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  1. Allen3

    Effect of ripple load on Li-ion battery

    There are always tradeoffs such as volume, weight, cost, operating conditions (primarily temperature), efficiency, reliability and lifespan (high voltage, high power capacitors are prone to early failure). A series inductor of course has the same effect as a parallel capacitor, or you can use...
  2. Allen3

    Effect of ripple load on Li-ion battery

    The only page I bookmarked is this one: http://www.electrochem.org/dl/ma/200/pdfs/0135.pdf . I remember seeing some other papers that looked at battery impedance in a lot more detail and contained similar graphs. I believe that above 5 KHz or so, the only additional effects you need to worry...
  3. Allen3

    Effect of ripple load on Li-ion battery

    Just papers that are publicly available and indexed by Google, which unfortunately isn't a lot. You might be able to find more in a good pay-walled research index. FYI, in addition to the effects described above, in some chemistries, local polarization of the electrolytes can occur. This...
  4. Allen3

    Effect of ripple load on Li-ion battery

    Thanks for the tip. That paper does say it applies to VLRA (lead–acid) batteries, not Li-Ion batteries, with 50/60 Hz ripple, not high frequency ripple. For the sake of completeness in this thread, I have learned that the skin effect can be important, i.e., at high enough frequencies, the...
  5. Allen3

    Effect of ripple load on Li-ion battery

    OK, thanks. I expected the battery would tolerate some amount of ripple, but I didn't know how much and what the tradeoffs were.
  6. Allen3

    Effect of ripple load on Li-ion battery

    Yes, DC+ripple will have higher I2R losses than just DC. Is that the only thing I need to worry about? Maybe the high frequency ripple affects (adversely or beneficially) the chemical reactions inside the battery. I don't know.
  7. Allen3

    Effect of ripple load on Li-ion battery

    I'm investigating the design of a bi-directional switching DC-DC converter that will be connected to a Li-ion battery. The goal is to make the switching frequency relatively high, in the range of 50-100 KHz. Due to the switching, the converter will place a load on the Li-ion battery that...
  8. Allen3

    an unknown error occurred during solutions

    In order to do a magnetostatic analysis, you have to combine all of the bodies into one part. Go to Geometry, at the bottom of the left pane, expand the parts list, select all of the parts, right click and select "Form New Part". Then do an Update to sync the changes, go to Model, expand...
  9. Allen3

    Bearing in wrist pin

    Hi Tmoose, The load in this application does not reverse direction. It is always compressive. The machine is cyclical, with a design speed of 1200 rpm. The cycle will start with the joint at a zero degree angle with no load. With the joint held stationary, the load will increase to about 50...
  10. Allen3

    Bearing in wrist pin

    I'm designing a machine with a moving joint that looks and functions exactly like the joint between a piston and its connecting rod in reciprocating engine. My thought is that I would use the same type of bearing. AFAIKT, a typical engine will attach the piston to the connecting rod using...
  11. Allen3

    "twisting" force on shaft in journal bearing

    This is kind of a newbie question. Let's say I have a horizontal shaft perfectly aligned in a journal bearing, and at running speed, the bearing is capable of carrying a load of 1000 pounds-force, and by that I mean that I can put 500 pounds of downward force on each end of the shaft, for a...
  12. Allen3

    minimize inefficiency in partial-admission turbine

    Thank you for your feedback. Just a quick follow up question: were the baffles placed relatively close to the rotor, or at some distance? Was the surface of the baffle smooth (to promote laminar flow) or rough, dimpled or radially grooved (to promote the development of a shearing layer)...
  13. Allen3

    minimize inefficiency in partial-admission turbine

    This is a question about aerodynamic friction in the context of a partial-admission impulse turbine. The working fluid will be air or some other gas. In this particular turbine, the buckets will be U shaped and will be symmetric, i.e., if the rotor were simply spinning by itself in the air, it...

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