cav ac203 alternator question

[crossley]

I'm using a 24v 60 amp ac203 alternator and type 460 control board,in fact the complete charging system from a scrap bus.

It's working very well, and gives me

60A at just over idle speed, 500 engine rpm,with a 2:1 step up ratio drive. It's not a self limiting alternator, it uses a shunt on the control board and two extra terminals,

M1&m2 on the 440 regulator box. I,m sure someone will know the type,was common on busses in the 1970's.

I get 27.7v on the "m" and 29.0v on the "H" setting on the regulator.it starts off in current control and limits itself to 60A till it reaches the above voltage settings, then goes into voltage control and it keeps the voltage constant while the current tails off. It works well for me, and most important it came free.

Question is, I have a redundant sterling digital alternator controller on hand here, is there any advantage in fitting this contraption, and can it be made to work in this application? I've got grave doubts, but it's nice and shiny and got a nice row of multi coloured led's. Is 29v ok for open cell batteries? have 110 A/hr start and 360A/hr domestics with a victron vsr "intelligent" splitting relay.

Just to give you an idea of my setup.

Anyone tried this before? Maybe my bargain basement system is a load of c**p and I should be looking at something more modern?

[Sir Nibble]

That's a bloody good system and should last forever. You say it works well for you so I wonder why you need to change it? I would be wary of mucking about with the current control as the machine is unventilated. If you pop the regulator open there is a trim pot that will allow you to tweak the voltage up if you must but really if I were you I would be pretty smug about that set up and let it be.

Bye the bye, the same brush holder as the AC5 goes in there and they are easy to check. Brush wear is the only cause of failure I have ever seen on these machines.

[crossley]

Ok, thanks for that sir nibble, I was just thinking about using the redundant sterling charge controller to extend the time in " current control". I'm thinking about fitting instead a switch between Med and High terminals to short circuit the internal resistor chain, giving me a manual switchable "boost" or equalising voltage feature instead. I'll leave it alone for now, set at High, as I'm not having to top up the batteries as yet.

I rebuilt the alternator, skimmed the slip rings, new brush holder,etc it's fighting fit now. I like to recycle things like this,

A day spent removing all this stuff from a scrap decker was a day well spent then, I'm even using the fast fuse box and the double pole isolator. My way of thinking is if this can cope with the heavy lighting load on a Decker, it's more than man enough for a narrow boat.

A constant 60A at idle is not a lot these days I know, but more use than nothing at idle and 120A at full revs,seeing how much time we spend at low revs.

The bus breakers at Barnsley have all the bits to make up something like this for next to nothing if anyone's having a go.

They do an 80A version also, but it needs a bit more revs for full output.

If you have a 24volt system then there worth having a look at.

Why do we have such large domestic battery banks on narrowboats? Motor caravans with similar domestic arrangements seem to manage with far less battery capacity. Maybe it's the weight.

[Sir Nibble]

I have a shrewd idea that if you open the reg you will find that "Hi" is a parking terminal with nothing connected to it! If you were to adjust the voltage setting through the roof and put the 440 and sterling in series then that might get what you're after with the sterling doing voltage regulation and the 440 current limiting.

[crossley]

You may be correct, I'll measure the resistance between low, med & high on my spare regulator. Another option would be to put a nice big wire wound multi turn pot between "low" and the sensing wire. I could have infinitely variable voltage control then!

That's what I like about this vintage stuff, dead easy to work on, well made and reliable. Plus you can experiment with it, and if you break it in the process it's not the end of the world. Plenty of into on the web about these,circuits etc I downloaded the entire manual in graphic detail quite easily.

What would a brand new alternator, control board, etc cost today?

Some underfloor engined coaches used a remote mounted alternator driven by shafts, through a speed increasing "transfer box" driven off the crankshaft nose. Leyland tigers had this. Wouldn't it be fun to try and use an old transfer box to speed up the drive from an old vintage engine to a nice big alternator? They weren't very big either as I recall.

