I'm looking for some inspiration here:

I would like to assemble some large 3 kF supercapacitors in series (with appropriate off-the-shelf balance boards, etc.) to build an 80 volt portable jump-start pack for boosting dead locomotives. (New batteries are $20,000, whereas a few dozen supercaps can be had second-hand for 1/20th that price.)

At 800 cranking amps my napkin math suggests I'll likely get around 5-8 seconds of cranking out of an 80 volt, 100 farad capacitor bank, depending on how much current the batteries contribute in parallel while cranking. This time frame - while brief - is generally sufficient to start a locomotive when the fuel injector racks are manually held in the wide-open position during cranking.

The problem I am faced with is that I do not want the capacitors to discharge before the engine start contactor closes. Given I only have 100 farads to work with, the fuel pump, other ancillary equipment and even the weak batteries themselves will quickly drain down the charge on the capacitors before it can serve it's intended purpose if it is delivered before the precise moment it is needed.

The idea I have is to employ a falling-edge trigger on the boost pack's output terminals to fire an internal starter relay. I would tune the trigger to activate in a latching mode when the battery voltage on the load side of the relay is drawn down below, say... 40-50 volts or so during starting?

Can anyone suggest a circuit architecture that might work for this purpose? I am a licensed electrician but I haven't dealt with board-level electronics much since tech school years ago. I could use some pointers as to where to begin.

Obviously level-shifting is going to be an issue considering locomotive electrical systems run at 74 volts DC. (The nominal float voltage for a 32 cell battery.) I think a voltage divider should suffice for voltage sensing purposes.

Input & ideas?

 

What are you using to charge the capacitors?

 

What are you using to charge the capacitors?

An off-the-shelf CC/CV buck-boost converter will be installed across the power contactors, interlocked with their auxiliaries. It will draw residual charge from the batteries (there's usually plenty) and feed it into the capacitor bank until it reaches 74 volts or so. An approximately 1 ohm sandstone resistor will be inserted in series with it's output circuit to protect it against an undervolt condition, should the capacitors ever reach a fully discharged state. Appropriate line and load side fusing will also be provided to quench arcing and prevent fire in the event that module fails, allowing all the hellish power of a supercap bank / locomotive battery / 15~18 kW locomotive auxiliary generator to be released inside that tiny little circuit board.

Also, part of the intent with having the power contactors latch closed when the trigger circuit activates is to allow the capacitors to be recharged rapidly by reverse current from the locomotive's auxiliary generator. Those are usually good for at least 200 amps continuous and are no joke. This trick will also work with any DC arc welder having a suitable open circuit voltage. (Most are between 50-90 volts.)

 

Can you use a separate diesel start contactor for the switch?
I 'inherited ' one when I put the dynamic braking on a unit to maneuver the Can Rockies
The are the same as their automotive cousin, but a much smaller version.

 

Can you use a separate diesel start contactor for the switch?
I 'inherited ' one when I put the dynamic braking on a unit to maneuver the Can Rockies
The are the same as their automotive cousin, but a much smaller version.

I'd love to if they weren't $1,000. The arc chutes on them are way better than any automotive relay in existence.

For now I found an import forklift contactor on the cheap which is allegedly good for 600 amps at 72 volts. The operative word here being "allegedly." At least it has a decent datasheet to go along with it, which is far more than can be said for most eBay imports. If it gives me trouble I'll pony up for something better. But considering I'm not anticipating much in the way of load breaking, my only real concerns are contact welding and thermal rise. So we'll see.

I thought about an SCR or a GTO, but the problem is those won't permit reverse current. I would have to resort to one hell of a triac if I wanted to go solid-state. And here again, voltage drop and thermal rise will be the biggest issues with a solid-state switch when pushing 800 amps.

Speaking of reverse current, I'm thinking about including an FRN-R-200 fuse in series with the relay to provide thermal protection in the event said relay gets inadvertently closed onto a dead short. I^2R means things (relay, busbar, jumper cables, etc.) could heat up quickly with an available fault current of about 9 kA on the capacitor side of things. 200 should be enough to provide about 20 seconds of delay at normal cranking current, whereas a fault of 2 kA or greater will cause it to open in less than a second.

