Why do some devices require 2 batteries instead of just 1?

[RealETH]

I know that it probably has something to do with the plus and minus thing on batteries, but why do most TV remotes (which last forever) require 2 batteries? Same counts for Xbox controllers and a whole bunch of other devices.

[Levent]

Yes, polarity can indicate how the power is being used (but not always). Usually its done to either provide twice as much the voltage and current or twice as much the capacity compared to single cell.

 

If you are interested, you can read more here.

https://en.wikipedia.org/wiki/Series_and_parallel_circuits

[Needfuldoer]

If the remote runs on 3v logic, a second battery holder costs less to implement than a voltage step-up converter circuit. 

[IkeaGnome]

Years of lobbying by the big battery companies. 

[TetraSky]

I'll try explaining it in an easy to understand way... Else there's pictures at the bottom that explains it as well.

 

2 batteries in parallel,  ◫

like a in a TV remote, means they have double the capacity(in mAh) available to power the device. This means longer time between needing to change the batteries.

If, for example, you think your xbox controller doesn't last long... It means you're using low mAh batteries. Not all AA are created equal.
My example here was bad, in a xbox controller or tv remote, they are still wired in Serial. It's more common in things like battery packs. I doubt you will see parallel batteries in your day to day. Some laptop batteries use this along with serial to up the capacity and voltage.
 

2 batteries in serial, ▭▭
means higher voltage, capacity is the same as if you had 1 battery. It means the device doesn't work with just 1.2V~1.5V that a single AA battery can provide, it needs a bit more than that. It also means you will have to change the batteries more often. Typically found in things with motors in them, like a toothbrush or a battery powered shaver.

 

 

Here's some drawings if it wasn't too clear.

 

 

source of the pictures plus more info on the subject: https://www.batterystuff.com/kb/articles/battery-articles/battery-bank-tutorial.html

Quote

AMP Hour is a unit of measure for a battery's electrical storage capacity. A manufacturer will subject the battery to a specific amp draw over a 20 hour timeframe in order to determine the AH capacity. The amp/hr rating can significaly change based on the given load applied for more information see our article: Peukert’s Law | A Nerd’s Attempt to Explain Battery Capacity.

 

Edited July 7, 2023 by TetraSky
I messed up my example. My bad.

[RollyShed]

16 hours ago, RealETH said:

I know that it probably has something to do with the plus and minus thing on batteries, but why do most TV remotes (which last forever) require 2 batteries? Same counts for Xbox controllers and a whole bunch of other devices.

Batteries in remotes are wired in series.

The electronics, the transistors in the remote, require 3 volts.

An AA or AAA battery is 1.5 volts so to get 3 volts they have to be wired in series.

 

Batteries are almost never wired in parallel or certainly not in items where the batteries are dry batteries and are replaceable.

In high current, high powered devices, sometimes with rechargeable 12 volt batteries or 24 volt batteries they might be in parallel.

 

Certainly never in a TV remote.

 

Do they ever teach chemistry in schools today? How a dry battery works?

[Holmes108]

What the....

 

I had no idea there was so much to the way batteries were (potentially) placed re: polarities, and voltage step up this and that. 

 

I just figured 1 battery was a little capacity. 2 batteries was more. 

 

The more I know!

[CerealExperimentsLain]

5 hours ago, Holmes108 said:

What the....

 

I had no idea there was so much to the way batteries were (potentially) placed re: polarities, and voltage step up this and that. 

 

I just figured 1 battery was a little capacity. 2 batteries was more. 

 

The more I know!

To be fair, two batteries in series, providing 3v, ALSO has twice the capacity as one battery.

[Holmes108]

18 hours ago, CerealExperimentsLain said:

To be fair, two batteries in series, providing 3v, ALSO has twice the capacity as one battery.

Well yeah lol. But I'm surprised there was some sort of a need for 2 batteries (outside of more power/capacity), at least in some devices in certain setups. I never knew that about them.

[RollyShed]

8 hours ago, Holmes108 said:

I had no idea there was so much to the way batteries were (potentially) placed re: polarities, and voltage step up this and that.

All very basic electricity. I'll also presume you have never used a DVM or know how a voltmeter works.

 

Basic electronics and component voltage requirements. Maybe read about transistors, FETs, capacitors, resistors and what makes the world go round....

