Could battery powered trains operate Guildford to London Bridge via North Downs?

[Bald Rick]

Stop dancing on the head of pin. Battery trains are a complete waste of time, whilst it may be an ideal solution for moving them around in a depot off of the trolley, it's a pointless & overweight solution for lines like the NDL, Marshlink etc.

Splash the cash, get the job done at today's prices, procrastination just increases the overall cost. Once it's done, it's there for good and as someone who lives along the NDL, it's time to get rid of FGW (or F**king Godknows When) and their smelly, noisy diesels and the nice clean & quiet electrics in with dual voltage capability, which would score well for extended journeys.

Robustly put. But not supported by fact. Or the extra £50m.

I forgot option 3). Leave it as it is. Cost £0.

 

[FenMan]

Robustly put. But not supported by fact. Or the extra £50m.

I forgot option 3). Leave it as it is. Cost £0.

Which underlines the problem of what to do with the NDL. Close it? Er, no. Sort it out once and for all? = expensive. The procrastination will continue for many years yet, I fear.

The nearby 3rd rail-electriified Ascot - Aldershot - Guildford doesn't exactly look a bargain by comparison, but the money's been spent now, so hey ho.

 

[RobShipway]

Which underlines the problem of what to do with the NDL. Close it? Er, no. Sort it out once and for all? = expensive. The procrastination will continue for many years yet, I fear.

The nearby 3rd rail-electriified Ascot - Aldershot - Guildford doesn't exactly look a bargain by comparison, but the money's been spent now, so hey ho.

In an ideal world, you would convert the existing 3rd rail electric to be OHLE and then convert the non - electrified parts to be OHLE as well, but that again is down to what money is available. Also, what stock would be able to be used on the route as well?

If SWT went for the extra 20 class 707's, then you would possibly be able to free class 450's to be converted to class 350's to be used on the route and have it run by SWT which for me would make more sense than FGW running the route. But then nothing with the rail network and TOC's in the UK is sensible.

 

[Minstral25]

I don't think it matters who runs the Gatwick to Reading semi-fast service, perhaps it could be passed to Gat-Ex and new swanky units would miraculously appear. However SWT would be just an ORCATS raid (is that right expression) into Southern territory - as if RDG-GTW for FGW isn't already.

The local (Stopping) services should be split I think. An extension of Guildford to Redhill section of service to ECR & London would generate a lot of traffic especially from Dorking and Reigate. Shame the line is electrified as it would make a better destination than Tattenham for the Cambridge Thameslink services but that's an opportunity missed.

I'm surprised the cost of Battery Units is so high making electrification more logical (although I suspect the electrification costs does not include the new units then required for the extra services.

 

[Peter Sarf]

I don't think it matters who runs the Gatwick to Reading semi-fast service, perhaps it could be passed to Gat-Ex and new swanky units would miraculously appear. However SWT would be just an ORCATS raid (is that right expression) into Southern territory - as if RDG-GTW for FGW isn't already.

The local (Stopping) services should be split I think. An extension of Guildford to Redhill section of service to ECR & London would generate a lot of traffic especially from Dorking and Reigate. Shame the line is electrified as it would make a better destination than Tattenham for the Cambridge Thameslink services but that's an opportunity missed.

I'm surprised the cost of Battery Units is so high making electrification more logical (although I suspect the electrification costs does not include the new units then required for the extra services.

Excellent. You just made me think of the 442s for a GATex limited stop service to Reading. I'll get my coat :roll:.

 

[swt_passenger]

I'm surprised the cost of Battery Units is so high making electrification more logical (although I suspect the electrification costs does not include the new units then required for the extra services.

The Modern Railways article a few months ago mentioned that the battery pack would need replacing every so many years, so perhaps 5 or 6 times (or more) over the EMU life and that accounts for most of the extra cost compared to a conventional EMU...

 

[Caravanman]

I don't have much idea about whether battery powered trains even exist? Our local council has invested in battery buses, and they seem to only last half a day before needing recharge. (According to the drivers...)

Have I missed out on hearing of the creation of a real battery powered train ?

Ed.

 

[swt_passenger]

I don't have much idea about whether battery powered trains even exist? Our local council has invested in battery buses, and they seem to only last half a day before needing recharge. (According to the drivers...)