Right now I'm thinking some manner of comparator with an adjustable voltage reference will work adequately as a trigger, and a simple 'OR' gate S-R latch will suffice for a trigger circuit.

My next task is to figure out some way of providing reverse polarity detection and interlocking to prevent the relay from closing in the event a bonehead maneuver is attempted. Getting two 74 volt sources backwards with hefty fault currents available is a recipe for a very bad day. (*Ahem*... FRN-R-200, see above.)

 

I'd love to if they weren't $1,000. The arc chutes on them are way better than any automotive relay in existence.

Wow, hefty price!
BTW, if you do decide on this method , I have (a new) one sitting on the bench waiting for someone in need.
Yours for the P/P if you need.
Where are you located?

 

Wow, hefty price!
BTW, if you do decide on this method , I have (a new) one sitting on the bench waiting for someone in need.
Yours for the P/P if you need.
Where are you located?

Minnesota.

My question is whether it's a spring-return or gravity-return contactor, as some locomotive relays are the latter. For a hand-portable application like this, overall weight and the ability for the contactor to remain open in any orientation are both considerations. I wouldn't want the output to become energized through the act of simply laying the unit on it's side for transport, bumping it, etc.

 

I'm looking for some inspiration here:

I would like to assemble some large 3 kF supercapacitors in series (with appropriate off-the-shelf balance boards, etc.) to build an 80 volt portable jump-start pack for boosting dead locomotives. (New batteries are $20,000, whereas a few dozen supercaps can be had second-hand for 1/20th that price.)

At 800 cranking amps my napkin math suggests I'll likely get around 5-8 seconds of cranking out of an 80 volt, 100 farad capacitor bank, depending on how much current the batteries contribute in parallel while cranking. This time frame - while brief - is generally sufficient to start a locomotive when the fuel injector racks are manually held in the wide-open position during cranking.

The problem I am faced with is that I do not want the capacitors to discharge before the engine start contactor closes. Given I only have 100 farads to work with, the fuel pump, other ancillary equipment and even the weak batteries themselves will quickly drain down the charge on the capacitors before it can serve it's intended purpose if it is delivered before the precise moment it is needed.

The idea I have is to employ a falling-edge trigger on the boost pack's output terminals to fire an internal starter relay. I would tune the trigger to activate in a latching mode when the battery voltage on the load side of the relay is drawn down below, say... 40-50 volts or so during starting?

Can anyone suggest a circuit architecture that might work for this purpose? I am a licensed electrician but I haven't dealt with board-level electronics much since tech school years ago. I could use some pointers as to where to begin.

Obviously level-shifting is going to be an issue considering locomotive electrical systems run at 74 volts DC. (The nominal float voltage for a 32 cell battery.) I think a voltage divider should suffice for voltage sensing purposes.

Input & ideas?

View attachment 344009

This cap is specifically for Locomotive Startup. You'll have to step up the voltage somehow, but here is the capacitor you want:


Vendor: https://www.greentechee.com/super-capacitor-cell_c31
CAP: GTSP-2R7-XXXMN4

Rated: 2.7V @ 350F

Datasheet:

 

Some 30 plus years ago I met a railroad engine Engineer. He told me a story of how a locomotive diesel engine was running but they couldn't get the engine to move. Diesel Electric engines run a generator that drives the traction motors. The diesel engines he worked with had "Air Starters". They used compressed air to crank over the engine. If there was ANY battery power left in the batteries the generator would pick that up and generate electrical power. Lights would come on, other electrical and electronics would go active AND the traction motors could be engaged.

He told me 'One night he was called out to that running diesel with no electrical power. His mission was to get the electrical part up and running. He took his flash light apart (two D-cell batteries) and with a coat hanger he grounded one battery to the engine generator and the other battery with the coat hanger he touched the stator (or rotor) wires briefly. Enough to excite the generator. That brought all electrical power back and the train could be driven. And the batteries would be recharged.'

I have no reason to doubt his story. As unlikely as it may seem, in principle it should work. As for modern diesel locomotives I don't know how they're constructed. Perhaps they are electrically started. Perhaps the video you posted is of a much smaller diesel locomotive. I don't know.