 

To produce a simple circuit for a TV remote an LED (light emitting diode) shines a pulsing light at the TV. The voltage across an LED is about 1.2 volts when conducting. The voltage drop across the switching transistor will be about 0.2 volts. We now need current limiting through the LED so more voltage drop. That is more than one battery's voltage.

 

So how does a battery driven mouse work with only one battery? Firstly it doesn't need such a powerful beam. Without pulling one apart I suspect it uses a voltage doubling circuit.

 

So yes, the remote could be designed to only use one battery but why bother? Size isn't a problem.

[RollyShed]

A bit more to the voltage drop across LEDs -

 

"Typically, the forward voltage of an LED is between 1.8 and 3.3 volts. It varies by the colour of the LED. A red LED typically drops around 1.7 to 2.0 volts, but since both voltage drop and light frequency increase with band gap, a blue LED may drop around 3 to 3.3 volts."

 

And batteries -

 

"The average alkaline AAA, AA, C, D, 9volt or button-cell battery is made of steel and a mix of zinc/manganese/potassium/graphite, with the remaining balance made up of paper and plastic."

 

"Household batteries are typically alkaline and the “acid” inside is less caustic than the acid in lead batteries as used in cars"

[Zodiark1593]

On 7/2/2023 at 11:23 AM, RealETH said:

I know that it probably has something to do with the plus and minus thing on batteries, but why do most TV remotes (which last forever) require 2 batteries? Same counts for Xbox controllers and a whole bunch of other devices.

A boost converter is certainly possible, and seen in premium flashlights and such (there are single-cell lights that boost voltage from 1.1v-1.6v to 3v, and some Cree XHP lights boost 3.2v-4.2v to 6v or 12v). 

However, boost converters are relatively expensive to implement, and require extra space on the board.
 

Also, depending on the application and the cells, you may end up with less than half watt-hour capacity. This is particularly the case with alkaline cells, where the high internal resistance rapidly cuts capacities as the load increases. 

[dalekphalm]

On 7/2/2023 at 7:05 PM, TetraSky said:

I'll try explaining it in an easy to understand way... Else there's pictures at the bottom that explains it as well.

 

2 batteries in parallel,  ◫

like a in a TV remote, means they have double the capacity(in mAh) available to power the device. This means longer time between needing to change the batteries.

If, for example, you think your xbox controller doesn't last long... It means you're using low mAh batteries. Not all AA are created equal.
 

2 batteries in serial, ▭▭
means higher voltage, capacity is the same as if you had 1 battery. It means the device doesn't work with just 1.2V~1.5V that a single AA battery can provide, it needs a bit more than that. It also means you will have to change the batteries more often. Typically found in things with motors in them, like a toothbrush or a battery powered shaver.

 

 

Here's some drawings if it wasn't too clear.

 

 

source of the pictures plus more info on the subject: https://www.batterystuff.com/kb/articles/battery-articles/battery-bank-tutorial.html

 

I'd just like to point out that just because two batteries are side by side, like you've shown under "2 batteries in parallel", does not actually mean they are wired in parallel.

 

In the case of a remote control, one clue is if the polarity of each battery is reversed in the battery holder (Meaning one has + at the top and - at the bottom, and the other battery has it reversed with - at the top and + at the bottom). If both were in parallel, you'd typically see both having + at one end and - at the other end, because they could use less wire/shorter traces.

 

I've rarely, if ever, actually seen a dual battery powered device in a parallel configuration. Every remote I've seen, including TV and Xbox remotes, had the polarity reversed for each battery, indicating they're almost certainly in Serial configuration - doubling the voltage instead of doubling the amperage.

 

This makes sense, because they can use short runs from the + terminal on one battery to the - terminal on the other battery - usually with the connection joining the batteries in serial at the bottom (or opposite) end, opposite where the electronics connect to the batteries.

[Holmes108]

44 minutes ago, dalekphalm said:

I've rarely, if ever, actually seen a dual battery powered device in a parallel configuration.

 

I've definitely seen it, relatively recently, but I can't for the life of my think of where it was. I know it though, because it really stood out to me at the time. I was very curious why it was different, even knowing nothing about batteries or electricity (as my earlier posts show).

[TetraSky]

1 hour ago, dalekphalm said:

I'd just like to point out that just because two batteries are side by side, like you've shown under "2 batteries in parallel", does not actually mean they are wired in parallel.

