If Sonia charges her EV to 85% at a 240v, 30 amp source, and her car’s battery has a capacity of 40 kwh, how long will it take before she can drive to her grandma’s house?
Darryl observed that he and Wanda are dinosaurs, to which observation Wanda added, “And the comet is coming”. As for me, that question makes me feel like Mr. Wilson did when he observed Dennis, Margaret, and their classmates in a math class dancing to some pop music.
Anyway, is the *Baby Blues" math story problem a legitimate one and, if so, what is the answer and how does one arrive at the answer?
Yes that was clearly what was intended as I said I misread it the first time.
I’m often pleasantly surprised at how good comic strips are at presenting realistic math. FoxTrot was particularly adept at this, including real math up through calculus.
Recent(ish) theories speculate that it is more likely to have been a large chunk broken off of an even bigger comet that broke into many pieces as it approached the sun.
Anyone remember which of the Dennis the Menace episodes had the scene I described? That was obviously a real math story problem as Dennis solved it, explaining quite clearly to Mr. Wilson how to solve it. At the moment searching the Internet is a hit/miss (mostly miss) thing because the 20th CPC conference only just concluded and it takes a while before we get back to normal after that.
Perhaps the best way to answer your question is to say that if you know the capacity of a battery and the rate at which it can be charged you can work out how long it will take to charge as a rough first approximation.
In reality the problem has gaps (like the one @beowulff mentions), plus you need to approximate. In reality charging is neither 100% efficient nor necessarily linear.
It’s been a while since I read Baby Blues, but aren’t the kids in that strip a little young for this type of math problem? Ohm’s Law even got in there (at least as far as I can tell, what with converting volts and amps to watts to kw/h).
Charging to 85% is a standard recommendation for EV’s - don’t habitually keep charging to 100%, stop at 80-90% except in special circumstances (like a long trip) and also avoid making it a habit to drain the battery below 10% or so. Even doing this a few times won’t wreck the battery, but doing it all the time will shorten the battery life. Same goes for high-speed supercharging. It doesn’t hurt the battery to do it from time to time, but the less you do so (slow overnight charging at 7.2kW instead) the more life your battery will have.
Definitely. She’s only about 8 or 9. You might want to give this to a HS physics class that’s learning the basics of electricity, but not grade school kids.
AIUI, chargers slow their charging rate as they approach 100%. I always thought this was because it’s harder to stuff more electrons into a battery as it gets full. But I’ve seen comments elsewhere that this is because the chargers don’t want to over charge the battery, since that might damage it. Perhaps both of these are right.
