March 10, 2005
Ebike in use

So the new bike has now been out for 2 actual trips, displacing, oh, perhaps several milligrams of greenhouse gases, assuming you don't count all the CO2 expelled by puffing and swearing. The first was a short round trip at night, where I learned that full-looking fenders can still leave your shoes soaked and splattered, and the second one to work today. The pack started out this morning at 26.4 V, and ended (after 10 km in 30 min at around 5 C) at 24.9. I'm paying some attention, because I'd like to figure out how bad the condition of the batteries are. They don't have many cycles on them, probably less than a dozen out of an expected life of 300 or so, but they are something like 5 years old at this point, which is I think fairly stale even for a properly maintained battery. Battery packs need to be thought of as perishable commodities, not capital investments, which can be a little frustrating if they dominate the running cost of the vehicle. 24.9 V corresponds to ~75% SOC according to Battery University, so maybe they are okay.


Today I learned that:



  • Top end gearing on the motor is not really adequate. At top speed, pedalling hard, the motor was unable to contribute much if anything. This is a safety thing: the faster you go, the fewer cars need to pass you, and the more patient they will be. Good thing I have a higher gear ready to put on.
  • Motors don't create additional stability on wet ice on sidewalks.
  • Everything needs to be tightened. Years of neglect followed by a few crashes will do that.
  • I arrived late, tired, and dirty. It wasn't supposed to be like this. Maybe tomorrow will be better.

Higher voltage systems are the other way to get higher speed, since (for a given motor) the voltage must overcome the back emf which is proportional to the rpm. 36V systems are common in ebikes and scooters, and 72V isn't unheard of. Higher voltage also cuts the current at the same power, which reduces the copper loss I^2 R which is the main loss in the motor. The first generation Prius ran at 144V, and the second generation runs at 700V, so the advantages of higher voltage in EVs seems to be appreciated. The disadvantages include safety, something not yet well developed in EVs. It's not that gasoline is safe, but everyone is used to the risks and knows how to handle various kinds of accidents. It will take time (and lots of racing) to develop this collective knowledge and experience for EVs.

Posted by TFox at 10:46 AM
New Blogger

No, I have not developed a new personality.

I invited my friend TFox (no relation to Terry Fox) to blog on this site. As you've probably already noticed, he cares about energy conservation and electric vehicles far more than I do, and I think it would be fair to say he's more liberal than I am on most issues. Overall, a good acquisition for sambal.org -- welcome to our corporate family!

Posted by Sam at 09:13 AM
Bible Study

Well, there's a big gap in my chart; I haven't done this since March 1. Oh well -- at least it's a rolling year-over-year thing. Within about two or three years I should have hit all of it.

Here's the link in case you're following along at home.

Matthew 13 - the parable of the sower. A strange story, because Jesus flatters the apostles, or else gives them a strong but very gentle rebuke. Anyway, the sower's seeds may fall:

  • by the wayside -- the Word is heard but not understood
  • on the rocky places -- a weak person who doesn't have the strength to carry on
  • among the thorns -- a person who allows wordly cares to take precedence over religion
  • on the good ground -- a good christian

    I'm somewhere between 2 and 3, I guess.

    Then: Leviticus. And apparently I missed all the exciting stuff about mixing different kinds of fibers, because today we have Leviticus 17-18: animal sacrifice and sexual rules.

    Leviticus 17 is simple: sacrifice your animals to Jehovah, and don't drink blood. And if you eat roadkill, you must wash your clothes and bathe, and then you will be unclean until evening.

    Leviticus 18. I see the influence of the oral tradition here -- "The nakedness of X, shalt thou not uncover. She is X; it is X's nakedness." Lays down the basic incest taboos: mother, sister, granddaughter, half-sister, blood aunt. Then some commonsensical (as opposed to blood) rules: father's brother's wife; son's wife; brother's wife. If you sleep with a woman, her daughters and granddaughters are off-limits. Don't marry your wife's sister while your wife is still living.

    Skip down to Leviticus 18:22 and we get to one of the more contemporarily interesting passages in the OT: "Thou shalt not lie with mankind, as with womankind: it is abomination." The most straightforward gloss of this translation is a blanket prohibition on homosexuality, of course. Various people argue that this is a ban on male temple prostitution, since this is in the context of things which the Canaanites do (like sacrificing babies to Moloch). Or a ban on homosexual rape -- I believe you have to attack the translation a bit to make that case. But in the context of chapter 17 -- where a man's allowed relations to various women are defined and relations to other men are completely ignored -- I think it's prety clear that (male) homosexuality in general was frowned upon.

    Why anyone would use a 4000-year-old oral tradition from a herding culture to inform contemporary moral decisions is another question.

    Posted by Sam at 08:56 AM