Electricity Escaping

[Way2go]

but as I understand it, typical SMPS switching frequencies are well into the kHz range. Dunno whether this is better or worse...

Better from a smoothness point of view.

It also would be better if they were used (and possibly are now) in home burglar alarm systems for the maintenance of the back-up battery which is one of those Yuasa lead-acid types. I've had to replace 3 of these due to cells going faulty and causing false triggering. Silly really when you consider that this battery does virtually no work, living just the charged life.

However perhaps not so good for Radio-Amateurs. A friend of mine hates them with a vengeance as in his words "they radiate all sorts of shit across the band". It apparently needs his remedial attention installing ferrite slugs to get them even half-way acceptable amongst the neighbours gear in his locality. And as for what he says about those mains routed ethernet extenders....

[Mothman]

I bought one of these 'Honda' marked batt chargers that sort of teases the batt back to life and cannot over charge.
Works just fine on all of the motors.

Andy

[electrokid]

A kHz is easily achievable on the motorway on a standard petrol of all flavours

The pulleys on the drive belt are arranged so that the alternator spins at a particular max speed - ratios are different between petrol and diesel to cope with the different max engine revs. But yes - a KHz is achievable - and it's at this maximum (and with the battery at or close to it's minimum - 11.6 to 12.0 volts) that the "rated" output of the alternator occurs - all other circumstances it is controlled to an appropriate level below it's max output. didn't put that very well but you probably get the jist.

aircraft electronics was I seem to remember 400Hz.

I thought that was a power distribution frequency rather than derived from an alternator - but I don't actually know - I've designed avionics but we were just using the 28v DC supply.

I recall reading about low frequency "resonators" that operated about 7Hz being developed that were supposedly capable of causing a building collapse. Tesla was supposed to have made a breakthrough on an early one of these that was almost pocket sized.

Now you see - you've mentioned one of my heroes so now I'm bound to rabbit on a bit Nikola Tesla and Keely before him designed resonators - and there are some anecdotes from the realms of "overtone singing" as well - that's people who are capable of producing more than one note at a time

For many years The Smithsonian museum had a sculpture of Westinghouse as "Father of Alternating Current" or somesuch description, and the brass plaque quoted a number of patents relating to 3 phase AC distribution etc - all the patents were Tesla's

And Marconi was "the facilitator" of radio rather than its inventor - most of the workings of radio were underpinned by around 20 patents - again they were from Tesla.

There was an occasion when Tesla, having left Westinghouse's employment was called back to sort out a power station problem that no-one else seemed to be able to fix - Westinghouse told him to "charge whatever he wanted". So Tesla visited the power station and chalk-marked one of the machines with a cross saying "change that machine and all will be well".

Sure enough the machine was changed and it fixed the fault - and the bill for $10,000 arrived with Westinghouse who returned it - asking for it to be "itemised".

Tesla returned the itemised bill...

To - making a chalk mark on one machine... $1
To - knowing which machine to mark... $9,999

On reliability I still would prefer a linear psu.

Damned right - I'm in the process of replacing all the 'electronic' lighting 'transformers' in the house with real transformers - the electronic ones are just too flakey - one day I'll write some stuff about SPFMA - Single Point Failure Mode Analysis - but not today - got things to do

However perhaps not so good for Radio-Amateurs. A friend of mine hates them with a vengeance as in his words "they radiate all sorts of shit across the band".

Indeed they do... even though, I'm currenty designing-in some SMPSUs between 5W and 500W - 40khz to 150KHz. I wonder how long it'll be before I chuck those out in disgust as well

[Dominic]

I expect you've sorted this by now, but, can you access the cells in the battery? - mine started loosing charge recently, and it was a couple of cells run dry - haven't seen a battery with accessible screw top cells for years, but thankfully mine is one of them, just topped 'em up and all is fine again.

[vulgalour]

Yes, the problem was resolved by plugging the alternator back in properly. The battery cells looked healthy, didn't appear to need topping up at all. I would've joined in with the electrics debate, but most of it was well above my head.

[KevR]

I bought one of these 'Honda' marked batt chargers that sort of teases the batt back to life and cannot over charge.
Works just fine on all of the motors.

Andy

That'll be an Optimate. I've been using them for years, especially on things that don't move much over winter like the digger, tractor and MX-5.

In fact I've ended up with loads of the things. I had one of the first in the early nineties (later struck by lightning) and I've just counted up to find I've got at least eight of them, from a simple 1997 version to the latest specific one for Lithium racing batteries, plus a workshop unit that does five batteries at once (doesn't do the desulphating bit, just keeps the batteries topped up). I think I probably need help... But then again I can't remember the last time I had to throw out a battery... The battery on the digger is probably ten or twelve years old now, still fires it up first turn.

