Transport for Wales Class 231 / 756 FLIRTs

[rftorf]

This was posted on a Facegroup page highlighting initial test runs of the 756 to Swindon from one of the drivers.

A couple weeks back on 002 we left Newport on battery with 77% . Somewhere around Wotton Bassett the engine started as batteries down to 28%
The engine will maintain battery levels 30-35% . Once at Swindon put the pan up and batteries were fully recharged in about 10-15 mins .
Very little difference in performance on battery to pantograph operation .
Lovely unit to Drive

 

[Envoy]

This was posted on a Facegroup page highlighting initial test runs of the 756 to Swindon from one of the drivers.

A couple weeks back on 002 we left Newport on battery with 77% . Somewhere around Wotton Bassett the engine started as batteries down to 28%
The engine will maintain battery levels 30-35% . Once at Swindon put the pan up and batteries were fully recharged in about 10-15 mins .
Very little difference in performance on battery to pantograph operation .
Lovely unit to Drive

That’s quite a way from Newport to Wooton Bassett. Good to know it can go that distance on battery power and it was not even fully charged to start - though I guess that is intentional.

 

[anthony263]

That’s quite a way from Newport to Wooton Bassett. Good to know it can go that distance on battery power and it was not even fully charged to start - though I guess that is intentional.

I think the batteries seem to have better range than stadler and tfw thought by the looks of it

 

[Dai Corner]

I think the batteries seem to have better range than stadler and tfw thought by the looks of it

The batteries will lose a bit of capacity with every charge/discharge cycle but hopefully still meet their specification for their design life.

 

[slowroad]

The batteries will lose a bit of capacity with every charge/discharge cycle but hopefully still meet their specification for their design life.

If my electric car is anything to go by (and it might not be), broadly following good battery management practice has resulted in negligible deterioration over 2 years. Not long, I realise.

 

[AdamWW]

This was posted on a Facegroup page highlighting initial test runs of the 756 to Swindon from one of the drivers.

The engine will maintain battery levels 30-35% . Once at Swindon put the pan up and batteries were fully recharged in about 10-15 mins .

I'm curious about this bit (and I know this isn't your information).

"Maintaining battery levels" in the absence of overhead power implies that the single engine can provide sufficient traction power without running the battery down. Maybe even though it's underpowered compared to a straight diesel FLIRT it can nevertheless manage good performance by using the battery for acceleration and charging it by dynamic braking and using excess engine capacity when available? (I.e. hybrid rather than bi-mode operation).

Something I had forgotten is that while a 231 has 4 engines (same as a 4 car Anglia 755), a 3 car 755 only has two. So a 3 car 756 has half the power on diesel of a straight-diesel equivalent, not a quarter (Wikipedia says 1290 hp, vs 640 hp for a 756).

(I presume they stick to even numbers of engines on the pure diesel versions for balance reasons).

 

[Bryson]

If the Diesel is charging the batteries then 640 hp is probably plenty. The post said that the engine started at 28% battery and maintained the battery at 30 to 35%. This suggest the traction power is still coming from the battery with the combustion engine providing range extension rather than direct traction power.

It is unusual for trains to maintain full power for extended periods so the engine can use the low demand times to catch up, the battery level will fall slowly when power demands are high but gain charge when demands are low.

 

[AdamWW]

The post said that the engine started at 28% battery and maintained the battery at 30 to 35%. This suggest the traction power is still coming from the battery with the combustion engine providing range extension rather than direct traction power.

It is unusual for trains to maintain full power for extended periods so the engine can use the low demand times to catch up, the battery level will fall slowly when power demands are high but gain charge when demands are low.

I agree.

If the battery is remaining at a constant level, then ultimately all the traction power is coming from the engine (apart I suppose from any energy recovered by dynamic braking).

Anyway, however you describe it, if this is the case then this would suggest that the units are capable of running on a completely non-wired route subject only to the capacity of the diesel tanks.

And, I suppose, wearing out the batteries more quickly than would be the case if they waited until the line was "fully" wired.

 

[Bryson]

I agree.

If the battery is remaining at a constant level, then ultimately all the traction power is coming from the engine (apart I suppose from any energy recovered by dynamic braking).

Anyway, however you describe it, if this is the case then this would suggest that the units are capable of running on a completely non-wired route subject only to the capacity of the diesel tanks.

And, I suppose, wearing out the batteries more quickly than would be the case if they waited until the line was "fully" wired.

