Peter,Glad to see your back.  Keep me in the loop for anything you find out 
about the CANbus hack for the Volt.  I havea 2014, best car I've ever owned! 

    On Friday, January 26, 2018 10:43 AM, Peter VanDerWal via EV 
<ev@lists.evdl.org> wrote:
 

 Date: Thu, 25 Jan 2018 09:40:23 -0800
From: "Cor van de Water" 
To: "Electric Vehicle Discussion List" 
Subject: Re: [EVDL] LiIon thermal management question (Chevy Volt)
Message-ID:
Content-Type: text/plain;  charset="us-ascii"

Peter,
Storing LiIion batteries is usually not the problem, although it is
recommended for long life to not store them fully charged, especially
not in hot environment.
Damage is done when (fast) charging in cold - the colder, the slower
they need to charge to avoid damage.
Nissan Leaf only has battery warmers, those will only come on when the
car is on or plugged in and below a certain temp (I believe -30)
I don't know about the Volt, it might simply stop maintaining the temp
when the EVSE is disabled, you can find out by simply trying and see if
the state of charge of the Volt changes when the EVSE is not enabled.
Cor. 
Thanks, Cor.
FWIW the Volt never allows the battery to fully charge or fully discharge.  
This means that even though it has an 18.4kWh battery, only 14kWh is available.
The thermal management does both heating and cooling.  From what I've read all 
(electrical) heating is done with resistance heaters, cooling is done with a 
heat pump (cooling mode only, i.e. AC)
'Fast' charging is also not an option.  While it does support Level-2 charging, 
it tops out at 3.6kW which is about 6% of the batteries maximum charge rate.

I suspect you may find that the Volt still uses energy to keep the battery 
within its desired temperature range, but simply uses battery energy instead of 
EVSE energy.  You should be able to detect that by watching the range after the 
car sits unplugged or the EVSE is disabled, compared to range after the car 
sits with the EVSE providing power overnight.

Mike
Thanks, Mike.
That's a good point.  I hadn't thought about it using the battery energy to 
maintain temp. 
I'll have to try leaving it unplugged and see what happens.  
However, I'm not sure if this would actually tell me anything.  It's possible 
that, even if it does use the batteries, I won't see a reduction in range right 
away.  It might just dig a bit more into the reserve so that it can provide the 
same 14kWh.
I gather that's what it does as the pack ages so that even after 6 years the 
'available' capacity remains the same as it was when new.
I'm far from a lithium expert, but I've read that while lead batteries lose 
performance at low temperatures, cold can wreck lithiums if you're not 
careful.  As I understand it, they should never be charged when their 
temperature is below freezing.  I think that even discharging them gets 
risky if they sink too far below 0 deg C.  

They also degrade faster (have shorter lives) when they get hot while fully 
charged.  They don't seem to like being fully charged at all.  The rule of 
thumb I read years ago for laptop batteries was that you should store them 
at 50-70% SOC. 

So I'd guess that thermal management is probably pretty important for your 
Volt's battery. 

BTW, welcome back to the EVDL, Peter.  It's been years since we've heard 
from you. Good to know you're OK.
Hi David, 
Yeah, it's been a while hasn't it?  I've been busy, but I have a new job that 
leaves me with a lot of free time, occasionally. 
Fortunately we rarely get below freezing and even then it's typically for only 
a few hours. Plus the Volt never allows the battery to get fully charged or 
fully discharged.
The geek in me wishes that Chevy would provided a way to get more detailed info 
about the battery, etc.  There is no SOC display, just a 10 segment display 
that shows how much of the allowed 14kWh you've used.  The predicted range 
display for a fully charged pack is not a constant, it varies significantly 
depending recent performance and possibly takes current environmental 
conditions into account.
There used to be a lot of information available through the OnStar link, but 
recently they have removed quite a lot of the data, including the data about 
battery level and charge state.
I've seen some folks are working on hacking the canbus to get at the data, so I 
might try that.
Thanks everyone.
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