Recharging batteries in place

Discussion in 'FAQs' started by mhdishere, Mar 23, 2004.

  1. mhdishere

    mhdishere Member

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    I'm just thinking out loud on this one, have enough other projects to keep me busy, but I hope what I'm thinking of is possible for the future.

    I'd like to light my passenger cars, but don't want to take power from the rails to do so because I'm doing DC and that means when the train stops the lights go off. So I'm thinking of hiding a couple AAA rechargable batteries in the roof where they won't show and turning the lights on and off with a reed-switch and a magnet-on-a-stick. Would it be possible to build a recharging circuit into the car itself, say with a plug on the bottom so I could just plug it into a power source to recharge? Or even thru the wheels so I'd just have to set the thing on a piece of track with juice flowing to it. This way I wouldn't have to keep taking the models apart, and as long as I could get one operating session out of a charge it would be fine.

    Has anyone tried anything like this?
  2. Fred_M

    Fred_M Guest

    Yes it is possible. I already have working cabeese and trucks. Check out http://www.the-gauge.com/forums/showthread.php?s=&threadid=8332 is for a trailer. I suggest using white or golden white LEDs and charging with a plug. The reason for the plug is you can then put the voltage regulating equipment outside the unit. Don't forget a limit resistor to keep your LED's safe during charging. If you have any questions ask and I (or somebody) will help you. The caboose is here http://www.the-gauge.com/forums/showthread.php?s=&threadid=8725 fred
  3. Fred_M

    Fred_M Guest

    One addition, the last trailer I built, and all future projects, will be fixed thus for plugs. In a hidden spot underneith I put in a brass phillips and straight screw. Theses become the charge ports (plugs) so I can charge with alligator clips. Saves money on sockets, saves labor on installing sockets, and the phillips is (guess?) ..... +. FRED
  4. billk

    billk Active Member

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    How long will the batteries last if all they are powering are some LEDs? (Is the recharging thing worth the effort, especially if it's not that hard to replace the batteries?)
  5. mhdishere

    mhdishere Member

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    I guess my question involves the connections to do the recharging, can I just hook the dead batteries up to a voltage source to recharge? What voltage?

    As I said in my original post, this is well down the line for me, I still have to get the layout built, but I'd really like to see lit coaches pulling my LPB commuters to work.
  6. ezdays

    ezdays Out AZ way

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    Ni-cad batteries run about 1.5 volts each and NMH just a bit lower. If you are using two batteries in series, the voltage source should be regulated to 3 volts. You should also use a small (10 ohm) resistor in series with the charging voltage to "float" charge the batteries. Basically what this does is limit the charging current to prevent overcharging the batteries. BE VERY CAREFUL TO NOT PUT MORE VOLTAGE ACROSS A BATTERY THAN IT IS RATED FOR. They get very hot and tend to blow apart.:oops:

    Your best bet is to recharge them separately and use a ready-made charger to do it. You can buy chargers just about anywhere including Wal-Mart, Radio Shack or most stores that sell electronics or batteries. It isn't worth the risk, and they don't cost that much anyway.:D :D
  7. N Gauger

    N Gauger 1:20.3 Train Addict

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    Maybe I'm reading this wrong, but If you take the magnet away friom the reed switch - the lights will go off again. Or are you saying you will leave the magnet attached to the car somehow?? :(
  8. Fred_M

    Fred_M Guest

    All that being said (I'm sure I'm doing it incorrectly), I recharge NIMH AAA batteries this way. For 2 AAA/550mAH of them I put a 3volt 300ma dc wallpack to them and a 100 ohm resistor in series with the 2 LEDs and batteries. The four battery flasher LED need 3v-5v. On them I use a 220 ohm resistor and charge them with a 6vdc 300ma wall pack. I leave them "burning" 24/7 as switches are too much problem. I have also left them to charge over the weekend by accident with no explosions or battery damage. The flasher LED works 2-3 weeks on a charge of 4 AAA. The 2 led used as tail lights last 1 week to 10 days. You decide if you can afford batteries, I got AAA NIMH for 50 cents each at a sale and purchased around 20 of them.:D The charge voltage needs to be greater than the battery voltage to overcome internal resistance of the batteries. On final note, RCers charge 7.2 volt NIMH packs from a 12.6 volt cigarette lighter plug in 10 min or until they start gettting hot and there is ancedental eveidence that batteries charged such may last longer than trickel charged ones. :D And right mikey, reed switches would work backward really. FRED
  9. mhdishere

    mhdishere Member

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    I guess I didn't know as much as I thought I knew about reed switches, I thought you could touch a magnet to it, turn on, touch again, turn off.

