“Well that’s obviously not right. An average route going an average of 13.6mph for an average of 6 hours gives an average distance of 82 miles, not 21.”
In my neighborhood, they stop to open the mailbox!
“So constant slow movement, top-and-go, will deflate your battery much faster (just like a regular gas/diesel!) “
Actually not. EV motors draw no current when stopped. Also, EV’s have regenerative braking.
Perhaps you ignore the fact that EV’s get better ‘mileage’ in the city versus highway.
Average USPS ROUTE:
Distance: 20.8 miles
Speed: 13.6 mph
Route time: 6 hrs
That average speed is average moving speed the time is total time. Think about how many times the postman gets out of the truck to walk packages up to the door. Only to creep up to the next address drop mail in the box then creep to the next door drop get out, walk get back in. The ratio of stopped to moving time is nearly four to one.
20.8 miles with an average moving speed of 13.6 is 1.5.. Hours of actual movement and 3.49 hours of hoofing it or idling sorting packages something I see my postman do at the end of the street for half an hour in the back of the truck getting things ready for his next blocks of drop offs moving things to be in arms reach for the next few streets drops.
I do a lot of city driving my S60 has multiple trip ODO and also has a current trip summary for every time you turn on the key and move it.
The metrics are total run time, total distance,total moving time,total stopped/idle time,total avg speed, avg moving speed,avg fuel econ, avg moving fuel econ.
That said in prime time snarled city traffic my avg total speed is frequently less than 15 mph with avg moving speeds in the mid 20s to cover 10 to 15 miles in the core of DFW. it is little surprise that a vehicle that literally goes door to door for an 8 hour shift would avg less than 20 mph. This type of drive cycle is ideal for a series hybrid drive train why because with a small battery pack to take up braking energy as regenerative 80% can ne returned to accelerate the vehicle to next stop dozens of feet away and then regen again. This is why Prius get 55+ mpg in the city they do better in stop n go due to regen. The other thing is since you can use a tiny 500cc or 800cc motor to run a generator of 25kw or so you then run it at peak efficiency only to.charge the pack when it gets low then shut it down again you never have the low BMEP operating points in a properly designed series hybrid. While a modern diesel might be 43% net eff. At a BMEP of 20 bar its much less than 12% at 2 bar which is low speed cruising off the motorway even at motorway speeds a 2L diesel is only pulling 5 bar BMEP or less and less than 25% eff. A small otto cycle petrol engine running at 15 bar is 40% eff. This is the operating point a series hybrid is designed for. Petrol motors are 1/3 the cost of diesels especially the small ones under a liter of displacement. You can get 75kw per liter at 3600 rpm and 15 bar with 40% net eff. Ideal for a stop go.duty cycle. A vehicle of mail truck size would be in the 50 plus mpg with a 500cc generator driving a 5kwh pack and a 100kw main motor LiFePO4 cells will easily take a 20C discharge rate which is pedal to the floor, how many times do you see a mail truck burn out? Most of the time its idling and burrrr twenty feet next mail box and screech to a halt only to burrrr at 1200 rpm to the mext mail box. Absolutely ideal for a series hybrid. For those routes that you know for sure are under 40 miles a 10kwh pack could cover the distance with out even needing a generator go full EV for those routes. The small 500cc genny removes the range anxiety set it up to be flexfuel easy to do with modern ECU and fuel injectors so you can run it on ethanol,methanol,butanol or any combo of those are biofuels makes the greens happy and much lower emissions than petrol. Better yet put a small CNG tank and run the 500cc off landfill or sewage treatment plant methane again the greens are happy. CNG is a hundred times cleaner than liquid petrol in particulates, twice as clean vs NOx, and has zero sulfur dioxide. Clean air friendly and oil lasts twice as long due to no fuel dilution or particulates on the rings or cylinder walls with gas based fuel. You could also use propane or butane to get the same effects.
This chart shows efficiency band larger at lower rpms.
EV HVH410 electric motor efficiency Credit: BorgWarner
