GetOffYourGas
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Re: Regenerative braking - why have the option to NOT have this?

Wed Aug 03, 2016 6:58 am

Nissan removed the 80% charge option in 2014. It made the car look better on paper.

The EPA took the average of the range at 80% and 100%, and put that on the sticker. 11/12 Leafs are rated at 73 miles, 13 at 75 miles, and 14+ at 84 miles. The battery didn't change in 2014. Nissan just removed the option to charge to 80%. Voila! The sticker range jumped from 75 miles to 84 miles!

I really hope Nissan brings back the option for the Leaf 2
~Brian

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jjeff
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Re: Regenerative braking - why have the option to NOT have this?

Wed Aug 03, 2016 7:59 am

GetOffYourGas wrote:Nissan removed the 80% charge option in 2014. It made the car look better on paper.

The EPA took the average of the range at 80% and 100%, and put that on the sticker. 11/12 Leafs are rated at 73 miles, 13 at 75 miles, and 14+ at 84 miles. The battery didn't change in 2014. Nissan just removed the option to charge to 80%. Voila! The sticker range jumped from 75 miles to 84 miles!

I really hope Nissan brings back the option for the Leaf 2

Thanks for the info, I knew the newer Leafs didn't have the 80% always like the '13's but I thought they still had it using the timer like on the '11 and '12s.
I agree it would be nice to have it back on the next gen Leafs and hopefully like Tesla does it where you can select from more than just 80%. It would also be nice to have the ability to regulate the amount of regen you want, like I've read you can do on the Teslas. That would be the best, people that didn't like regen could turn it way down and those that like a lot could turn it up, give us the choice Nissan.
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GetOffYourGas
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Re: Regenerative braking - why have the option to NOT have this?

Wed Aug 03, 2016 8:05 am

Tesla gets all of this correct because they approached EVs from a clean slate. They did what made sense given the nature of the battery / motor / regen / etc systems that they had.

Nissan et. al. got this wrong because they approached EVs as just another car. So they went out of their way to make it behave like any other car in their lineup. As a result, we lose access to a lot of the potential that an EV drivetrain offers. On the flip side, there is less of a learning curve to initiate drivers into an EV. It's a tradeoff.

I don't mind the "default" behavior of the car being that it acts like an ICEV. I just hope that more cars give us the option to change that if we desire. The eGolf is a good step in the right direction.
~Brian

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JCPanosh
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Re: Regenerative braking - why have the option to NOT have this?

Fri Sep 02, 2016 10:37 pm

As a first EV, I love my Nissan Leaf, but things like this regen issue really baffle me. Let's take a look at 6 years down the track.
2010/11 Nissan create this car and it is the first one. there is a lot of consultation but in their wisdom they decide to build it "like" an ICE so that it does not alienate people, but then they do a futuristic (at the time) design, so that alienation happened anyway, so they should have either built it looking like an ICE or they should have built it working like an EV. Fast forward 6 years and the car does not look all that futuristic, so better acceptance (but it has not appreciably changed in style, either). But the car does not have all the EV features it could have, either. Very little development of the way the car drives or can be tweaked. Apart from B mode regen, what else has changed?

It's all software. In 6 years you could employee a programmer and let them run amok with the system, it is a really cheap investment and could pay big dividends. Just listen to the community and see what ideas work. So why does it feel that has not been done? Probably because the computer system is really small? not much storage, not much CPU power? no idea as I have never seen specs for that part. Maybe it is just an Android type tablet (probably not, but certainly possible).

So here's my input to the regen discussion. I have a 2012 model in Australia. Sounds very similar to the Chinese model but mine does not remember I was last in ECO mode, I have to double shift everytime to put it into ECO mode. I'll see if there is a firmware upgrade at my next service, doubtful, but maybe lucky and this is added. It's just software, so why not give me s settings option to ask what mode I want to be in? Too easy, probably don't understand what it is when I first drive the car, but two days later I would be going to that option and changing it to my preference.

