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Re: Nissan Engineering Team Visit Dec. 3rd: Recap

Posted: Tue Dec 06, 2011 10:12 pm
by TurboFroggy
On the DTE meter topic: my 2000 Ford Ranger EV has a pretty darn accurate DTE guage. It doesn't jump around like our Leaf's does, it is rock solid and very accuate. I think how Ford does it is measue the KWH in/out from the pack then make a judgement based on the power draw with lots of averaging/samples. This smooths out the DTE meter reading and makes a much more sane and accuate reading.

Maybe Nissan should study one of the older Ranger EVs as Ford had this figured out 10+ years ago... :mrgreen:

Re: Nissan Engineering Team Visit Dec. 3rd: Recap

Posted: Tue Dec 06, 2011 10:40 pm
by EricBayArea
I'm not an engineer but part of the issue that was raised was that the batteries are multiple, and not one singular unit. In addition, they do not have individual monitoring that would be necessary to accurately determine their charge... or at least something like that.

Re: Nissan Engineering Team Visit Dec. 3rd: Recap

Posted: Tue Dec 06, 2011 10:50 pm
by Herm
Poppycock!

they need to smooth it out, people drive the same way every day, it averages out.. just use an average number for miles/kwh and keep track of the remaining capacity.. easily done to +/- 5%. It wont be long before someone programs a phone to display that using the can-bus 281 field.

Re: Nissan Engineering Team Visit Dec. 3rd: Recap

Posted: Tue Dec 06, 2011 11:02 pm
by cwerdna
Herm wrote:Poppycock!

they need to smooth it out, people drive the same way every day, it averages out.. just use an average number for miles/kwh and keep track of the remaining capacity.. easily done to +/- 5%.
When I was at the front of the room w/several others (pretty sure w/Mark Perry) after the meeting was over, my recollection was that he said the GOM used to jump around all over the place and that the TSB referenced smoothed it out. Hopefully someone else can either correct or confirm the conversation and elaborate more...

As for "people drive the same way every day", you can't make the assumption. Cars can be switched between different drivers and cars don't always follow the same routes. This gets back to the problem of predicting the future... My Prius has been going on totally routes and to different destinations all over the place, if you looked at my drives over the past few weeks.

Re: Nissan Engineering Team Visit Dec. 3rd: Recap

Posted: Tue Dec 06, 2011 11:36 pm
by TonyWilliams
TurboFroggy wrote: I think how Ford does it is measue the KWH in/out from the pack then make a judgement based on the power draw with lots of averaging/samples. This smooths out the DTE meter reading and makes a much more sane and accuate reading.

Maybe Nissan should study one of the older Ranger EVs as Ford had this figured out 10+ years ago... :mrgreen:
You recognize that Gary's SOC meter does not do anything more fancy than display Nissan's data? They already have that info.

Re: Nissan Engineering Team Visit Dec. 3rd: Recap

Posted: Wed Dec 07, 2011 1:31 am
by Herm
cwerdna wrote: As for "people drive the same way every day", you can't make the assumption. Cars can be switched between different drivers and cars don't always follow the same routes.
Sure you can, most people drive to work everyday using the same route, at the same time, in the same traffic jam, and at the same speed, and usually the same person is driving that car.. obviously for a small minority this wont work.

How would a GOM that uses a 2 week average impact you?.. is there another way to satisfy your special needs for those special days?

Re: Nissan Engineering Team Visit Dec. 3rd: Recap

Posted: Wed Dec 07, 2011 1:35 am
by TonyWilliams
Herm wrote: How would a GOM that uses a 2 week average impact you?.. is there another way to satisfy your special needs for those special days?
Have an "expert" page on the nav that you can select data for you future trip.

Re: Nissan Engineering Team Visit Dec. 3rd: Recap

Posted: Wed Dec 07, 2011 8:47 am
by TEG
TurboFroggy wrote:On the DTE meter topic: my 2000 Ford Ranger EV has a pretty darn accurate DTE guage. It doesn't jump around like our Leaf's does, it is rock solid and very accuate. I think how Ford does it is measue the KWH in/out from the pack then make a judgement based on the power draw with lots of averaging/samples. This smooths out the DTE meter reading and makes a much more sane and accuate reading.

Maybe Nissan should study one of the older Ranger EVs as Ford had this figured out 10+ years ago... :mrgreen:
My 2000 Ford Ranger DTE isn't 100% linear. Sometimes it will drop quicker than usual in the bottom half of the range and cause a bit of range anxiety. At least in part, I concluded the following:
#1: If you leave the car off charge sitting for a while (many days / weeks) then the aux battery gets drained.
#2: If you then drive, the DC/DC has an extra traction pack load to recharge the aux battery.
#3: As a result the DTE starts dropping quicker on that trip than usual.
I got in the habit of making sure I would always put it back on charge for a while just before driving it.
I also noticed that the DTE could start dropping quicker when it got cold out.
But, yeah, a lot more smoothed out, and more of an estimate than the GOM.

Re: Nissan Engineering Team Visit Dec. 3rd: Recap

Posted: Wed Dec 07, 2011 9:01 am
by TEG
cwerdna wrote: When I was at the front of the room w/several others (pretty sure w/Mark Perry) after the meeting was over, my recollection was that he said the GOM used to jump around all over the place and that the TSB referenced smoothed it out. Hopefully someone else can either correct or confirm the conversation and elaborate more...
Yes, I was there. Heard the same. I mentioned "maybe a longer history of data, and more smoothing would help some."

I had a conflicting thought:

#1: Having a raw number to remember is handy as you get out of the car and walk somewhere for a while.
(e.g., Remembering to self that I have 50 miles range available as I ponder my next trip in the car.)
#2: Having a numeric value makes it seem like fact then it lets you down if you don't actually achieve that number.

So in some ways, a gas gauge style needle instead of a raw number might help avoid people getting so "up in arms" over the inaccuracy of the number even thought it isn't as memorable as a specific number.

By the way, using the RangerEV as and example again, it has a needle, not a specific number, which made it clear it was an approximation. Gas cars tend not to have a "distance to empty" indicator at all, so perhaps it makes sense to only show approximate "amount of fullness" of the battery, and not even try to project range? (From the gas days: "Hey, how far can we go?"..."I don't know exactly, but I have only 1/4 tank so we need to think about stopping for gas if we want to go someplace far.")

Another idea - if they had the screen real-estate to support it, they could have the "min/max" circles on the NAV map showing projected driving range that way all the time instead of a numeric gauge. It makes it clear it is an estimate, and gives you and idea of your possible trip area without showing a specific number.

Re: Nissan Engineering Team Visit Dec. 3rd: Recap

Posted: Wed Dec 07, 2011 9:36 am
by JohnOver
Herm wrote:
cwerdna wrote: How would a GOM that uses a 2 week average impact you?.. is there another way to satisfy your special needs for those special days?
How about a modification of that thought... When the car starts up it uses a long-term average (2 weeks?). It then uses the same algorithm that it uses now for the rest of the driving cycle.

This would solve the issue I have with the DTE calculations. Every morning, I drive 35 miles to work. The first 11 miles are a descent down 1800', then freeway driving after that. On the return trip, it's 24 miles on the freeway then 11 miles climbing 1800' (at 60 MPH, or I'll be killed).

This causes the DTE to calculate incorrectly twice a day. Every day when I get in the car at home (getting ready to go down hill) it thinks I'm still going to be climbing 1800' at 60 MPH. When I get in the car at work, it has forgotten about yesterday's uphill, and is now overestimating my range based on the morning commute.

Kadota-san are you listening?