Have I missed out on hearing of the creation of a real battery powered train ?

Ed.

There was a trial of a temporarily modified Electrostar earlier this year, thread here: http://www.railforums.co.uk/showthread.php?t=110705&highlight=IPEMU

 

[AndyNLondon]

I don't have much idea about whether battery powered trains even exist? Our local council has invested in battery buses, and they seem to only last half a day before needing recharge. (According to the drivers...)

Have I missed out on hearing of the creation of a real battery powered train ?

Network Rail & Greater Anglia have fitted a class 379 unit with batteries and have been testing it in service. Apparently it can do 60 miles on the batteries, and charges while running on the wires, with two hours charging for an hour running from batteries. See
http://www.networkrail.co.uk/news/2...f-prototype-battery-powered-train-begin/?cd=3 & http://www.railmagazine.com/news/network/2015/01/13/battery-powered-electrostar-enters-traffic.

 

[HarleyDavidson]

Network Rail & Greater Anglia have fitted a class 379 unit with batteries and have been testing it in service. Apparently it can do 60 miles on the batteries, and charges while running on the wires, with two hours charging for an hour running from batteries. See
http://www.networkrail.co.uk/news/2...f-prototype-battery-powered-train-begin/?cd=3 & http://www.railmagazine.com/news/network/2015/01/13/battery-powered-electrostar-enters-traffic.

In that case the idea of using a battery powered unit is a "dead duck", because it wouldn't spend much more than 70'-90' on juice at the very top end and then you still have to factor in the power usage of the unit for all on board systems and auxiliaries & control functions.

So that would give you a 30' deficit to make up per trip and that's provided that there's no delays, get delayed that 70-90' on juice becomes even less and therefore the chances of flat batteries are even greater, especially as an electric unit is considerably faster on the electric rail, than on batteries and of course that means less time on the juice to recharge.

The simplest, easiest and cheapest option is to just get the juice rail or OHLE installed, the signalling done before the transfer to the ROCs and be done with it. None of this fannying around with battery powered junk, which will undoubtedly fail due to "flat" or "low" batteries causing chaos for hours.

As I have said, I've worked the line, I know where you could install things pretty easily with road access, you can even install the latest substation equipment by shipping it in by rail to site as you can with DC containers (aka TP huts).

 

[hwl]

In that case the idea of using a battery powered unit is a "dead duck", because it wouldn't spend much more than 70'-90' on juice at the very top end and then you still have to factor in the power usage of the unit for all on board systems and auxiliaries & control functions.

So that would give you a 30' deficit to make up per trip and that's provided that there's no delays, get delayed that 70-90' on juice becomes even less and therefore the chances of flat batteries are even greater, especially as an electric unit is considerably faster on the electric rail, than on batteries and of course that means less time on the juice to recharge.

The simplest, easiest and cheapest option is to just get the juice rail or OHLE installed, the signalling done before the transfer to the ROCs and be done with it. None of this fannying around with battery powered junk, which will undoubtedly fail due to "flat" or "low" batteries causing chaos for hours.

As I have said, I've worked the line, I know where you could install things pretty easily with road access, you can even install the latest substation equipment by shipping it in by rail to site as you can with DC containers (aka TP huts).

For me the logic in Battery EMUs is that it allows the signalling and electrification work to be spread out over time rather than needing to be totally complete to run and electric service on day 1 which make the work logistically and cash flow easier as then would then be less strict deadlines to guarantee hitting which all push the costs up.

 

[NSEFAN]

For me the logic in Battery EMUs is that it allows the signalling and electrification work to be spread out over time rather than needing to be totally complete to run and electric service on day 1 which make the work logistically and cash flow easier as then would then be less strict deadlines to guarantee hitting which all push the costs up.

I suppose if we could control the timescales of the industry more strictly, you could cascade the BEMUs used for infill electrification schemes around the country as each line gradually has electrification done. I don't think we can rely on the industry in its current form to be so organised.

This is also assuming that it's cheaper to do electrification in stages, rather than a total route modernisation au Network Southeast.

 

[hwl]

Robustly put. But not supported by fact. Or the extra £50m.

I forgot option 3). Leave it as it is. Cost £0.

Option 3 is potentially only zero in the short term.
You would need new or cascaded DMUs in 20 years and the signalling would need renewing any way at some point.