Same with regen. Ok, so new car has "D', "B" and "ECO", where ECO can be combined with B or D. Again, it is just a software parameter I suspect, so why not give us s settings option? D mode regen - Off, Low, Medium, High. B mode regen - Off, Low, Medium, High. If the regen works on kw (0-24) and has a resolution of 6kw, then those options make good sense. My model has D and ECO, so I just set mine accordingly.

Let's look at Cruise Control. Plenty people tell us there is an energy penalty because of it. I agree, it works like an ICE cruise control and not like a low range EV where every kw counts. The cruise control aggressively tries to maintain the speed, mostly. So if it drops below speed it kicks in and gets up to speed again. In D mode that is great, just what I want D to do, be responsive and snappy. But it does the same thing in ECO mode, not what I want. In ECO it should increase power until there is acceleration and then hold it or back off. I don't care if it takes 1 minute to go from 50 back to 60 (ok, maybe a little bit faster), but I don't need to get from 50-60 in 1 second when I am in ECO mode.

Going downhill with Cruise Control is a disaster. Puttering along at the speed limit and hit a steep downhill, regen kicks in to slow the car down but it is only about 10kw, so the car just keeps on building up speed, almost double the limit by the time I decided to override it and use the brake pedal, guess what regen went to 20kw and slowed the car down. Surely the program should be "keep applying regen amont until we either slow the car down to the limit or we reach maximum regen"? If I use Cruise Control I want the car to maintain a set speed, within reason, not let it get out of control (faster down a hill or slower up a hill).

Now the issue of the 100% battery and regen. On my 2012 the regen starts to work at about 90% battery (as reported by LeafSpy SOC). My Leaf only charges to about 93% (82% SOH), so I get to 90% pretty quickly once I start driving. At 90% the regen is very small, maybe the 6kw mark (one bubble), certainly not over 10kw. When I get to 80% SOC the regen can go to 30kw as you see it reported on the energy screen. no matter what the SOC I rarely see it go about the 30kw marker, but it can do that (not sure of the exact conditions yet). Ok. so if the regen has nowhere to go, then dumping the excess into the heater element would be one option (that can take a bit of power). The SOC drops reasonably quickly and the regen can go into the battery fairly quickly. The other option is just a big ol' resistor or heat sink. Obviously these are good cold weather solutions, maybe not so useful in the Summer. Friction brakes dump heat everytime they are used, so maybe there is a method to dump the heat for excess regen in the same sort of way. It should be very transitory as the SOC gets to the point where the battery can be recharged will be reasonably quick.

For that poster who lives at the top of the hill, without the 80% charge cut-off option (2012 has this as part of timer option, manual override goes to 100%) your only option is to calculate the time to charge to x% and then unplug when you reach that time. I think one poster suggested using an end timer, but you need to set the end timer to a time after you actually would leave, eg: leave at 8:00am, set end timer to 8:30 or 9:00, then the charge is that much less than 100% when you actually leave because the charging is trying to get to 100% by 8:30 or 9:00 but has actually only gotten to 80% or 90% by 8:00 when you leave. Pretty simple but does not work if you don't know when you will leave or you are trying to maximise off-peak power (my off-peak finishes at 7:00am, but I leave at 8:00am, so no good for me to do it thks way).

Imagine if someone (listening Nissan?) made their software open source. Maybe restricting access to critical system parameters so you could not (for instance) disable the brakes, but allowing all the other parts of the system to be tweaked. Look at what reverse engineering LeafSpy has achieved, and I am sure if those people had access to the source of the system they would have made a program 10 times better than it is. Maybe they could inject codes onto the CAN or EV bus so I could set my own regen values. The possibilities would be interesting and potentially the Leaf would be a better car because of all the development this side of the system would get.

Now, if only I could make the heater work using ECO settings when I am in D mode...

Tsiah
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Re: Regenerative braking - why have the option to NOT have this?

Sat Jan 07, 2017 1:16 pm

garsh wrote:I've said before that I'd like to add a big-old resister. Whenever the battery is too full, shunt the regenerated power to the resistor. That way you always have full regenerative braking available, and the brake performance can always be the same, instead of having diminished regenerative braking when the battery is full.

