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  1. Z

    nicd pack charger(finished)

    Nice individual, fan-cooled heatsinks! I have a feeling that these tenergy batterys have a lot less capacity than the label says. I tested my 2.4 ah sub-c pack and only got 1.7 ah at a 3.5a rate but hopefully they just need some breaking in. So if the "C" is less, then C/10 might be cooking them.
  2. Z

    nicd pack charger(finished)

    Yeah, much simpler! Thanks Fechter. I was thrown off by the LM317's 37v limit but it only sees the difference between the power supply and the batteries. A battery temperature sensing circuit or switch could turn off the adjustable leg.
  3. Z

    nicd pack charger(finished)

    Cool, I'll try something like that. I need to read up on darlington transistors cuz I still don't understand how this circuit works. Couldn't you use a circuit like this as a battery charger? What program are you using to do these circuits?
  4. Z

    nicd pack charger(finished)

    oops, the zener didn't work. I guess it needs only 50mA but at 62V my 1k resistor went up in a cloud of smoke :oops:
  5. Z

    nicd pack charger(finished)

    I tried using a separate bridge rectifier with the different transformer taps but I couldn't get it to have a common ground between the rectifiers. I also want to try a different charger using a zener and resistor to regulate a tip42 power transistor. I'm not looking for anything real...
  6. Z

    nicd pack charger(finished)

    the lm339 output sinks to ground so you need a pull-up resistor on the output. With the feedback loop I was hoping to control the oscilation frequency so maybe it wouldn't be so electrically noisy or maybe the mosfet would run cooler. It's definately needed when comparators are used with...
  7. Z

    nicd pack charger(finished)

    Here's the constant current circuit I drew up based on thermistor circuits I've made. The one I've been using has different resistor values since I use what I hack off scrap equipment. The mofset and lm339 comparator are stocked at radio shack for a couple bucks. The mosfet heatsink gets hot...
  8. Z

    nicd pack charger(finished)

    Don't forget to multiply by 1.4 when going from AC to DC. My two 24v AC transformers are producing 67v DC. http://www.hardingenergy.com/pdfs/NiMH_NiCd_Design.pdf shows you may need almost 1.6v/ea to charge nicds. I just got 80 tenergy sub-c's and so far they seem to be full at 1.43v/ea when...
  9. Z

    nicd pack charger(finished)

    Dirty_d, I use two $10 24v/2amp radio shack transformers in series to power my 48v nicd charging circuit. With a bridge rectifier and capacitor from an old tv I get around 67v. Maybe combine a 24v and 12v transformer for less voltage? I've been using a circuit very similar to yours but it...
  10. Z

    Safe's Electric Bike Project #003

    It doesn't take much spring pressure to keep them together because they are so snug in the PVC. I've bashed mine against the floor with no disconnect registered on the multimeter. I used wood plugs with pins instead of fittings so that the tubes can be bundled tighter and taken apart faster...
  11. Z

    Found free source for nicad.. should I bother?

    I've been doing the same thing...picking through 100's of used nicds. The dead ones would be mixed in the middle of the packs so I pulled the tabs off the rest and put them in pvc pipes with a spring on the end. It's taking forever so if your time is worth more than the $2/ea for new cells...
  12. Z

    Safe's Electric Bike Project #002

    The ABS battery packs aren't solderless, it's just a container for premade nicd packs. I haven't been able to melt my PVC/spring loaded packs but I haven't found a high amp 48v power supply to really test them. I used pinned wood blocks in the ends instead of PVC fittings so that the tubes can...
  13. Z

    Safe's Electric Bike Project #002

    I made a PVC holder for 10 cells for testing purposes. Hmmm... bike rack stacked with pipes with capped ends and red and black wires sticking out? I'd be shot by Homeland Security before I got to the end of the block! Better keep yours well hidden in your frame. I'll try overcharging at 1C...
  14. Z

    Safe's Electric Bike Project #002

    Another benefit is that you can shake them out of the tube and toss out the "runts" easily. I've found a few of my old cells that go to 0V sooner than the others.
  15. Z

    Safe's Electric Bike Project #002

    I just thought of a possible problem, heat. I've melted PVC pipe but that was with my solar panel water system and it gets pretty hot. My laptop's batteries get lap scalding hot, how about nicds? Maybe holes drilled in the pvc where the batteries touch would ventilate heat. These subC...
  16. Z

    Safe's Electric Bike Project #002

    Just found this site, lots of info! I had the same idea of using all my old nicds (which have broken welds!) from my old powertools for some sort of battery pack. I think they are sub-C. Anyway, I found they fit perfectly into 3/4" Class 200 sprinkler pipe. Seems like it would make a...
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