• Content count

  • Joined

  • Last visited

About Rule69

  • Rank
  1. Allow me to toss out some ideas that are probably wrong. This may annoy somebody who really knows sufficiently to get them to post a correction. Both PWM and MPPT can work with 36 cell panels. In some conditions MPPT has the potential to get more power out of the panel than PWM. PWM (pulse width modulation) should be able to control a panel with any number of cells. PWM acts like a fast switch that disconnects the panel from the battery for some portion of time as needed to regulate the battery voltage. MPPT (maximum power point tracking) is intended to work where the ideal panel voltage is significantly greater than the battery voltage. MPPT uses a DC-DC converter that tries to keep the panel at its maximum power output (volts x amps) independently from the battery voltage. When the battery becomes full enough that its voltage needs to be regulated the MPPT controller will use PWM to limit the current sent to the battery. Each cell in a solar panel makes around half a volt ideally. A typical 36 cell panel in perfect conditions produces as much power as it can at about 17 volts. A MPPT controller would try to operate that panel at about 17 volts in those ideal conditions. The power output would be 17 volts times whatever amps the panel could produce. A PWM controller would operate at the panel at the battery voltage. The power output would be the battery voltage times the amps the panel produces. When the battery voltage is low and the ideal panel voltage is high MPPT may get significantly more power out of a panel than PWM. In ideal conditions a 28 cell panel's voltage would be around 28 times 0.47volts. That voltage is near the float voltage of many 12 volt batteries. In real world conditions and subtracting the voltage drop of a blocking diode, a 28 cell panel will rarely be able to raise the voltage of a 12 volt battery high enough to damage it (or to fill it completely). So, an external controller isn't required.
  2. Hmmm... At the drop of a hat I can tie a bowline one handed, behind my back, eyes closed while drinking beer. I have to look at the instructions for a diamond knot or button knot (now my fav) if I haven't tied one recently. Maybe I need more practice. I do enjoy making up a batch from time to time. They're nice to have and to give away. Much appreciate the testing and instructions that you and Allen provided.
  3. ^^^ Nice. Even better you can get a newest activity list that excludes PA (or whatever) by unchecking the "unread" status. Awesome find.
  4. Upper right corner of the post, very faint though. Becomes more visible if the post is in focus (eg. you have a cursor in the post somewhere).
  5. +1
  6. Nice. But, as nearly as I can make out there's no way to edit the markup. That's going to make responding to long quotes one section at a time hard. Doing responses inside quotes in different colors gets unreadable fast. I suppose we can cut from the quote and paste into new quotes with the new editor. That's not elegant.
  7. China shock? Anyway, plenty of good batteries come out of China. The Full River AGMs get decent reviews and, AFIK, most or all of the large Lithium Iron Phosphate batteries are Chinese products.
  8. Apparently they're Chinese manufactured AGMs. NTTAWWT. Just that, give or take a bit of optimization, I'd expect them to perform similarly to other lead acid batteries. Mainsail seems to have done some research on them here including the MSDS.
  9. IME, it's the coils that go bad (not often IME, thankfully) I suppose if one had a powerful magnet one could pop off the coil (usually easy) and stick the magnet in its place. That might open the valve. Under threat of raw ramen one might dissect a speaker... No me. I'm fearless in the face of crunchy noodles.
  10. IIRC, those sails demanded a lot of small trimming inputs to work well. It has been ages but I remember giving them constant bumps both to get out of the hole and to maintain speed even when fully powered up. I ~assumed~ the effective flying shape wasn't well represented by the static wing shape. Ie. something magic was going on wrt time. A person with good shoulders can deliver quick, relatively powerful pumps to a windsurfer sized sail. No so much at larger scales with traditional manual power. Maybe ETNZ has an ability to pulse significant power and is looking to make gains with an effect that doesn't show up on traditional steady state analysis?
  11. I suspect they aren't doing one to the exclusion of the other. For any given apparent wind there should be some ideal lift distribution and angle of attack. Tom Speer's paper has been influencing this kind of discussion for a while. He lays out a method for approaching the math.
  12. Practical Sailor?
  13. Got an NMEA 2K interface for all of that? In theory a person could build that. I'd ditch the Arduino and go with a PSoC 5LP. IIRC, you get hardware support for CAN, UARTs (in case you want 0183 connectivity), I2C or whatever the baro needs, and or other stuff and a good ARM core. The dev kit is affordable (similar to Arduino) and has a programmer built in. The trivial task of going from bits to a system are left as an exercise for the reader. Actually, I'd just stick with the perfectly adequate barometers I have. But that doesn't sound very exciting.
  14. Just happened across "Physics Toolbox" for android. It includes a recording barometer. Seems quite nice.