# [EVDL] leaft one-year experience



## EVDL List (Jul 27, 2007)

You made a mistake in your math: when going downhill, you are losing 2kW to
drag/friction and putting 8kW back into the batteries, so the motor is
generating 10kW overall. On uphill, you do 18-2=16, so on downhill you
should do -8-2=-10.

That gives you an efficiency of 10kW/16kW = 62.5% That sounds quite good to
me.

85% is quite good efficiency for converting mechanical energy back into DC
electrical energy in real-world driving conditions. Then after that, you
see further losses in the battery and converting back to mechanical energy.

Assuming the battery itself is 85% efficient (7% voltage sag on drive and
7% voltage rise on regen) and the motor/controller are also 85% efficient
while driving (which is much better than series-wound efficiency), you
would expect to see a total efficiency of mechanical on regen to mechanical
on drive of 0.85*0.85*0.85 = 61%. You're actually seeing about 62.5%
efficiency; that looks about right to me.

Considering brake pad use, this varies quite a bit with how hard you brake;
braking more softly over a longer distance will put less wear on the pads.

-Morgan LaMoore




> Peri Hartman <[email protected]> wrote:
> 
> > I've had my leaf for a year now and took it for the one-year service, which
> > is required for the warranty. All the tests they did scored perfect. And
> ...


----------



## EVDL List (Jul 27, 2007)

> Peri Hartman wrote:
> 
> > Anyone care to comment on this? Am I expecting too much?
> 
> ...


----------



## EVDL List (Jul 27, 2007)

Sorry, I worded that poorly. The motor isn't generating 10kW, the incline
is giving you a push equivalent to 10kW.

On drive, you are spending 18kW from the pack to fight the incline and
friction. Fighting friction takes 2kW, so you are spending 16kW to fight
the incline.

On regen, the incline is accelerating you and is fighting friction and
regeneration. Fighting friction is electrically equivalent to 2kW and the
motor adds a farther 8kW of load (plus inefficiencies), so the incline is
helping you with the equivalent of 10kWh.

That is where 10kW/16kW = 62.5% efficiency comes from.

-Morgan LaMoore



> Morgan LaMoore <[email protected]> wrote:
> 
> > You made a mistake in your math: when going downhill, you are losing 2kW
> > to drag/friction and putting 8kW back into the batteries, so the motor is
> ...


----------



## EVDL List (Jul 27, 2007)

Just for reference, Bob Rice told me that he had 150k miles on his Prius
without brake pad replacement.

George Swartz







> You made a mistake in your math: when going downhill, you are losing 2kW
> to
> drag/friction and putting 8kW back into the batteries, so the motor is
> generating 10kW overall. On uphill, you do 18-2=16, so on downhill you
> should do -8-2=-10.
>
> That gives you an efficiency of 10kW/16kW = 62.5% That sounds quite good
> to
> me.
>
> 85% is quite good efficiency for converting mechanical energy back into DC
> electrical energy in real-world driving conditions. Then after that, you
> see further losses in the battery and converting back to mechanical
> energy.
>
> Assuming the battery itself is 85% efficient (7% voltage sag on drive and
> 7% voltage rise on regen) and the motor/controller are also 85% efficient
> while driving (which is much better than series-wound efficiency), you
> would expect to see a total efficiency of mechanical on regen to
> mechanical
> on drive of 0.85*0.85*0.85 = 61%. You're actually seeing about 62.5%
> efficiency; that looks about right to me.
>
> Considering brake pad use, this varies quite a bit with how hard you
> brake;
> braking more softly over a longer distance will put less wear on the pads.
>
> -Morgan LaMoore
>
>
>


> Peri Hartman <[email protected]> wrote:
> >
> >> I've had my leaf for a year now and took it for the one-year service,
> >> which
> ...


----------



## EVDL List (Jul 27, 2007)

Answers and comments:
- I did this in "D" mode. I have not been able to detect any difference in
energy use between "D" and "Eco". Yes, you have to press the accelerator
further in Eco, but the the results are the same. And, there's a bit more
coasting regen in "Eco", but if you tap the brakes it seems you can get the
same amount of regen - sometimes. Very hard to tell.

- Willie, if you are able to normally coast to stops, then you probably
aren't using regen very much. That's ideal, but something I can't
realistically achieve in city driving. I really need regen to be as
effective as possible.

- Morgan, I see your point. So, yes, it seems I should be using 8kw for the
actual regen power. And 62% does sound better. The part I can't reconcile
is why I have so much brake wear.

Break wear: I'll speculate here. After considering the regen is 62, maybe
70% efficient, I need to look at other scenarios. Realistic driving for me
isn't constant 25mph. I start & stop, change lanes, accel up steep hills,
etc. I wonder at what threshold regen kicks out and brakes apply? I bet
I'm braking hard enough to disable regen. 

Anyone else notice anything about regen cutting out?

Peri

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Morgan LaMoore
Sent: Friday, June 22, 2012 9:00 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] leaft one-year experience

Sorry, I worded that poorly. The motor isn't generating 10kW, the incline
is giving you a push equivalent to 10kW.

