Why Am I Getting a Reading of 0.3 Amps When Connecting AA Batteries in Parallel?

In summary: But I'll have to take it apart to be sureIn summary, your multimeter is not measuring the current your battery is supplying because the resistance is too high. You can get more current with two batteries in series, but the current may not be as high as you expect.
  • #1
zach_wildmind
32
11
Hey, so I tried to get a lot of Amps and primarly my tool are batteries, so I have 3 batteries that I have connected together in parallel (+ with the + and then - with the -) they are 1.6V Kirkland batteries that are all brand new. So when I took a machine I have to calculate the voltage and amps from a single batter i got 1.6 V which is what was supposed to be and I got 0.3 amps which is I guess normal for a AA battery? However when i connected them with a stripped down telephone wire (copper) and measured the same quantities I was expecting to get 1.6V and 0.9 amps... You know, pretty simple math there... However I got 1.6V and 0.3amps... My batteries are well connected but I keep getting a reading of 0.3 amps... What is happening? P.S the machine I was referring to is a multimeter.
 
Physics news on Phys.org
  • #2
zach_wildmind said:
However when i connected them with a stripped down telephone wire (copper) and measured the same quantities

Connected them how? Please show a diagram of all the connections, and the load, and where you make measurements. You can use the UPLOAD button next to POST REPLY and PREVIEW to insert pictures into your post.
 
  • #3
Ok so in the pic you can see (could be a bad pic but enough details tbh)
 

Attachments

  • 2018-06-19 18.08.23.jpg
    2018-06-19 18.08.23.jpg
    25.2 KB · Views: 594
  • #4
I can't be certain of the circuit you are describing but it doesn't surprise me that the current that your battery or batteries were supplying would have been the battery volts divided by the resistance of the "machine" you were using. (possibly 1.6/0.3 = 5.33Ω) This would be the same for any number of batteries in parallel and it suggests that your batteries are each quite capable of delivering 0.3A without dropping any significant volts.
So I reckon that your Multimeter is the thing that's limiting the current. Its internal resistance makes it unsuitable for doing the measurement that way.
If you want to find how much current your batteries can supply, you need a range of known resistances lower than 5.5Ω and you need to measure the Voltage across the resistor. You can then do I = V/R to find the current that the battery is supplying. I'd imagine that an AA battery could supply up to 2A for a brief time.

What current can you get with two batteries in series? I would think you could expect higher than 0.3A; possibly 0.6A but the internal resistance of the batteries may limit the current to a bit below 0.6A.

PS You should make sure that you cave good contacts around your circuit it's no good just holding meter probes and juggling around with multiple batteries (sorry if that is obvious for you). Also you should take care that components don't get hot with high currents and burn your fingers.
 
  • Like
Likes Merlin3189
  • #5
sophiecentaur said:
I can't be certain of the circuit you are describing but it doesn't surprise me that the current that your battery or batteries were supplying would have been the battery volts divided by the resistance of the "machine" you were using. (possibly 1.6/0.3 = 5.33Ω) This would be the same for any number of batteries in parallel and it suggests that your batteries are each quite capable of delivering 0.3A without dropping any significant volts.
So I reckon that your Multimeter is the thing that's limiting the current. Its internal resistance makes it unsuitable for doing the measurement that way.
If you want to find how much current your batteries can supply, you need a range of known resistances lower than 5.5Ω and you need to measure the Voltage across the resistor. You can then do I = V/R to find the current that the battery is supplying. I'd imagine that an AA battery could supply up to 2A for a brief time.

What current can you get with two batteries in series? I would think you could expect higher than 0.3A; possibly 0.6A but the internal resistance of the batteries may limit the current to a bit below 0.6A.

PS You should make sure that you cave good contacts around your circuit it's no good just holding meter probes and juggling around with multiple batteries (sorry if that is obvious for you). Also you should take care that components don't get hot with high currents and burn your fingers.
Ah that might be why to be honest... And yes lol I do know about the connections it's because I took it apart not too long ago and I hadn't put it back together so when he asked for the picture I just put them side by side, and in series you'll get the same current but different volts... However looking at the machine I do think there is a cap of current it will measure as there seems to be a 320mA logo but seems to be faded, so quite possibly it does have a cap. Thank you!
 