It seems to me like using super-caps should prove possible, but in MY mind I see such a large 18,000 HP diesel engine (or even bigger) would take a lot of power to crank over. Use of compressed air and an air driven starter would seem more mechanically feasible. I've seen super caps start a car, but I've not yet seen SC's start a full size truck, diesel or gasoline. Not saying it's not possible, just questioning the practicality of it. But a TRAIN ENGINE? I can't get my head around that one.

 

This cap is specifically for Locomotive Startup. You'll have to step up the voltage somehow, but here is the capacitor you want:
View attachment 344113

Vendor: https://www.greentechee.com/super-capacitor-cell_c31
CAP: GTSP-2R7-XXXMN4

Rated: 2.7V @ 350F

Datasheet:

Thanks, but 350 farads is _tiny_ compared to the ones I've got on order. About 1/10th the capacity, and likely 1/10th the rated discharge current also. That, and those appear to be Asian import parts. Asian supercaps have a reputation.

I've got a set of 30 name-brand Maxwell Boostcaps on order, to the tune of 3,000 farads each. Modular end supports, busbars and balance boards also as pictured in my original post.

 

Some 30 plus years ago I met a railroad engine Engineer. He told me a story of how a locomotive diesel engine was running but they couldn't get the engine to move. Diesel Electric engines run a generator that drives the traction motors. The diesel engines he worked with had "Air Starters". They used compressed air to crank over the engine. If there was ANY battery power left in the batteries the generator would pick that up and generate electrical power. Lights would come on, other electrical and electronics would go active AND the traction motors could be engaged.

He told me 'One night he was called out to that running diesel with no electrical power. His mission was to get the electrical part up and running. He took his flash light apart (two D-cell batteries) and with a coat hanger he grounded one battery to the engine generator and the other battery with the coat hanger he touched the stator (or rotor) wires briefly. Enough to excite the generator. That brought all electrical power back and the train could be driven. And the batteries would be recharged.'

I have no reason to doubt his story. As unlikely as it may seem, in principle it should work. As for modern diesel locomotives I don't know how they're constructed. Perhaps they are electrically started. Perhaps the video you posted is of a much smaller diesel locomotive. I don't know.

It seems to me like using super-caps should prove possible, but in MY mind I see such a large 18,000 HP diesel engine (or even bigger) would take a lot of power to crank over. Use of compressed air and an air driven starter would seem more mechanically feasible. I've seen super caps start a car, but I've not yet seen SC's start a full size truck, diesel or gasoline. Not saying it's not possible, just questioning the practicality of it. But a TRAIN ENGINE? I can't get my head around that one.

Firstly, we're talking prime movers to the tune of 600 to 3,000 horsepower. (In my case.) Modern units are around 4,500 horsepower. To get 18,000 horsepower you'd need to assemble a substantial MU consist of multiple locomotives.

Secondly, most diesel locomotives are electric start. Some of the newer ones have air starters, but that's an optional upgrade with it's own drawbacks and limitations. (Namely in that you only get one shot to start the engine. If it doesn't fire on the first try then you're S.O.L. without an external source of compressed air to refill the tanks.)

Older locomotives (like the ones I deal with) crank the engine by motoring the main DC generator. It takes around 600-800 cranking amps at 64 volts to do the job. The capacitors I am using have a maximum discharge current rating of 900 amps, and an available short circuit current rating of 9,000 amps. Put 30 of them in series and that comes out to 100 farads at 80 volts. At a rate of 500 amps (assuming the batteries aren't *totally* dead), it will take about 8 seconds for the bank to drop from 80 volts to 40 - and that's not even accounting for a tapering discharge current. The math suggests it should work...

My concern is how well a set of jumper cables will be able to deliver all that power. I'm guessing I might have trouble with the teeth of the alligator clamps, and the crimp connections for the leads on the same. I may have to resort to using a pair of welding stingers to clamp onto the knife switch blades onboard the locomotive to get a low enough resistance, but we'll see.

 

Firstly, we're talking prime movers to the tune of 600 to 3,000 horsepower. (In my case.) Modern units are around 4,500 horsepower. To get 18,000 horsepower you'd need to assemble a substantial MU consist of multiple locomotives.

