hpr-knowledge-base/hpr_transcripts/hpr1398.txt

Episode: 1398
Title: HPR1398: Batteries Part 1
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr1398/hpr1398.mp3
Transcribed: 2025-10-18 00:47:35

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Umm...
Hello and welcome, hacker public radio audience. My name is Mr X. Welcome to my 5th HPR
podcast. It's been a while and I must apologise for the long interval that's passed since
my last show. I've just started by thanking the HPR people for making all this possible.
I would never have pulled my first podcast together without making this service available.
It's truly a wonderful and invaluable resource on these here intertubes. If you have something
interesting or some busting passion, why not share it with the rest of us? It really
isn't that hard and even if you only manage one show that's fine and great. But who
knows you might even go on to enjoy the challenge and just more shows? If I can do it anyone
can. I plan to make this a two-part show. Hopefully you won't need to wait too long for
the second part. The topic today is batteries. I must start by saying I am no expert. I
really started looking at batteries in more detail when I acquired a rather expensive
rechargeable shaver and a rechargeable battery within it failed prematurely. This compelled
me to go searching for the truth about why batteries fail. In the process of this I found
out about memory effect which I've heard many individuals mention and which I've seen
written in numerous equipment packaging and in various instruction manuals. I'm here
to tell you that there's probably not what you think it is. I'll talk more about this
later on in the podcast. I am conscious that these days most devices do not use discrete
batteries and perhaps to some extent it could be argued that some of this discrete battery
stuff is redundant. When was the last time you had to open a battery compartment and replace
a battery? Most modern devices come with a specialist battery pack, often one which is
either difficult or even impossible to change because of this we prematurely threw more
more stuff away. The user manual does not clearly explain how to look after your battery
or in fact sometimes gives a bad advice which will ensure the early death of your battery.
Either the manufacturers don't know much about the battery they are fitting or is it deployed
to speed up the built-in obsolescence? Ask yourself would they not include a bad
trick compartment if they wanted you to keep the devices a long time? In reality there's
probably a variety of reasons why a bad trick compartment isn't included. You can make
up your own mind about this. A year from now I wonder how many tablets will be confined
to the bucket. Often conveniently for the manufacturer batteries are not covered by
the warranty, yet they often fail to give clear instructions about how to prolong battery life.
For these reasons I would argue that the information in this podcast is even more important
than ever as the damn batches are so difficult and expensive to replace.
Batches convert chemical energy into electricity and they all work in a similar way. A battery
consists of one or more electrical chemical cells, this point is important, the multi-cell
battery is at the heart of battery failure. A single cell battery in isolation is much more
likely to reach old age, again all will be revealed later on in the podcast. Think of a multi-cell
battery, it's a package of small individual batteries linked together and covered in a single
wrapper giving the illusion of a single battery. More voltages produced by stacking multiple cells
together. Inside each electrochemical cell are two metallic plates, called electrodes. Between
them is a chemical bridge called an electrolyte. In a carbache the electrolyte is sulfuric acid.
The electrolyte allows charged electrons to gather one electrode to travel to the other.
The transfer of electrons is the basic principle all batteries use.
Led acid batteries are typically commonly used in cars where the first kind of rechargeable batteries.
They first started being used around 1860 but it wasn't until 2011 that we fully understood how they
worked. The characteristics of batteries can be altered to some degree by changing the physical
construction of the electrolyte and electrodes. However, even greater changes can be heard by using
different materials. A lead acid cell for example, normally produces two volts. So a traditional
carbache consists of six cells, each cell producing two volts. Six cells multiplied by two volts
gives an 8-bit voltage of 12 volts. The cells are connected so that the positive
electrode of one cell is connected to the negative electrode of the next cell. This is known as
connecting the cells in series. They're connected in the exact same way that you would load
some cylindrical batteries into a cylindrical flashlight. This is in fact all the multi-cell
batteries. Again, think of sticking a pair of batteries together, connecting them all together
in series, wrapping it all up in plastic, leaving only the first positive terminal on the last
negative terminal visible. This is all the battery packers. Common arc lane cells produce a nominal
voltage of 1.5 volts. From this you can tell that a common AA battery is a single cell battery.
An arc lane PP3 square battery, commonly used in smoke alarms, is an example of a multi-cell
battery because it produces nine volts. Remember an arc lane cell normally produces 1.5 volts.
Inside a PP3 battery is a stack of six individual cells. These cells are all connected in series.
Each cell producing 1.5 volts. Six times 1.5 equals nine.
The nominal voltage produced by a rechargeable nickel metal hydride cell is 1.2 volts.
