There's actually an interesting thread in progress regarding exactly this question over there, right now. Seems that some modern charging systems - notably Ford - make use of a stepped output voltage from the alternator, controlled by the EMU. The highest output of over 15 volts seems to be as a result of, amongst other things, outside air temperature, to compensate for the slightly different charging requirements of a cold battery against a warm one. Maybe the Disco uses the same or a similar system, and it's not working correctly ?
I believe it messes up the voltage regulation if anything in the charge circuit goes high-resistance, such that the regulators end up putting out a higher voltage than they should.
Check on the battery type. If it is the Ford smart charge system then the battery should be a silver cadmium battery and will charge at 15 or more volts. The voltage is not only a function of the the smart charge controller but also of ambient temperature. I have this system on my Cmax and it was the subject of a recall where the batteries were becoming discharged in cold weather and failing to start especially the diesels. If the OP has this system then it is vital that any replacement batteries are of the silver cadmium type. Another characteristic of the Smart Charge system is the delay in reacting to a heavy load on the battery. I notice that the heater blower gets considerably louder/faster tens of seconds after pulling away with heavy loads such as lights and heated front screen switched on. On my other older car, the fan speeds up instantly after pulling away.
Blowing bulbs is obviously unacceptable so the vehicle should still be checked under warranty.
Assuming that there isn't some form of regulator between the battery and the car +v rail. What happens in a car with one of these "over voltage" charging systems? Surely the whole vehicle +v rail doesn't also rise or you end up chewing bulbs... There is more to this over voltage charging system than meets the eye.
Simply because the type of person who buys such a vehicle tends to be the type who falls for all this type of hype, and probably uses oxygen-free copper 'cables' for their hi-fi type stuff...
Well, our truck's practical and comfortable, and it's over 40 years old*. I have no problem with those aims - I just don't follow the logic of over-complicating fundamental vehicle systems (or things like loading it up with trim that's just going to add weight and get scuffed/wrecked)
although only 2wd right now until I find a 4wd donor - it's on the to-do list...
Hmm, noise is a good one... although every "larger than car-size" vehicle I've been in has seemed noisy, modern or otherwise, so I'm not sure I'd appreciate attempts to make it just a little bit quieter.
I suppose you have expensive tax and MOTs over there (and less space on average), so it's harder to run several vehicles and just use the most appropriate one for a job :(
I don't really see that controlling the alternator output by the engine ECU is over complicating things. Actually makes a deal of sense. The ECU already controls idle speed and the two are interrelated. Means it can also reduce the output when full power is called for.
We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Dave Plowman (News)" saying something like:
The problem then is the need to keep a calcium battery properly up without substantially shortening the lives of the vehicle lamps. There would be very little leeway in it and the slightest wander of the voltage control would be popping bulbs - which is what seems to be happening. So much for progress. Of course, every lighting circuit could be individually or collectively voltage protected, but that would add a significant cost.
Well, I'm not guilty of oxygen-free cables. I do, however, have 3 runs of high quality cable from my tri-anps to my Linn Isobariks. Does that count ? :-)
As to the choice of vehicles:
I live near Aberdeen, and commute to Montrose daily, over either the Netherly road or the Slug road. These can become difficult sometimes in winter. With the disco, it's a much more pleasant experience than with my old Audi A4.
We are members of the Gordon Skiers (
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) , which requires us to be at the Lecht ski centre for 09:00 on a Sunday morning. I routinely cart 5 or 6 kids to the lecht, or Glenshee, along with all their ski gear for race training. The disco is absolutely the tool for this. Sunday mornings at the snow gate at Cock Bridge at 8:30, there's a queue of a dozen discos and other 4wd, mostly from the club, waiting for the snow blower to clear a good enough path for the gates to open. Last Sunday, we ended up at Glenshee, but a bit late. The car park was full, and Plod was patrolling up and down making sure no-one parked on the road. I was able to go into the 'full' car-park, and drive up a fairly off-road snowfield at the enge of the car-park, and park there ( as had other discos etc ). At the end of the day, I towed 2 stuck rear-wheel-drive BMWs out of the car park :-) Fantastic conditions, BTW.
Summer brings sailing, and I'm towing lasers and dart catamarans around the place. Disco is again the tool of choice.
Motorway blast down to in-laws in Shropshire, the disco is an impeccable motorway cruiser.
Given the mix of uses I have, I can't think of any single vehicle that would suit me better.
There were certainly plans to utilise a 36V system (although it was to be referred to as a 42V system), the higher voltage meaning lower losses for the high power consumers, allowing thinner (lighter) wiring, smaller motors and powerful, fast starters - permitting engines to be shut off when stationary. 36V is as high as they could go while keeping peak voltages on the ac side to around the 50V considered safe for dc systems that people may come into contact with. This would of course require various voltages for different systems, but was considered to provide a useful fuel saving. Apparently the idea was killed off by the difficulties of switching higher dc voltages without erosion of the switch contacts and by the prospect of much higher voltage hybrids with inverters and ac drives.
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