    Sigh.
  10. Fred_M

    Fred_M Guest

    Sorry, all the reed switches I know of are normally open unless there is a magnet close by, then they stay on only as long as the field is present. Easier to install a small slide switch. FRED
  11. ezdays

    ezdays Out AZ way

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    It is possilble to "bias" a reed switch with a weak magnet such that a strong magnet will cause it to actuate and the weak one will hold it in place after the other one is removed. it requires putting a magnet at the other side to restore it. Tricky at best, especially if in a train where the movement could cause the switch to change on its own.

    I have a thought, but I'd need to know how many LEDs in a car and how long the station "stop" times are. This is the only time you really need to be concerned about having power backup to the lights.
  12. Ray Marinaccio

    Ray Marinaccio Active Member

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    Could a regulated trickle charger, powered by track voltage, be installed in the car to keep the batteries charged?
    In theory this would eliminate the flickering and when the train is at a station the batteries will keep the lights lit. A timer circuit could be built in to shut the lights off after a certain amount of time to eliminate the need for an on and off switch.
    (Also just thinking out loud.)
  13. krokodil

    krokodil Member

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    Sometimes it is easier to use a high capacity capacitor (named as GOLD CAP). This works with low current LEDs few hours and you cannot overcharge.

    The only limitation they may not get more voltage as specified (you have to add a small Zener diode (stabilizer) and in series with a resitor. You can charge the capacitor from the track (you have to rectify the track voltage with a small bridge). When the capacitor is charged (very fast) the LEDs will light and go off the the capacitor is discharged - no switch is needed.
  14. Fred_M

    Fred_M Guest

    Sure, it just adds to the cost and complexity. The timer circuit would still need an on switch. One could also do as krock suggests and instead of a battery use a cap (like a memory cap) for the "battery". Trouble is them caps are kind of big and might be hard to hide all that electronic stuff in a detailed interior of a passanger car. FRED
  15. mhdishere

    mhdishere Member

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    Like so many of my ideas, this seemed like a good one until I got into the details. I think I'll put my effort into the layout for now, maybe sometime down the road I can worry about installing lights so my LP commuters can read the LP newspapers on the way to their LP jobs.
  16. Fred_M

    Fred_M Guest

    Like so many things there is more than one way of doing things, and you can make it as complicated as you want (or listen to others ideas). But really, just 2 white leds and 3 or 4 batteries will get you what you want. That's how I do it, I KISS. If you let them they would have you putting a nuclear powerplant in each car to power the lights. Don't let everybodies elegant high tech methods scare you off a basically good idea/project. :( FRED
  17. Pitchwife

    Pitchwife Dreamer

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    Instead of using the reed switches to turn the lights on, use them to activate a "flip flop" circuit that would run the lights. When the reed switch closes it sends a pulse that turns the flip-flop on and remains on until it gets another pulse. Then your magnet on a stick would work. It's a little more complicated but not much and would do what you want it to.
  18. Fred_M

    Fred_M Guest

    How about a schematic?
  19. Pitchwife

    Pitchwife Dreamer

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    The first one I found is at http://www.uoguelph.ca/~antoon/circ/alt1.htm There may be more out there but this one is fairly simple. Just substitute the reed switch for S1. Also I would use a solid state relay instead of the mechanical one that is shown. that will draw less current, mount on the same PC board and allow you to use AA or AAA batteries instead of the 9v. 3 or 4 should be plenty depending on available space.
    If you need help refining the circuit just let me know. Hope this helps.
  20. Fred_M

    Fred_M Guest

    I'll give it a try.:) Thanks...(for the nuke:D ) FRED