This can cause a problem when you're substituting arc lane batteries with rechargeable ones.
Consider if you want to replace the standard batteries in your shining digital radio.
The radio uses six standard batteries. This means the digital radio expects an nominal voltage of
nine volts. When you substitute the batteries with rechargeable ones, you can't understand why the
thing only runs a short time then dies. Six 1.2 cells would produce 7.2 volts. Probably the same
voltage is six flat arc lane batteries. Your digital radio is fully to thinking the batteries are flat.
The more cells the device use, the greater the difference between the common arc lane batteries
and rechargeable nickel metal hydride ones. Some modern devices either ought to detect this or
have a manual switch to get it for this situation. Memory effect was first observed on early satellites.
It was found that the battery voltage on orbiting satellites was prematurely dropping.
These early batteries used nickel cadmium batteries. These I believe are no longer available
due to environmental concerns. It was found that the voltage drop was caused by the fact that
batteries were going through an identical charge and discharge cycle on each rotation around the
earth. After a few cycles of this, the batteries developed the memory effect, causing the voltage
to drop off prematurely. The thing about memory effect is that it is reversible by repeating the
charge and discharge cycle a few times. In modern satellites, the charge and discharge times are
randomised and this stops the memory effect from being developed. Another place where memory
effect was observed was in doctor's pages. The doctor would have his pager with him throughout the
shift. At the end of each shift, the pager would be returned to a charging station when it was charged
overnight. Again, the charge and discharge times were identical day after day, allowing the memory
effect to build up. You will probably never encounter memory effect during normal day to day
operation of battery equipment. I believe it is quite difficult to demonstrate even in a lab.
As I said before, memory effect is reversible. Some battery charges have a discharge function on
them to individually discharge each single cell battery. In my opinion, this facility is really
of little benefit, since she will be very unlikely to come across memory effect in day to day use
of your battery equipment. We now know that the premature failure of batteries is nothing to do with
memory effect, so what in earth is going on? There is one thing above all other things that
time after time cause batteries to fail, and I am going to let you in on the secret. It is all
to do with linking multiple cells together in series. When a device draws current from a multi-cell
battery, all the cells within the battery back linked together start to discharge. The problem
is that no two cells are identical, even if they are manufactured at the same time using the same
equipment. There will still be many differences in each cell. These differences lead to one cell
becoming flat before all the others. The voltage from this cell collapses, and the voltage from
the surrounding cells reverse charges the flat one. This is indeed very bad for the cell concerned.
Reverse charging a cell is very bad, and an nickel cadmium battery causes conductive
dendrite crystals to grow. These crystals effectively short out parts of the battery,
are rapidly reducing the capacity of the cell. Next time you use the device, the battery pack goes
flat more quickly, because one of the cells is damaged. It inevitably gets reverse charged again.
This causes a death spiral of the whole battery pack. Note, only one cell in the pack is damaged,
but this doesn't help much, as you undoubtedly won't be able to replace the individual cell,
and it's likely you'll find it difficult and possibly expensive to find a suitable
specialist replacement battery pack. On top of all this, you may not even be able to get into your
device in order to replace the battery if it's something like your average tablet. If the device
uses discrete individual batteries, you still need to locate the faulty cell. If you replace the faulty
cell, the chances are the capacity won't match the remaining cells. This is why instruction manuals
often say not to mix and match you chargeable batteries. The number one thing above all else
that kills batteries is driving them flat. Imagine you're using a battery drill. As you drill,
you start to notice that the drill is ever so slightly slowing down. At this point,
one of the cells within the battery pack is being very quickly destroyed. Stop immediately,
if possible, put the drill on charge. Above all else, stop drilling. Find the
temptation with every fiber of your body. Continuing even for another minute will
catastrophically damage the single, flat cell, causing the whole battery pack to fill within a few
charged discharge cycles. You might imagine that your device might switch off automatically,
and will save you from the destruction of your battery pack. I would advise you not to rely on
this, as no matter how complex the circuitry, it cannot know the state of each individual cell within
the battery pack. Damage can still easily occur, it is far better to stop using the device
long before it shows any signs of being flat. Here's another common scenario, which leads to the
same destruction of your precious battery pack. If you have a device that gradually sucks power from
the device, imagine something like maybe a portable MP3 player, a satnav, ebook reader, or perhaps
your favourite tablet. Go and stand by these devices draw power. My Sansa Clip MP3 player has a
terrific battery life, but it has an internal clock within it which only came to light when I was
running rockbox on it. I don't find the clock particularly useful, but the very fact it has one
means the MP3 player is continually drawing a small amount of current from the battery,
even when it is seemingly turned off. If I was to leave the MP3 player for months on end without
charging it, then the battery of a pack would be driven flat, causing the failure of the whole
battery pack. This is something you need to watch out for. My Sansa Clip is over four years old,
and still has a great battery life. I recommended the same player to a colleague at work a few months
back, or recently asked him how he was getting home with his player, and he said not too bad,
but it tends to go flat all the time, so I tend to use my phone now. I suspect he'll let the
thing go flat. If you're not going to use a device for a long time, and disconnect the battery,
this will save it. Unfortunately, you can't do this with the sealed devices such as the MP3 player
or tablet. I would imagine many of these devices will go in the bin, built in obsolescence strikes again.
