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  1. C

    Hobby King LiFePo4

    It will probably work but I would suggest buying a123 pack from cellman if you want lifepo4 chemistry. Much better odds of getting few years of reliable service from those cells.
  2. C

    Hobby King LiFePo4

    They have comparable (lowish) energy density to a123 26650 but without electrical and mechanical robustness of a123 cylindricals. And the price difference is not that much either. Not sure they make much sense. OTOH if HK offered us pre-built packs of a123 20ah prismatics that would have been a...
  3. C

    even simpler/cheaper LVC :)

    I assume you are going DIY route. What chip do you want to use to detect the HVC threshold ? Is it HVC only or HVC/balancer ? I can probably help you interface the chip output to the signaling chain.
  4. C

    even simpler/cheaper LVC :)

    You mean transistor only or transistor/comparator version ? Transistor-only chain will not be accurate enough for HVC/balancer application (even if it can be designed). Comparator-transistor chain can be modified fairly easily for HVC/balancer apps. I think fechter and Gary already have few...
  5. C

    Recumbent BikeE for Comfort and Efficiency

    My wife rides slow and gentle, it is perfect for her needs. However when I try to ride it - the front spins when starting at full throttle (even on a dry pavement). Otherwise handling is not affected.
  6. C

    Recumbent BikeE for Comfort and Efficiency

    Here is another EbikeE that I built for my wife. Shot in the process of charging with the balancer attached (you can see bunch of white LEDs on the top of the battery).
  7. C

    even simpler/cheaper LVC :)

    That is exactly how it works, except the top cell which needs to be mirrored (there is no voltage "above" the top cell to make it exactly the same). It gets a bit tricky when the transistor goes below Vce saturation (typically around 0.15-0.25V) and the gain starts dropping which leads to chain...
  8. C

    even simpler/cheaper LVC :)

    I have finally built and tested this LVC-lite circuit for a 16s A123 pack. The pictures from this thread were lost so here is another one: As I said before it is not as precise as multi-TC54xx chain but for a123 lifepo4 cells the LVC detection accuracy is quite adequate. The circuit is...
  9. C

    Radial lacing on X5 and Strong 24"

    Does this common wisdom of bicycle wheel building really translate well to the large diameter hubs like x5 or HS/HT ? I am not so sure. Every broken spoke on my 26" x5 wheel (and there were many) failed at the nipple because of wrong entry angle at the rim. Radial gives perfect entry angle and...
  10. C

    even simpler/cheaper LVC :)

    LTSpice. It is a nice completely free SPICE simulator with graphical front end supported by Linear Technology.
  11. C

    even simpler/cheaper LVC :)

    Warning, the following post is for perfectionsists and analog circuitry fans only :) Here is the temperature compensated version with the ideal/regular top segment (not practical as it requires extra power supply for current source I1). It is quite accurate and can be used for analog...
  12. C

    even simpler/cheaper LVC :)

    About 4uA, good for few decades, perhaps more...
  13. C

    even simpler/cheaper LVC :)

    No, it is split more or less evenly, not exceeding single cell voltage, certainly not full pack voltage. The top segment sources current proportional to the cell voltage which is propagated along the chain. This current causes equal voltage drop across resistors at each stage. If any stage sees...
  14. C

    even simpler/cheaper LVC :)

    I've been toying around with current-mode chaining of LVC circuits in the simulator recently and realized that you can build a super-cheap LVC using just one TC54 chip and current mode transistor chain as a sensor/aggregator. It will not have the same threshold accuracy and temperature stability...
  15. C

    New CellLog-based BMS "Lite"...

    What I was wondering is what is the voltage at the 431 output when its reference input is held above the threshold? Is it equal to 2.5V (reference) or does go to near-zero like on TC54xxx ? This determines value of load resistor and power dissipation split. BTW if you worry about individual...
  16. C

    New CellLog-based BMS "Lite"...

    There is a 200ma shunt regulator version - AP431 made by Diodes Inc (albeit for a somewhat higher price). BTW am I correct that 431 cathode can not go below the reference input ?
  17. C

    turnigy wattmeter - is Ah reading cycling ?

    I also got one of these HK-010 and in the watt meter mode it does indicate Ah continuously, so it is indeed possible to use it as cheap fuel gauge. But there are few convenience issues also: (i) you must press a button to enter watt-meter mode every time you start the trip, (ii) if you exit...
  18. C

    Is Regen Braking bad for Lipos?

    In your case rheostatic braking makes perfect sense. There was a large thread on it a while ago.
  19. C

    Is Regen Braking bad for Lipos?

    Actually it is not that bad. Controller/motor combos that we use are fairly lossy, typical efficiency is around 70% and it works both ways: for a 1W mech. power at the wheel we need like 1.4W of battery power during acceleration and get back about 0.7W during regen deceleration. Simplifying a...
  20. C

    Is Regen Braking bad for Lipos?

    This is controller specific. Kelly does not require throttle management for coasting (although it can be programmed this way), on my setup regen is controlled by brake lever with ratiometric hall sensor.
  21. C

    Is Regen Braking bad for Lipos?

    In a programmable controller regen cutoff voltage should be set at or slightly below full pack voltage. Unless you live at the top of large hill this is not really an issue. I've used proportional regen for two seasons with zero problems. It does not offer huge efficiency increase in my riding...
  22. C

    A123 20AH cells source?

    OMG! Now we have our own customs that want to give us hard time. Perhaps it is time to move to some reasonably civilized SE Asia place. I kind of like the food there (except insects, dogs and cats :? ). I know that A123 had some patent issues that restricted them from selling products in US but...
  23. C

    A123 20AH cells source?

    Anyone willing to contribute some personal time and arrange a small group buy from Mavizen ? :-). I need at least 25, perhaps 40-50 pcs.
  24. C

    New Crystalyte Motor series (HT35 / HS35 and HT24 / HS24)

    Are we talking about the same hub :) ? I guess sensored and sensorless setups may have different sound level/pattern but this much different ? Or is it a QC problem ? My X5+steel frame has two resonance spots causing very unpleasant high frequency frame vibration but outside these spots it is...
  25. C

    New Crystalyte Motor series (HT35 / HS35 and HT24 / HS24)

    How does HT/HS series compare to 9c and x5 in terms of rolling resistance ? Closer to 9c or x5 ?
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