Yes - The energy is indeed all coming from the engine but a high peak power is not required because the battery can still supply the peak power needs whilst the diesel maintains a constant lower output.

Regenerative energy from braking is a bonus. I guess at some point (>35%??) the engine will shut down again until the battery falls back to 28%.

 

[AdamWW]

Yes - The energy is indeed all coming from the engine but a high peak power is not required because the battery can still supply the peak power needs whilst the diesel maintains a constant lower output.

Regenerative energy from braking is a bonus. I guess at some point (>35%??) the engine will shut down again until the battery falls back to 28%.

Yes exactly.

And as you suggest presumably there is some hysterisis built into the system so that the engine isn't constantly being turned on and off again as the battery level passes through the trigger point.

 

[Signal_Box]

That’s quite a way from Newport to Wooton Bassett. Good to know it can go that distance on battery power and it was not even fully charged to start - though I guess that is intentional.

Especially with powering up out of Severn Tunnel and the long climb towards Patchway, combined with 100mph running along the mainline via Hullavington to Swindon pretty good indeed.

But, that’s a steady constant run without station stops and empty not loaded to the rafters with rugby fans.

 

[Bob Price]

I was under the impression that these units were hybrid power. So as the batteries run down the diesel is used to power them up on the move. So power is fed back using the one engine and also from braking. Also operational power is overhead and batteries combined.

 

[56xx]

Noticed recently the internal cab end step edges starting to crumble on some 231s. Yesterday 231 002 was sporting new plastic edges.

 

[Rhydgaled]

The batteries will lose a bit of capacity with every charge/discharge cycle but hopefully still meet their specification for their design life.

If my electric car is anything to go by (and it might not be), broadly following good battery management practice has resulted in negligible deterioration over 2 years. Not long, I realise.

It's been a good few years since I was involved in buying a laptop, but when I was I noted that DELL would only provide a 1 year warranty/guarantee on the battery, even if the consumer was buying a 3 year warranty/guarantee on the rest of the laptop.

Perhaps more-relevant to the current discussion, I have read in the last year or two that the range of electric road vehicles (forget whether it was buses or cars, but I expect both are similarly effected) also decreases quite considerably in cold weather. Presumably this would also impact class 756 operation and perhaps explains why the diesel generator was considered necessary despite the rumours that they would be able to perform their duties without using the diesel at all once the wires are ready.

If the Diesel is charging the batteries then 640 hp is probably plenty. The post said that the engine started at 28% battery and maintained the battery at 30 to 35%. This suggest the traction power is still coming from the battery with the combustion engine providing range extension rather than direct traction power.

I was wondering last night whether the diesel generator can actually power the traction motors directly or whether it only charges the battery and the power from the battery is then used to move the train. Another, probably over-simplistic, way of putting it would be "are they wired in series or wired in parallel". Does anyone here know for sure?

 

[slowroad]

It's been a good few years since I was involved in buying a laptop, but when I was I noted that DELL would only provide a 1 year warranty/guarantee on the battery, even if the consumer was buying a 3 year warranty/guarantee on the rest of the laptop.

Perhaps more-relevant to the current discussion, I have read in the last year or two that the range of electric road vehicles (forget whether it was buses or cars, but I expect both are similarly effected) also decreases quite considerably in cold weather. Presumably this would also impact class 756 operation and perhaps explains why the diesel generator was considered necessary despite the rumours that they would be able to perform their duties without using the diesel at all once the wires are ready.


I was wondering last night whether the diesel generator can actually power the traction motors directly or whether it only charges the battery and the power from the battery is then used to move the train. Another, probably over-simplistic, way of putting it would be "are they wired in series or wired in parallel". Does anyone here know for sure?

VW battery guarantee is 70 percent capacity at 8 years or 100k miles, so they must expect quite a bit better than that.

 

[Bryson]

I was wondering last night whether the diesel generator can actually power the traction motors directly or whether it only charges the battery and the power from the battery is then used to move the train. Another, probably over-simplistic, way of putting it would be "are they wired in series or wired in parallel". Does anyone here know for sure?

Stadler's data sheet for the 756 describes it this way:

 

[Energy]

If my electric car is anything to go by (and it might not be), broadly following good battery management practice has resulted in negligible deterioration over 2 years. Not long, I realise.

Should be better, they use Lithium Titanate batteries which have better longevity than Lithium Ion batteries used in most electric cars.

