I'm a latecomer to this thread, but some very interesting stuff here.
I've often thought about a battery powered loco and recharging the batteries from the track.
It seems very attractive at first. Just power most of the rails, don't power the turnouts, and leave long dead sections where a reversing loop would be in a normal track powered layout.
But when you start looking closely, it is just not practical.
For example, like Dave said, the inrush current when the batteries want a charge would be a very heavy load on the components picking up track power. You would need a lot of heavy components to handle this. Rewiring and high current pickup stuff would be a real problem to fit and would cost a lot.
If you limited the inrush current so as not to destroy the stock pickup "parts" in a stock loco, then you would severely limit your ability to recharge the batteries. Combine this with less than perfect track cleanliness and you have a problem. If the track is perfectly clean all the time, then why run batteries?
All of the extra electronics required to put this in the loco will take up a lot of space, and gel cells are not small to begin with, so you again have some severe limitations in what locos can run, or you always have trailing battery cars.
But, I will give you another severe limitation or cost factor: I am one of the people that do charge some batteries with the "constant, fixed voltage" method.
It CAN work. But there are 2 factors that will make it impractical for you. The difference of even a few hundredths of a volt will greatly change the charge. I have found in over 10 years of doing this exact method that I need to set the voltage exactly for EACH pack, and regulate to about 1 or 2 hundredths of a volt. This means each regulator needs to be set for EACH pack. Further, you cannot regulate to this accuracy with anything as inexpensive as your cheap 3 terminal regulator. I use precision laboratory power supplies, and read out the current and voltage to hundredths.
Also, as the battery ages, the terminal voltage to reach the appropriate charge changes. Normally it goes down. Thus without adjustment, you will soon be overcharging batteries.
I have battery packs with the proper charge voltage marked on them on a sticker, to .01 volt. I also monitor the terminal charge current, and as the battery ages, I update the sticker with the new terminal voltage. It does work, but I really believe it is not at all practical, since you have no way to monitor and update this unless you put voltage and current meters in every loco, AND observe terminal charge conditions.
As Dave is fond of saying, been there, done that.
And I only have 2 degrees and no phd, but, theory is a starting point, experience is the confirmation.
Regard, Greg
Visit my site: http://www.elmassian.com - lots of tips on locos, rolling stock and more.
Click here for Greg's web site
Dave,
How about this. Rig a restraining board across the charging track which would be deployed as the loco comes slowly into the siding. After the loco is stopped by the restraint, increase the voltage until the wheels start to slip. This will automatically clean the wheels and the track thus assuring good contact. After a few seconds stop the wheels and allow the batteries to charge. When it's time to leave, retract the restaint and off you go.
Waddayathink? You know, when you're retired you just have too much time to come up with off-the-wall ideas like this.
Walt
I run my annie with NiCads for about 3 or 4 hours and I'm ready to quit and go in...my HLW Mack has run for over 10 hours on 9.6 NiMH over the course of a few days w/o charge...simple....When finished, take the tender into the garage and plug into MAHA charger...go to bed, get up next day and run trains!
Engines could also be powered from trail cars if needed...no need to charge on track...seems like a wasted effort and funds/time that could be spent elsewher....
Q10
cale
I'd go with NiMH batteries (good energy density) with a thermistor embedded in the stack to control an on-board charging circuit with a timing circuit to establish a trickle charge. I still like the charging track idea except for the dirty wheels problem. Or, since the on-board power circuit is isolated from the wheels, how about some sort of sliding contact surfaces mounted somewhere on the loco that come in contact with a power source when brought into the charging track? No dirty wheels to worry about.
If something like this could be made to work, then the only thing you'd ever need to remember to do is to bring the loco into the charging track occasionally.
Charging off the track is pointless.
You need clean track.
You need track power.
Once you maintain both......you can run trains on straight DC.
On-board chargers take up space.
Space is at a premium in some locomotives. Chargers often create heat. We don't need heat in enclosed locomotives.
Charge rates, unless regulated (more space and heat) can either not keep up with the battery use or blow them up.
Charging "tracks" are one of the MOST useless things ever thought of.
Your wheels are now quite dirty from running outside on dirty rails, or even wet.
Pickups are dirty.