Fully electrification or IPEMU then allows more DMUs to be cascaded elsewhere rather than potentially building new DMUs so there is a potential offset there. It depend on the accounting boundaries.

IPEMU means any upgrade work on signalling can be done more flexibly hopefully reducing costs for electrification in due time.

 

[HarleyDavidson]

It would be far cheaper to buy the electrification equipment in bulk and do two lines, so you get the discount that bulk purchasing gets (or should!) you and then put it in a nice NR owned warehouse until required.

It's easier to do things with a blockade of X number of weeks, as it allows things to be done without interruption or interference and it could/should actually be far quicker too in theory & practice.

The benefits of having a whole electric railway are cleaner, quieter, faster train services and for both NDL & either Marshlink or Uckfield lines a far better & resilient service to boot. And a side effect of NDL going electric is that they can ship just about all Turbo's to the West Country and then they can benefit from better/longer trains too.
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Excellent. You just made me think of the 442s for a GATex limited stop service to Reading. I'll get my coat :roll:.

Actually you can lambast me for saying it, but that's not a bad idea & in fact quite sensible as you will have 5 coaches, 1600 hp available which would be ample for the NDL, you probably wouldn't need to extend many platforms by much & you could use SDO for those which can't be practically extended due to bridges or level crossings intervening and they're comfortable too.
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Not to mention how either third rail or OHLE electrification wouldn't work on the North Downs on a significant number of occasions between approximately late October and late February each year. Winter conditions round there can be very unforgiving. You're effectively skirting the bottom of a very exposed set of quite high hills. I for one do not fancy having to dig trains out of the snow in the more exposed parts of Buckland or Gomshall.

More tosh.

The 3rd rail got stuffed because of the stupid lightweight shoegear that modern trains use.

I'd describe the shoes that are on them now as "Summer Weight" ones, if you replaced them with more durable heavy or "Winter Weight" ones you'd do better, a bit like summer & winter tyres for a car.

OHLE if done correctly would be OK as none of the NDL is particularly exposed compared to other lines and wouldn't be overly exposed at all.
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I don't think it matters who runs the Gatwick to Reading semi-fast service, perhaps it could be passed to Gat-Ex and new swanky units would miraculously appear. However SWT would be just an ORCATS raid (is that right expression) into Southern territory - as if RDG-GTW for FGW isn't already.

The local (Stopping) services should be split I think. An extension of Guildford to Redhill section of service to ECR & London would generate a lot of traffic especially from Dorking and Reigate. Shame the line is electrified as it would make a better destination than Tattenham for the Cambridge Thameslink services but that's an opportunity missed.

I'm surprised the cost of Battery Units is so high making electrification more logical (although I suspect the electrification costs does not include the new units then required for the extra services.

SN do an ORCATS or LENNON raid on SWT land anyway on that joke (and that's precisely what it is!) of a service that they attempt to run between VIC/LBG & Guildford, which regularly fails to appear or terminates short at Effingham or Leatherhead.

XC do another on GW with that feeble excuse of a single daily service to/from Guildford (if that's what you can call it?), which again regularly fails to materialise due to the most puerile & feeble of excuses. We know what it's there for and that's purely for route knowledge retention as it saves XC from booking crews route knowledge refresher day, nothing more, nothing less.

And that can be proven, when you get engineering work between Reading & Southampton and over 50% of the Bournemouth XC services terminate at Reading, that's because they won't pay for other drivers & TMs to learn the section from Reading to Southampton via Guildford.

 

[DelW]

If SWT went for the extra 20 class 707's, then you would possibly be able to free class 450's to be converted to class 350's to be used on the route and have it run by SWT which for me would make more sense than FGW running the route.

To be fair, the line did improve when it was transferred from Southern to Western regions of BR (late '70s?). I go back far enough to remember the days of operation by the infamous 'Tadpoles' - with their 1 & 1/2 coaches of 2+2 seating. At that time services ran to Tonbridge rather than Gatwick.

SN do an ORCATS or LENNON raid on SWT land anyway on that joke (and that's precisely what it is!) of a service that they attempt to run between VIC/LBG & Guildford, which regularly fails to appear or terminates short at Effingham or Leatherhead.

