Battery Power

Garden Railroading
21

Hi Mark.

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?

22

Tony,

The only difference would be the voltage you set for the voltage regulator. Everything else would be the same.

Mark in Utah

23

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.

24

Well as I am bored waiting for the train -let me see if I can help him out of the pit he just jumped into…

Let us work from First Principles.

He charges the loco from the tracks from a 30V AC flux. For example using 4 1N4001 diodes.

He rectifies the flux into DC and somehow he stores it let us say in a large capacitor -lets try 5 Farads at 50V working 200 Ampere ripple, (Siemens Jd 8200 series would be a good match). Then lets say he uses that to drive a good old fashioned stabilised PSU using a 2N3055 and a Zener. HexFETs tend to “twitchy” unless driven hard.

He then says he needs an adjustable voltage and current regulator. I was always brought up to “believe” the accepted charging rate for a NiCd is 10% of the output -so if you don’t mind Tony I will use that as my guide. Fuji L200C would be my choice (0-60V in, 2.8 to 36V out, at 2 Amperes max).

Oh, and Tony -you asked who would be contemplating using SLA in their latest loco -the answer is me. This is steam electric loco I will use the on board SLA to drive the electronics and fans for the burners.

regards

ralph

25

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

26

My reasons for prefering SLA has very little to do with the chemistry or energy density. But a lot to do with the easy Lucar terminals and conveniently shaped packages they come in!!! I use the high weight for traction and the nice rectangular shapes make for easy design of installation. Most of my locos use a 6volt supply so I have on hand tens of 6V 4.5Ah SLA -I pull one from the charger rack slide the flat one out of the top and play trains again.

I did try some of the early NiMH and was not impressed with the long charge times -I do know that things have improved.

regards

ralph

PS -new loco dynamo has been tested and can produce 8 Volts…

27

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

28

Filter Capacitor (what Filter Capacitor?) In my design brief above I mentioned a Siemens jd series POWER capacitor. And in order to help you out again here is the design for the dynamo to bogies power supply for my steam electric locomotive. Although it is not shown the variable resistor in both PWAM output boards is the ganged.

I use Pulse Width Amplitude Modulation, rather than Pulse Width Modulation -because I feel based on visual smoothness that my models (using multiple motors at high current) they seem to be more “content” this way. I have no technical data -other than the way they smoothly accelerate up to 8 or 15mph (scale) and back down again. I use a Johnson 5 pole motor normally running at 6V with 3A each.

viz:

regards

ralph

29

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?

30

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.

Walt

31

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

32

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

33

just noticed this thead and have always thought about a charging station idea. As far as batteries problem a cell phone battery setup works like what you want, my power goes down I can plug it in and it will charge till needed, it can charge and discharge as needed, even both at once.

34

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