter battery why not wrap a few turns of its charge cable wire around a reed relay ......current drops to low level and reed opens.....and that can work a relay ....KISS ....push switch across reed to re set it after the next start ...

[Bagpuss]

dont see the piont in diconnnecting engine battery once it is fully charged ..the current taken will be very small and if the battery is nearing the end of its life you are risking a non start.

 

the output from W is high frequency half wave rectified AC and it will not be affected by the action of the voltage regulator ......if you want to disconnect the starter battery why not wrap a few turns of its charge cable wire around a reed relay ......current drops to low level and reed opens.....and that can work a relay ....KISS ....push switch across reed to re set it after the next start ...

 

I've never heard of a reed relay before... however wrapping the 50mm² cable around it might perceivably be a challenge.

 

edit... love Smelly who must check whether he's logged into SWMBO's profile...

Edited August 4, 2009 by Bagpuss

[pistnbroke]

well you want to monitor alternator output dont you....so a length of 3mm welding wire wrapped around a 6 mm rod wont be too difficult will it ,,,suggest you google reed relay ...look at a CPS /maplin/radio spares catalogue ..get a large one say 50 mm long ..it will cqoute the amp turns to close it ....

[Smelly]

well you want to monitor alternator output dont you....so a length of 3mm welding wire wrapped around a 6 mm rod wont be too difficult will it ,,,suggest you google reed relay ...look at a CPS /maplin/radio spares catalogue ..get a large one say 50 mm long ..it will cqoute the amp turns to close it ....

Did quite a bit of googling yesterday but couldn't find a reed relay that spec'd as you describe... Suggest me up?

[WotEver]

Did quite a bit of googling yesterday but couldn't find a reed relay that spec'd as you describe... Suggest me up?

 

Don't worry about it Smelly. Our antipodean friend is talking nonsense. As you quite rightly stated, wrapping 50mm charging cable around a 5mm diameter 50mm long reed relay would prove somewhat difficult.

 

Here's a little picture showing how they're used:

 

Cheers,

Tony

[pistnbroke]

One thing you will find is that that I dont talk nonsense ....a reed relay is a very good cheap current sensing device just part of the electronic bits and pieces you can get .....what you need is the reed only ..not a minature with a coil around it . if I read this right then you wanted to know when the current to the starting battery had dropped so you could use its output for other purposes ......so you . can makethe coil out of say 3 mm brazing rod and wind around a small bar in a vice ...then adjust turns and spacing of wire to signal when the current has dropped to the level you want ...so Whatever watch your lip (_!_) hole

Edited August 10, 2009 by pistnbroke

[WotEver]

One thing you will find is that that I dont talk nonsense ....a reed relay is a very good cheap current sensing device just part of the electronic bits and pieces you can get .....what you need is the reed only ..not a minature with a coil around it . if I read this right then you wanted to know when the current to the starting battery had dropped so you could use its output for other purposes ......so you . can makethe coil out of say 3 mm brazing rod and wind around a small bar in a vice ...then adjust turns and spacing of wire to signal when the current has dropped to the level you want ...so Whatever watch your lip (_!_) hole

 

So you're suggesting that Smelly makes two breaks in his 50mm alternator feed in order to connect a short length of 3mm brazing rod in series.

 

Absolute nonsense and stupid to boot.

 

Tony

Edit to add that I'm fully aware of what reed relays are, and was probably using them while you were still in nappies. I suggest you take your time getting to know the personalities on this forum prior to making assumptions about what folk may or may not know.

Edited August 11, 2009 by WotEver

[pistnbroke]

not sure what pills you are on but your alternator output cable would not be 50 mm2 more like 8 mm2 and some 3 mm rod is 1.5 x 1.5 x 3.14259 is 7 mm2 which is fine ......perhaps you need to understand that the magnetic field created by the small coil on the reed will keep its contacts closed until charge current falls ..that can activate your switching circuitry .which is what you were trying to detect ...

 

If I have been talking electircal techno crap I have doing it for 40 years and have degrees and certificates to prove its total crap

[WotEver]

If I have been talking electircal techno crap I have doing it for 40 years and have degrees and certificates to prove its total crap

 

It's CW back off holiday!!

 

And yes, Smelly's (and mine, and many other's) charging lead is indeed 50mm

 

T.

[Smelly]

It's CW back off holiday!!

 

And yes, Smelly's (and mine, and many other's) charging lead is indeed 50mm

 

T.

