How much current can be produced from a battery cell

Thread Starter

Kelvin Lee

Joined Oct 22, 2018
109
Dear Sir/Madam,

I read both https://www.allaboutcircuits.com/textbook/direct-current/chpt-11/battery-ratings/ and https://www.allaboutcircuits.com/textbook/direct-current/chpt-2/calculating-electric-power/ but cannot answer my question.

Many STEM users connect an MCU like Microbit with a motor, even though it can provide 3.3V to the motor, the motor cannot be started up because of the limited output current. It explains only voltage be considered, the current is also the factor.

I want to make a box that can produce different voltage output for daily testing use, I want to have a 4x1.5V battery cell as input voltage and then use a DC-DC Step-up to meet my need when test. How can I know the maximum current of the battery cell can produce? How can I measure it?

Best regards,

Kelvin.
 

Thread Starter

Kelvin Lee

Joined Oct 22, 2018
109
Thanks for your information, using 1.5V cell because it is convenient to buy it from the market. If we don't have the datasheet, can we measure it?
 
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Papabravo

Joined Feb 24, 2006
12,407
The short answer is yes. The battery will supply whatever current the load requires for as long as it can. When it can no longer supply the required current at the nominal terminal voltage, that voltage will drop. This behavior is asymptotic in theory, never actually reaching zero. In practice the voltage and current get too small to measure.
 
How can I know the maximum current of the battery cell can produce?
Data sheets like the one @Yaakov will help. Some sites will give you outright peak current capability (not saying that they are necessarily dead accurate). See https://www.batteries.com/collections/aa-aaa-batteries/products/energizer-ultimate-lithium-aa-battery-8-pack-1-5-volt-lithium-iron-disulfide-lifes2-l91 for example.
  • Max Discharge: 3.0 Amps Continuous (single battery only) 5.0 Amps Pulse (2 sec on / 8 sec off)
  • Max Rev Current: 2 uA
There are also plenty of battery life calculators around:

https://www.digikey.com/en/resources/conversion-calculators/conversion-calculator-battery-life
http://www.calculatoredge.com/electronics/battery.htm

Surprisingly, I don't see one here on AAC and they have a rich selection of calculators - I may have missed it. I have used the digikey one before and like it.

Hope it helps.
 

Audioguru

Joined Dec 20, 2007
11,251
I think a battery holder has poor contacts that cannot carry much current. I had the contacts in a flashlight melt through the plastic battery holder when the current from AA alkaline cells was only 200mA.
 

oz93666

Joined Sep 7, 2010
669
It would be much more sensible to go for lithium cells ... rechargeable for thousands of cycles , much higher capacity , and fairly cheap ...and can deliver awesome currents ....

Some 18650 cells only slightly bigger than AA can deliver 20 or even 30 A @ 3.6 V

Standard ones are comfortable with 6A
 

oz93666

Joined Sep 7, 2010
669
....What is the maximum current you want from the batteries? Demanding too much can result in exploding batteries.
More ridiculous scaremongering ...can you back that up to any videos of AA cells "exploding" Or any other type of cells exploding from delivering too much current???...I'm sure there would be many on youtube if it was the case ...

Are you trying to scare newcomers away from electronics???
 

WBahn

Joined Mar 31, 2012
24,709
More ridiculous scaremongering ...can you back that up to any videos of AA cells "exploding" Or any other type of cells exploding from delivering too much current???...I'm sure there would be many on youtube if it was the case ...

Are you trying to scare newcomers away from electronics???
Oh, they CAN explode. It's rather rare for typical alkaline cells, although if you are using cheap off-brand batteries the chances go up because these are often not properly vented.

Some battery types are, such as some lithium chemistries, are much more susceptible to it.
 

dl324

Joined Mar 30, 2015
8,964
More ridiculous scaremongering ...can you back that up to any videos of AA cells "exploding" Or any other type of cells exploding from delivering too much current???...I'm sure there would be many on youtube if it was the case ...
Who needs Youtube??

From the manufacturer's data:
upload_2019-4-13_20-41-9.png
IMO, they forgot to mention not shorting the batteries...
 

oz93666

Joined Sep 7, 2010
669
Oh, they CAN explode. It's rather rare for typical alkaline cells,
Beyond all doubt , totally impossible for alkaline cells to explode . The internal resistance is so high , this limits the current too much to generate significant internal heat ... you can short circuit them and they hardly get warm.....

