Battery powered/Radio controlled locos

[Robin2]

The Deltang units that I have can measure the battery voltage. I have them programmed to transmit that to my PC.

 

Also, it is my understanding that with a suitably low charge voltage a single LiPo (which is all I have room for) won't overcharge within a reasonable period (obviously I wouldn't leave it on charge for 24 hrs or while unattended).

 

...R

[raymw]

In LI-ion batteries ('infolithium' the type used by Sony et al in cameras), there was a microprocessor in the battery casing, which communicated with the charger. There was also extensive protection devices - pressure release valves, etc.  within the battery. It was possible to charge these at 4.1V per cell, with no fancy charger/communication, etc. It was not possible to fully charge them.

 

For the cheaper li-po cells, I do not think there are any safety features built into the cells, and although it may be possible to 'top-up' the charge, say from 3.8V to 4.1V with a simple voltage source, I think if you were trying to charge from the end-point voltage to 4.1V, there may be problems. For experimentation, I'd suggest long leads, maybe out of doors   .

Edited November 13, 2014 by raymw

[Robin2]

 

'top-up' the charge, say from 3.8V to 4.1V

That's what I am doing.

 

...R

[davetheroad]

I have no intention of doing this but would it work?

 

Connect each of the 4 charging circuits on my charger to an isolated section of siding or a bufferstop.

 

Park 4 locos on those sections.

 

each loco has a set of rail pickups (or buffer pickups) and a bridge rectifier? to ensure the electrical trickery is flowing in the correct direction.

 

each loco uses a single battery with a voltage booster. Plus a switch of course.

 

Switch the loco to charge and the battery would be topped up to 4.2V controlled by the charging circuits in the charger.

[Rabs]

This would probably be fine if you pick up and place the loco on and off the charging track, or you flick a switch when it's stationary.  Driving the loco onto an active charging point would cause problems I think.  The extra current of the motor could confuse the charge management IC and make it think that the battery was short circuited, so it would then automatically turn off.  No way to know for certain though without knowing what chip your charger uses, it could be fine.

 

Nearly all lithium ion and lithium polymer battery packs have the following safety features built in:

PTC thermal cutout (basically a thermal switch to disconnect the battery if it gets too hot because of a short circuit, usually set at about 80C)

Undervoltage protection (to prevent you over discharging it, which causes crystal growth on the electrodes of the batteries, which destroys the capacity of the batery and greatly increases its resistance.  This is usually set at about 3.5V)

Overvoltage protection to prevent it being over0charged (causes swelling and rupture in some battery chemistries, usually set at about 4.3V)

 

Some also have a dedicated current measurement to prevent excessive discharge and charge current, in addition to the PTC.  This is rarer though.

 

If anyone is concerned about safety and wants to peel back the cover over the electronics in their batteries to  take a photo I'd be happy to help identify what's there.

[fallen]

Dave,

 

I think there would be a problem with the rectifier.

 

The rectifier would be important as otherwise the voltage would be applied the wrong way round if the loco was the wrong way on the track.

 

However, the charger monitors the voltage on the cell to determine the state of charge, and adjusts the current accordingly. It also uses this to decide when the cell is fully charged and stop the charge. The additional voltage drop across the rectifier would confuse this and at the very least would prevent the cell being fully charged. It might prevent the cell being charged at all.

 

Frank

[davetheroad]

Dave,

 

I think there would be a problem with the rectifier.

 

The rectifier would be important as otherwise the voltage would be applied the wrong way round if the loco was the wrong way on the track.

 

However, the charger monitors the voltage on the cell to determine the state of charge, and adjusts the current accordingly. It also uses this to decide when the cell is fully charged and stop the charge. The additional voltage drop across the rectifier would confuse this and at the very least would prevent the cell being fully charged. It might prevent the cell being charged at all.

 

Frank

OK, glad I did not try it!