Anyway, late to this thread and also curious about the missing battery light on the dash. Whilst on one of my dashes back to the UK last weekend, got back in car to be greeted with a feeble click from the solenoid - flat battery, no warning from battery light. Fortunately happened outside Nick the 2CV man's house, so jumped it, then checked charging voltage. Zilch. Realised/remembered that battery light hadn't been coming on before startup the previous day or so. Nick produced a 'special Citroen alternator hitting stick, with associated mallet' and gave the alternator housing one sharp tap with the engine running. Charge voltage immediately restored, and battery warning light now working as it should (ie coming on with ignition, going out as soon as engine starts. So, I can imagine that the tap might have loosened a stuck brush or something, but why would the battery light be affected at the same time?

[electrokid]

I can imagine that the tap might have loosened a stuck brush or something,

It does sound as though it has loosened a stuck brush. I don't know whether there's one or two on the BX range of alternators but in an alternator brushes only run on a slipring (as opposed to a commutator) and can get stuck or get intermittant when they are on their last legs and the spring(s) that keep them in contact with the slipring are on the very last bit of movement they have available.

If that's the case then this alternator is likely to fail again in a matter of days - a few weeks at the most.

I don't know how the lamp circuit within the alternator works - but it may be that it needs the brush to be in contact with the slipring for it to work (for it to show when the ignition is turned on). That's a guess but there is some logic behind it.

[MULLEY]

I've been giving my alternator a tap now & again for the last few months, still going

[KevR]

If that's the case then this alternator is likely to fail again in a matter of days - a few weeks at the most.

Yep, going to change it soon - time to do the cambelt and water pump anyway so I'll do it all at the same time - got a few on the shelf. Any advice on testing/cleaning the one I end up fitting? Worth replacing the brushes etc?

[electrokid]

Sounds like a good time to replace it anyway then

I guess refurb depends on the condition in which you find it but since you have time to work on it when it's off the car there's no reason for skimping on it. I'd replace brushes if it's obvious that there's a fair amount of wear on them - if the spring looks as though it has a fair amount of travel still to go and the brushes look in reasonable nick then I wouldn't bother. If you do replace then make sure you get the right replacement if you can find it - if you have to buy a larger brush and file it to size then make sure it is man enough for the job - brushes for low voltage have a greater brass content - brushes for high voltage stuff like hoovers etc have low brass content and will wear out much more quickly. If you have to file it to size then be as precise as you can - they should be run dry without any lubricant but still need to slide easily in the mounting - if it's too loose and can wobble in the mounting it might get stuck. The brushgear only drives a relatively small amount of current into the rotor to create a magnetic field - it doesn't carry the high current of the alternator output so if you have to look for a suitable brush to modify to fit then you don't need one with a big fat wire attached - a skinny wire will do the job.

Sometimes the slipring can wear to a slight oval shape - it needs to be circular of course - and clean - spin the rotor and gently hold some wet-and-dry 400 grade or higher against it then blow the dust away with an air line or bicycle pump. Turn the rotor slowly and observe any slight movement of the brush to check for roundness - if there's any movement then it needs to be skimmed in a lathe.

When my alternator front bearing siezed last year I looked through the drawings and found that the front bearing type is common to most of the alternator variants for the BX - it might still be readily available - possibly under a different part number for other PSA models - you might be able to locate that by chatting with your local PSA parts department if you can find or already know someone who really knows their stuff. I haven't looked yet but I imagine that's a press fit.

But then the usual rules apply - if it looks good then it probably is good

The simplest test is to spin the rotor by hand with a voltmeter connected between the big output terminal (+) and the metalwork (-). If that's producing a voltage then all is probably well - if it's not then grab another one to work on.

[KevR]

All good advice I'll bear it in mind. Part of me hopes it needs sorting on a lathe, on account of how I've just got oen....

[KevR]

Just to resurrect this thread.... Two months on from the original alternator problem, and no issues since, so I forgot all about it. Until the last couple of days, on yet another whistle-stop tour of the UK (800 miles in two days). Alt packed up on the A34 in the middle of the night on sunday - tap with a wheelbrace and all was fine but it's needed a couple more taps since. Home now, and it's working fine ( I think it just doesn't like going to England) but this time I really will get round to changing it!

[Defender110]

Perhaps just full of brush dust, try a blast out with compressed air although they brushes will need doing too when nowt left.