TexasLeaf
Posts: 70
Joined: Wed Mar 21, 2018 5:37 am
Delivery Date: 21 Mar 2018
Leaf Number: 303111

MAX BATTERY TEMPERATURE AND CHARGE SPEED ON LONG TRIPS

Sun Aug 19, 2018 12:20 pm

As I identified in the “Using air conditioning to reduce battery pack temperature” thread, the steady state battery temperature rise is 2.67 degrees F per kW: (127-87)/15. So if you are traveling at 60 mph (consuming 14 kW) and you don’t want to charge at less than 14 kW then your power flow (in and out) would be a continuous 14 kW. At this continuous power rate your battery is going to rise about 37 (14x2.67) degrees F above ambient.

As I identified in the “2018 charging speed compared to battery temp gauge” thread, the maximum temperature that the battery can charge at 14 kW is 123 degrees F. So the maximum temperature where you can maintain 60 mph and charge at 14 kW all day long is 86 (123-37) degrees F. And the maximum temperature where you can maintain 70 mph (20 kW) and charge at 20 kW all day long is 67 (120-(20x2.67)) degrees F.

How about if you want to travel at 70 mph all day and you want to charge at a full charge rate, how cold does it have to be then? If you assume that you are going to charge at 40 kW then your continuous power rate is going to be 26.7 kW; (20 kWh (1 hour at 70 mph) + 20 kWh (40 kW for half an hour))/1.5 hours. The maximum ambient temperature you can maintain this rate would be 19 degrees F; (90-(26.7x2.67)).

If you are wanting to travel a very long distance at 60 mph or more and the ambient temperature is 86 degrees F or more then you are going to have trouble with battery overheating. You wouldn’t have to push your car much beyond these limits to put your car in “Turtle” mode. If you want to travel beyond these limits then you probably need to work on some alternative strategies to keep your battery cool.

Also as I identified in the “Using air conditioning to reduce battery pack temperature” thread, the cabin AC can be used to cool the battery. The cabin air basically cocoons the battery so the cabin air temperature becomes the ambient air temperature in the calculations. But the cabin AC cooling is limited, you can only use the cabin AC to increase your continuous consumption by a few kW but not much more.

arnis
Posts: 904
Joined: Sat Jan 23, 2016 3:21 pm
Delivery Date: 23 Jul 2014
Leaf Number: 015896
Location: Estonia, Europe

Re: MAX BATTERY TEMPERATURE AND CHARGE SPEED ON LONG TRIPS

Mon Aug 20, 2018 9:20 am

Air around the battery is flushed with the help of front condenser fans.
How do you get cabin air touch battery case without switching on front fans?
Short range EVs <30kWh -- Medium range: 30-60kWh -- Long range: >60kWh
Charging: Trickle <3kW -- Normal 3-22kW -- Fast 50-100kW -- Supercharging >100kW

TexasLeaf
Posts: 70
Joined: Wed Mar 21, 2018 5:37 am
Delivery Date: 21 Mar 2018
Leaf Number: 303111

Re: MAX BATTERY TEMPERATURE AND CHARGE SPEED ON LONG TRIPS

Tue Aug 21, 2018 4:19 am

arnis wrote:Air around the battery is flushed with the help of front condenser fans.
How do you get cabin air touch battery case without switching on front fans?


Your post is not relevant to the thread topic and indicates you have a lack of knowledge on how the Nissan Leaf is built. The power flows indicated are with the AC off so there would not be any condenser fan air flow or heat. But even with the AC on very little if any condenser air flow or heat can get to the battery pack and what does get to the battery pack is negated by heat transfer from the air conditioned cabin floor.

arnis
Posts: 904
Joined: Sat Jan 23, 2016 3:21 pm
Delivery Date: 23 Jul 2014
Leaf Number: 015896
Location: Estonia, Europe

Re: MAX BATTERY TEMPERATURE AND CHARGE SPEED ON LONG TRIPS

Wed Aug 22, 2018 12:27 pm

Explain.
Also as I identified in the “Using air conditioning to reduce battery pack temperature” thread, the cabin AC can be used to cool the battery. The cabin air basically cocoons the battery so the cabin air temperature becomes the ambient air temperature in the calculations.
Short range EVs <30kWh -- Medium range: 30-60kWh -- Long range: >60kWh
Charging: Trickle <3kW -- Normal 3-22kW -- Fast 50-100kW -- Supercharging >100kW

Return to “Batteries & Charging”