Wasn't the whole line a Victorian equivalent of an ORCATS raid? As a tentacle of the SER going deep into LSWR territory I think it was an intruder from the start. Even in the 1960s the then local management appeared to want to close it down - the Tadpoles were a last ditch way of providing some post-steam stock, though I can't now remember who devised them.

 

[HarleyDavidson]

To be fair, the line did improve when it was transferred from Southern to Western regions of BR (late '70s?). I go back far enough to remember the days of operation by the infamous 'Tadpoles' - with their 1 & 1/2 coaches of 2+2 seating. At that time services ran to Tonbridge rather than Gatwick.



Wasn't the whole line a Victorian equivalent of an ORCATS raid? As a tentacle of the SER going deep into LSWR territory I think it was an intruder from the start. Even in the 1960s the then local management appeared to want to close it down - the Tadpoles were a last ditch way of providing some post-steam stock, though I can't now remember who devised them.

Service improved under the auspices of the Western Region? Did it hell (Censored version)!

Those ignorant sods gave us lousy dirty smelly 3-WR sets colloquially known as 3 WReck or stink bombs.

They slashed the stopping service to virtually non existent between Guildford and Redhill, so from one early train at around 0530/0600 hrs & hourly all day to something like 2200 at night, it went to 3 in the morning & 2 during the day & 3 in the evening, then the last one more or less as now 2318.

The service is still dire and you can't generally go from one station to the next without going beyond it & return. And it's so darn unreliable with trains regularly running late and missing out stops (if not all of them!) that's happened more than a few times in the last few weeks.

DaFT need to take the NDL off of FGW and give it to either SWT or TGSN although hopefully not, as they're just as hopeless as FGW in regard to time keeping, with their mad idea of portion working!

 

[Peter Sarf]

I dont think icing up of the third rail is a particular problem on the North Downs Line. I used to live near Sole Street Bank which rises up from the Medway valley to the top of the North Downs. I also used to use the North Kent lines. These suffered from icing up but are far more exposed to the cold damp air blowing off the North sea.

As for quality of service. I used to commute from Strood to Edenbridge every day around 1983 on DMUs. The morning service from Tonbridge towards Redhill was er non-existent. The train just used to fail to be there. Coming home the late running service to Tonbridge used to arrive late enough for me to see the departure of my connection to Paddock wood where I had to change trains again. If you asked the staff what was going on they used to ignore you.

The (Sothern region ?) staff who drove the Tadpoles were quite friendly judging by the nice view I had of the line when I was about 14 !.

As for the problem of the battery unit. If the 379 takes 2 hours to charge while being used for one hours use on batteries then 90 minutes running on the DC would give 45 minutes on battery. Its not necessary to fill the batteries right up. So I am unsure if HarleyDavidson's concerns fit in. I must admit I have no idea where the train could get to if it can do 45 minutes/45 miles beyond the DC third rail at Reigate. Obviously half that if it turns round and comes straight back.

If the 442s are too long then fill up the leading ends of both driving coaches with batteries !.

 

[HarleyDavidson]

I dont think icing up of the third rail is a particular problem on the North Downs Line. I used to live near Sole Street Bank which rises up from the Medway valley to the top of the North Downs. I also used to use the North Kent lines. These suffered from icing up but are far more exposed to the cold damp air blowing off the North sea.

As for quality of service. I used to commute from Strood to Edenbridge every day around 1983 on DMUs. The morning service from Tonbridge towards Redhill was er non-existent. The train just used to fail to be there. Coming home the late running service to Tonbridge used to arrive late enough for me to see the departure of my connection to Paddock wood where I had to change trains again. If you asked the staff what was going on they used to ignore you.

The (Sothern region ?) staff who drove the Tadpoles were quite friendly judging by the nice view I had of the line when I was about 14 !.

As for the problem of the battery unit. If the 379 takes 2 hours to charge while being used for one hours use on batteries then 90 minutes running on the DC would give 45 minutes on battery. Its not necessary to fill the batteries right up. So I am unsure if HarleyDavidson's concerns fit in. I must admit I have no idea where the train could get to if it can do 45 minutes/45 miles beyond the DC third rail at Reigate. Obviously half that if it turns round and comes straight back.

If the 442s are too long then fill up the leading ends of both driving coaches with batteries !.