Yes, you're correct. My mistake. A GP18 is 1,800 HP, not 18,000. Still, AFAIK, they're air started.

Secondly, most diesel locomotives are electric start. Some of the newer ones have air starters, but that's an optional upgrade with it's own drawbacks and limitations. (Namely in that you only get one shot to start the engine. If it doesn't fire on the first try then you're S.O.L. without an external source of compressed air to refill the tanks.)

While I'm no authority on locomotive starters - I often hear the freight yard not far from my house. When the air current is just right I can almost hear the engineer's conversations. Hearing the starters go off - I often hear the whine of a turbine air starter. But that's when the air is just right.

I understand the drawbacks such as having one shot to start the engine. I've heard diesel trucks with air starters as well, though that has been many years since I heard that sound. In the time of my recollections I'm sure a lot has changed. But dead batteries are also one of the drawbacks of having an electric starter. As your project suggests, you have to drag a starter cart out to a locomotive just to get it started. At least that's what I'm thinking. Again, I'm not the expert on this topic, so if I'm wrong - educate me.

Been searching the internet and found this:
https://rtexrail.com/emd-gp-general-purpose-locomotives/

 

My question is whether it's a spring-return or gravity-return contactor, as some locomotive relays are the latter. For a hand-portable application like this, overall weight and the ability for the contactor to remain open in any orientation are both considerations. I wouldn't want the output to become energized through the act of simply laying the unit on it's side for transport, bumping it, etc.

I will check it and post a pic, it is brand new for sure. I seem to recall it is spring return?
I used to visit a company in Minnesota to fix a DC generator control for a RR scrap yard crane

 

Firstly, we're talking prime movers to the tune of 600 to 3,000 horsepower. (In my case.) Modern units are around 4,500 horsepower. To get 18,000 horsepower you'd need to assemble a substantial MU consist of multiple locomotives.

Secondly, most diesel locomotives are electric start. Some of the newer ones have air starters, but that's an optional upgrade with it's own drawbacks and limitations. (Namely in that you only get one shot to start the engine. If it doesn't fire on the first try then you're S.O.L. without an external source of compressed air to refill the tanks.)

Older locomotives (like the ones I deal with) crank the engine by motoring the main DC generator. It takes around 600-800 cranking amps at 64 volts to do the job. The capacitors I am using have a maximum discharge current rating of 900 amps, and an available short circuit current rating of 9,000 amps. Put 30 of them in series and that comes out to 100 farads at 80 volts. At a rate of 500 amps (assuming the batteries aren't *totally* dead), it will take about 8 seconds for the bank to drop from 80 volts to 40 - and that's not even accounting for a tapering discharge current. The math suggests it should work...

My concern is how well a set of jumper cables will be able to deliver all that power. I'm guessing I might have trouble with the teeth of the alligator clamps, and the crimp connections for the leads on the same. I may have to resort to using a pair of welding stingers to clamp onto the knife switch blades onboard the locomotive to get a low enough resistance, but we'll see.

Use some proper DLO cables for the jumpers with a proper crimp terminal on the end to bolt both sides solid.
https://www.awcwire.com/power-cable...el-locomotive-cable?page=3&pageSize=8&sort=50
https://wesbellwireandcable.com/pro...lo-cable/dlo-diesel-locomotive-cable-535-mcm/

https://www.elecdirect.com/lug-comp...6gQJ4SUbBfl2jUgKDLM9v_kh5HYNn5G6S-CFoPT-DqieT


DLO jumper cable and a 4/0 wire. We use them for current feeds for high power mass analyzer magnets of at least one Tesla.

 

Use some proper DLO cables for the jumpers with a proper crimp terminal on the end to bolt both sides solid.
https://www.awcwire.com/power-cable...el-locomotive-cable?page=3&pageSize=8&sort=50
https://wesbellwireandcable.com/pro...lo-cable/dlo-diesel-locomotive-cable-535-mcm/

https://www.elecdirect.com/lug-comp...6gQJ4SUbBfl2jUgKDLM9v_kh5HYNn5G6S-CFoPT-DqieT

View attachment 344126
DLO jumper cable and a 4/0 wire. We use them for current feeds for high power mass analyzer magnets of at least one Tesla.