Put it on a charge track, and if it's a smart charger, the dirt will give erroneous readings and not charge properly, if at all.
One guy several years ago devised such a plan. Figured three or four locomotives, the current required, made a charger, parked them after one session, turned the charger on and went to bed.
Next morning he had three dead locos and one melted over the trucks.
Three locos had dirty enough wheels to not allow the charge, so the whole rate went into one loco.
Use a jack. Plug it in, you KNOW it's plugged in and charging.
Don't try to re-invent the wheel.
Oh, one more thing.
You set the rate up high enough, and have very dirty track, when the loco gets to powered track, the inrush of current for the loco, control system, and charger can take the springs out of pickups.
Someday I'll actually buy a locomotive and build a railroad, so maybe my personal experiences over the last 15 years will matter, eh?
The Home of Articulated Ugliness
Sorry for the delay - bad week at work. Give me some time & I'll get back to this. I haven't forgotten this.
The basic layout that Cabbage thew out is correct. For voltage regulation there's a 3-terminal adjustable voltage regulator available cheap, puts out about half an amp. A filter capacitor is not required, most train power supplies and battery chargers lack them.
As for the fluctuating speed of the locomotive, that would depend on the stiffness of the batteries you're using and the drive control. If the drive control operates independant of the battery voltage (current control) then it becomes a non-issue. Nickle-metal-hydride batteris are failry stiff and compact. Ni-Cads are a tried and proven battery, with less energy density, not quite as stiff a supply, but also lower cost.
Time to get back to work.
Mark in Utah
Hello Ralph.
Seems to be no response.
Not surprising really.
What I was asking for is not easy to do. I built and operated just such a track power pick up rectified system supply/charger for NiCd cells many years ago. Whilst they worked quite well and could provide a settable 10% rate for a specific voltage/mah rating any other voltage/mah rating required different settings. Plus the overhead voltage required was such that the speed change when the power supply to the loco was interrupted was very noticeable. No doubt todays sophisticated electronics would be able to cope, but quite frankly I doubt the market for such a system would be large enough to warrant the devlopment costs.
Given that most people who choose to go with battery power do so to avoid the expense of installing track power and the ongoing maintenance, the added complicated loco wiring defeats the original purpose.
Most battery R/C people operate are quite happy to swap cells in a trail car. For those who use onboard batteries I developed a simple circuit that utilises the battery charging jack so that it can take the voltage provided by extra batteries in a trail car to extend the run times for as long as you like. The onboard batteries are disconnected as you plug in the extra batteries and can be saved for light loco running around the yards when switching.
BTW, I have no axe to grind with LSA batteries. Other than they are somewhat bulky, difficult to install in smallish locos and are limited in the range of voltages. I certainly agree they are low cost but their energy density has long been surpassed with other chemistries. The low cost SLA batteries sold in Australia have poor power sustainability in that, unlike NiCd cells which hold their voltage until almost discharged and then crash, they drop voltage in a linear line. This means the useable voltage diminishes as the run proceeds. I understand the better quality Gel Cells do not exhibit such behaviour.
Best wishes,Tony Walsham (Remote Control Systems) http://www.rcs-rc.comModern technology. Old fashioned reliability.
Hi Mark.
You sound like a pretty clever fella.
For us lesser mortals, how about a circuit diagram for an on board charger that will power a locomotive drawing say 3 amps at 14.4 volts, and charge say, 14.4 volts of 2400 mah NiCd Sub C cells. Because different chemistries have different charging requirements, the same charger should also be capable of powering a loco that draws no more than 1 amp and charging 18 volts of 2000mah NiMh AA cells.
If you are not in a position to build a prototype I will be glad to build one to your specifications. I can have it independently tested, and report back.
Tony,
The only difference would be the voltage you set for the voltage regulator. Everything else would be the same.
Thank you for the reply.
Theory is great. With the greatest respect, until you actually produce such charging systems, the theory remains just theory.
Your reply refers only to Gel cells. Nobody I know who wants on board batteries installed inside a loco considers gel Cells any more.
My question was:
"If so, would you be so kind as to show us old fellers, who have been designing and building battery R/C systems for 20 odd years, how to do it with anything other than lead acid Gel cells."