[davetheroad]

This would probably be fine if you pick up and place the loco on and off the charging track, or you flick a switch when it's stationary.  Driving the loco onto an active charging point would cause problems I think.  The extra current of the motor could confuse the charge management IC and make it think that the battery was short circuited, so it would then automatically turn off.  No way to know for certain though without knowing what chip your charger uses, it could be fine.

 

Nearly all lithium ion and lithium polymer battery packs have the following safety features built in:

PTC thermal cutout (basically a thermal switch to disconnect the battery if it gets too hot because of a short circuit, usually set at about 80C)

Undervoltage protection (to prevent you over discharging it, which causes crystal growth on the electrodes of the batteries, which destroys the capacity of the batery and greatly increases its resistance.  This is usually set at about 3.5V)

Overvoltage protection to prevent it being over0charged (causes swelling and rupture in some battery chemistries, usually set at about 4.3V)

 

Some also have a dedicated current measurement to prevent excessive discharge and charge current, in addition to the PTC.  This is rarer though.

 

If anyone is concerned about safety and wants to peel back the cover over the electronics in their batteries to  take a photo I'd be happy to help identify what's there.

Interesting!

 

My answers would be No, No, No, No

 

do many hobby aircraft and heli packs have these features?

 

I short circuited a battery by accident and the result was spectacular but small, it was only a 150 mAh single cell.

 

over discharge protection is built into the loco controller board. Set at 3V for a single cell. i will see what the vendor thinks about 3.5V

 

over charge protection is built into the charger. Batteries peak at 4.2V

 

My most common 160mAh single cells have a rated constant discharge of 25C, that 4 amps, as my locos all draw less than 0.2amps i am not worried, maybe??

 

each charging circuit on the charger is limited to 0.3amp

[Rabs]

Ah, ok.  I've not peeled apart one of these tiny batteries myself - sorry, I didn't mean to spread disinformation.

[raymw]

A  tad ot, but prof. Land, he that invented? the polaroid camera, had a flat primary cell in his film packs for some cameras. It was some unusual chemistry, designed to be capable of providing high energy pulses for driving the flash, focussing mech and other bits. You could cut the battery pack in half with a pair of scissors, but that generally welded up the blades. (never tried it myself - the batteries were far too useful).

 

Dave, you won't need the rectifier if you pick up through the rails and, say, another contact via a third rail/similar or rammed up against the buffers. Do that, and you won't have to fiddle with contacts bearing on wheels, etc. It shoild not be too difficult to fix a standard concentric power socket to the loco, under buffer beam, say, and drive the loco onto a matching plug fixed under the buffers, and then easy to use a separate  charge lead off track if needed.

 

The nominal voltage of a lipo cell will be in the region of 3.6V so your 3V minimum should be fine if fully charged you get 4.2V . Also, referring to the links I gave earlier

 

Just as with other kinds of lithium-ion cells, the voltage of a LiPo cell depends on its chemistry and varies from about 2.7-3.0 V (discharged) to about 4.20-4.35 V (fully charged), for cells based on lithium-metal-oxides (such as LiCoO₂), and around 1.8-2.0 V (discharged) to 3.6-3.8 V (charged) for those based on lithium-iron-phosphate (LiFePO₄).

[Andy Reichert]

 

This is another part of the extra equipment and cost issues I have with battery power.

 

Just this one train has 2 locomotives and 14 cars, 13 of which should be illuminated both day and night, although at different intensities.

 

That's 15 batteries and at least 2 R/C receivers I don't currently need, if no track power.

 

The layout requires close to six similar mainline trains, four commuter suburbans which might only be 6 cars, and about six 8 car subway sets.  Perhaps as many as 150 battery units always charged in ready to go mode. And handling that number of "plug connections" would be a nightmare. If I used  track charging, I might just as well wire the whole layout anyway.

 

But although my roster is biased to illuminated passenger, it's certainly well below the average number of locos for a typical US basement layout.