 

[Annetts key]

If you have a large capacity battery and electric traction motors, the logical arrangement is for the ICE generator to recharge the battery. In other words, the generator, battery and traction motors are “connected in parallel”. Where the power from the generator goes depends on the loading on the traction motors.

All cells and batteries are affected by temperature, to a greater or lesser extent, how much depends on the chemistry used, the construction and if the manufacturer has provided heating or cooling systems.

 

[Bob Price]

A look at the 756's with some footage from me of 231's.

A photo of vegetation clearance at Penarth

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[Annetts key]

A look at the 756's with some footage from me of 231's.

Photo/video still not showing up for me.

 

[pokemonsuper9]

Photo/video still not showing up for me.

there's an embedded youtube video, link below
youtu.be/oDa6nCdKoq4

 

[Bob Price]

Here's a screen capture of it. Keiran is worth a follow as he takes a lot of photos of the works around the valleys.

 

[Annetts key]

Cheers

 

[Jez]

A look at the 756's with some footage from me of 231's.

A photo of vegetation clearance at Penarth

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Nice video.

As we know the 756 is tri mode and also has a much lower top speed to the 231's which makes sense given the 231s will eventually do more long distance runs on the main line from Cardiff-Cheltenham and also Bridgend-Cardiff for the Masetegs.

But the only visual difference between the 756 and 231 is that the 756 has 'Metro' on them, the average passenger wouldn't notice the difference between both fleets id imagine.

 

[Rhydgaled]

the only visual difference between the 756 and 231 is that the 756 has 'Metro' on them, the average passenger wouldn't notice the difference between both fleets id imagine.

And an extra set of doors on the 4-car 756s compared to a 231 (the non-driving coach that doesn't have the toilet is different in a 756 compared to a 231).

 

[Jez]

And an extra set of doors on the 4-car 756s compared to a 231 (the non-driving coach that doesn't have the toilet is different in a 756 compared to a 231).

Ah yes id forgotten about that. Any reason for the extra set of doors? What's in that space on the 231s?

 

[Rhydgaled]

Ah yes id forgotten about that. Any reason for the extra set of doors? What's in that space on the 231s?

The various documents don't entirely agree on the number of seats/tables etc. but think that space is just filled with normal 'airline-style' seats on the 231s. I would guess that the difference is because Rhymney to Llantwit Major is a slightly shorter trip than Maesteg to Cheltenham Spa and dwell times were considered to be more important in the Core Valley Lines, so the 231s have more seats and less space for standing passengers. However, I would have expected the 756s to also have a higher-density layout with fewer table bays but that doesn't appear to be the case (if anything, the 756 might actually have more bays than the 231). The Maesteg, Ebbw Vale and Cheltenham Spa routes are also not subject to the Castlefield Doctrine which saw dwell times prioritised above all else in north, mid and south-west Wales.

 

[Jez]

The various documents don't entirely agree on the number of seats/tables etc. but think that space is just filled with normal 'airline-style' seats on the 231s. I would guess that the difference is because Rhymney to Llantwit Major is a slightly shorter trip than Maesteg to Cheltenham Spa and dwell times were considered to be more important in the Core Valley Lines, so the 231s have more seats and less space for standing passengers. However, I would have expected the 756s to also have a higher-density layout with fewer table bays but that doesn't appear to be the case (if anything, the 756 might actually have more bays than the 231). The Maesteg, Ebbw Vale and Cheltenham Spa routes are also not subject to the Castlefield Doctrine which saw dwell times prioritised above all else in north, mid and south-west Wales.

Yes considering the majority of the routes the 231/756 are used on they do have a significant amount of table seats. Good dwell times will be important on the Maesteg-Cheltenhams/Ebbw Vale too I imagine given they will call at stations between Cardiff and Bridgend. Plus any delays on the Maesteg branch can have a big impact on the main line.

 

[AdamWW]

But the only visual difference between the 756 and 231 is that the 756 has 'Metro' on them, the average passenger wouldn't notice the difference between both fleets id imagine.

The discerning observer might note the presence of a pantograph on the 756s and the associated 25 kV rooftop wiring.

But I don't think that most passengers would look up there or pay much attention if they did.

 

[MikePJ]

One quick question to folks in the know: I’ve noticed that the PA on the 231s often cuts in and out when the conductor is speaking. Is this down to a “gating” circuit on the microphone cutting off if the conductor’s voice is too quiet, or is it something else?