Class 150s - Flashing tail lights

[whole diary]

[Kingfisherdart]

This evening I noticed that the train forming the 2008 arrival into Weymouth (150249) had flashing tail lights whilst stabled in platform 3. They were flashing regularly - like the tail lamps fitted at the rear of loco-hauled trains and freight trains.

Only when the driver started the engines, and revved them did the lights show a solid red light.

Any purpose for the flashing? I wasn't aware of the units being fitted with this feature.

Regards,

Luke

[Sprog]

This 'flashing' is not an intentional thing but instead is due to the A.S.C. (Auxilary Supply Contactor) on the vehicle dropping in and out repeatidly, thus cutting the supply to the units Auxilary systems (interior lighting, tail/marker/headlights, heating etc.). The A.S.C. is controlled by the L.V.R. (Low Voltage Relay) which via a L.V.P.U. (Low Voltage Protection Unit) detects if the Voltage of the batteries drops below a specified level. If you are somewhere quiet, you can usually hear the 'clunking' of the A.S.C. opening and closing repeatedly.

This usually occurs due to the Auxilary batteries on the unit having low charge due to either defective/degraded batteries or a fault with the charging system on the unit. All DMUs^▸ (Diesel Multiple Unit) have two sets of 24V batteries, Start & Auxilary, the Start Batteries being responsible for all of the vehicles primary systems & as the name suggests, Engine Starting, hence why the Unit presumably started up OK. As soon as the units engines are running and the deisel engine has been sped-up from idle speed using the 'Compressor Speed Up' switch (to build up Air pressure), the shaft-driven Alterntors (Hydostatically-driven on a Class 158) that supply the charging system will be electrically excited and hence supply the vehicles auxilary batteries, thus provding suffcient voltage (Usually 24V +/- approx 2V) not to trip the L.V.R. and hence keep the A.S.C. closed.

Hope i havent gone to 'technical' for you!

[Kingfisherdart]

Fantastic - not too technical in the slightest. Thanks for the answer

Presumably the driver of our train (2307) started it and left it running to keep the batteries charged for the morning. The thing is still ticking over now - presumably will be all night to ensure it doesn't fail with flat batteries in the morning?

Luke

[Sprog]

Possibly yes. Depends on the circumstances.

For example, during the 'Winter' period, as part of the additional Winterisation maintenance procedures, stabled units must be started and ran every few hours to keep sufficient air, heat & battery charge (as the batteries take a hammering during the cold weather).

The unit may be a known duffer and, as you suggested, could have been started to ensure that the batteries do not run totally flat & cause problems tomorrow. The units are fitted with timer relays, so when none of the Drivers desks in the unit(s) is 'open' - ie. A drivers key inserted & D.S.S.W. (Direction Selector Switch) away from the OFF position - the units(s) engines will shut down after 15minutes. So to allow the unit to carry on running past this point, a desk would have to be deliberately left open (which is a common practice) providing the Unit & its driving cabs are secured & locked (A requirement during train stabling anyway).

If this is the case, this will only be a short term/temporary 'fix' and the unit will be scheduled in for repair/maintenance ASAP. It may be that Maintenance are aware of the fault, but the unit is very near to a planned Exam, so the problem (which whilst being an inconvenience having to run the unit/monitor the battery charge, is not a safety issue) can be endured until the unit is stopped for Exam.

However, even with a 'good' set of batteries, as the engine is idling as opposed to running at high-revs when out in traffic, it is really only trickle-charging the Batteries. And sometimes in rare cases, no matter how much you attempt to charge the batteries, if they are so far gone that they are not taking charge, then it is a futile fuel-wasting exercise anyway!

If a vehicles Start batteries have run totally flat aswell as the Auxs, then a 'last resort' option is to use a 24V portable 'boost pack' that supplies a short burst of external power to enable the engine to be cranked & hopefully started. (Unfortunately we cant just use a set of jump leads!!). Often, if a vehicle is sat around at a maintenance depot awaiting components/resources, the batteries can run flat and will require topping (de-ionised water) and a decent sustained charge from a Static depot battery charger before they maintain a good charge.