You'll get 8' running on the juice between Reading & Wokingham, another 13' between Aldershot Sth & Shalford Jn and ~26' between Reigate & Gatwick (which I'm using for this as it's where the service runs to/from at the current time).

So that equates to 16+26+52 = 94' on the juice.

But you then have 14' of off juice running between Wokingham & Aldershot Sth, plus another 20' between Shalford & Reigate on steep gradients. So that's 34', but of course you have to double it for both ways, so that's 78' of off juice. Would those batteries hold out, especially as there's going to be a deficit between the amount of charging & discharging. I severely doubt it.

 

[Bald Rick]

So that's 34', but of course you have to double it for both ways, so that's 78' of off juice.

Or even 68'. What was that quote about statistics...

But of course if these are dual voltage battery trains, they might be extended west of Reading to, say, Oxford. And the equation changes.

 

[Class 170101]

And turnaround time to be factored in as well. Minimum of 10 minutes at each end.

As for the Rolling Stock in the short term that cost may be also zero if not all the Class 319s find a home up north.

In terms of the battery train when I saw it in use it did not work pan down in both directions.
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This is one of the lines that I know quite well and have worked over in the past & no it wouldn't be hugely expensive either. The last costings were in the region of £30-50m for the electrification of the two missing sections.

However as the line hasn't had any serious infrastructure upgrades in over 40 years, you'll need to factor in the resignalling as well, which will probably mean an overall cost of £50-60m to give the line a complete update and soon NR will have the perfect opportunity to do it, when the line gets transferred to Basingstoke ROC & Three Bridges ROC.

They need to extend the platforms at most stations, increase the line speeds in several key sections (there's absolutely no reason why linespeeds in excess of 75mph shouldn't be possible), shorter signalling sections should be easily achievable using the lightweight stuff that they used in the Fens.

Power supplies in difficult locations away from roads? You're having a laugh aren't you?

Most locations are quite easily accessed from either the local road network, a substation at Shalford Junction or Shalford station easy access, another sub at Albury (Brook)/Shere Heath again easy access, another at Dorking West or Deepdene which could be used to power both NDL and supplement the Horsham line & final one at Buckland (Betchworth) again accessible from either Rectory or Lawrence Lanes. Simple easy access and TP huts or DC containers are now prefabricated and easily transportable to their corresponding locations and assembled on site.

The other direction you can have a feed from the Substation at Aldershot North, you then already have a Sub at Farnborough for the SWML, another Sub at either Sandhurst or Crowthorne, before joining the already electrified Reading - Waterloo section at Wokingham, where there's already a substation.

Apologies for my ignorance but presumably access to the National Grid is required as well? I guess this isn't always near the road access points discussed above?
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On the basis of the above:

Option 1) electrify. Cost £30-50m. Cost of track and signalling alterations to permit electrification £10m. Cost of new electric trains (fleet of 10x4 car) for the route £50m (as by the time this has been electrified, there will be no spare electric stock). Total £90-£110m

Option 2) battery trains. Cost of new battery trains, same size fleet. £70m. Total £70m.

Closer than I thought, but no contest.

And that's assuming £30-50m for electrification, which feels light.

£30m to £50m does sound light but I would wonder when these figures were last complied - given inflation etc. Also given NR's recent 'success' in electrification projects in terms of the budget....

However £70m for battery trains as yet not fully tested - see above reference the Class 379. Also commented above some 'free' trains aka Class 319s if not needed in ther north.

In terms of electrification might a Paisley Canal style scheme but for 3rd Rail be more viable instead?

 

[HarleyDavidson]

Or even 68'. What was that quote about statistics...

But of course if these are dual voltage battery trains, they might be extended west of Reading to, say, Oxford. And the equation changes.

Oops, my bad. Drinking a nice bottle of red wine & maths is not a good thing to attempt.
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And turnaround time to be factored in as well. Minimum of 10 minutes at each end.

That's provided it's on time. I've known turnaround times as little at 4-5' if there's a different crew taking it on. I still wouldn't invest in battery driven units for passenger use, it's folly and technology is untrustworthy.

As for electrical power from National Grid that's easy enough too, the line is crisscrossed by roads & powerlines.

 

[Minstral25]

It doesn't sound as if battery technology is up to it yet.

