RodHam
Posts: 26
Joined: Wed Dec 16, 2015 7:50 am
Location: Montreal Quebec

Battery Temperature, isn't 20c the sweet spot?

Tue Dec 22, 2015 5:58 am

I decided to check the battery temperature after preconditioning for my usual departure time of 6:10AM. The car is connected to a Juicebox Pro 40, the car is fully charged thru the night and at precisely 3hrs to departure time the EVSE indicates a draw of 0.7 kW as the car starts testing or whatever it does towards preconditioning. The outside temperatures was a balmy 4c and at 6:10AM I disconnect the EVSE, start the car and unlock the service menu to see the battery temp, which was only 10 Celsius! I thought that the battery performs best at 20c.

The Juicebox Pro 40 shows a temp of 15 to 20c during charging but I failed to notice the temperature on the Juicebox application during preconditioning, will check it tomorrow morning.

Is there a reason why my battery is only 10c and all online specs say 20c is the best operating temperature?
Rodney
2015 i3 BEV Lodge with winter tire kit. Juicebox Pro 40a EVSE
2005 Honda S2000
1976 GMC Palm Beach motorhome

janner
Posts: 235
Joined: Sun Jan 25, 2015 5:24 am
Location: Bath, UK

Re: Battery Temperature, isn't 20c the sweet spot?

Tue Dec 22, 2015 10:22 am

Rodham - Very interesting post. How did the 0.7kW vary throughout the three hours of Precon and what happened when the cabin heating started up?

Our local BMW i3 R&D guy said that the battery pre-con heater was 1kW but there is a larger spike of power than this when my car precons albeit over the three hours I typically use from 1 to 1.5 kWHrs. Others seem to use more energy than this and I have seen some claim that as much as 5kWHrs can be used - bit surprising to me.

On battery temperature I suspect that the preconditioning gets the battery into the 'comfort zone' of 10 - 25 deg C and once driving the battery will reach 20 deg C before the cooling system cuts in.
2015 i3 ReX Solar Orange, Loft interior world. BMW professional, 19" turbine-spoke 429 wheels, DC rapid charging, driving assistant plus.

RodHam
Posts: 26
Joined: Wed Dec 16, 2015 7:50 am
Location: Montreal Quebec

Re: Battery Temperature, isn't 20c the sweet spot?

Tue Dec 22, 2015 10:52 am

This should show power consumption during preconditioning a total of 1.669 kWh or $0.12 of Quebec Hydro electric
Image
I did leave the battery temp showing during the first 15 minutes of the drive and the temp stayed steady at 10c.
Rodney
2015 i3 BEV Lodge with winter tire kit. Juicebox Pro 40a EVSE
2005 Honda S2000
1976 GMC Palm Beach motorhome

janner
Posts: 235
Joined: Sun Jan 25, 2015 5:24 am
Location: Bath, UK

Re: Battery Temperature, isn't 20c the sweet spot?

Wed Dec 23, 2015 1:47 am

Rodham

That's really good information, Thanks.
2015 i3 ReX Solar Orange, Loft interior world. BMW professional, 19" turbine-spoke 429 wheels, DC rapid charging, driving assistant plus.

janner
Posts: 235
Joined: Sun Jan 25, 2015 5:24 am
Location: Bath, UK

Re: Battery Temperature, isn't 20c the sweet spot?

Tue Dec 29, 2015 12:08 pm

Rodham

The graph is very interesting, thanks. As you have the equipment to measure things, would it be possible to post a graph of level 2 charging, particularly the last hour before 100% and the following hour.
2015 i3 ReX Solar Orange, Loft interior world. BMW professional, 19" turbine-spoke 429 wheels, DC rapid charging, driving assistant plus.

RodHam
Posts: 26
Joined: Wed Dec 16, 2015 7:50 am
Location: Montreal Quebec

Re: Battery Temperature, isn't 20c the sweet spot?

Tue Jan 05, 2016 11:36 am

janner wrote:Rodham

The graph is very interesting, thanks. As you have the equipment to measure things, would it be possible to post a graph of level 2 charging, particularly the last hour before 100% and the following hour.
See next post for an expanded view of the graphs.
Rodney
2015 i3 BEV Lodge with winter tire kit. Juicebox Pro 40a EVSE
2005 Honda S2000
1976 GMC Palm Beach motorhome

RodHam
Posts: 26
Joined: Wed Dec 16, 2015 7:50 am
Location: Montreal Quebec

Re: Battery Temperature, isn't 20c the sweet spot?

Tue Jan 05, 2016 12:02 pm

Well the temperature has finally dropped to -20c or -4f here in Montreal with lots of snow and ice.
It seems that preconditioning will warm the battery to a temperature range that I don't understand. At -20c it only warms the battery pack to -2c or 28.4f (verified on 3 separate preconditioning). These are set departure time preconditioning.

I'm including graph images from my EVSE for your enjoyment. This image shows the entire charge and preconditioning.
Image
This image is an expanded view of the charge portion.
Image
This image is an expanded view of the preconditioning portion.
Image
Edit: Corrected my assumption about the temperature shown on the Juicebox App (Jan 06 7:32AM)
The service menu shows a battery temp of -2c or 28.4f, another effect of the colder pack is the greatly reduced recapture braking force and much higher kWh/100km numbers to maintain any kind of speed. The battery pack does reach +10c within 15 or so minutes of driving.
Last edited by RodHam on Wed Jan 06, 2016 5:33 am, edited 1 time in total.
Rodney
2015 i3 BEV Lodge with winter tire kit. Juicebox Pro 40a EVSE
2005 Honda S2000
1976 GMC Palm Beach motorhome

alohart
Posts: 2368
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: Battery Temperature, isn't 20c the sweet spot?

Tue Jan 05, 2016 12:33 pm

I'm pretty certain that a JuiceBox and its app know nothing about an EV's battery pack temperature. My JuiceBox reports its circuit board temperature which I'm guessing is what its app is showing. That would explain the low temperatures that you are seeing.
Aloha,
Art

2014 BMW i3 Arravani Grey, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging, JuiceBox EVSE

Jeffj
Posts: 252
Joined: Mon Sep 15, 2014 12:32 pm
Location: Boulder, CO

Re: Battery Temperature, isn't 20c the sweet spot?

Tue Jan 05, 2016 12:37 pm

Hi Rodham - I have a Juicebox Pro also, and I've seen the temp meter, but my question is how do you know that the temp being reported is the battery temp? Is there something in the protocol between the car and the EVSE that indicates battery temp? I can see the display being the temp of the Juicebox itself, and make myself believe that the Juicebox might only warm up to -2C (18C above ambient) while its delivering charging current.

RodHam
Posts: 26
Joined: Wed Dec 16, 2015 7:50 am
Location: Montreal Quebec

Re: Battery Temperature, isn't 20c the sweet spot?

Tue Jan 05, 2016 12:57 pm

Jeffj wrote:Hi Rodham - I have a Juicebox Pro also, and I've seen the temp meter, but my question is how do you know that the temp being reported is the battery temp? Is there something in the protocol between the car and the EVSE that indicates battery temp? I can see the display being the temp of the Juicebox itself, and make myself believe that the Juicebox might only warm up to -2C (18C above ambient) while its delivering charging current.
When I get into the car and disconnect it, I unlock the service menu and check the battery temp and I thought it always matches what I see in the App, besides the EVSE is outside in -20c ambient. I will check again tomorrow morning!
Rodney
2015 i3 BEV Lodge with winter tire kit. Juicebox Pro 40a EVSE
2005 Honda S2000
1976 GMC Palm Beach motorhome

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