[billh]

I found one of these at the side of the road. It had fallen off a bus, been dragged along by its wires for a distance and come to rest in the gutter. A bit battered but the drive shaft was undamaged. I think the rating on it was 2kW/80A. Would it perform well at 12v with the right regulator? .Co-incidence, but,many years ago I found a CAV AC5 in similar circumstances, that has since served 25 years in a boat now, it just needed a new fan!

Bill

[crossley]

I,ll have to start looking more closely in gutters in future then!

Found a locking wheel nut socket yesterday in the gutter if that counts.

Don't think they did a 12v version of the ac203, the rotor is wound for 24v anyway, even If you did muck about with the stator connections it's doubtful if you'd get full output with 12v on a 24v rotor winding though. Must be easier options. How's this for a c**p idea, go to a 3 wire system like they did in old houses with dc mains.

Earth the centre tap between two 12v batteries, use the positive pole for engine electrics etc as normal, and the negative pole for domestic supply. Connect your 24v alternator across both ends, and hey presto! Your in business. Get one of those solid state battery balancer thingies to level things up a bit.

Might make the anodes last a bit longer as well. Or not..

[crossley]

Just had a look at two spare 440 reg's , both read low to med 250 ohms,med to high 250 ohms, low to high 500 ohms. Opened them to have a look and the low,med& high terminals go to a resistor chain as in the circuit diagrams. The sensing wire is connected to B+ inside the control board so it must be measuring battery +ve voltage.

So if I connect a 500 ohm wirewound pot in series with this lead, take it to "low" terminal,I will have in effect a variable voltage control to tweak at will between 25 and 29 volts approx. How good is that?

No trim pots inside either, must be very old ones had the trimpots inside.

[Eeyore]

Just had a look at two spare 440 reg's , both read low to med 250 ohms,med to high 250 ohms, low to high 500 ohms. Opened them to have a look and the low,med& high terminals go to a resistor chain as in the circuit diagrams. The sensing wire is connected to B+ inside the control board so it must be measuring battery +ve voltage.

So if I connect a 500 ohm wirewound pot in series with this lead, take it to "low" terminal,I will have in effect a variable voltage control to tweak at will between 25 and 29 volts approx. How good is that?

No trim pots inside either, must be very old ones had the trimpots inside.

That sounds useful.

The 60amp AC203 were retrofitted to British Rail 1950s built railcars, many of which still run on preserved lines.

The installations often replaced 30 volt dynamo systems, so I wonder whether that sort of voltage would be reliably achievable by increasing the resistance a little?

Steve (Eeyore)

Edited December 23, 2015 by Eeyore

[crossley]

I've seen mine at 29v when all batteries are fully charged,so 30v should be easily achievable, the only limiting factor I can see is the p.i.v rating of the diodes in the rectifier.

30v is a strange voltage, did the railcars have nife ( nickel iron)alkaline batteries originally? Railways could afford such luxuries on the grounds of reliability and very long life, in nationwide fleets it makes economic sense not to be changing batteries all the time, but the first cost is very high.

It'd be interesting to cost a new

bank of nife batteries nowadays.

[Sir Nibble]

I must admit I think I have got confused with the more usual 440 regs as used on AC5/7.

I would say that anyone who has a low revving engine counld do no better than an AC 203 or AC 7. Provided you want 24 volts of course, splitting it across 2 batteries not a good idea!

[crossley]

No, but there Is some POTENTIAL in the idea, to my CURRENT train of thought, though I'm encountering some

RESISTANCE to the idea!

If I was clever, I'd be able to get inductance and capacitance in too.

But I'm a bit thick!

Was hoping to provoke more of a reaction about this c**p idea but only sir has nibbled upto now!

He's not the kind of bloke you'd try and gainsay when it comes to marine electrics! Me? I'm just a clanky.

Lefty loosey, righty tighty.

[WotEver]

It would appear that you have met with some IMPEDANCE to progress. You could perhaps be INDUCTED into Snib's gang if you have sufficient CAPACITY. Beware of the MOLES that abound in these areas though - especially the one named JOULES for he has much POWER.

[crossley]

Ok, that's enough!

I'm looking forward to visiting the boat day after boxing day, stay overnight, got a few jobs to do.some bottles of real ale onboard need to be responsibly disposed of too.