 

No problem for DCC, although I'd probably need multiple power districts Boosters)  given the number of illuminated cars running.

 

Andy

[Robin2]

each loco has a set of rail pickups (or buffer pickups) and a bridge rectifier? to ensure the electrical trickery is flowing in the correct direction.

 

each loco uses a single battery with a voltage booster. Plus a switch of course.

 

 

My system is a bit like that.

 

I feed a regulated DC voltage to a fiddle-yard track - below the upper level for a LiPo cell (after allowing for the rectifier voltage drop)

My locos have a rectifier (because I can't be sure which way the loco will be facing while charging and to prevent one loco from charging another)

If I drive the loco into the fiddle yard it starts charging - but at a low charge rate.

 

...R

[davetheroad]

My system is a bit like that.

 

I feed a regulated DC voltage to a fiddle-yard track - below the upper level for a LiPo cell (after allowing for the rectifier voltage drop)

My locos have a rectifier (because I can't be sure which way the loco will be facing while charging and to prevent one loco from charging another)

If I drive the loco into the fiddle yard it starts charging - but at a low charge rate.

 

...R

I wonder if it is possible to source a charge regulator circuit that would fit in a loco? I which case you could leave the loco on the track condfident the battery would not overcharge.

 

I roughly calculate that if you use a single battery and voltage booster with a 9V output divide the battery mAh capacity by 3. For a 12V output divide by 4.

 

I presume you could parallel connect similar batteries for more mAh ?

[raymw]

Plenty of charge regulators here, for pennies  http://uk.farnell.com/webapp/wcs/stores/servlet/Search?st=MCP73831&catalogId=15001&categoryId=700000004279&langId=44&storeId=10151

 

The data sheets will give you the circuit and few extra components required.

 

Best wishes,

 

Ray

[Ken Anderson]

I wonder why little mention has been made of throw away dry cells.

I've been investigating the use of packs of say 4 or 6 AA Duracells, but still have to do more work.

My feeling is that for something like the Ixion 0-6-0 one could get at least a couple of days playing trains at home or a days worth at an exhibition. Obviously such a loco doesn't just go round and around a loop continuously, and doesn't have to go full speed.

Edited November 18, 2014 by Ken Anderson

[davetheroad]

Plenty of charge regulators here, for pennies  http://uk.farnell.com/webapp/wcs/stores/servlet/Search?st=MCP73831&catalogId=15001&categoryId=700000004279&langId=44&storeId=10151

 

The data sheets will give you the circuit and few extra components required.

 

Best wishes,

 

Ray

Thanks for the link, maybe i won't try this as i have enough difficulty in installing a neat package as it is. wires everywhere!.

[davetheroad]

I wonder why little mention has been made of throw away dry cells.

I've been investigating the use of packs of say 4 or 6 AA Duracells, but still have to do more work.

My feeling is that for something like the Ixion 0-6-0 one could get at least a couple of days playing trains at home or a days worth at an exhibition. Obviously such a loco doesn't just go round and around a loop continuously, and doesn't have to go full speed.

I looked at this as well. It might be OK for those who are willing to pay for the 'fuel' on a regular basis. The problems i found were the batteries did not deliver enough volts and those that did could not deliver the required constant amps output.

 

Take a standard 9V cell. Fits rather neatly in most tenders and can have a lot of mAh. Then you find the voltage sags and it can't deliver the amps.

[raymw]

fwiw, if you want relatively stable volts, then rechargeable Nicads will be best- 1.2V per cell, until they keel over at the end. Li-po voltage varies considerably as it discharges, but has a higher energy density.  As mentioned earlier, if you want optimum performance at a consistent voltage, you will need a voltage regulator. If you use a decent regulator, that will allow you to use different types of cells.

 

Here is a link to some power curves for lipos http://www.rcgroups.com/forums/attachment.php?attachmentid=936121

Your battery may well be different. It will be temperature dependent too.

