dhanson865 wrote:I did my 12 hour trip with a lot of L2 charging on a 3.6KW car
ok, makes sense. in my case i was nearly 100% DCQC (aside from two L2 charges at 3.6kW specifically where the nissan owned infrastructure was dead and i couldn't make it to the next DCQC without some help)
Something to keep in mind on your 100+ mile trips.
The charging speeds of L2 and chademo in mph are
L2 16a (3.6KW charger in the car) about 11 mph
L2 27.5a (6.6KW charger in the car) about 22 mph
old Chademo about 80 mph
new chademo faster than you care about.
the 6.6kW charge times don't affect me (my used leaf is a 2012 SL with only the 3.3kW onboard charger and no way to upgrade)
but wait: "new chademo"?? i didn't know there was such a thing. can you link to an example in plugshare/similar so i can see what to search for?
Now think that those speeds are miles per you sitting still for one hour, meaning if you charge at 22 mph, you are sitting still for 4 hours to drive 88 miles (at 60 mph that is 88 minutes). That means your total speed for that leg of a trip is 88/328*60 or 16 miles per hour.
i'm sorry, but i dont' see where that "328" is coming from?
the numbers you provided seem to use ~25kw as the average for a DCQC session and i've seen similar numbers elsewhere. in fact that's what i used to plan my trip.
25kW * 1hr = 25kWh; @3.6mi/kWh that gives me a charging rate of 90mph (somewhat optimistic compared to your numbers, but not much and it is based on my actual mi/kwh rating which was spot on with my expected rating when planning the trip)
to travel beyond my battery range i figured on the following formula:
[time spent charging] = [total distance - initial range]/[90mph]
for my troublesome trip each leg was 107 miles so round trip was 214. i estimated my initial range at 64 miles from 100% SOC. so the formula worked out at:
[time spent charging round trip] = [(214mi - 64mi) / 90mph] = 1.67hr
or for the first leg:
[time spent charging first leg] = [(107mi - 64mi) / 90mph] = 0.48hr
clearly i expected to spend more time charging on second half than on the first half of the trip.
[total drive time] = [charge time] + [distance/velocity]
for the first leg i figured that would be: [0.48hr] + [107mi/60mph] = 2.26hr
for the return trip i figured it would be: [1.67hr - 0.48hr] + [107mi/60mph] = 2.97hr
I planned for an additional 30 minutes each way in case my mi/kwh were significantly lower than initially planned, so my "flight plan" included two 30 minutes stops on the first leg and a total trip duration of ~3hrs.
actual chademo charging rates were much slower for me, taking 1hr+ where i expected only ~0.5hr. i also charged more often than planned. this, coupled with hunting for a charger that wasn't out of order (on both legs) put my actual driving time in each direction at ~6hrs.
If you drove 50 instead of 60 you'd spend less time charging and your average speed would increase.
this makes sense too. though the ratio of driving to charging time is less important than the total duration of the trip. taking it to the extreme i could drive ~20mph the whole way and get close to 5mi/kwh to drastically improve my driving:charging ratio... but it would be slower than riding a bicycle (where i never have to stop to charge and would stop to eat/etc about the same frequency).
using the above math:
[initial range scaled by 5.0/3.6] = [64mi] * [(5.0mi/kWh) / (3.6me/kWh)] = 88mi
[25kW*1hr] * [5.0mi/kWh] = 125mph rate of charge.
[time spent charging round trip] = [(214mi - 88mi) / 125mph] = 1.0hr
[time spent charging first leg] = [(107mi - 88mi) / 125mph] = 0.15hr
i would spend less time charging but more time driving:
[total duration] = [1.0hr charge time] + [214mi / 20mph] = 11.7hr
so the net result is the same trip duration, more or less. i'm jot sure i could have found backroads as direct as the highways i was on (so distance may have increased) and surely all the stop lights and city traffic would have lowered my mi/kWh rating (i would have driven right through Boston and surrounding urban areas).
In fact if you drove 30 mph instead of 60 you'd get there quicker assuming the trip is long enough that you can't make it on a single charge and you have to charge on L2 with a 6.6KW charger.
funny that i just wrote out a 20mph equivalent to this comment based on DCQC. i can't charge at 6.6kw so the ratios are different for me but based on the above i doubt my total trip duration would have improved by driving more slowly.
If you have a Chademo or multiples to use along the way it will be faster to keep up with traffic but if you have to charge at L2 for any reason you are better off slowing down, you'll get there sooner driving slow.
thankfully i did find chademos along my route. with a 3.3kW L2 charger i wouldn't have risked the drive at all without knowing before hand that there were a good number of chademos along the route. now if only the chargers at nissan dealerships were dependaly functional and not parked in by dealership owned inventory.... yeah i am still frustrated by that and i'll repeat that Coastal Nissan deserves a cold shoulder from EV drivers and potential buyers. apparently it is quite normal for them to park ICE inventory in the EV spots and if you get there after hours there is no one around to move them out of the way.
It'd take a lot of math to determine the exact ideal speed because efficiency is best around 12 mph and you likely want to drive 3 to 5 times that fast. The practical option is to drive as slow as you can without causing an accident if you know you have to drive to an L2.
the absolute best mi/kWh rating i've gotten over a 10+ mile trip, even driving <20mph on backroads, was 5.2mi/kWh. i can just about hit 5.0mi/kWh if i drive carefully even up to ~30mph, but i have to annoy the folks behind me as i slowly stagger away from stops or cruise to the next stop without using my brakes.
in my experience there doesn't seem to be any gain for driving less than ~20mph and nearly zero difference between 20 and 30mph. above 30 and i do see an immediate drop in mi/kWh. i haven't tracked how the lower end of the ratings scale at speed though since i so rarely drive on highways (and when i do i'm generally on a trip that is more important to me than tracking these things for future reference).