Fire the old Gardner up, and get some amps in the batteries! It's been a month now, with one thing and another since I managed to visit and run the engine. Hope I've not killed the batteries, they seem such fragile things nowadays looking at all the battery related postings on here.

[Sir Nibble]

Hope I've not killed the batteries, they seem such fragile things nowadays looking at all the battery related postings on here.

Don't worry, people on here are unrealistically precious about batteries.

[crossley]

Yes, I know what you mean, it's turned into something of a fetish for some, agonizing over the minutiae of battery charging.though the cost of some of these enormous battery banks must be eyewatering.

I'd worry too if I had a couple of grand in batteries slowly sulphating in a Marina somewhere.

I lost an old family friend earlier this year who worked for Oldham batteries in Denton for many years.

His job was to go round all the mines in the UK looking after the battery electric underground loco's

And miner's cap lamps. He was a mine of info on batteries, used to call the acid gravy for some strange reason. Nobody bought batteries back then, I think half of Stockport had knocked off Oldham batteries on their cars. They made special military tank batteries that were perfectly square in shape, about 14" square for challenger tanks. I had one in a Landover for years, bloody thing wouldn't die! Sold it with the rover eventually. He didn't muck about mollycoddling batteries either.

But then again he wasn't paying for them.

Were batteries better in the good old days? We had dynamos on cars when I was a nipper, everyone seemed to have flat batteries in winter time. My dad bought one of those oxford oil cooled welders that was also a battery charger. You could start a dead flat car off the bloody thing. I literally boiled a battery dry with it as a nipper. Tried to trickle charge it overnight at about 90 amps then wondered where all the acid had gone in the morning. Still got one under the bench in the shed.

[Teaman]

Hello All,

 

A bit late in the day, given your post dates, but I'm looking for information on the A460 24 regulator, particularly circuit schematics if there are any.  Pictures of the components would be great too.  I can offer what I have on the CAV AC203 60/A460 arrangement used on BR DMUs Class 108.

I want to determine if by fault or design, residual rotor magnetism, remanance, can be destroyed.

 

Your help would be greatly appreciated.

[Jen-in-Wellies]

Welcome to the forum.

Calling @Sir Nibble

[Iain_S]

14 hours ago, Teaman said:

Hello All,

 

A bit late in the day, given your post dates, but I'm looking for information on the A460 24 regulator, particularly circuit schematics if there are any.  Pictures of the components would be great too.  I can offer what I have on the CAV AC203 60/A460 arrangement used on BR DMUs Class 108.

I want to determine if by fault or design, residual rotor magnetism, remanance, can be destroyed.

 

Your help would be greatly appreciated.

It can dissipate.  We had a Perkins generator which wouldn't fire up because there was no residual magnetism in the field coils. Cured by firing it up with a battery on the field connections at the regulator. Have to be very careful with this, as it's very easy to blow the regulator. Easiest to use a separate battery from the generator's start battery.

[Teaman]

Yes, from the point of view it can "vanish", I agree.  However, the AC203 is a self-excitation alternator, ie not designed to lose its rotor magnetism.  What I've found so far on remanence loss points to electrical issues, such as reverse current.  Hence the want for schematics, manuals etc.

[BEngo]

Disappearance of remanent magnetic field is common, over time.  The alternator is designed to self excite, and will do so if used fairly regularly, because that refreshes the rotor magnetism. Leave it for a few months, particularly if it is vibrated, and some or all of the remanant magnetism will have gone.

 

The answer then is to disconnect the regulator and flash a magnetic field into the rotor.  Get the connections the right way round! Reassemble and it should ackle as intended.

 

N

[Sir Nibble]

I've not had a lot of experience with the 203 and it's an unusual system. I used to deal with them on later Bristol buses, but where Bristol buses are concerned, "later" is a relative term. One thing I do remember is a conversation with a guy who wanted to sell me a gauss meter particularly for the AC 203. According to him, they are prone to a partial winding failure which leaves the rotor unable to achieve magnetic saturation. This may just be sales talk, I can't comment further except to say that a nice bright warning lamp may well cure the problem.