 

About 15 years ago I wrote an article comparing battery types, primarily concerning high power situations, you may find it interesting. Things have moved on since then, but the fundamentals are still true. http://yertiz.com/rwc/batart.htm

 

Best wishes,

 

Ray

[Ken Anderson]

I wondered if someone might mention cost.

But mains electricity also costs money, it just gets hidden.

[davetheroad]

fwiw, if you want relatively stable volts, then rechargeable Nicads will be best- 1.2V per cell, until they keel over at the end. Li-po voltage varies considerably as it discharges, but has a higher energy density.  As mentioned earlier, if you want optimum performance at a consistent voltage, you will need a voltage regulator. If you use a decent regulator, that will allow you to use different types of cells.

 

Here is a link to some power curves for lipos http://www.rcgroups.com/forums/attachment.php?attachmentid=936121

Your battery may well be different. It will be temperature dependent too.

 

About 15 years ago I wrote an article comparing battery types, primarily concerning high power situations, you may find it interesting. Things have moved on since then, but the fundamentals are still true. http://yertiz.com/rwc/batart.htm

 

Best wishes,

 

Ray

1.2V per cell is just too low. there is limited space in a 00 scale tender.

 

so for now lipos are the best option if you don't mind the voltage drop on discharge.

 

for me it is not just the capacity etc of the cells but whether they are readily available in a useable form with easy to use connectors etc.

 

There are lots of 2S and 3S batteries available but guess what? most of them are slightly too large to fit in 00 scale easily. We have an internal width of no more than 30mm or a little less and most of those batteries are 30mm or more wide!.

 

Then there is the problem of run time. If you are happy with run times of a hour or so between recharges as I am, fine. If you demand run times of several hours, some say 8 hours or more, you may well be dissappointed!. I will say having a loco running for 8 hours would drive me insane.

[Ken Anderson]

I did mention Ixions O gauge loco as my interest is 7mm.

[Andy Reichert]

I wondered if someone might mention cost.

But mains electricity also costs money, it just gets hidden.

 

Unless you are comparing mains vs. throw away batteries, that's not a fair statement.

 

You are going to use at least as much mains electricity charging the rechargeable batteries, as you would running the locos directly. It's the same energy, just a delayed way of delivering it.

 

Andy

[davetheroad]

I did mention Ixions O gauge loco as my interest is 7mm.

There should be no problem fitting in the radio bits. Is it a Hudswell Clarke or a Manning Wardle?

 

for both you might need some imagination to fit batteries?

 

How many amps do you need etc etc

[raymw]

Hi Dave

 

an AAA cell is about 44mm long by 10.2mm diam (approx) You could maybe build a pack, and use a regulator to step up to whatever voltage you want, but if a lipo does the same job, why bother? Have you looked at phone batteries? They may be of a more useful size.

 

I've one, 42mm by 63mm by 6mm  1200mA 8.7V (the 8.7 is peak volts, I guess) cost a fiver. A stack of them would fit nicely in O gauge loco's, and I'm pretty sure smaller batteries are available. Of course, said battery from ebay, at that price, may not be too 'safe' nor the rating be accurate. You can get rechargeable PP3's (9V) in various chemistries. What is the exact size of the space you've got in the tender?

 

If you're using insulated wheels, wipers, etc, so you can recharge the battery in a siding, why not have the whole track energised, then the battery will need to be of minimum capacity, being used more as a stay-alive to get you over tricky point-work, bad joints, etc?

 

Always remember, 'if it was easy, every body would be doing it'.

 

Best wishes,

 

Ray

[Ken Anderson]

Andy, throw aah.

Dave, Ixion.

 

But I'm pursuing this purely for my own fun and amusement.

I'm a great fan of using Duracell technology - many years ago I used to design things that would sit on the seabed for years and still function when required to do. Some clever tricks with passive components worked wonders.

 

That's me I'm done - off to Hospital again on Friday.