 

In the case of a remote control, one clue is if the polarity of each battery is reversed in the battery holder (Meaning one has + at the top and - at the bottom, and the other battery has it reversed with - at the top and + at the bottom). If both were in parallel, you'd typically see both having + at one end and - at the other end, because they could use less wire/shorter traces.

 

I've rarely, if ever, actually seen a dual battery powered device in a parallel configuration. Every remote I've seen, including TV and Xbox remotes, had the polarity reversed for each battery, indicating they're almost certainly in Serial configuration - doubling the voltage instead of doubling the amperage.

 

This makes sense, because they can use short runs from the + terminal on one battery to the - terminal on the other battery - usually with the connection joining the batteries in serial at the bottom (or opposite) end, opposite where the electronics connect to the batteries.

You're absolutely correct, I was probably half asleep when I wrote that. It certainly makes no sense the way I explained it with the remote.
Though I've definitely seen batteries in parallels, it is a lot more common in larger battery packs and in some other devices. Where you'd have rows of batteries in parallel to achieve higher current and then these rows are wired in serial to get a higher voltage.

[RollyShed]

12 hours ago, Holmes108 said:

 

I've definitely seen it, relatively recently, but I can't for the life of my think of where it was. I know it though, because it really stood out to me at the time. I was very curious why it was different, even knowing nothing about batteries or electricity (as my earlier posts show).

How do you know they were wired in parallel?

They can be placed in parallel in a case but be wired in series.

I can guarantee there are no devices with dry batteries wired in parallel.

[Holmes108]

5 hours ago, RollyShed said:

How do you know they were wired in parallel?

They can be placed in parallel in a case but be wired in series.

I can guarantee there are no devices with dry batteries wired in parallel.

 

Sorry, I just meant I've seen 2 double A's both facing the same direction, which is what I thought we were talking about, but as I mentioned earlier, I know absolutely nothing about this stuff.

[RollyShed]

8 hours ago, Holmes108 said:

 

Sorry, I just meant I've seen 2 double A's both facing the same direction, which is what I thought we were talking about, but as I mentioned earlier, I know absolutely nothing about this stuff.

Yes, same direction is not necessarily how they are connected.

 

1.) A question here as this is a technical world, did you (or other readers of this thread) have any teaching of Physics, Chemistry and Biology when at school?

 

2.) I presume you don't have a DVM (multimeter / voltmeter) or even know how one works?

 

At a time where the whole world runs on electricity for everything, transport, communication, heating, cooking, making everything needed, this lack of knowledge and teaching seems surprising. Some might say not surprising, keep the masses ignorant, it is safer.

 

The above, for myself, Yes, all 3 subjects at school.

DVM (multimeter) I have 4 here and a couple of my mother's ones at another place.
Another place I go to during the week to meet up and socialise and do things such as woodwork, metalwork and a cup of coffee (or tea) there are at least 3 DVMs.

[thrasher_565]

the wii re chargeable battery fits in the wavebird...

[mmaatt747]

On 7/8/2023 at 8:17 AM, Holmes108 said:

 

Sorry, I just meant I've seen 2 double A's both facing the same direction, which is what I thought we were talking about, but as I mentioned earlier, I know absolutely nothing about this stuff.

My Roku remotes are this way.

[RollyShed]

6 hours ago, thrasher_565 said:

the wii re chargeable battery fits in the wavebird...

So?

They are most definitely not standard AA dry batteries. It also has nothing to do with the original question.

[Holmes108]

3 hours ago, mmaatt747 said:

My Roku remotes are this way.

I have a couple of rokus so that's probably where I saw it yep.  

[thrasher_565]

1 hour ago, RollyShed said:

So?

They are most definitely not standard AA dry batteries. It also has nothing to do with the original question.

they used aa and i had a recharging doc for the wii controller and one day looking at it it was the same as the wave bird. thow don't think the back fits on cant remember.

 

most all the question has be awnserd

[TetraSky]

33 minutes ago, Holmes108 said:

I have a couple of rokus so that's probably where I saw it yep.  

 

Can confirm from a short google search. Feels weird and unnatural. 

[RollyShed]

Having them facing the same way is for those who can't get their heads round them facing in opposite directions.

 

The picture above seems to show non-rechargeable AA cells.