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Discussion Starter #1
Since I'm often an ambassador of the Volt/EV (as probably most of us are), I figured I should brush up on the topic of why batteries perform worse in the cold.

Here's something from About.com Why Do Batteries Discharge More Quickly in Cold Weather?

My guess is someone(s) here will do a better job explaining the chemistry/physics.
 

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In very simple high school introductory chemistry terms,
Batteries work on chemical reactions. Pulling energy out, the reaction works in one direction. Recharging it runs backwards.

Generally speaking, chemical reactions go faster with higher ambient temperature, because there is more available free energy to help kick start the reaction. (If it was a reaction that could happen spontaneously, that's bad. Think boom.)
Lots of energy in the environment means lots of chemical reactions can start up.
Activation energy can be for multiple requirements of a reaction. It could be to break existing bonus, so that new molecules can form. It cal also be simple movement.
In a warm environment, molecules have lots of energy and are moving around quickly. Eventually some bump into each other and the reaction starts. If they're cold, they move slower, and takes longer to get a reaction going.

This is not specific to lithium batteries, just general chemistry.
 

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Discussion Starter #4 (Edited)
Thanks, I am mostly looking for good ways to explain it.

I've been saying whatever newfangled mind blowing battery technology comes out, it will be also be effected by temperature. Now if this theoretical breadbox sized battery gets 500 miles of range in 65F degree temperature that might not be much of a big factor but that same battery won't get 500 miles of range in -5F. Even without considering climate control. Right?
 

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There are just so many components to a vehicle that change with temperature, that its not just getting less power from the battery, but using more power to do the same job.
For example, tire rolling resistance changes, air resistance changes and so much more.

I forgot to mention internal resistance as well. That's battery specific, though.
So in the general sense of chemical reactions running slower at cooler temps, we also have the batteries construction affecting how it performs at different temperatures.
When its cold, it has more resistance to the flow of electrons, which means less energy gets out as usuable power. This warms the batteries, though, so its technically a good thing when they're really cold. They get a bit warmer and release more energy, repeat.
But if you're starting warm, less energy is wasted to resistance, and you get more usable power.
 

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As another poster noted, there's a big difference between "why batteries perform worse in the cold" and "why battery powered cars perform worse in the cold."

The battery does give somewhat less energy in the cold due to the effect of weather on the chemistry - but that's a minor effect compared to the other factors for the car.

All of the loads become larger - more rolling resistance from stiffer tires and thicker fluids, more air resistance from denser cold air.

Most important of all, though, is the electric heat. Gas cars use engine waste heat to warm the cabin and defrost the windows, so they only lose efficiency from the increased loads noted above (and extended open-loop warm up periods - and people idling them by remote start to get the heat.) Electric cars are so efficient that they don't generate enough waste energy to effectively warm the car (though on long trips the Tesla is set up to harvest the waste heat to reduce the impact.)

Instead, the electric car has to take some of the precious reduced supply of electricity and use it to warm the cabin - in the current generation mostly through a PTC type coolant heater (the Volt uses this approach like most of the others; in our case it has a 6.5 kW capacity.) That's the real killer for electric car range in the cold - keeping the windshield clear and the passengers warm.

(This is also why seat heaters should be standard and are a necessary option for all the EVs - the seat heaters eat tens of watts instead of thousands while delivering more heat to the people instead of the outside. Doesn't help with the windshield, of course.)
 

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Actually, battery powered cars actually perform BETTER in the cold than their ICE counterparts ... once you take into account the true lost efficiencies of the two. The issue is that ICE cars can just be refilled with petrol products to compensate. EVs have to be recharged, and that's more noticeable in the current social environment,

As for explaining, it's just the way energy works. In cold, it takes more energy to do the same thing. That applies to both electric cars and gasoline cars.
 

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This remined me of an experiment that a fellow sudent in my high scholl did in the late 1960's. He discovered that an electrolyte in liquid form works best when at the boiling point, which is when the molecules, atoms, and ions in the solution are the most active (have the most energy due to heat). In his experiments, the source of heat was external (a Bunsen burner), but in a lithium-ion battery most of that energy has to be internal unless an outside source (the coolant in the TMS) can supply it. So the Volt can use its TMS to heat the battery while still charging (using the plug-in power source), and this is why the Volt can work better in the winter than an air-cooled (and thus air frozen!) TMS in the Leaf and other EVs.

I don't have a Volt, and I live in a tropical isaland, so I have no real-time experience here.
 

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Batteries are electrochemical devices. Chemical reactions are often slowed by reduced temperatures. Know this and you're essentially done explaining.
 

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"Most important of all, though, is the electric heat.'
It's always puzzled me why they don't use heat pumps. Any electrical energy used directly for heating can be multiplied many times (typically 3-5). I can understand why in the Volt since they are trying to maximize electric range and it is so convenient (although expensive) to heat with gasoline -- and you have an engine just sitting there all ready to make hot water for you. But in the Leaf and Tesla, direct heating electrically makes no sense at all -- unless the weight penalty is just too great. If so, maybe developing a new ultra compact heat pump would be a real winner for some enterprising entrepreneur.
 

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"Most important of all, though, is the electric heat.'
It's always puzzled me why they don't use heat pumps. Any electrical energy used directly for heating can be multiplied many times (typically 3-5). I can understand why in the Volt since they are trying to maximize electric range and it is so convenient (although expensive) to heat with gasoline -- and you have an engine just sitting there all ready to make hot water for you. But in the Leaf and Tesla, direct heating electrically makes no sense at all -- unless the weight penalty is just too great. If so, maybe developing a new ultra compact heat pump would be a real winner for some enterprising entrepreneur.
Some of the cars - including the i3 BEV and the Model S - do use a heat pump. But heat pump efficiencies fall off when it gets cold - and so does both the heat output and the duty cycle (have to defrost the evaporator coils...) As a result, all of the cars have direct resistance heating, even the ones with heat pumps - and for shorter trips in real winter weather the cars are mostly on the resistance coils instead of the heat pumps they use on longer trips or when it is warmer out.

This is especially true in cool/cold wet climates, because most cars use the same parts for the A/C and Heat Pump - and when you first start the car you need to defrost the windows, which is ideally accomplished by heating and drying the air at the same time - but the A/C core can't be both the hot end and the cold end at the same time, so they run the A/C side cold and heat with resistance instead.

GM used a heat pump on the EV1 with its So Cal and AZ only market - but something they saw in those results convinced them to go pure resistance with the first generation Volt. A heat pump may reappear as time goes on - but unless they get a lot better than they are now, they'll never replace resistance heat in all cases for EVs.
 

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Actually, battery powered cars actually perform BETTER in the cold than their ICE counterparts ... once you take into account the true lost efficiencies of the two.
Not after the fact that the 75% of energy that was waste heat in summer from gasoline - can now be used to heat the cabin and engine oil in winter, is accounted for.
 

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"Something they saw" - Price?
I don't know - there's never been any documentation on that decision released outside of GM that I know of. It might have been price, or performance in the cold, or something else. That's why I put it the way I did. The Volt inherits a lot of genes from the EV1 program (no identical parts AFAIK,) but they chose to change that piece of it.
 

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Not after the fact that the 75% of energy that was waste heat in summer from gasoline - can now be used to heat the cabin and engine oil in winter, is accounted for.
Aside from the newest generation Prius, you can't harvest the third of the heat that goes out the exhaust. Admittedly, the third that goes into the water/oil is usually more than people need after a little while so it's likely academic. :)
 
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