A simple question of battery thermal management

[sfk]

As far as thermal management of the battery pack is concerned this is what I understand -

- putting a lot of power into or taking a lot of power out causes a built up of heat in the battery pack. ie. heavy and sustained acceleration and regen, and also rapid charging
- batteries perform badly when very cold. ie in snowy conditions
- not managing the thermal requirements of the battery pack will effect the performance and possibly cause lasting damage

- battery packs that get too hot will need a cooling system, either air or liquid, otherwise their output will need to be artificially throttled
- battery packs operating in cold temperatures will need battery heating to operate efficiently

Next question: what are the ideal operating temperatures? (Nissan Leaf gen 1 or 2 battery)

Is a car that is used for steady speed commuting (100kph) ever likely to produce excessive heat in the battery pack that will require a cooling system?

Would a medium speed charger (6-10kw) require active cooling of the battery pack or is that just necessary for ultra high speed charging (50kw etc)?

[johu]

In my experience heating is more important than cooling. In winter I suffer up to 30% range decrease (subzero temps) and noticeable power loss.
So in winter I see like 15°C heat build up on a 60km commute. Which is logical because the internal resistance is so high. In summer I don't see any additional heat generation from driving.

Sustained 100kph and 6-10kW charging of the Leaf battery sounds like your a good distance away from needing a cooling system. Heating - depends on your climate.

[sfk]

Thanks for the info. Since I'm planning to use a Leaf drive system in a car of similar weight whilst driving as conservatively as possible and since the Leaf has no battery thermal management I thought I wouldn't either.

In New Zealand where I live I would expect to have half a dozen or so frosts during winter and cold but not Sub zero temperatures the rest of the season. Some sort of fluid heating circuit would be great but not sure how much effort to engineer. Certainly don't want fluids and batteries socializing...!

[arber333]

Thanks for the info. Since I'm planning to use a Leaf drive system in a car of similar weight whilst driving as conservatively as possible and since the Leaf has no battery thermal management I thought I wouldn't either.

In New Zealand where I live I would expect to have half a dozen or so frosts during winter and cold but not Sub zero temperatures the rest of the season. Some sort of fluid heating circuit would be great but not sure how much effort to engineer. Certainly don't want fluids and batteries socializing...!

Problem is not the immediate cold or heat. Real enemy is prolonged cold or heating when the whole battery thermal mass is taken out of scope. Last month i left my EV parked in the airport when i was abroad on bussiness. In those two days there was below 0°C in the night. When i returned i departed normally but cell voltages fell off the moment i accelerated from the ramp! I had to drive only up to 70km/h and i switched off regen. After some 25km batteries heated up enough so i could drive at 100km/h without tripping LV alarm.

I would recomend using Webasto fuel heater for those freezing days. Putting a PPC heating tube inside battery box similar like floor heating in a house. To regulate you could use a household thermostat valve that would open below say 5°C and let the fluid run through the box. Since webasto would run whenever you would actively sit in a vehicle batteries would get the same treatment driver would get.

Or you could use 7W lizzard heaters and have the m connected to a single AC line from the charging port. They have their own thermostat inside.
https://www.ebay.com/itm/7W-14W-20W-Hea ... :rk:2:pf:0