# Charging batteries from track power?



## dawinter (Jan 2, 2008)

Does anyone use constant track power to charge the batteries? 










Could someone connect USAT sliders to a reverse loop detector (to insure consistent polarity) that would feed a battery charger that would charge an on board battery to the decoder/motor in the engine? 

Seems a better way to run trains than to (a) worry about feeding track power throughout a large layout and (b) charging batteries without an external charger on or off the layout. 

You could just pull into a station track or service track and the batteries would be charged while you wait. 

Dave


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## Art (Jan 3, 2008)

What I do is put the charging lead into a connector that is on the fuel tank and it looks like I'm pumping diesel into the tank. Now if it is steam.... well you have me. I don't like charging but do use battery for some of my locos. 

Art


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## DKRickman (Mar 25, 2008)

I've thought about taking this one step further, and putting constant voltage on the rails all around the layout. That way, the batteries would never drain. They would serve only to skip over any dead spots, meaning that they could be much smaller, possibly even large capacitors. 

Just think of it, a system with all the disadvantages of both track and battery power! ;


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## dawinter (Jan 2, 2008)

Right! 

As I'm going to be doing further experiments with AirWire down the road I had to ask myself why would I need to remove engines to charge when there is sufficient charge current already on my 'track power' layout? 

The advantages of AirWire and but with no recharging unit. The reverse loop detector will always assure that the charger gets the same polarity even when that track polarity changes. I think anyway.  

Dave


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## craigcoffman (Jan 2, 2008)

I did this at one point. I was already running fixed polarity fixed voltage on the track (24.5) volts. This made it easy to trickle charge a 19.2V battery pack with a 1 ohm resistor figuring in losses for the needed bridge rectifier between the track & the batter pack. But you also need a diode in parallell with the resistor for the electrons to flow thru when running off of battery power (as opposed to the resistor), so that drops your effective voltage from the pack enough so that you do notice when dirty track causes the failover to battery power. 

Also, at a trickle charge, the batteries rarely get a chance to fully re-charge, unless you leave the loco on a powered siding overnight, meaning they will eventually run down & require taking out, or taking the loco inside to charge, depending on how you have it setup. 

So in the end, it ends up being more work for less satisfaction that just going battery, IMHO.


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## TonyWalsham (Jan 2, 2008)

Good luck in your quest. 

If and when when you can get a system working that will cater for all types of battery chemistry, all voltages and is reasonably priced, please let us know.


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## dawinter (Jan 2, 2008)

Posted By craigcoffman on 06/05/2008 4:33 PM
I did this at one point. I was already running fixed polarity fixed voltage on the track (24.5) volts. This made it easy to trickle charge a 19.2V battery pack with a 1 ohm resistor figuring in losses for the needed bridge rectifier between the track & the batter pack. But you also need a diode in parallell with the resistor for the electrons to flow thru when running off of battery power (as opposed to the resistor), so that drops your effective voltage from the pack enough so that you do notice when dirty track causes the failover to battery power. 



Very good points. I printed it off and stuck it in my 'notes' for sometime in the fall/winter. I appreciate your experience with this idea. 



Also, at a trickle charge, the batteries rarely get a chance to fully re-charge, unless you leave the loco on a powered siding overnight, meaning they will eventually run down & require taking out, or taking the loco inside to charge, depending on how you have it setup. 



Being inside already it may actually be of some use. We'll see what develops with this.. 


So in the end, it ends up being more work for less satisfaction that just going battery, IMHO.




You could be right.


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## dawinter (Jan 2, 2008)

Posted By TonyWalsham on 06/05/2008 4:34 PM
Good luck in your quest. 

If and when when you can get a system working that will cater for all types of battery chemistry, all voltages and is reasonably priced, please let us know. 






/DesktopModules/NTForums/themes/mls/emoticons/laugh.gif 

I can see that happening. 

/DesktopModules/NTForums/themes/mls/emoticons/laugh.gif


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## Greg Elmassian (Jan 3, 2008)

Several people have reported success, a simple charger that is basically regulated output somewhat below nominal battery voltage. This way it never overcharges the battery. 

My contention was that this produces varying voltage to the rc system, and thus irregular speeds. 

If I was to do this, I would put a full fledged charger on board, but then, the charger would get constant interruptions, and any charger worth a darn is microprocessor controlled, and would then reset. 

Really does not sound like a great system yet. 

Regards, Greg


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## K27_463 (Jan 2, 2008)

AS Greg alluded to , there is a problem with charging while rolling. When a battery goes on a charger, the charge cycle does not start instantly. There is a reaction delay(chemical/molecular) that takes place first. Charging commences at some finite point after voltage is applied to the cells. The interval is small but present none the less. Charging while rolling would present enough intermittent contact -unless you had PERFECTLY CLEAN rails- that the actual charge cycle would always lag the input such that it is unlikely any significant charge could result. Rolling wheel contacts are really very poor contacts. Direct dc motor drive works because the motors have inertia and the available power levels are high to drive the armature easily. (why track power locos stall at slow speed often) but the actual contact is very inconsistent. 
Now, charging from rails while stationary is certainly commonly done , but rolling will really never get much charge into the battery pack., plus you will never know the actual state of charge in your packs, since charging is intermittent, and as Greg said, any processor based charge will constantly reset. 
Jonathan/EMW


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## dawinter (Jan 2, 2008)

