The 2012 Leaf manual says this on Page EV-5 about freezing and heating.
The focus appears to be on the effects of reduced battery (power) output
at freezing temperatures, and the prevention of freezing of the lithium
battery. (With the main reason to prevent freezing related performance
issues.)
"The Li-ion battery heater helps to prevent the Li-
ion battery from freezing and helps to prevent
significant reductions in the Li-ion battery output
when the temperature is cold. The Li-ion battery
heater automatically turns on when the Li-ion
battery temperature is approximately -4F
(-20C) or colder. The Li-ion battery heater
automatically turns off when the Li-ion battery
temperture is approximately 14F (-10C) or
higher."
"The Li-ion battery heater does not
operate if the available Li-ion battery
charge is less than approximately 30%
and the charger is not connected to the
vehicle. To help prevent the Li-ion
battery from freezing, do not leave the
vehicle in an environment if tempera-
tures may go below -4F (-20C) unless
the vehicle is connected to a charger."
One thing is unclear...if one has an already frozen Leaf, and wants to
minimize the risk of any lithium plating issues during cold charging, is
it better to:
1.) connect an EVSE and hope the built-in heater will (evenly) bring
temperatures up before it actually begins charging, or
2.) wait for the Leaf to get somewhere above the ~0F mark, and then
connect the EVSE, at which point the built-in heaters and charger can
take over as it sees fit?
Knowing what we know about the Leaf's limited battery thermal management
capabilities, and what we've read about the effects of very low temps on
lithium cells, my guess is the second option is safer (if one doesn't
strictly need the car during the very cold period). For the Tesla Model
S, on the other hand, my guess is the liquid cooled/warmed battery
thermal management system will be able to keep things in a better
overall state, even if it were allowed to freeze.
(There is a subcategory of option 1...charge rate control. Perhaps using
an EVSE set to a low rate is preferable in very cold conditions as a way
to enforce that the charger doesn't force much current into the pack.
For the Leaf, 0.1C of the 24 kWh pack translates to 2.4 kW. The included
Level 1 EVSE is 120v 12a = 1440 watts, but can be upgraded to 240v 16a.)
-hk
On 01/06/2014 06:01 PM, Cor van de Water wrote:
David,
How much do your Lithium batteries heat up when charging? Do you have
measurements? From what I have heard and seen, the fact that Lithium is
typically charged between 20 and 80% for max life, there is no
significant heating in this range of SoC during charging. I am not sure
about the heat
produced above 80% but I suspect that the only significant heating is
from
bypass regulators in the BMS and they only come on *after* the cell is
done charging, so it does not help to avoid damage from occuring when
charging in the cold. I do have cells that heat up during charging, but
those are not Lithium.
Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.info
Skype: cor_van_de_water Tel: +1 408 383 7626
-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of David Murphy
Sent: Monday, January 06, 2014 3:18 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Charging Lithium Below Freezing
Well, I wouldn't interpret this as you can't use them. This is a data
point that says (1) charge current needs to lowered at lower temps (2)
that the manufacturer won't guarantee the cycle life if you charge below
0 degrees C.
So perhaps one should use a heater below 0C. And charge at lower current
in cold weather. The batteries will heat up while charging as well,
which should help
David
Sent from my iPhone
On Jan 6, 2014, at 1:02 PM, Mark Hanson <[email protected]>
wrote:
Message: 13
Date: Mon, 6 Jan 2014 11:13:52 -0800
From: David Murphy <[email protected]>
So does that mean you can't use Lithium below 0C / 32F ? That doesn't
make any sense for those who live in the northern latitudes & Canada. I
charge about .1C anyway (13 amps on CALB 130ah batts). I've charged at
20F but tonight it'll be 0F in VA. What about folks in Minnisota like
Lee? I guess they use battery heaters but I thought most chemistries
you could charge cold just take a bit longer due to higher internal
resistance.Best Regards,Mark
To: Electric Vehicle Discussion List <[email protected]>
Subject: Re: [EVDL] Charging Lithium below freezing, should I drive
my
gas car?
Message-ID:
<cahtzjazxhv3i2+ugau3ms_tyrnddvywyf2-dwjkt846nd7c...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
So the cells I am talking about are referred to as Lithium Ion
Polymer, not
sure if that is the same chemistry...
The specs for these type of cells define three temperature ranges for
charging. (cell temp, of course, not ambient)
from 0C to 10C
0.1C max Constant Current (CC) to 4.2V, 4.2C Constant Voltage (CV) to
0.05Cmin cut-off
10C to 23C
0.5 max CC to 4.0V, 0.2C CC to 4.2V, 4.2V CV to 0.05C
23C to 45C
0.5C CC to 4.2V, 4.2V CV to 0.05C
for discharge, the oeprating temp is -20C to 60C
Hope that's helpful...
david
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