Do you have a solution for NiCd or NiMh cells?
This system seems to be more than I'd ever need...
My "Annie" runs on 14.4v batteries for well over 3 hours...with my MAHA charger it takes about the same time to get a good charge back into them...
I have a HLW Mack that has run for over 6 hours continous on 9.6v NiMH on my Main Loop.....and still has some juice left in it...no telling how long that dude will run?
Straight Battery made more sense to me...and I have been pleased...NO track wiring needed or wanted....
With my kids and the RR construction in process, 3+ hours seems to be more than enough for me...if I were to need more, I could hook up my AMS Stock Car with the 18v NiCad pack inside.....
"work smarter not harder"
I have not built such a system, but it follows some tried and true princples that I've used on many other systems for years. Right now I'm using a variation of it to regulate the voltage for my tortoise switch machines for my indoor HO layout. Simplicity is the key. Here's what you need:
Full-wave bridge rectifier - Takes power from the rails and corrects the polarity no matter which direction you place the locomotive on the rails, or even if You have AC running on the rails. It costs under $2, is a black platic square with 4 leads on it.
Adjustable Voltage Regulator - Feeds the batteries the precise voltage they need for float charging. Float charging is the voltage that you can keep the batteries at forever without boiling them dry. For lead-acid batteries it's 2.25 volts per cell, or 13.5 volts for a 12V battery. They're self current limiting. You want to limit the current to approximately double the current draw of the locomotive. For example, if the locomotive draws 1.5 amps, you want a 3 amp limit. This is not a hard and fast rule, but gives you a starting point. You may need to add a power transistor to give the regulator a boost in capacity. You'll need to mount them both on a heat sink, as it'll dissipate 18 watts of heat worst case. The last regulator I bought cost $0.50 and had a 1/2 amp output. A power transistor to boost it up would cost around $2. A few resistors are pennies apiece. The heat sink is the big ticket item, for around $5.
Power Supply - For a 13.5 VDC battery system, you need 13.5 + 1.2 (rectifier drop) + 3 (regulator drop) + 2 or 3 for voltage drop on the rails. This puts you at a 19.7 to a 20.7 VDC supply. The only problem you get from a higher voltage supply is more heat to be disipated by the on-board voltage regulator for the batteries. You also need to have enough "poop" to feed the maximum draw of the locomotive, which in this example would be at least 3 amps. You can also use an AC supply, which should be in this case 20.7 / Sqrt(2) = 14 VAC.
As for maintaining track power, you can pick and choose which sections of track you want to insist have power, and which sections of track you'll allow to be hit or miss. If you only want to make sure you have power in the staging yard, so be it. The more track that has power to it, the more run time you'll have before the batteries run down. You can make up for it some by instead of doubling the output of the regulator, tripling it.
As for cost, using discount parts I could cobble a system together for a locomotive for around $10 and would be the size of a deck of cards. While this may cramp the space in a locomotive, you could make up for some space by using smaller batteries.
I'll have to dig around a bit to get some possible part numbers and such if anyone's interested. To be honest, I'm surprised that it's not standard issue for a garden railroad.
Mark, have you actually built and tested such a system?
If so, would you be so kind as to show us old fellers, who have been designing and building battery R/C systems for 20 odd years, how to do it with anything other than lead acid Gel cells.
We would be particularly interested in knowing how you overcame the never ending intrusion of nature which will ultimately make 100% of the track dirty, without any cleaning. Also, how you maintained continuity in the track without having expensive clamps on each joint.
How also do you prevent the sudden inrush current the batteries demand when the loco passes from an extended dirty section into an area where track pick up is possible again? How do you regulate the current required for the differing battery chemistries and capacities?
By combining the batteries with a continuous charging circuit in the locomotive you end up with the best of both worlds.
1. You install the batteries so you can run continuously and not worry about the track conditions.
2. You power the rails so you don't have to change batteries, but then have to keep the track clean.
3. In combined operation you install the batteries, charge the rails, operate as a battery system, and don't sweat cleaning the track.
Lets say the rails only make electrical contact with the locomotive 50% of the time (highly unlikely). While you have contact, you're charging the batteries while you run. While you've lost contact, you're running off the batteries. On a purely battery system you'd have to change out the batteries fairly often. On a hybrid system you may NEVER have to change out the batteries, but you'd enjoy all of the benefits of a battery system without the headaches.
