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Alternator Paralleler Circuit


chris w
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I think that what we see here is two people arguing slightly different points so as an involved and not quite innocent bystander I will elaborate...

 

Gibbo, you mentioned "efficient" charging. At that I assume you meant the best energy into the battery assuming the amount of energy generated to put into it.

 

Chrisw, were you in fact talking about "quicker" charging, whereby higher charge currents will more speedily charge things, although not so efficiently in terms of energy consumed?

Nope, I think you've been smoking something :lol: I don't think that's what Gibbo and I have been debating.

 

The relay lands tomorrow; I think it's a really good idea and will be following your circuit closely Chris as I like the deliberate act of switching it on and not being able to re-instate that system without further deliberate action from me come engine stopping time.

 

Depending on whether Bagpuss is game for putting a coat of paint on (and we've got extra red in the strive for a purple boat so it's entirely possible :lol: ) them it'll either be this weekend or next that the job gets jobbed. The PV panel will just have to keep the batt's happy in the meantime. :lol:

If I can help with any advice, please feel free to PM me.

 

Chris

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PS. If you've already got a S****G**** and you want to do this you're going to need the big relay anyway. And for a relatively small extra amount of dosh you can do all this very easily :lol:

 

Not trying to sell anything, but it is far simpler to install and not too much more expensive if you've already got one.

 

Oh and I can confirm Chris's findings that with under revved alternators at tickover it really does make a huge difference. As he said, a doubling of charge current at tickover is quite normal.

 

Gibbo

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But for the wong reason.

 

There is no optimal charge current.

 

Gibbo

There has to be an optimal current IF you insist all the points lie on a straight line on log paper (ie: an exponential curve)

 

Chris

Edited by chris w
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There has to be an optimal current IF you insist all the points lie on a straight line on log paper (ie: an exponential curve)

 

Chris

 

Finish the PM excercise then continue here. You will come round to agree that adaptive charging doesn't work. Honest :lol:

 

Gibbo

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Finish the PM excercise then continue here. You will come round to agree that adaptive charging doesn't work. Honest :lol:

 

Gibbo

That's as maybe, but what about the log paper? You will have to end up admitting that was a red herring or the maths holds up. The maths only falls if log paper is not needed. Then we can explore whole new vistas. C'mon just admit that was an RH.

 

Chris

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That's as maybe, but what about the log paper? You will have to end up admitting that was a red herring or the maths holds up. The maths only falls if log paper is not needed. Then we can explore whole new vistas. C'mon just admit that was an RH.

 

Chris

 

Wait until we finish. There is a lot more yet!

 

Gibbo

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Nope, I think you've been smoking something :lol: Unfortunately when I posted that I hadn't been, I'm running short so am saving it for bedtime :lol:

 

 

If I can help with any advice, please feel free to PM me. Ta.

 

Chris

 

One ask... can I just solder the diodes across the relays?

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One ask... can I just solder the diodes across the relays?

Taking the quench diodes off didn't solve the auto-switch off issue and YES you can solder the diodes across the relays. Double check you have them the right way round (ie: reversed); ie: cathode of the diode to the positive side of the relay coil and the anode of the diode to the negative side of the relay coil.

 

I still have to try Sir Nibble's idea of using the domestic regulator as a comparator only (see earlier post) to achieve auto switch-off. It sounds like a great idea but gods move in mysterious ways!!! At the end of the day a simple 90 minute timer will do just as well and that is easy to arrange electronically. So there is a plan B.

 

Chris

Edited by chris w
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I still have to try Sir Nibble's idea of using the domestic regulator as a comparator only (see earlier post) to achieve auto switch-off.

 

Chris

 

Hmm, soldering to little bits of spring sounds like a good way for a novice such as I to kill a good alternator... Maybe I'll look for a timer circuit at Maplin's when I've a better signal.

 

Ave a cuppa tea, ave another one! :lol:

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Hmm, soldering to little bits of spring sounds like a good way for a novice such as I to kill a good alternator... Maybe I'll look for a timer circuit at Maplin's when I've a better signal.

 

Ave a cuppa tea, ave another one! :lol:

Maplins only do a short timer kit (a couple of minutes). But, electronically, it is very easy to make a 90 minute timer. If I end up going down that route, I'll make 2 and let you have one for a nominal fee.

 

Chris

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Remove the domestic alternator regulator, cut the link between -ve brush and regulator, I would leave enough metal on the brush to curl it under the lip on the plastic brush box to secure it in place the same as the opposite side of the brush. Then connect a wire to the regulator side of the break and earth the relay through it. Now when the reg opens at 14.2 volts the voltage will not fall in response as the PDAR will continue to conduct, therefore the reg should remain open, not just long enough to drop the relay but until the engine is stopped.

 

I have modified one of my spare A127 regs as you suggest but haven't had time to put it on the boat yet (will do it sometime over the weekend hopefully).