Posted By K27_463 on 06/05/2008 11:18 PM
AS Greg alluded to , there is a problem with charging while rolling. When a battery goes on a charger, the charge cycle does not start instantly. There is a reaction delay(chemical/molecular) that takes place first. Charging commences at some finite point after voltage is applied to the cells. The interval is small but present none the less. Charging while rolling would present enough intermittent contact -unless you had PERFECTLY CLEAN rails- that the actual charge cycle would always lag the input such that it is unlikely any significant charge could result. Rolling wheel contacts are really very poor contacts. Direct dc motor drive works because the motors have inertia and the available power levels are high to drive the armature easily. (why track power locos stall at slow speed often) but the actual contact is very inconsistent. 
Now, charging from rails while stationary is certainly commonly done , but rolling will really never get much charge into the battery pack., plus you will never know the actual state of charge in your packs, since charging is intermittent, and as Greg said, any processor based charge will constantly reset. 
Jonathan/EMW




Very interesting points and most informative. You have probably pointed out the only real reason we don't see more of this. 

Thanks. 

Dave


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## DKRickman (Mar 25, 2008)

Has anyone tried getting rid of the batteries entirely? Keep a constant fixed voltage on the rails, which provides power directly to the R/C reciever in place of the batteries. A fair sized capacitor could be useful to bridge any dead spots in the track. Basically, it would function like a DCC system, with all the wiring simplifications, but with radio control instead of digital commands through the rails. It would even be possible to run high voltage (greater than 24V) AC, with it's inherent advantages regarding lower resistance losses, and step it down with a transformer inside the loco.


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## Del Tapparo (Jan 4, 2008)

Posted By DKRickman on 06/06/2008 9:02 PM
Has anyone tried getting rid of the batteries entirely? Keep a constant fixed voltage on the rails, which provides power directly to the R/C reciever in place of the batteries. A fair sized capacitor could be useful to bridge any dead spots in the track. Basically, it would function like a DCC system, with all the wiring simplifications, but with radio control instead of digital commands through the rails. It would even be possible to run high voltage (greater than 24V) AC, with it's inherent advantages regarding lower resistance losses, and step it down with a transformer inside the loco.




Aristo-Craft 
Loco-Link


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## craigcoffman (Jan 2, 2008)

Posted By DKRickman on 06/06/2008 9:02 PM
Has anyone tried getting rid of the batteries entirely? Keep a constant fixed voltage on the rails, which provides power directly to the R/C reciever in place of the batteries. A fair sized capacitor could be useful to bridge any dead spots in the track. Basically, it would function like a DCC system, with all the wiring simplifications, but with radio control instead of digital commands through the rails. It would even be possible to run high voltage (greater than 24V) AC, with it's inherent advantages regarding lower resistance losses, and step it down with a transformer inside the loco.




Yes, this is how I ran exclusively, up until recently. Constant polarity fixed voltage on the rails simplifies a lot of things.. like reversing sections (Y or loop) & I came up with a simple relay based detector/reverser for that. It also allows, with multiple receivers, independent multi-loco operation, in either direction, which is fun provided you have good passing sidings. I used Aristocraft on-board TE receivers. 


I also setup capacitor based backups for a few locos... some, which had power sharing from multiple dedicated powered passenger cars, did not really need it, as the higher voltage on the rails (in my case 24.5VDC) made power pickup problems few. 


However, for short-wheelbase locos, or locos that never ran with other powered locos or trail cars, capacitor based power-backup helps a lot. But it's tough to get enough capacitance to really make up for more than very short power interuptions. IIRC, i used 3 or 4 2500 mf capacitors in parallell, & these would still not do much more than provide enough "umpf" to get over short dirty spots. (That is still pretty nice though). 

As far as running AC, & voltages greater than 24V, I think you would run afoul of local ordinances there, as 24V is usually the cut-off for a "low-voltage" system. Check it out though. I don't think much would be gained from any higher voltage, plus having to rectifiy the AC, then regulate it down (with a voltage regulator rather than a transformer) would just add more unneccesary steps/complications. 24V tolerates a lot of bad track joints, dirty track etc., without being high enough to really hurt anything/anyone if they short the tracks. That said a screwdriver will certainly try to weld itself down, a wet frog gets frozen in place if he touches both rails & operators with sweaty t-shirts who in-advertendly lay across the tracks get a pretty good shock. If you do AC or even DC, don't forget to have bridge rectifier in between the track pickups & your capacitors (changing direction of the loco would flip the polarity fed to the capacitors.) I also put a resistor in line to slow the capacitor recharge to prevent mega-amp draws that would cause wheel-arcing, wire-heating, etc. 


FWIW, even with a track cleaner, I found that wheels get dirty often enough to be a pain, & since my dog seemed determined to chew in half any exposed track-feeders, I've since gone battery. I'm not saying it's better, but once you start messing with charging on-board batteries or providing on-board capacitance, it is just almost easier to go battery. MY run times got progressively shorter as well, making the run-times from battery packs totally acceptable.


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## Greg Elmassian (Jan 3, 2008)

DING DING! 

AirWire... runs DCC sound decoders, and you can use the QSI that way too. 

Regards, Greg 

Posted By DKRickman on 06/06/2008 9:02 PM
Has anyone tried getting rid of the batteries entirely? Keep a constant fixed voltage on the rails, which provides power directly to the R/C reciever in place of the batteries. A fair sized capacitor could be useful to bridge any dead spots in the track. Basically, it would function like a DCC system, with all the wiring simplifications, but with radio control instead of digital commands through the rails. It would even be possible to run high voltage (greater than 24V) AC, with it's inherent advantages regarding lower resistance losses, and step it down with a transformer inside the loco.


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