Search results

Date Relevance Most replies

  1. P

    Is this Ping 20Ah 48v 32s 2P or 8s 2P?

    It seems to me that this one is 8S4P configuration. It is visible 8 BMS wires on top, missing BMS wire for most negative contact (B0 or B-). B1 BMS wire is black one and B8 (or B+) is red. Definitely not 48V.
  2. P

    Another BMS project using single cell modules

    Here's 20S BMS: The 6.2R/2W resistors are mounted on bottom of Al bar (50*5*250mm). The BMS has been tested with 16S/8A charger and 200W 24VDC halogen light bulb (inrush current >30A), no problems found even in communication. As this BMS is to deliver away, everything is additional isolated...
  3. P

    Battery quits after 10-20% discharge

    If it is LiIon/LiPo it's probably at the end of its' life, but this is not the case for LiFePO4 batteries. Only way is to measure individual cell voltages at end of charging (with charger still connected) and after it dies under load. - If all cells have similar voltage - the pack is at the end...
  4. P

    am i shafted with some fake steel nickel strips?

    Nope, it is 0.02cm3. 10x10x0.2mm is 20mm3, in order to convert to cm3, you have to divide this figure by 1000.
  5. P

    16-18S BMS options? Where to buy?

    Most important detail is missing: balancing current. I'd be surprised if your BMS has balancing current above 100mA, it is probably around 60mA or even less...
  6. P

    DIY Powerwall pack build

    It's even worse: have you observed the connections? Between bus bar and crimped lug is inserted a nut, which is not brass, as well as the screw??? Maybe guy knows how to solder, but he definitely needs some education for wiring... :roll:
  7. P

    Acceptable BMS draw

    About connecting optocoupler to charger: do you have any electronics repair service in your neighbourhood? Most electronic techs can solve this problem quickly...
  8. P

    16-18S BMS options? Where to buy?

    Take care about balancing current first. Check these 16 resistors close to balance connector, which value is written on them? Usually such BMSes have low balance current (~60mA) and thus it is not advisable to use couple cells for light... In addition, it is advisable to check standby current...
  9. P

    Help a pedestrian trying to understand how to wire up a BMS?

    You did not connect yellow wires to plus pole of the battery... Plus pole for charger and for controller should be connected there (+ pole of the battery) too.
  10. P

    New to Custom Battery packs.

    Do you really believe that it is possible to put almost 10Ah into 18650 case??? My advice: forget any Ultrafire cells.
  11. P

    No output from battery pack

    If you brought that cell to only 3.0V before putting the battery on the charger, it is highly probable that that cell is still flat. It is important to check the voltage on that cell when your charger stops charging the battery. Before you replace faulty cell, try to charge it to 3.7-3.8V after...
  12. P

    Help a pedestrian trying to understand how to wire up a BMS?

    It looks like most positive cell triggered LVC as it has only 3.4V and LVC has been set to too high voltage... The BMS still can be good enough... As I see, other cells are also almost flat as their voltage is between 3.5 and 3.6V... Try to charge the pack (it is almost empty) and check cell...
  13. P

    What is my watt meter telling me?

    As the BMS will cut out on low voltage, it is obvious that the available energy will not be same at e.g. 0.05C discharge and at 1C discharge rate due voltage sag... In addition, the delivered energy is also reduced by losses on internal resistance of the battery. In other words, the Ah ratio of...
  14. P

    Battery amp Vs phase amp?

    Maybe this picture helps: In the bottom diagram the battery current is shown in orange colour and the phase current is shown in orange and green colour. The phase current is 120A and the battery current is only 30A... Usually phase current is limited through peak current (in this case ~143A)...
  15. P

    Connection order Bestech PCM/BMS

    B-, then sampling wires (push in the connector first negative side), then (if exists) B+ and after that the rest.
  16. P

    Another BMS project using single cell modules

    10uA quiescent current means ~82mAh per year imbalance charge per year... 82mAh charge balancing can be sorted within couple hours even with cheapest balancer... :D Think that after couple years you'll have much bigger problem with difference in self discharging currents between cells... I...
  17. P

    Regen braking and BMS

    Yes, you can charge the battery through load side of the BMS, but in such case BMS doesn't protect battery from overcharging. Usually this is not a problem as you almost never charge battery more than you discharge it during normal drive... I have problem at home as when I go with bicycle to...
  18. P

    Another BMS project using single cell modules

    Single cell voltage sag is easy to detect through LVC alarm of cell module, which is sent automatically if the module is not polled. In short, the central module is not needed even to poll the cells when discharging as it will receive the alarm message when particular cell reaches low voltage...
  19. P

    motor draws huge current at startup.

    As gogo said, try with resistor...
  20. P

    motor draws huge current at startup.

    Oops, I again missed the point... :oops: It's better to use controller as it can give soft start and you can regulate the speed... These controllers are pretty cheap. What is nominal power of the motor? What is max current? Think that you can find new controller for <1kW/48V motor for less...
  21. P

    motor draws huge current at startup.

    According to your description of the problem, I'd say that magnets lost the flux, or otherwise you have short circuit in armature winding... Is it easy to turn the rotor when motor is disconnected? If yes, try to short the contacts and try to turn again in order to see is it still easy to turn...
  22. P

    Arduino based charge balancer

    You should add clamping diodes as transistors have inductive load (relay coils)... BTW, relays are bit expensive, this idea is usable only if you have surplus of relays... It's still better and cheaper to go with individual cell modules... I found that only minor changes in my cell module...
  23. P

    How to wire BMS

    :oops: Guy, thank you for correcting me. I was looking to wrong BMS (which has different labels: P-, Out- and B-) when was writing the post. Found other BMS with same labels as in this topic, the charger must not be connected to P-, as you said.
  24. P

    Flash charging

    Sorry, I'm not impressed with such solution... Couple reasons against: 1. Too big peak power will make problem in energy transportation. 2. High C rate charging of batteries shortens their life. 3. There are probably more problems (interference, high magnetic fields, etc.), but first two are...
  25. P

    How to wire BMS

    The charger minus side can be connected to P- too. It is good to know if you want to use only one connector for connecting load or charger.
Back
Top