Recommendations
Most devices now come with specialist batteries, such as lithium ion or lithium polymer. These
batteries have very high energy densities, approaching that of a small hand grenade,
because of this you need to be very careful charging them. You have no choice but to use the
charger supplied by the manufacturer. However, if you're using a device with discrete,
rechargeable batteries, then choose a slow trickle charger. You may find it quite difficult to
get a slow charger, as everywhere you look, there are fast chargers boasting about how fast they
can charge, playing the wonderful consumer numbers game. Suckering the poor consumer yet again,
these fast chargers pulse charge batteries, which means you won't obtain the full capacity
of your battery. The battery will also tend to fail a bit quicker. However, the failure time will
still be nowhere near as quick as driving a battery flat, which you remember can happen just
by leaving the device sitting unused. Just like the charger companies, the battery manufacturers
are also playing the marketing numbers game. Just like the digital camera which must have the
biggest megapixel count, the image may only be interplated and the crammed in megapixels count
will undoubtedly increase image noise. The same numbers game goes on for batteries, everything
is a trade off. The current trend for bugs on the discrete nickel metal hydrate batteries
is to increase the capacity. Capacity is measured in amp hours. A 1 amp hour battery can theoretically
maintain a current drain of 1 amp for 1 hour. A 4 amp hour battery can theoretically contain
a current of 4 amps for 1 hour. Small discrete batteries use the measure milliamp hours.
1000 milliamp hours equals 1 amp hour. I can remember my first set of nickel cadmium 80 batteries,
having a capacity of 500 milliamps. This means these batteries could maintain a current drain
of half an amp for 1 hour. Nickel cadmium batteries were replaced by nickel metal hydrate batteries.
I think these started coming out with a capacity of around 700 milliamp hours. Over time these
capacity crept up and up and I think they have now reached a whopping 2700 milliamp hours.
This means these tiny 80 batteries can maintain a current drain of 2.7 amps for 1 hour. Incredible.
They may think this is great, what can be wrong with continually increasing capacity.
Well remember this numbers game is a compromise as the capacity goes up, so there's a discharge rate.
These 2.7 amp hour batteries will be flat within a month just to think about a shelf.
They are also more liquid to feel quickly. However, if you're using them at high
discharge rates, like for example in a high speed remote controlled car,
where battery is exhausted very quickly, then these batteries may be exactly what you need.
You may also want to consider a fast charger as you may be impatient to get out with your
model and race again. Remember if you're not using the batteries like this, then you might do
better to get a lower capacity battery with slow charger. Again, you may think this difficult
as everyone thinks bigger is better. 2,100 milliamp hour 80 batteries are a good compromise,
having a decent capacity and a reasonable discharge rate, giving a reasonable charged shelf life.
At this point I should maybe make it clear that allowing batteries to go flat,
naturally over time with no current drawn is perfectly safe and will not destroy the batteries.
This is because no current is flowing between the cells. Even the tiniest of currents will destroy
cells as one collapses it is averse charged by the neighboring cell. This is why it is always
best to remove batteries from a device if it is not going to be used for a long time.
A descending order of importance. 1. Don't drive batteries flat.
2. If you're not using the device, disconnect the battery. 3. Don't mix and match batteries.
4. Where possible use a slow charger. 5. Topping up the device is not a bad thing.
6. Leaving a device when charged for a long time is only okay if it is being trickle charged.
5. Conclusion.
Okay, I hope you enjoyed this podcast. That's about it for this episode. Next time in part 2,
I'm going to try and give you real life examples of battery usage. I'll try to pull together some
show notes for the podcast which if I do, will be available at HPR. I can be contacted at
mrx at hpr at googlemail.com. That's mrxathtpr the at symbol googlemail.com.
So until next time, thank you and goodbye.
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