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  1. Aerowhatt

    Ping 36v 20 ah, 5000 mile review.

    Simply put on a ping BMS the whole battery charges equally until the highest cell reaches a voltage set point where a resistor is switched across that high cell to burn off some of the charging current to just that cell. Since the charger charges faster than the resistor burns off the power, the...
  2. Aerowhatt

    What's up with my battery?

    I guess it all depends on what your needs and abilities are. I think at best one should actually have experience with something before trashing it. Two of the ping packs I have ride as a range extender on a bike which peaks out at 9,900 watts DC input. For less than double the price of the...
  3. Aerowhatt

    ping 36V20Ah problem

    That's normal. The higher voltage is mostly surface charge so it has no depth to it. Probably 30 to 60 minutes at the 100ma discharge will bring them down pretty close to the others. You will know how close at the end of the following charge cycle of the whole battery. The other thing you can do...
  4. Aerowhatt

    What's up with my battery?

    Sounds like a waste of time repairing the BMS. Running the cells up to 73 amps and more with a short circuit, every cell is marginal if not toast at this point. That's why the BMS has current protection to start with. Other LiFePO4 batteries have come down some but are still harder to get what...
  5. Aerowhatt

    ping 36V20Ah problem

    It sounds like the BMS and charger are both doing what they are supposed to. As you can imagine with the charger only connected to the cells by the BMS a few seconds every three minutes the effective charge rate on those low cells is in the neighborhood of .15 amps instead of 3 amps. It will...
  6. Aerowhatt

    Mixing chemistries for most economic performance and range

    It just sounds like inexperience talking to me. After thousands of EV miles it's versatility that one really ends up wanting/needing. Sizing and tailoring for a specific commute doesn't give versatility. "Can't take the bike today not enough range while pulling the trailer" . . . "Well probably...
  7. Aerowhatt

    ping 36V20Ah problem

    It sounds to me like the BMS is kicking the charger out at too low of a voltage for the balancing circuits to be sending power to the resistors to be burned off on the high cells. Those two resistors on the high cells should be getting warm in just a few minutes after plugging the charger back...
  8. Aerowhatt

    ping 36V20Ah problem

    It sounds like you were measuring the voltages right after disconnecting the charger, is that correct? If so then the voltages are low. I've got a similar ping on the bench which hasn't been topped up in a few weeks and it measures 40.4 Volts. Since you have the BMS uncovered one simple check...
  9. Aerowhatt

    Mixing chemistries for most economic performance and range

    That's a good point, calendar life is a significant consideration. Interestingly though the calender life has to be taken with the fine print. For the older LiPO it was said to loose 20% of capacity in 2 years. Well if you figured some head room on capacity initially that helps some. I'm in a...
  10. Aerowhatt

    Mixing chemistries for most economic performance and range

    I don't have it documented online. I'll list basics here and I can answer any other details you need. I also have some external photos I could send you. It’s an ugly little motorcycle but a great performer. Just like the plain girlfriend that treats you right. She gets better looking the...
  11. Aerowhatt

    Mixing chemistries for most economic performance and range

    This combination is just too far apart to make work without some serious intervention. Even if you raise the cell count on the NiMh to compensate for the high internal R you would need a step down converter to avoid overvolting the LiPO at the beginning of the discharge. Sometimes it's just too...
  12. Aerowhatt

    Mixing chemistries for most economic performance and range

    Yeah, making the main pack the low output pack is the opposite of the systems I have done. I've taken systems with enough power on tap already but insufficient range. Then added range with a different chemistry(bonus is you get more power too). To go the other direction and have a Ping as the...
  13. Aerowhatt

    Mixing chemistries for most economic performance and range

    You are correct that the booster pack provides more current if you increase the resistance on the capacity pack (we must also remember how small the change I recommended was). But that's only one aspect of the real world system performance. Urban Ev's spend significant time coasting and stopped...
  14. Aerowhatt

    Mixing chemistries for most economic performance and range

    You're still thinking one battery at a time. It's a system with two power sources. It really doesn't effect the booster pack capacity in practice. Unless of course you are doing nothing but flat out top speed run with no stops, or climbing a mountain pass. Most of the applications are for stop...
  15. Aerowhatt

    Mixing chemistries for most economic performance and range

    Just a note about resistance and paralleling two non matched batteries. If they are both conected to the load then having resistance in between one of them and the load isn't as bad as it seems. Intuatively adding resistance produces alot of heat and wastes power. This is very true in a single...
  16. Aerowhatt

    Mixing chemistries for most economic performance and range

    Looking forward to your results. One combination I haven't fooled with is NiMh and LiPo. From using both in airplanes before my guess is the LiPo will do more of the work at higher loads. I think it's a great idea to publish results for everyone to use as guidelines. The Informations usfulness...
  17. Aerowhatt

    Mixing chemistries for most economic performance and range

    This is a good and simple solution that I mentioned in passing earlier. Basically it's a motor controller with the right amp limit set at full throttle between the lower power output pack and the rest of the system. There is some loss in doing this and considerable expense in high power Fets...
  18. Aerowhatt

    Mixing chemistries for most economic performance and range

    There is something to be said for the exercise of design and mental experiemnts. Hey, alot of great things have come from this aproach. It all depends on what your time frame goals are. I also agree that when it comes to expensive batteries and protecting one's health and property, safety...
  19. Aerowhatt

    Mixing chemistries for most economic performance and range

    It could be either way. SLA's of the same size but different brands and internal construction can have IR's up to three times of some others. Nicads usually don't have that broad of a range but it's not far behind. The simple voltage sag measurement under the same load for each battery tested...
  20. Aerowhatt

    Mixing chemistries for most economic performance and range

    Yes checking the amperages in action is a necessity. Basically though you only need to look at your low output pack. (I believe that the high output pack should be such that it can handle peak loads alone) You just need to make sure your setup doesn't draw too many amps from the low output pack...
  21. Aerowhatt

    Mixing chemistries for most economic performance and range

    All these ideas are just far more complicated than needed. Basically if you go whole hog on electronic controls you spend enough time (that you could work some overtime) and money to double the a123 packs capacity. That partially solves issues all by itself. The simplest electonic way to go...
  22. Aerowhatt

    Mixing chemistries for most economic performance and range

    Boy you guys sure over think this stuff. I would be riding with it by now. Aerowhatt
  23. Aerowhatt

    What kind of helmet do you use?

    That's an excellent and insightful point. When reading studies like these most people brains compare the numbers automatically "no helmets" to "all helmets". As you point out, the results are far more dramatic when one realizes that many riders were already wearing helmets before the law was...
  24. Aerowhatt

    What kind of helmet do you use?

    I'm not going to argue with you further, clearly you need to be right. Good enough, we can agree that a full face downhillers helmet like ypedals "Gyro" is a pretty good choice for 25 to 30 mile per hour e biking. I go with something as light with a much stronger shell. Having raced mountain...
  25. Aerowhatt

    What kind of helmet do you use?

    Really . . . a myth huh? It would be pretty hard to back up scientifically. Simply because multi angle video of all crashes is hard to come by. It's common sense though that a lighter helmet wth a trimmer profile would be less likely to catch on road cracks etc. and try to change your momentum...
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