 

Aye! 50mm, fitted it at the same time as the relay gubbins, recycled forklift battery cable to be precise. I came up with about a .4v drop across the 10mm cable I was previously using so ditched it and got the big guns in; unsurprised that we'd killed a set of batteries in 18 months.

 

It didn't matter too much as the alt' controller would have dealt with the drop once I fitted it (in a vain attempt too save the batteries) but using less energy, even if it's 0.5RPM off the engine is, in my book, a good thing (although I'll never tell Bagpuss that she shouldn't be using the 2nd lappy ).

 

It seems, when next I've got the time, and in all fairness it'll probably be next year when the BSC is approaching, that i'll doctor that spare reg to go ChrisW's route (unless I've given it away to a needy boater by then). In the short term, i have a system which significantly increases the charge into my batteries and reduces engine running time and hence dino's burned

 

However, I'm not familiar with welding rod, but am aware at cruising revs I would be pushing 30 or 40 amps through it. I don't want it to get hot... at all... which is what welding rod seems, to me, to be designed to do. In the interests of impartiality, a small coil of 8mm2 might be feasible, but jointing it to the 50mm; and I am not forgoing that, seems problematic. Bearing in mind my engine is running every other day and we cruise 2 or 3 weekends of the month I would need to be absolutely certain of the joint's worth; I wouldn't trust a soldered joint.

[WotEver]

However, I'm not familiar with welding rod, but am aware at cruising revs I would be pushing 30 or 40 amps through it. I don't want it to get hot... at all... which is what welding rod seems, to me, to be designed to do. In the interests of impartiality, a small coil of 8mm2 might be feasible, but jointing it to the 50mm; and I am not forgoing that, seems problematic. Bearing in mind my engine is running every other day and we cruise 2 or 3 weekends of the month I would need to be absolutely certain of the joint's worth; I wouldn't trust a soldered joint.

 

Absolutely.

 

There's nothing wrong in theory with using the magnetic field from the charging cable to hold on a reed relay (which in turn would switch another relay) but in practise cutting your 50mm charging cable to insert a piece of rod would be an absurd thing to do. It wouldn't get hot at 40A (well, it would raise by a degree or two from ambient) but you'd be introducing two more resistances at the joins, the joins would be highly problematic to achieve, reed relays are fragile things to have in an engine bay (they're just a glass encapsulation), the rod would need to be fully insulated in order to avoid shorting the turns, and you'd need to do a lot of experimenting with the number of turns to get the relay to close and open at the right time, even if it were possible.

 

All in all a nonsense suggestion.

 

Tony

[Nige123]

OK I did try to read all 25 pages about this but I must admit to feeling my life was too short......

 

the idea sounds like a sound one & I thought it must have been done before? then I looked on my new boat & as far as I can see my 2 80Amp alternators seem to go to my " Sterling AD12160AMp RS485" http://www.sterling-power.com/products-altbatt.htm & this bit of kit seems to use the charge from both alternators to charge what ever batteries need it most & will also use the 240v shore power to do the same!

 

Is this right or am I just dreaming here?

 

I would think most people that have twin alt' set ups mould like to use this idea but many may want an insurance "if my boat starts fire" legal type solution & maybe this is it???????

 

ps

I have no shares in Sterling products must be others you can buy....

[WotEver]

... this bit of kit seems to use the charge from both alternators to charge what ever batteries need it most ...

 

Not according to the link you supplied. Both diagrams in that link show the box as being nothing more than an external Alternator Controller for a single alternator.

 

This thread is about paralleling two alternators to get extra charging power.

 

Regards,

Tony

[Smelly]

Not according to the link you supplied. Both diagrams in that link show the box as being nothing more than an external Alternator Controller for a single alternator.

 

This thread is about paralleling two alternators to get extra charging power.

 

Regards,

Tony

 

The bumpf does say it can be used with 2 alts however... The vast majority of the discussion on this thread has been about getting one alt to cut out once; thus opening the paralleling relay when a) the charge voltage rises above the nominal charging voltage of an unregulated alternator running in parallel with a regulated one which means that one alternator can happily supply the amount of current the battery will accept.

 

Also, accepting the risk of boaty catching fire is virtually nil, the system we've been discussing is about 200 quid cheaper than Mr Sterlings.

[rogerc]

hi

 

very interested in this topic as i have been thinking about paralleling my altenators instead of buying an alternator controller. i have got lost wading through 25 pages. does the original basic circuit work OK the discusssion is about auto drop out? and secondly is there a problem of pushing 100A + through the the battery and buckling the plates?

 

cheers

 

roger