Yeah, locomotive cable is good stuff. It makes wrestling 700 kcmil service entrance conductors paralleled 7 ways through a wireway into a top hat for a 4,000 amp main breaker a lot easier. ...Which is to say that it makes it even remotely possible at all, lol. Good luck doing that with ordinary THWN-2 or XHHW.

When we jump one locomotive off of another (presuming we can get the first one started in the first place), we often use beam clamps to squeeze the tails of set screw lugs down onto the knife blades. The problem with this is that you are left with energized beam clamps at the end of the process which need to be removed with metal tools. Lil' bit of pucker factor, lol. Hence the idea of perhaps using welding stingers instead. Those are insulated, are designed for 300+ amps in some cases and can be applied and removed without tools.

For context:



At the end of the day it might just be best to double up a second set of ordinary jumper cables and call it good.

 

Yeah, locomotive cable is good stuff. It makes wrestling 700 kcmil service entrance conductors paralleled 7 ways through a wireway into a top hat for a 4,000 amp main breaker a lot easier. ...Which is to say that it makes it even remotely possible at all, lol. Good luck doing that with ordinary THWN-2 or XHHW.

When we jump one locomotive off of another (presuming we can get the first one started in the first place), we often use beam clamps to squeeze the tails of set screw lugs down onto the knife blades. The problem with this is that you are left with energized beam clamps at the end of the process which need to be removed with metal tools. Lil' bit of pucker factor, lol. Hence the idea of perhaps using welding stingers instead. Those are insulated, are designed for 300+ amps in some cases and can be applied and removed without tools.

For context:

View attachment 344131

At the end of the day it might just be best to double up a second set of ordinary jumper cables and call it good.

If the need to jump start is infrequent then regular welding stingers will likely work for a while. I've done it before in a pinch to test a power supply but melted a few teeth in the process.

Your jobs sounds pretty cool as I like older mechanical machines. Most of what I do takes a lot of current but is totally electrical in nature.

Several ton electromagnets to manipulate beams.


A bad coil.






Beam flight path laser alignment.


Three phase equipment transformers to feed the machines.

 

This is the contactor, darned heavy!

 

If the need to jump start is infrequent then regular welding stingers will likely work for a while. I've done it before in a pinch to test a power supply but melted a few teeth in the process.

Your jobs sounds pretty cool as I like older mechanical machines. Most of what I do takes a lot of current but is totally electrical in nature.

Several ton electromagnets to manipulate beams.
View attachment 344133
View attachment 344134
A bad coil.

View attachment 344135

View attachment 344138

View attachment 344139
Beam flight path laser alignment.
View attachment 344140View attachment 344142
View attachment 344141
Three phase equipment transformers to feed the machines.

 

Thanks, but 350 farads is _tiny_ compared to the ones I've got on order. About 1/10th the capacity, and likely 1/10th the rated discharge current also. That, and those appear to be Asian import parts. Asian supercaps have a reputation.

I've got a set of 30 name-brand Maxwell Boostcaps on order, to the tune of 3,000 farads each. Modular end supports, busbars and balance boards also as pictured in my original post.

I beg your pardon- I must have missed a zero when I looked up your part. You are correct, you're capacitor is much better, and a good value. I understand your concerns with Chinese equipment- it really depends on who you buy from. I have bought Chinese parts for 15 years, and have never had a problem. In some cases, they are the ONLY place to source specific components in quantity at cheap enough prices (like socket pins for VFDs). As always. BUYER BEWARE IMHO.

I've attached a datasheet for your part here, so others can chime in.

 

This is the contactor, darned heavy!

Oh yeah, that's the real McCoy! Everything with "Vapor-Clarkson" stamped on it is darned heavy, lol. A good thing too, because EMD put those start contactors in a VERY inconvenient place on their late-model SD9s and SD18s... Sandwiched between the front and back mounting planes of the switchgear rack! Right behind that heavy-ass slate switchboard for all the fuses and the battery knife. Not a part you ever want to have to change!