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even those who aren't actively searching for a new

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0:35

Question of the Week from

0:37

the Naked Scientists. Hello

0:45

and welcome to question of the week.

0:48

This week we're answering this question sent in

0:50

by listener Michael who asks what

0:52

kills a car battery that hasn't been driven or

0:55

started in a while? Good question,

0:57

Michael. Returning to a car after

0:59

a few weeks or so can lead to

1:01

a frustrating struggle as the only thing preventing

1:04

the car from operating is one flat battery.

1:06

But why does this happen? We put

1:09

in a call to University College London's

1:11

Rod Gerbis. There's a process

1:13

called self discharge which which all batteries

1:15

undergo to some extent and then there

1:17

is sort of the battery becoming flat

1:20

fully degraded and not possible to be

1:22

regenerated and that can unfortunately

1:24

happen with lead acid batteries which are

1:27

the type of sort of starter batteries

1:29

in internal combustion cars. So the process

1:31

of self discharge is really one of

1:34

fighting against the nature of all batteries. When

1:36

we charge batteries up what we're doing is

1:38

putting them into a semi

1:41

unstable state thermodynamically speaking

1:43

and this is the equivalent of pumping water

1:45

up to a hill up to a high

1:47

reservoir. Okay we're giving the battery that potential

1:49

energy but we're also it also

1:51

means it's in a state where it really wants

1:53

to get rid of some of that energy and

1:56

in some cases that can lead to favoring some

1:58

what we call side reactions using

2:00

small percentage of the charge stored in a

2:02

battery. So that happens in lead-ons in batteries,

2:04

lithium-ion batteries, lots of different types of batteries.

2:06

Some of them lose their charge

2:08

relatively quickly and have a shelf life of

2:11

maybe a few months. Others will lose just

2:13

a couple of percent in a year or

2:15

something like that. Most often it's reactions with

2:17

the electrolyte. This is the sort of liquid

2:20

in the batteries that carries the charged

2:22

ions back and forth between the electrons.

2:25

And then often that will use a

2:27

very small percentage of the capacity.

2:29

These side reactions, these self-discharge reactions,

2:31

are more likely to happen when the battery

2:33

is in a high state of charge. And

2:36

so leaving the battery very, very charged will

2:38

accelerate those reactions, as will increase temperature. So

2:40

what we can do to avoid that is

2:42

to maybe store the battery partially

2:45

charged, not leave it in high states of

2:47

charge for a long time, not overcharge it,

2:49

not leave it in warm conditions, et cetera.

2:52

Sage advice there. Thanks to Michael for

2:54

the question and Rod for the answer. Next

2:56

time, we're answering this question by listening to

2:58

John, who asks, why is it that

3:00

the body replaces its cells every year or

3:03

so? It's not clear why this

3:05

is beneficial from an evolutionary perspective. My old

3:07

arm was working just fine, thank you very

3:09

much. A valid observation, John, and

3:11

we shall have an answer for you. Next

3:14

time. In the meantime, if

3:16

you think you know the answer or have a question

3:18

of your own, you can send it in as a

3:20

voice note to chrisathenakidscientist.com or check

3:22

out our forum at thenakidscientist.com. Forward

3:25

slash forum. Question of

3:27

the Week is part of

3:29

the Naked Scientists podcast and

3:31

supported by The Wellcome Trust

3:33

and UK FAST. Look us

3:35

up online at nakedscientists.com. Thank

3:37

you. powers

4:00

the world's best podcast. Here's the

4:03

show that we recommend. Hi,

4:10

I am Dori Schaffrier, the co-host of the

4:12

podcast Forever 35, which is all about the

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things we do to take care of ourselves.

4:16

And starting next week, we have a new

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an author, journalist, and a podcaster. Yay! Elise

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and I are going to be getting

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into a lot of the same topics

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that we've always talked about on Forever

4:30

35, like skincare, like getting older. And

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of course, Forever 35 faves, like

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butt care and Costco. She

4:38

said Costco. I said it.

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I'm so excited to be coming along on

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this journey. I am so excited to have

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you. So listen to Forever 35 wherever you

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helps creators launch, grow,

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everywhere. It's at www.forever35.com.

4:59

And I'll see you next week.