[Chris from Nailsea]

Thank you, lukefarley and Sprog, for posting such detailed technical information here.

I certainly followed most of it ... and is it therefore worth us considering adding a new board on this forum, for just such technical issues - rather than put them in the already very busy 'Across the West' board?

If our members are in favour of this, I'll do it: please comment!

[inspector_blakey]

For lots of clanging bells and a surfeit of flashing lights you can't beat the yanks - here's an Amtrak train arriving at Trenton NJ (those blue flashes aren't from the catenary, they really are strobe lights mounted on the cab roof!)

http://www.youtube.com/watch?v=yFN2Dfj63g8

[JayMac]

Thank you, lukefarley and Sprog, for posting such detailed technical information here.

I certainly followed most of it ... and is it therefore worth us considering adding a new board on this forum, for just such technical issues - rather than put them in the already very busy 'Across the West' board?

If our members are in favour of this, I'll do it: please comment!

Maybe we can call it the "I'll get me coat...." board!!!

[eightf48544]

The most intereting thing to me on this topic is it illustrates how primative batterry technology still is.

So for all the hype of battery electric cars they are still a long way from replacing the internal combustion engine except as inner city runabouts.

Another case for electrification provided the conductor shoe or pan is in contact and there's power available turn the switch and go. After waitng the necessary time for the computer to boot, the test/fault diagnostic routines to run. GRS (radio?) and sattelite positioning to lock on,  ERTMS^▸ (European Rail Traffic Management System.) (!) to activate,  the driver to programme his route. By this time the air may be up to pressure and the train can finally move. But you still have have battries to provide emergency power when the traction current is switched off.

Are modern trains getting too complicated...discuss.

[devon_metro]

Are modern trains getting too complicated...discuss.

I think the Desiros are a good example, the computer controls everything and is well known to throw up faults and hinder the progress of the train, let us not forget the fact that simple inserting another coach will require a whole software rewrite.

Compare that to the "Slammers" - they just worked!

[Tim]

Are modern trains getting too complicated...discuss.

I think the Desiros are a good example, the computer controls everything and is well known to throw up faults and hinder the progress of the train, let us not forget the fact that simple inserting another coach will require a whole software rewrite.

Compare that to the "Slammers" - they just worked!

Not just too complicated also too heavy and too power hungry (witness the huge power upgrade needed when the slammers were replaced) although the trend for wieght and energy consumption is now on the way back down. 

The problems with computers is that they are obsolete so quickly.  Add and extra coach to a Pendalino and you either need to source a 10 year old computer for it or come up with a software bodge so the new unit can talk to the old.

I remember an early trip on a Voyager (it must have been an early one as the smell of Sh*t and my consequent aviodance of them had not yet started).  After a delay pulling out of Cheltenham and the driver seen walking along the platform from one cab to the other and then back again with a huge ringbinder, we got a announcement along the lines of "sorry for the delay but the train has crashed", then the lights flickered and a second accouncemnt "sorry for alarming anyone, I meant to say that the computer had crashed and needed to be restarted" , before pulling out.   

[Cruithne3753]

I think the Desiros are a good example, the computer controls everything and is well known to throw up faults and hinder the progress of the train, let us not forget the fact that simple inserting another coach will require a whole software rewrite.

Sounds like badly written software... they weren't thinking modular and scalable, just ad-hocking a load of "spaghetti code".

[The SprinterMeister]

However, even with a 'good' set of batteries, as the engine is idling as opposed to running at high-revs when out in traffic, it is really only trickle-charging the Batteries. And sometimes in rare cases, no matter how much you attempt to charge the batteries, if they are so far gone that they are not taking charge, then it is a futile fuel-wasting exercise anyway!

It doesn't alway help on some of the sets the engine idling speed appears to be too low. There one 143 running around idling at about 600rpm (instead of the usual 775 - 800rpm) on one car. Funnily enough the lights seem to hold up ok on that one. Having seen whats involved in resetting the idle revs in the VOMI, it doesnt appear to be the easiest job in the world to do.