 

However, a further modification is needed after bench testing it. With that link cut, the output transistor is now an open collector and it will not switch properly unless its collector is tied to the positive rail (in lieu of the rotor's normally doing this). I tried various resistances and it was still switching fine even with a 47K resistor in there. I ended up putting in a 4.7K to ensure a reasonable level of current to stabilise things (~3mA).

 

So I have 2 wires coming out of it now. One wire, which is the output transistor collector, which will go to the relay earth and another wire, which is connected to the field brush, which will go off to the Sterling PDAR field connection.

 

Will let you know what happens when the relay is connected.

 

Chris

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I have modified one of my spare A127 regs as you suggest but haven't had time to put it on the boat yet (will do it sometime over the weekend hopefully).

 

However, a further modification is needed after bench testing it. With that link cut, the output transistor is now an open collector and it will not switch properly unless its collector is tied to the positive rail (in lieu of the rotor's normally doing this). I tried various resistances and it was still switching fine even with a 47K resistor in there. I ended up putting in a 4.7K to ensure a reasonable level of current to stabilise things (~3mA).

 

So I have 2 wires coming out of it now. One wire, which is the output transistor collector, which will go to the relay earth and another wire, which is connected to the field brush, which will go off to the Sterling PDAR field connection.

 

Will let you know what happens when the relay is connected.

 

Chris

 

Chris you've scrambled your head with quadratic equations and battery internal resistances.

 

You don't need that extra resistor there. The relay coil will do the same job.

 

Gibbo

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Chris you've scrambled your head with quadratic equations and battery internal resistances.

 

You don't need that extra resistor there. The relay coil will do the same job.

 

Gibbo

Professional reply: Of course that's right, but I'm thinking more from the testing point of view, so that the reg can be tested independently of the relay.:lol:

 

Honest reply: In my haste at bench testing, and suddenly seeing a problem with the switching, I forgot I was even going to put a relay on it! :lol:

 

Chris

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Very interested in this thread. I have split batts .... 4 on alt for fridge and 4 on 2nd alt for domestic. Starter batt off split charge relay from fridge alt. Would i be better off connecting alt outputs in parallel, ditto batts? As you have suggested. If the answer is yes could you provide finalised drawing, i lost the plot somewhere 8 or 10 posts ago.

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It's generally better to have all the batteries linked together into one bank. Here is Gibbo's explanation. Only the starter battery should be separate.

 

As for the circuit for joining the alternators, it's probably best to wait until Chris and Gibbo have finished playing tennis to see what they come up with...

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It's generally better to have all the batteries linked together into one bank. Here is Gibbo's explanation. Only the starter battery should be separate.

 

As for the circuit for joining the alternators, it's probably best to wait until Chris and Gibbo have finished playing tennis to see what they come up with...

 

Chris and Gibbo are merely errr... deciding whether adaptive charging, i.e. with a PDAR or Adverc system actually works. If you're into serious alternator surgery then hold tight for a fuller explanation of Sir Nibble's switching method, otherwise if you follow Chris's first post then you'll come up with a system whereby you won't use your domestics to start the engine unless you want to... you just need to remember to switch it off or your starter batt will fall out with you....

 

Niloc, that's a very unusual setup and I wonder whether, where you've a bank running off both alt's that you'd really need it; the rationale of the system is to use a largely redundant engine alt to it's full capacity as opposed to leaving it idle. I'd need to leave it to our resident wrestlers experts as to whether you'd be better off to consolidate one BIG bank with two alt's looking at the one bank tho. I suspect the man from Peukert will say YES!

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The man from Peukert - he say YES.

 

eg: let's say you have 2 banks of 2 x 110AH batteries. Ignore the starter battery, that should always be separate (unless charging).

 

If you join them together into one bank of 4 x 110AH, you will have double the capacity. YES?

 

NO!! you will have MORE than double the capacity due to the Peukert factor (google for it). The maths is fairly complicated for most mortals but the bottom line is that 4 x 110AH joined together have 23% MORE capacity combined than 2 individual banks of 2 x 110AH.

 

So you are getting some reasonably significant additional capacity for FREE simply by joining them all together.

 

Chris

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Understand Peukert. Can you get a problem if one alt fails ? Or does it depend on the fault? At present if one alt goes down, at least i have one to fall back on. If it is foolproof and you finalise your design will give it a go.

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Hi,

 

For auto switch-off of the alternator parallel connection I'd try the following circuit:

 

gallery_2174_346_1078.gif

 

I'd expect that using D+ is a bit less risky than using the alternator field connection as far as unwanted feedback/oscillation goes.

 

The two lamps are there to further reduce the chance of feedback.

 

Lamp 1 is about the same power as the relay coil and is to help the latch relay open quickly. It can also be used as an indicator lamp to show the alternators are in parallel.