Lithium have lower internal resistance , but can also be shorted without any danger of "explosion".... the only way to get anything approaching an explosion is to puncture with a nail or similar , and even then not a true explosion , but hissing and flames ...see the many you-tube videos of people doing this.
 
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oz93666

Joined Sep 7, 2010
669
Who needs Youtube??

From the manufacturer's data:.
Such things are written by lawyers to protect from any imaginable law suit ... "don't stick battery in your ear ... eating cells may cause sickness "...

This is so obvious I'm surprised some here believe it ..... what is the internal resistance of an AA alkaline ??? below 1 Ohm .... even shorted less than 1W internal heat .... these cells can only "explode " by reaching very high temperatures...... Try it !!!
 

WBahn

Joined Mar 31, 2012
24,709
Such things are written by lawyers to protect from any imaginable law suit ... "don't stick battery in your ear ... eating cells may cause sickness "...

This is so obvious I'm surprised some here believe it ..... what is the internal resistance of an AA alkaline ??? below 1 Ohm .... even shorted less than 1W internal heat .... these cells can only "explode " by reaching very high temperatures...... Try it !!!
The internal resistance is a mathematical model approximating the terminal voltage-current characteristics. It is NOT a physical resistance that dissipates power within the cell -- that is a completely different process model.
 

oz93666

Joined Sep 7, 2010
669
The internal resistance is a mathematical model approximating the terminal voltage-current characteristics. It is NOT a physical resistance that dissipates power within the cell -- that is a completely different process model.
My understanding is the internal resistance of a cell ( at a given current) is just that .... An alkaline cell with 1 Ohm int resistance , with a 1 Ohm load connected will have a total circuit resistance of 2 Ohms , hence current of 1.5/2 = 0.75 A ... to find heat generated in cell I x I X R = 0.75 x 0.75 x 1 = 0.562W
 

Yaakov

Joined Jan 27, 2019
1,547
My understanding is the internal resistance of a cell ( at a given current) is just that .... An alkaline cell with 1 Ohm int resistance , with a 1 Ohm load connected will have a total circuit resistance of 2 Ohms , hence current of 1.5/2 = 0.75 A ... to find heat generated in cell I x I X R = 0.75 x 0.75 x 1 = 0.562W
For the record, a new AA cell shorted across my Fluke 287 in 10A current mode produced 6A. No fuses were harmed in this test, fortunately, I wasn't sure if I was going to see more then 10A.
 

oz93666

Joined Sep 7, 2010
669
For the record, a new AA cell shorted across my Fluke 287 in 10A current mode produced 6A. No fuses were harmed in this test, fortunately, I wasn't sure if I was going to see more then 10A.
Hmmm,,,,, I'm surprised how high a current you could get Yaakov ...

A search confirms your figure ..." A typical battery has an internal resistance of between 1 and 0.1 ohms, limiting its power output to a few watts."

And ..."Internal resistance depends on temperature; for example, a fresh Energizer E91 AA alkaline primary battery drops from about 0.9 Ω at -40 °C, when the low temperature reduces ion mobility, to about 0.15 Ωat room temperature and about 0.1 Ω at 40 °C.. "

That would indicate the resistance of your amp meter and connecting wires is less than 0.1 Ohms ... perhaps about 0.05.

So at 6Amps , with cell internal resistance of 0.1 Ohms the cell heats up at 3.6 Watts ..mildly warm
 
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Yaakov

Joined Jan 27, 2019
1,547
Hmmm,,,,, I'm surprised how high a current you could get Yaakov ... that would indicate the resistance of your amp meter and connecting wires is around 0.1 Ohms

But a search confirms that figure ..." A typical battery has an internal resistance of between 1 and 0.1 ohms, limiting its power output to a few watts."

And ..."Internal resistance depends on temperature; for example, a fresh Energizer E91 AA alkaline primary battery drops from about 0.9 Ω at -40 °C, when the low temperature reduces ion mobility, to about 0.15 Ωat room temperature and about 0.1 Ω at 40 °C.. "
The rated burden voltage for that meter is .04V/A
 

MrChips

Joined Oct 2, 2009
19,280
Simple. Why not try it and find out for yourself?
@Yaakov 's observation is confirmed by mine.

A fresh AAA cell can deliver 3A while shorted.
A fresh AA cell can deliver 10A while shorted.
 
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