So what about hybrid trains, with a Diesel motor that can be switched on in a compartment next to one of the cabs (replacing first class?), providing power for electric motors that drive the train when there is no third rail but fully compatible with current stock.

We could get Boris to promote them and call them "New Thumpers for North Downs"

 

[hwl]

It doesn't sound as if battery technology is up to it yet.

So what about hybrid trains, with a Diesel motor that can be switched on in a compartment next to one of the cabs (replacing first class?), providing power for electric motors that drive the train when there is no third rail but fully compatible with current stock.

We could get Boris to promote them and call them "New Thumpers for North Downs"

You should be able to fit one of these under a 23m body shell:
http://www.mtu-report.com/Service/News/Diesel-goes-electric-Hybrid-drives-prove-themselves-in-trials

So now need for an in compartment thumper replacement. I think Bombardier will be offering it as an option on Aventra.

From what I gather the 379 trial didn't have the biggest available set of battery packs but just enough for the trial.

 

[HarleyDavidson]

It wouldn't have enough guts to climb the bank from Shalford to Abinger (Welcome Bridge) or Whitedown Lane as it's otherwise known.

And diesels may well be falling out of favour due to health concerns.

 

[Minstral25]

It wouldn't have enough guts to climb the bank from Shalford to Abinger (Welcome Bridge) or Whitedown Lane as it's otherwise known.

And diesels may well be falling out of favour due to health concerns.

Diesels may be falling out of favour but where we haven't got third rail we need something to power the trains - Gas Turbines? Let's get the APT out for tests.

It seems amazing that the little North Downs line is such a problem in rural Surrey. It's not as if we have any mountains down here.

Perhaps then a bigger MTU and replace First Class with it as previously suggested - It'll be lovely to have a Thumper back

 

[Peter Sarf]

You'll get 8' running on the juice between Reading & Wokingham, another 13' between Aldershot Sth & Shalford Jn and ~26' between Reigate & Gatwick (which I'm using for this as it's where the service runs to/from at the current time).

So that equates to 16+26+52 = 94' on the juice.

But you then have 14' of off juice running between Wokingham & Aldershot Sth, plus another 20' between Shalford & Reigate on steep gradients. So that's 34', but of course you have to double it for both ways, so that's 78' of off juice. Would those batteries hold out, especially as there's going to be a deficit between the amount of charging & discharging. I severely doubt it.

By my reckoning the 379 manages half as long on battery only as it does charging & running on the electric power supply. So, using your figure, 94 minutes on the juice would give 47 minutes on battery. But you reckon 68 (2*34) minutes is needed on battery so it is not going to work by 21 minutes. That is roughly eleven minutes each way if everything else works fine (no delays and good batteries).

Along the lines of the Paisley Canal suggestion perhaps enough electrification can be done cheaply to get rid of that eleven minute gap. Actually if eight minutes of route were electrified there would be a gain of four minutes on battery life/range. So eight minutes of route electrification gets rid of twelve minutes battery use each way. So Network Rail could electrify the easy bits and/or power hungry bits (up a gradient or group of stations where all services stop).

I can see that the best use of a Battery EMU would be on routes not completely electrified but where the gaps are sporadic so not the whole of one end of the route. That could be the North Downs Line. However what we normally need is something that can run on the outer reaches of a network beyond the currently electrified conurbation.

For the third rail electrified part of Southern I can only think of five cases.
Basingstoke to/from Exeter - hopelessly far off the juice.
Basingstoke to Southampton via Salisbury - not sure what percentage of this is gaps, most of it ?.
Oxted to Uckfield - probably too far but doable with some infill (charging at the Uckfield terminus).
Hastings to Ashford - probably OK as its part of a through service from Brighton, both ends are already electrified.
North Downs line - as above it seems the most doable as the gaps are spread out if some more electrification is done.

The above indicates a not very large requirement so would a manufacturer be interested. Possibly yes as a prototype derived from a production train (class 379) already exists. I wonder if Vivarails D78 conversion would be useful for any of these with a third rail capability left in. Plenty of power hopefully (for the chalky mountains) but a restrictive top speed for most of the five cases.

Of course the 442s have a better top speed . Maybe convert all of them to Bi-Modes . Pity about the door spacing . All credit to Minstral25 for triggering that idea.