Lets face it, the batteries are there to carry you though those areas where you've lots electrical contact, or maybe are tired of trying to maintain electrical contact, right? By aknowledging the uncertainty of the track power, but by being willing to make use of it whenever it decides to grace us with its presence, we still can put it to good use keeping us moving down the track.
P.S. Just because you're running on batteries does not necessarily mean that you'd have no use for power on the track.
I have a major question.
What do you want?
If you want to run battery, You do not want track power. You have a charging station. You are using batteries to eliminate track power.
I you want continous running. You use unlimited track power. If you are looking to over come drity spot drop outs. You run feeders from other pick ups to your power units.
If you are just looking for very short power loses feeding your onboard electronic speed and direction control. Place a couple of very large filter capacitors. They will help to jump the gaps in track power.
The sealed UPS batteries that you use have several strikes against them:
1. UPS systems have an agreesive re-charge program in order to quickly recover from any momentary outage. Often the batteries are operated at the equalize voltage, and not at the proscribed float voltage. (Higher than optimum float voltage) This causes a higher amount of gassing of the battery and a resultant water loss. In order to have a satisfactory battery life this must be adjusted for a proper float voltage for the batteries.
2. Sealed batteries are unable to have their water reserves replenished easily. It CAN be done, but you have to know what you're doing AND it's usually not cost effective from a commercial perspective.
3. If a battery is exercised often, it's happiest being exercised around the 50% level of charge. The top 10% of charge creates by far the most wear and tear (and gassing) on a battery.
4. Virtually all of the sealed battery banks I've run into commercially I've had torn out and replaced by flooded cell units. The ongoing replacements and questionable reliability of them has rendered them virtually worthless in my industry. The lessons learned though in making a flooded cell battery live a very long time can be carried over.
To have good reliability with sealed Pb batteries, they must be operated at the correct float voltage, and not at the equalize voltage. In order to set this you must know if they are a lead-alcium or lead-antimony alloy. Most likely to be lead-calcium, as this gasses less, but costs more.
Another thing it to not be so anal for having the batteries "topped off" before running them. It takes +24 hours to fully charge a battery at the float voltage, but less than 8 to get to 90% of capacity.
If the on-board charging circuit maintains the battery at float, the battery should be happy, even if it is not kept at 100% charge.
Mark in Utah, EE, PE
cabbage wrote:There are basically two types of UPS. In the constant draw type the mains is rectified fed to the batteries and the the batteries run the inverter -thus they are NEVER out of circuit. This EATS batteries and is normally reserved only for extreme emergency equipment (baby monitors and ICU equipment in hospitals for example). The normal standby type uses a charged bank of batteries with a detector that flips the circuit to the inverter and normal power is resumed (there may be a delay of 1/120th to 1/100th of a second before it operates fully)....regardsralph
Ralph,
It is incorrect that this type of a system, if properly designed, eats batteries. Any wear and tear on the batteries is caused by poor charger design.
Communications systems all over the world operate on float-charged DC systems, where the load is powered from the batteries directly, and a charger continuously maintains the proper voltage across the battery bank. The result is that virtually no current goes into the batteris, and almost all of the current is used to serve the load. Flooded lead acid batteries on such a system routinely operate for 40 years with nothing more than routine maintenance.
It is a similar system that I propose to operate within a garden locomotive.
I think most people have tried to charge the batteries from the rails by trying to maintian the voltage at the power supply. Correct me if I'm wrong. If so, this is fundamentally flawed and won't work.
Has anyone tried to mount the charging / voltage regulation circuitry in the engine, and float charge the batteries by monitoring their voltage locally? You'd run the track voltage, at lets say 18 volts, and regulate the voltage at the proper 13.7 volts across the batteries. It would be failry easy to create the circuit to do so that would maintain the same voltage accross the batteries when idle or at full load. Only when the track power disappears would the battery be called upon to run the locomotive. No over-charging could occur.
I'm an HO modeler that has toyed with going to G for the yard. I'm also an EE in the power industry, so we run into this sort of thing all the time but at MUCH different scales.
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