[Sprog]

However, even with a 'good' set of batteries, as the engine is idling as opposed to running at high-revs when out in traffic, it is really only trickle-charging the Batteries. And sometimes in rare cases, no matter how much you attempt to charge the batteries, if they are so far gone that they are not taking charge, then it is a futile fuel-wasting exercise anyway!

It doesn't alway help on some of the sets the engine idling speed appears to be too low. There one 143 running around idling at about 600rpm (instead of the usual 775 - 800rpm) on one car. Funnily enough the lights seem to hold up ok on that one. Having seen whats involved in resetting the idle revs in the VOMI, it doesnt appear to be the easiest job in the world to do.

Very awkward (risk, amoungst other things of pressurised fuel spraying in your face during the process!!!) & we are technically not allowed to do it under the warranty conditions of the Engines.

[smithy]

This 'flashing' is not an intentional thing but instead is due to the A.S.C. (Auxilary Supply Contactor) on the vehicle dropping in and out repeatidly, thus cutting the supply to the units Auxilary systems (interior lighting, tail/marker/headlights, heating etc.). The A.S.C. is controlled by the L.V.R. (Low Voltage Relay) which via a L.V.P.U. (Low Voltage Protection Unit) detects if the Voltage of the batteries drops below a specified level. If you are somewhere quiet, you can usually hear the 'clunking' of the A.S.C. opening and closing repeatedly.

This usually occurs due to the Auxilary batteries on the unit having low charge due to either defective/degraded batteries or a fault with the charging system on the unit. All DMUs^▸ (Diesel Multiple Unit) have two sets of 24V batteries, Start & Auxilary, the Start Batteries being responsible for all of the vehicles primary systems & as the name suggests, Engine Starting, hence why the Unit presumably started up OK. As soon as the units engines are running and the deisel engine has been sped-up from idle speed using the 'Compressor Speed Up' switch (to build up Air pressure), the shaft-driven Alterntors (Hydostatically-driven on a Class 158) that supply the charging system will be electrically excited and hence supply the vehicles auxilary batteries, thus provding suffcient voltage (Usually 24V +/- approx 2V) not to trip the L.V.R. and hence keep the A.S.C. closed.

Hope i havent gone to 'technical' for you!

a bit more info to add,on a class 150/2 the alternators are self exciting so if the driver just started engines without operating the compressor speed up then charging will not start and over time the aux batteries would still drain to the point of operating the low volt board.also to clarify there is no seperate low volt relay it iis all part of the low volt protection unit.
i am also under the impression 150249 has got a known problem with aux power being lost when sat idling the engine needs speeding up to kick start the charging,this would suggest to me the brush's or slip rings in alternators are worn and thus losing field voltage at low rpm.also 143's have similar charging system but have been modified to excite as soon as engine is started i think 150/2's are going to get the same mod soon

However, even with a 'good' set of batteries, as the engine is idling as opposed to running at high-revs when out in traffic, it is really only trickle-charging the Batteries. And sometimes in rare cases, no matter how much you attempt to charge the batteries, if they are so far gone that they are not taking charge, then it is a futile fuel-wasting exercise anyway!

It doesn't alway help on some of the sets the engine idling speed appears to be too low. There one 143 running around idling at about 600rpm (instead of the usual 775 - 800rpm) on one car. Funnily enough the lights seem to hold up ok on that one. Having seen whats involved in resetting the idle revs in the VOMI, it doesnt appear to be the easiest job in the world to do.

Very awkward (risk, amoungst other things of pressurised fuel spraying in your face during the process!!!) & we are technically not allowed to do it under the warranty conditions of the Engines.

the engine rpm can be raised safely if the correct tool is available,the tool screws in to rear of fuel pump to stop fuel leaking while running and allows the adjustment screw to be turned,failing that screw adjuster in half a turn refit blank plug and run engine up that is usually enough if only slightly low