 

Lamp 2 is to help the contactor open more slowly. It's power rating must be carefully chosen, high enough to help the contactor open more slowly, but not so high that it enables the contactor to stay closed. It may even be best to use 2 higher power bulbs in series.

 

Operation is as follows:

 

When D+ is at 12V after the engine has started, the pushbutton is pressed to latch the relay and enable the contactor.

 

When D+ drops to 0V as the other alternator takes over, the latch relay opens.

 

At this instant, Lamp 1 is lit, and so its resistance is high. This helps the current in the latch relay coil decay quickly and so allow the latch relay to open quickly.

 

Also at this instant, Lamp 2 is unlit, and so it's resistance is low. For a short while as it heats up, it allows current to be conducted through the contactor coil despite the latch relay being open, and so allow the contactor to open more slowly.

 

The 2 horizontal diodes are blocking diodes to stop the latch relay being inadvertently powered through the contactor coil or Lamp 2.

 

The circuit may also be used for a parallel starting capability, depending on what feed is used from the ignition switch. For parallel starting to be enabled, the feed must remain at 12V while the engine is started.

 

cheers,

Pete.

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<snipped>

 

Pete that's quite nifty.

 

So you can do a few more calcs:-

 

The SW180-2 (the continuously rated one) has a coil resistance at room temperature of 13 Ohms

 

Once closed the relay opens when the current through the coil drops to around 225mA

 

The coil resistance (obviously) increases as the coil heats up.

 

The tolerance on drop out current is quite wide and measured values show anything between about 175mA and 275mA

 

Gibbo

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Hi,

 

For auto switch-off of the alternator parallel connection I'd try the following circuit:

 

gallery_2174_346_1078.gif

Pete.

I suspect you will still get the same problem as I got, viz: the regulator switches at very high speed, far faster than the switch-off times of the relay and/or contactor, thius preventing the relay's dropping out.

 

I tried Snibble's idea with the regulator and, surprisingly, the PDAR would not work unless the regulator open collector output (as modified) was connected to the PDAR. ie: there was no charging at all. I shall speak to Charles Sterling tomorrow to see if there is a way around this.

 

For those following this thread, and to avoid confusion, the paralleling bit works perfectly. The refinement is just to have it switch-off automatically rather than have to remember to switch it off. I shall probably put a simple 60 or 90 minute timer on the circuit that disables the relay after this time.

 

Chris

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I suspect you will still get the same problem as I got, viz: the regulator switches at very high speed, far faster than the switch-off times of the relay and/or contactor, thius preventing the relay's dropping out.

 

But..... once the PDAR takes the voltage above the other reg voltage, the reg won't switch on again until after the paralleling relay has opened. If you keep the snubber on the main paralleling relay it will have a long opening time (I reckon about 60mS with a 1N4007), but if you remove the snubber from the other relay it will have a very quick opening time. Once that has opened (in say 5mS) it won't switch on again. Then 50mS later the big one opens, the reg will start to go again and both relays will remain open.

 

I tried Snibble's idea with the regulator and, surprisingly, the PDAR would not work unless the regulator open collector output (as modified) was connected to the PDAR. ie: there was no charging at all. I shall speak to Charles Sterling tomorrow to see if there is a way around this.

 

Well....... In post #52 I did say...........

 

You could be right but there's something telling me that the PDAR doesn't bark up until it sees 12 volts on the D+ terminal, which it will never see if the internal reg isn't working. I'm not certain on this, I could well be wrong which is why I asked it as a question.

 

and was wholeheartedly slagged off and told I was talking cr*p.

 

There is something telling me (again) that for some reason the PDAR has to have something different done with it if there is no working internal reg.

 

Gibbo

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But..... once the PDAR takes the voltage above the other reg voltage, the reg won't switch on again until after the paralleling relay has opened. If you keep the snubber on the main paralleling relay it will have a long opening time (I reckon about 60mS with a 1N4007), but if you remove the snubber from the other relay it will have a very quick opening time. Once that has opened (in say 5mS) it won't switch on again. Then 50mS later the big one opens, the reg will start to go again and both relays will remain open.

 

 

 

You could be right but there's something telling me that the PDAR doesn't bark up until it sees 12 volts on the D+ terminal, which it will never see if the internal reg isn't working. I'm not certain on this, I could well be wrong which is why I asked it as a question.

 

and was wholeheartedly slagged off and told I was talking cr*p.

 

There is something telling me (again) that for some reason the PDAR has to have something different done with it if there is no working internal reg.

 

Gibbo

 

I don't think it's a sound method if it relies on precise timings of the relay's interacting with the snubber network. It's too much "Select-on-Test". One might as well just put in a 90 minute timer and be done with it. Afterall, that's what chargers and alternator controllers do to bring the acceptance cycle to an end.

 

With regard to the PDAR, the PDAR IS seeing 12v on the D+. There is a monitor wire from the PDAR to the D+ which is still in place. As I said, I'll bounce it off Mr Sterling tomorrow.

 

Chris

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