On 26 Mar 2015 at 19:57, Ben Goren via EV wrote: > That's the idea behind my suggestion of a "remaining (usable) kWh" > gauge ...
Sounds good to me. Solectria had a simple answer to this. They gave you a straightforward amp- hour meter. As you drove, it counted up; as you charged, it counted down. When the charger shut off, it zeroed itself. Since it didn't count down as you drove, it didn't need to know what the total battery capacity was. In fact, it expected you, as the driver, to have a clue about that. The drive inverter protected the (lead-gel) battery by limiting drive current to keep its on-load voltage from dropping below 10.5vpc. So even if you didn't buy the optional voltmeter/ammeter combination, you knew from the way the car felt when you were reaching a critical battery voltage level. You learned that when the meter read, say, 40 amp-hours, your car's acceleration started to weaken, because of that 10.5vpc clamp. (When driven carefully, Forces could do a mile per amp-hour - about 150Wh/mi. James Worden was a fantatic for efficiency, sometimes to a fault.) When the amp- hour meter started getting close to that point, you started thinking about finding a place for the car to sip some electrons. You learned that your usable battery capacity depended on driving conditions, just as folks who drive 80mph know they're going to have stop for fuel miles sooner than those who are driving 60mph in the same kind of ICEV. So you adjusted. You learned what cold temperatures did to your range. You learned that battery capacity declines with age. You compensated for that too. This sounds complex, but it worked surprisingly well, because (believe it or not), aware EV drivers LEARN. Natural intelligence! They're at least as good as computers in judging how much farther they can drive their EVs. In fact, hundreds - probably thousands - of conversion EV owners since the 1960s and 1970s have done just fine with nothing but simple expanded-scale voltmeters. They learned what the meters read at various speeds and loads when they had range left, and what the meters read when they were getting close to their limits. There are still plenty of good drivers who can interpret instruments. A lot of them are right here on the EVDL. Ed Blackmond's description of how he reads his 2011 Leaf's gauge - "I know I can travel 10 miles on the last bar" - is a perfect example. But smarter cars tend to make dumber drivers, and automakers now design to this low standard. Liability is on their minds too. Hence ever-more-complex computerized EV remaining-range "guess gauges." And hence, eventually, self-driving cars, EVs I hope, which someday I suspect will be so smart and concerned for your welfare that they'll tell you, "I'm sorry, that destination is too dangerous. I'm not allowed to take you there." But that's another matter entirely. I think. Uh, does this tinfoil hat make me look taller? David Roden - Akron, Ohio, USA EVDL Administrator = = = = = = = = = = = = = = = = = = = = = = = = = = = = = EVDL Information: http://www.evdl.org/help/ = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Note: mail sent to "evpost" and "etpost" addresses will not reach me. To send a private message, please obtain my email address from the webpage http://www.evdl.org/help/ . = = = = = = = = = = = = = = = = = = = = = = = = = = = = = _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