 

[HarleyDavidson]

By my reckoning the 379 manages half as long on battery only as it does charging & running on the electric power supply. So, using your figure, 94 minutes on the juice would give 47 minutes on battery. But you reckon 68 (2*34) minutes is needed on battery so it is not going to work by 21 minutes. That is roughly eleven minutes each way if everything else works fine (no delays and good batteries).

Along the lines of the Paisley Canal suggestion perhaps enough electrification can be done cheaply to get rid of that eleven minute gap. Actually if eight minutes of route were electrified there would be a gain of four minutes on battery life/range. So eight minutes of route electrification gets rid of twelve minutes battery use each way. So Network Rail could electrify the easy bits and/or power hungry bits (up a gradient or group of stations where all services stop).

I can see that the best use of a Battery EMU would be on routes not completely electrified but where the gaps are sporadic so not the whole of one end of the route. That could be the North Downs Line. However what we normally need is something that can run on the outer reaches of a network beyond the currently electrified conurbation.

For the third rail electrified part of Southern I can only think of five cases.
Basingstoke to/from Exeter - hopelessly far off the juice.
Basingstoke to Southampton via Salisbury - not sure what percentage of this is gaps, most of it ?.
Oxted to Uckfield - probably too far but doable with some infill (charging at the Uckfield terminus).
Hastings to Ashford - probably OK as its part of a through service from Brighton, both ends are already electrified.
North Downs line - as above it seems the most doable as the gaps are spread out if some more electrification is done.

The above indicates a not very large requirement so would a manufacturer be interested. Possibly yes as a prototype derived from a production train (class 379) already exists. I wonder if Vivarails D78 conversion would be useful for any of these with a third rail capability left in. Plenty of power hopefully (for the chalky mountains) but a restrictive top speed for most of the five cases.

Of course the 442s have a better top speed . Maybe convert all of them to Bi-Modes . Pity about the door spacing . All credit to Minstral25 for triggering that idea.

Doing things in bits & pieces only increases overall costs and ultimately pointless, you either do it or you don't. With electrification there's no ½ measures. If you skimp on things, such as the amount of power available to draw on, then it will only come back and bite you hard on the backside, with power restrictions or unexpected outages.

 

[OliverS]

By my reckoning the 379 manages half as long on battery only as it does charging & running on the electric power supply. So, using your figure, 94 minutes on the juice would give 47 minutes on battery. But you reckon 68 (2*34) minutes is needed on battery so it is not going to work by 21 minutes. That is roughly eleven minutes each way if everything else works fine (no delays and good batteries).

Along the lines of the Paisley Canal suggestion perhaps enough electrification can be done cheaply to get rid of that eleven minute gap. Actually if eight minutes of route were electrified there would be a gain of four minutes on battery life/range. So eight minutes of route electrification gets rid of twelve minutes battery use each way. So Network Rail could electrify the easy bits and/or power hungry bits (up a gradient or group of stations where all services stop).

Add 10 minutes for turnaround at each end and you are up to 114' on the juice compared to 136' needed (68' *2). Infill 4' running time in each direction and you get 122' running vs 120' needed. For instance add third rail from Shalford Jn to Shalford and from Aldershot Sth to North Camp and you are done.

The problem being that you are relying on that 2 to 1 ratio being true for the lifetime of the battery, which might be unjustified. And that there is a 10min turnaround at both ends. Terminate short at Redhill and the numbers don't work as you've lost 40' of charging.

But extending the London to Reigate services to Guildford does seem reasonable. 45' mins on juice to 20' off juice ignoring turnaround times.

 

[HSTEd]

Well you can reduce the cost of third rail electrification if you accept no ability to regenerate. Since you can get away with greater substation spacings as you can use the entire 900-450V available range for voltage drop (earth voltage rise).

 

[JamesRowden]

But of course if these are dual voltage battery trains, they might be extended west of Reading to, say, Oxford. And the equation changes.

Perhaps a North Downs battery train service could be formed of the following services of which at least the first two of the first three listed below inter-work to provide enough recharge time:

• 1tph Reading-Guildford-Portsmouth
• 1tph Reading-Gatwick
• 1tph Newbury-Gatwick
• 1tph Guildford-Redhill-Victoria

I think that the extended services to Newbury, Portsmouth and Victoria would provide some reasonable benefits for passengers.