On drive, you are spending 18kW from the pack to fight the incline and
friction. Fighting friction takes 2kW, so you are spending 16kW to fight
the incline.

On regen, the incline is accelerating you and is fighting friction and
regeneration. Fighting friction is electrically equivalent to 2kW and the
motor adds a farther 8kW of load (plus inefficiencies), so the incline is
helping you with the equivalent of 10kWh.

That is where 10kW/16kW = 62.5% efficiency comes from.

-Morgan LaMoore



> Morgan LaMoore <[email protected]> wrote:
> 
> > You made a mistake in your math: when going downhill, you are losing 2kW
> > to drag/friction and putting 8kW back into the batteries, so the motor is
> ...


----------



## EVDL List (Jul 27, 2007)

> Peri Hartman wrote:
> 
> > - Willie, if you are able to normally coast to stops, then you probably
> > aren't using regen very much. That's ideal, but something I can't
> ...


----------



## EVDL List (Jul 27, 2007)

On 6/22/12 9:59 AM, [email protected] wrote:
> Just for reference, Bob Rice told me that he had 150k miles on his Prius
> without brake pad replacement.

Very believable, and a lot depends on how you drive. I have almost 200k 
on a Honda Civic VX with no brake pad replacement (and of course no 
regen available as it's not an electric vehicle but I do use engine 
braking). As with my EV I drive the Honda for efficiency, without racing 
to lights and stop signs, and with gentle brake usage when needed. It 
also helps that it's a relatively light vehicle.

Another factor for an EV is charge level. If a Leaf is charged to 80%, 
there's immediately still room to store some regen energy, but if it's 
charged to a higher percentage there's less immediate available battery 
capacity for regen.

Cheers,
-Jamie


> George Swartz
>
>
>
>
>
>
>
>> You made a mistake in your math: when going downhill, you are losing 2kW
>> to
>> drag/friction and putting 8kW back into the batteries, so the motor is
>> generating 10kW overall. On uphill, you do 18-2=16, so on downhill you
>> should do -8-2=-10.
>>
>> That gives you an efficiency of 10kW/16kW = 62.5% That sounds quite good
>> to
>> me.
>>
>> 85% is quite good efficiency for converting mechanical energy back into DC
>> electrical energy in real-world driving conditions. Then after that, you
>> see further losses in the battery and converting back to mechanical
>> energy.
>>
>> Assuming the battery itself is 85% efficient (7% voltage sag on drive and
>> 7% voltage rise on regen) and the motor/controller are also 85% efficient
>> while driving (which is much better than series-wound efficiency), you
>> would expect to see a total efficiency of mechanical on regen to
>> mechanical
>> on drive of 0.85*0.85*0.85 = 61%. You're actually seeing about 62.5%
>> efficiency; that looks about right to me.
>>
>> Considering brake pad use, this varies quite a bit with how hard you
>> brake;
>> braking more softly over a longer distance will put less wear on the pads.
>>
>> -Morgan LaMoore
>>
>>
>>


> Peri Hartman<[email protected]> wrote:
> >>
> >>> I've had my leaf for a year now and took it for the one-year service,
> >>> which
> ...


----------



## EVDL List (Jul 27, 2007)

> Willie McKemie <[email protected]> wrote:
> > Since I've gotten the SOC/gid meter, I believe we have lost (or never
> > had) a significant amount of battery capacity. 100% charge gives
> > ~240 gids rather than the expected ~280 gids.
> ...


----------



## EVDL List (Jul 27, 2007)

> David Rees wrote:
> 
> > Sounds like you're on the MNL forums - I assume that you haven't lost
> > the 12th capacity bar yet? Out of curiosity - where do you live, what
> ...


----------



## EVDL List (Jul 27, 2007)

I think 85% is too low efficiency for LiFePO4 (not regen overall, the cells). 
When my car regens around 100-130A the pack voltage increase is on the order
of 4-5V, 36 180Ah cells, nominal 115V pack. Also, it doesn't have to be
below 80% SOC to have room for regen. With just 4-5Ah used it will take up
to around 60-70A regen without driving the pack V up to my User_Overvoltage
setting in the controller (which cuts out regen). With greater than 10Ah
used it will take well over 100A. It is not a Leaf -
http://www.evalbum.com/3060 - and it is set up for regen control with the
accelerator only. In normal driving I apply the mechanical brakes only at
stop lights/signs, and only when the car is going less than about 5-10 mph,
so you using your mechanical brakes much more than I am to get that much
wear. 

In addition to rolling resistance, air drag, and drive train losses, there
are also motor and controller losses during regen. I measured energy into
the pack during slowing with regen on level ground. The ratio of the energy
into the pack to change in car kinetic energy was 54%. Considering rolling
resistance and drag force losses, drive train (~10%), motor and controller
losses (~15% combined), it seems regen should be over 80%. That was with
outside temps in the 20's F, so higher drive train losses than in summer.

--
View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/leaft-one-year-experience-tp4655910p4655942.html
Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com.

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev


----------

