Do batterys like cold or heat?

i was ready to provide an answer until i read the 'smarter than you' part.:noidea:

 

Ok I think I can help. (I am ignoring the 'smarter than you' part)
Batteries like it cold.
The Car surrounding the battery like it warm and uses MUCH more energy when cold. Engine oil is thicker, Grease is thicker, the driver uses the heater more, drivers run the lights more in the winter, so on and so on.

Batteries die in the summer due to heat, batteries die in the winter due to increased load.

 

Warm batteries function better but have shorter shelf life. That is why you stored fresh old-fashioned flashlight batteries in the frig until they were needed, then heated them up with a lighter when they were almost, but not quite, dead.

The frig may backfire on modern batteries if your room air is humid enough to condense on the batteries when the frig door is opened.

 

In general terms, chemical reactions happen at a slower pace when it's colder to batteries chemically break down slower when they are cool. Good for storage.

OTOH, batteries can put out more energy when they are warm for the same reason, chemical reactions are generally faster at higher temperatures.

 

In general, cold weather is better for batteries. When it gets too hot, they are more prone to failure and have higher internal resistance.
There is an optimum temperature range for the operation of any battery, and that temp is going to be technology dependent.
For your Prius, I would not even think about it. They are designed to operate over most any temperature range in which human beings could survive.

 

Try to start a car at -20. They may last longer but they're essentially useless and their CCAs go south fast.

 

With some additional complications. 1) Each battery type is basically completely different. All life on Earth is closer (in terms of energy conversion) than one battery to another. 2) It isn't a matter of wanting to be hot or cold, but rather of having a range of temperatures that it works best at. 3) Some components of some battery chemistries can have additional problems (e.g. freezing) at certain temperatures.

Give up the idea that it is simple, and read the recommendation of the battery manufacturer, and you should be fine.

 

The problem at -20 is not the battery; it is the viscosity of the engine oil.
That is why god made engine pan and engine block heaters.

 

^^ Oh, it is the battery too. As temperature falls, so do cranking amp ratings. That is why the same god who made engine block heaters also make electric battery blankets.

 

Maybe a little off topic but the Prius performs best in the 60 to 80 F range for best mpg. Bob Wilson and others have data graphs that show this.

Most non-automotive batteries are recommended to operate around the 72 F range.

 

That has nothing to do with the battery. This is not an EV; it is a hybrid and the better efficiency at that temp range has to do with the gas engine efficciencies, not the electric motor or battery.

 

The answer is a bit more complex...

Your hybrid battery has a state of charge (SOC). Let's say it's 80% at 80 degrees F. As the battery cools, the SOC will drop. However, the battery maintains the same amount of energy. So you could be at -20 at 20%, but let it warm, and you'll end up back at 80%...

Batteries do not like to run hot - that will shorten its life (and is why most manufacturers run coolant through their batteries). The Fisker Karma actually has an AC system cooling its battery (via coolant).

I believe some manufacturers utilize a heater *and* a cooler depending on the batteries internal temperature. When it's -20 you want to warm it up, but when it's 120, you need to cool it down...

Since the Prius is a tiny battery, they air cool it - though you will find many times when you want to press 'EV' mode, and it won't let you go into it - one reason is battery temperature.

 

that has everything to do with the battery. extensive mpg logs show that the battery likes it at 73-76 degrees... (i think it's right around there... the numbers a little mixed in my head)

i was waiting for someone to toss up a temp and when they did, someone denies it...

i think of it all in this simple manner.. if you keep the cab at a good comfortable temp, the battery will be at a good temp. if you spend the last mile in EV, and burn the battery down, then shut off the car.. you might as well assume that the pack was warm and is no longer cooling since the car is off, so it's just holding all that heat till it slowly cools off...

so... if it's cool outside, crack the windows.. if it's warm, run climate control.. it saves you and the battery. don't do anything crazy that will warm up the battery too much like long EV runs or extensive mountain climbing.

when i was doing solo runs, i used to let the car sit till all the fans and such shut off under the hood.. if the engine and inverter are cooled down, i could hope the battery had a semi chance to cool....

which brings me to my last mesh of points... if i ever did speed runs or simple mountain runs and then shut off the car, battery soc will drop while the car is off... internal temps were high... when you start back up the car is a turtle for a good few miles till the engine assist more and it can cool down a bit.

btw.. i've ran the car in 15 degree weather with it sitting outside in the snow for a few days.. it's a turtle till the battery warms up.... so back to the whole ~74 degree preference...

 

This is a hybrid and not an ICE only vehicle. If this efficiency was due just to the ICE then why is mpg more affected by hot and cold than ICE only vehicles.

That is why the battery cooling air comes from the cabin and not just outside air. If you are comfortable then the batteries stand a better chance of being in their most efficient temperature range. A good reason to run your AC in the hot summer weather.

Any more comments in bold

 

Yes. You are a fool if you think that the difference in MPG between the seasons has much, if anything, to do with battery temp.

The priority for the ICE is for reduced air pollutants. Therefore, in the winter, it expends extra energy warming up the engine fluids and the catalytic converter.
In the hot summer, extra energy is consumed by the air conditioning.

The Prius likes the cool Spring and Fall temps the best, and will provide the best MPG at that time because it is not expending extra energy on other tasks.

By the way, the traction battery in the Prius is NOT "SMALL." The 12v battery is and is primarily used for computer boot-up. The Prius does not really have much of priority for 12v battery temperature. On the other hand, the traction battery is NiMH and is the one that has air cooling.

 

You are mighty strong with your words. No need to be. Be careful who you call a fool.

Yes, the ICE has to run the AC in summer and run more in the winter for cabin heat, but there is also inefficiencies in the battery to add to this. There has been plenty written about this in this forum if you care to read what others have to say rather than just inserting your own opinions.

I am fully aware that the HV battery is the one that has air cooling. I did not mention the battery being small.

 

The battery inefficiencies due to seasonal variations in Earth temperatures are trivial compared to those present in space applications. I am speaking from 25 years experience in the field of EE.

Most of what has been posted here is based on pure speculation.

 

... because we express efficiency with a highly nonlinear measure -- miles per gallon -- that accentuates small difference on the hybrid end of the scale and masks large differences on the gas guzzler end.

If we used a more reasonable measure -- gallons per 100 miles (see Cwerdna's many links to a 'gallonage' article -- the bulk of this misperception would quickly disappear.

 

My 2 years of experience with my Prius and now monitoring battery temps with a ScanGauge parallels V8Cobrakid. On my daily commute when the battery is above 100 F my mpg is lower than normal. Once the cabin cools down and the battery temps drop the mpg increases.

I also monitor AC wattage and realize that the AC wattage drops as the cabin cools down. But as the AC wattage drops the mpg does not return to what I consider normal. It does not return to "normal" until the battery temp cools down in the 90F range.

That is more than just speculation to me. If I am missing something here please explain.

By the way, I also have 25 years of experience in the field of EE.