Batteries and the cold

[Mussels]

We have all heard how batteries don't work so well in the cold but I'm wondering how. I'm charging indoors so I guess the energy stored in the battery is constant.
When the battery gets cold I guess it doesn't supply enough electrical energy which is why the bike is slower. If it's not releasing the energy as quickly does this mean the battery will last longer or is extra stored energy being lost as heat?

 

[flecc]

It's simply that batteries are chemical devices and all chemical reactions depend on heat. That's why labs have bunsen burners of course.

The chemical reactions of a battery are seriously impaired in the cold, both with regard to current issuing and current retention. It's a mistake to think that if X amount of electricity has been put in, a consistent amount will come back out. What will come back out depends on the temperature of the chemical reaction that produces the electricity.

Rather than thinking of a battery storing electricity, it's best to think of charging as manufacturing a chemical potential. To then use that chemical potential to produce electricity requires the right conditions, adequate temperature in particular. The further away from the ideal conditions, the less electricity will be manufactured.
.

 

[torrent99]

It's simply that batteries are chemical devices and all chemical reactions depend on heat. That's why labs have bunsen burners of course.

The chemical reactions of a battery are seriously impaired in the cold, both with regard to current issuing and current retention. It's a mistake to think that if X amount of electricity has been put in, a consistent amount will come back out. What will come back out depends on the temperature of the chemical reaction that produces the electricity.

Rather than thinking of a battery storing electricity, it's best to think of charging as manufacturing a chemical potential. To then use that chemical potential to produce electricity requires the right conditions, adequate temperature in particular. The further away from the ideal conditions, the less electricity will be manufactured.
.

However, if the battery were brought to a warmer temperature we should be able to liberate some of the "missing" energery shouldn't we? (As a child when the batteries in my toys ran out I used to put them on the radiator to get a little bit of extra life, until they cooled down again). The energy has still been stored it's just that the chemical reaction is just to slow at low temperatures to liberate it usefully.

Cheers

Steve

 

[Footie]

flecc posted:
The chemical reactions of a battery are seriously impaired in the cold, both with regard to current issuing and current retention.

Ok, (just to add a thought or two) if one lived somewhere really cold (Artic for instance).
An electrically powered vehicle would not be any good .... unless .... one heated the battery storage area.
So, would the cold effect the electricity (being used) in the cables or is that unaffected?
And what power source could one use to get it warm in the first place - solar?
Chicken and egg problem?
.

 

[flecc]

However, if the battery were brought to a warmer temperature we should be able to liberate some of the "missing" energery shouldn't we? (As a child when the batteries in my toys ran out I used to put them on the radiator to get a little bit of extra life, until they cooled down again). The energy has still been stored it's just that the chemical reaction is just to slow at low temperatures to liberate it usefully.

Cheers

Steve

Yes Steve, but "some" is the operative word, not all. The position is similar to that when a li-ion battery is overloaded and chemical tiring occurs. Leaving it to rest enables the battery to carry on, the longer the rest the better, but the total available current and range then is greatly reduced from what it would have been normally.
.

 

[torrent99]

flecc posted:
The chemical reactions of a battery are seriously impaired in the cold, both with regard to current issuing and current retention.

Ok, (just to add a thought or two) if one lived somewhere really cold (Artic for instance).
An electrically powered vehicle would not be any good .... unless .... one heated the battery storage area.
So, would the cold effect the electricity (being used) in the cables or is that unaffected?
And what power source could one use to get it warm in the first place - solar?
Chicken and egg problem?
.

Yes a new battery technology is needed for cold conditions....

Speaking of which did anyone see the Gadget show a couple of weeks ago?
They featured an electric screwdriver powered by capacitors! Didn't last long per charge, but it recharged in 45 secs! So the technology is getting there...

Cheers

Steve

 

[flecc]

Ok, (just to add a thought or two) if one lived somewhere really cold (Artic for instance).
An electrically powered vehicle would not be any good .... unless .... one heated the battery storage area.
So, would the cold effect the electricity (being used) in the cables or is that unaffected?
And what power source could one use to get it warm in the first place - solar?
Chicken and egg problem?
.

You're right that electrical power is very limited in extreme cold. For example, diesel engines in cold climates often don't have starter motors, but use cartridge start instead. Those I'm familiar with have a small turbine impeller on the crankshaft with a loading chamber for a blank shotgun cartridge. When fired it's sufficient to spin the crankshaft a few times for the engine to fire up.

Cables aren't a problem in cold weather, and by implication, motor windings as well. It's quite the opposite in fact, since at absolute zero (-273 degrees C, 459 degrees F), all resistance disappears allowing unrestricted current flow and incredible motor efficiency.

It's just those chemical batteries that are the problem.

Solar power for heat generation is always a bit unlikely, but in Arctic climes where the sun is so low at all times, probably out of the question.
.

 

[moon]

Does the battery generate heat as its working? What if we had little puffa jackets for the battery would that help efficiency?

 

[flecc]

Does the battery generate heat as its working? What if we had little puffa jackets for the battery would that help efficiency?

Some heat is added, but of course that is wasted energy from the reaction so it's undesirable. In practice there's not enough to be useful and it's doubtful that an insulating jacket would be any help, even on a pre-warmed battery where the battery mass warmth will soon be lost in very low temperatures.

Batteries really are a dead end for very low temperature use at present. Since fuel cells are also chemical devices, they don't seem to offer a solution either. Supercapacitors could, but research progress seems to be very slow after some early advances.
.

 

[RobNYC]

About a month ago, I made a 12 mile round trip in -5°C windy conditions on my Quando, on a new Li+ battery. Some moderate hills were involved. Through Manhattan traffic, so lots of stops and starts. I was concerned that the battery would not get me there because of the cold. Took me about 30 minutes each way. The battery held up beautifully, with the yellow light just flashing on as I arrived at my destination. I took the battery inside for the day and charged it. I'm thinking that charge might not have been necessary since I was riding home with a warm battery, but I did not want my battery to stop moving me in THAT cold. And, one does NOT want to peddle a Quando without power more than six or seven feet. I got home easily in the same conditions later that day.

So, since my battery is new and I can take the battery indoors with me, I feel pretty good about ebiking this winter even though it is often below 0°C here. My daily commute is about 6.5 miles with one killer hill. I'll take the battery indoors on days where the temp is 7°C or less.

It's forecast to be about -9° or -10°C and very windy tomorrow morning. I'd still prefer to ebike than take the subway. I only have to go 4 local stops but it takes twice as long as biking and is expensive and often aggravating.

 

[musicbooks]

About a month ago, I made a 12 mile round trip in -5°C windy conditions on my Quando, on a new Li+ battery. Some moderate hills were involved. Through Manhattan traffic, so lots of stops and starts. I was concerned that the battery would not get me there because of the cold. Took me about 30 minutes each way. The battery held up beautifully, with the yellow light just flashing on as I arrived at my destination. I took the battery inside for the day and charged it. I'm thinking that charge might not have been necessary since I was riding home with a warm battery, but I did not want my battery to stop moving me in THAT cold. And, one does NOT want to peddle a Quando without power more than six or seven feet. I got home easily in the same conditions later that day.

So, since my battery is new and I can take the battery indoors with me, I feel pretty good about ebiking this winter even though it is often below 0°C here. My daily commute is about 6.5 miles with one killer hill. I'll take the battery indoors on days where the temp is 7°C or less.

It's forecast to be about -9° or -10°C and very windy tomorrow morning. I'd still prefer to ebike than take the subway. I only have to go 4 local stops but it takes twice as long as biking and is expensive and often aggravating.

Almost as cold as Glasgow

bw
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