But that's an extra expense, and you have to figure out how to safely dissipate the generated heat.


That's how trains do it... Massive braking resistors!

Nubo wrote: The alternative That is what diesel-electric locomotives use. REALLY big ones. Converts the excess electricity into LOTS of heat.

Light rail trains do it too. Much better braking than the friction brakes can do.

garsh
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Re: Regenerative braking - why have the option to NOT have this?

Sun Jan 08, 2017 2:33 am

Tsiah wrote:That's how trains do it... Massive braking resistors!

Yeah, I worked at GE Transportation Systems for five years building locomotives. ;)
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Durandal
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Re: Regenerative braking - why have the option to NOT have this?

Mon Jan 09, 2017 10:58 am

The fact that most of these changes that we want could easily be configured via software, but Nissan doesn't seem very interested in adding any of these feature sets is rather bothersome. Annoying, I would even say. Nissan isn't too keen on "fixing" anything unless it is absolutely necessary. Their continuously variable transmissions are a good example, expanding the warranty on them in the 2000 era models, but not for the 2014 era. Ours went out at 45,000 miles, and they pretend like their CVTs don't have issues. It wasn't until ours was completely failing that they replaced it, even though it exhibited symptoms of failure long before then. :x
Pulled the trigger on going EV on 10/2016 with a 2012 Leaf, and a Tesla Model 3 reservation expected to receive in late 2018.

gene
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Re: Regenerative braking - why have the option to NOT have this?

Tue Jan 17, 2017 2:00 pm

Durandal wrote:The fact that most of these changes that we want could easily be configured via software, but Nissan doesn't seem very interested in adding any of these feature sets is rather bothersome. Annoying, I would even say. Nissan isn't too keen on "fixing" anything unless it is absolutely necessary. x
This shows the contrast between Nissan and Tesla. Amazing to me is how much time Tesla spends following the Tesla forums. Many of the ideas forum members bring up on the Tesla forum end up being implemented by Tesla often in the form of over the air software updates.
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IssacZachary
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Re: Regenerative braking - why have the option to NOT have this?

Thu Jan 19, 2017 2:27 am

Too bad there isn't a plug and play ultra capacitor pack solution. An ultra capacitor pack would take a lot of stress off of the traction battery. If set up right, the battery probably would never see any regen current and would never see any high acceleration current. It would basically just trickle feed the system, putting out around 15kW maximum. The ultra capacitor pack would usually soak all the regen current and then give most of the acceleration current. You'd never need to worry about your battery's temperature or state of charge. It would have full regen capability in nearly every situation except going down a long hill with a fully charged battery.
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Re: Regenerative braking - why have the option to NOT have this?

Fri Jan 20, 2017 2:00 pm

My challenge with regen is in living at the top of a 700' hill with a steep, twisty 2 mile gravel road. If I have room for regen, it only really works if I stay off the brake pedal. As soon as I start controlling speed with the brake pedal, the system fades regen out and goes entirely friction due to unequal wheel speeds on gravel (regen is front wheel only). That is the proper choice for safety, so I'm not complaining there. As well, it's better than the sudden ABS cutout of regen on hybrids I've experienced, where you feel an abrupt decrease in braking and must depress the brake pedal further to compensate. My LEAF blends it far better.

Descending that hill gives me at most a net 0% energy use due the the gravel. After a couple of small hills on the way down I start getting one bubble of regen at the bottom, but that's about it. Going back up, it uses about 3% SOC on my 30 kWh pack.

In the end, the massive disc brakes dump the kinetic energy into heat, and we need friction brakes anyway, so adding dynamic motor braking via a resistor bank and fans would seem to be extra complexity for minimal functional gain. I do happily run the climate control on the way down, though.

I'd still prefer the option to limit charging to a percentage I select so I can charge at the top of a hill and recover some energy heading back down. In the end, though, I realize it wouldn't be all that much of a net gain.
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