[Oeva-list] Leaf battery
Theoldcars at aol.com
Theoldcars at aol.com
Sat Apr 30 14:49:48 PDT 2011
The Leaf software update is also said to help give more accurate dash
range according to Nissan.
The Peukert effect does have a very large impact on lead acid batteries
but little on lithium.
For anyone not aware of the Peukert effect. It is when you drain a battery
at higher loads you lose capacity. For example if you take a 100 Ah lead
acid battery that rating is usually arrived at with a 5 amp load for 20 hours
5 amps X 20 hours = 100 amp hours. This is not the amp rate you use
driving an EV but a 20 hour time a common rating of lead acid batteries. .
If you take that same 100 amp hour lead acid battery and put it under an
EV load of 50 amps it will last only about one hour 1 hour X 50 amps = 50
amp hours. Take a 100 amp hour rated lithium battery and your actual
capacity is not much less then the rating. See discharge curve at this link
Note that even at 100 amp hour rate your able to still get 100 amp hours
but the cell voltage is less. This shows that the cell is able to deliver the
same rated capacity but it is being done at a lower voltage. The voltage
drop off increases as the state of charge decreases. Just like all
batteries your cycle life will be less with higher loads and the impact will be g
reater with higher loads in a lower state of charge.
Nissan recommends using the pack between 50 to 80 percent state of charge
for maximum life. I have set my Leaf to charge to 80% and I try not to go
under 50 miles of range. You don't have to do this but if you can it will
give you the very longest pack life. I would not be surprised if the pack
would be good for 150,000 to 200.000 miles doing so.
Date: Fri, 29 Apr 2011 18:20:12 -0700
From: Alan Batie <alan at batie.org>
Subject: [Oeva-list] Leaf battery
To: oeva-list at oeva.org
Message-ID: <4DBB63CC.70006 at batie.org>
Content-Type: text/plain; charset="iso-8859-1"
I've been looking at the Carwings data for that trip to Portland a
couple weeks ago, and either the estimator is being awfully conservative
(which would make sense except for the reports of people running out of
juice early), or the energy consumption sensor/calculation Carwings is
using is faulty, or the battery is smaller than they say:
Battery spec: 24kwh
Carwings report for the return from McMinnville (where it got a 100%
charge that Sunday): 11.7kWh 48.6miles 4.2miles/kWh
Range estimator/battery gauge: 66% (27 miles remaining)
kwh capacity derived from usage: 11.7/.66 = ~18kwh
The 66% is consistent with 27 miles remaining after going 48 miles.
I'm guessing Peukert at work...
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