  • #6
zach_wildmind said:
and in series you'll get the same current but different volts.
That's just an assertion which will only apply if the batteries are going into current limit (which I doubt, for AA cells). If the resistance of the meter is the main resistance in the circuit then the current should go up with the volts - unless there is something else going on that you haven't mentioned.
 
  • #7
sophiecentaur said:
That's just an assertion which will only apply if the batteries are going into current limit (which I doubt, for AA cells). If the resistance of the meter is the main resistance in the circuit then the current should go up with the volts - unless there is something else going on that you haven't mentioned.
Oh I didn't know about that, will read/research more about that. Thank you!
 
  • #8
Amperage is something you measure in a circuit. You don't have a circuit, you just have a bunch of batteries. Sitting there by themselves, the amperage is zero.

So what you really did is short them with the multi-meter. You are lucky you were only using batteries and weak ones at that, otherwise you would have burned-out or burned the fuse out of your multi-meter.
 
  • Like
Likes nasu and sophiecentaur
  • #9
russ_watters said:
Amperage is something you measure in a circuit. You don't have a circuit, you just have a bunch of batteries. Sitting there by themselves, the amperage is zero.

So what you really did is short them with the multi-meter. You are lucky you were only using batteries and weak ones at that, otherwise you would have burned-out or burned the fuse out of your multi-meter.
No no, I do have a circuit, that picture was just the set up of how the batteries were connected...
 
  • #10
zach_wildmind said:
No no, I do have a circuit, that picture was just the set up of how the batteries were connected...
Right. So measuring amperage is meaningless. A bunch of batteries doesn't have an amperage.
 
  • Like
Likes sophiecentaur
  • #11
russ_watters said:
Right. So measuring amperage is meaningless. A bunch of batteries doesn't have an amperage.
Well it's to build an electromagnet... But I need a lot of amps.
 
  • #12
zach_wildmind said:
Well it's to build an electromagnet... But I need a lot of amps.
so have you built your coil ?
if so, how many turns on what size former and what wire gauge ?
 
  • Like
Likes russ_watters
  • #13
davenn said:
so have you built your coil ?
if so, how many turns on what size former and what wire gauge ?
This can be a difficult exercise for someone not familiar with the business. @davenn wants that information so that you can work out the resistance as well as the magnetic field it can produce.
If you have a battery then the coil needs to have as many turns as possible, consistent with the battery volts and the available current. It's best to have some idea of a plan for coil winding or you can have too few turns and less Field than you could get - plus you could be taking more current than the battery can supply comfortably. Too many turns and the battery will not have the Volts to put sufficient through the coil.
This is not highly critical but it's worth while getting somewhere near an optimum.
 
  • #14
davenn said:
so have you built your coil ?
if so, how many turns on what size former and what wire gauge ?
I've been testing more... So far I've got around a bunch of iron nails together around a cm in radius and I've wrapped around 600 times on it. I'm just trying to figure out the best option
 
  • Like
Likes sophiecentaur
  • #15
zach_wildmind said:
I'm just trying to figure out the best option
You will certainly benefit from choosing things 'right'. That will involve having an idea about the resistance per metre of the wire you are using so that you can get the maximum sustainable current from your batteries.
If you can find just how much current the battery (or several in parallel) can supply (with the procedure I was describing above), you can use the best number of turns for the job.
 
  • #16
I more don't have the skills/knowledge for that.. I am more doing a project to keep myself busy/hobby. I'm a young man who gets ideas of how to possibly help people and then try to pursue it...
 
  • #17
zach_wildmind said:
I more don't have the skills/knowledge for that.. I am more doing a project to keep myself busy/hobby. I'm a young man who gets ideas of how to possibly help people and then try to pursue it...
It is worth while trying to get somewhere near the 'best' performance from anything you are making - for yourself or others. It's a simple matter of finding the diameter of the wire first and estimating the length that you used for the coil. I can help you to find what the resistance of that coil is. We can then decide, on the basis of that, whether it's better to use more or fewer turns of wire. If you could also measure the battery volts with and without the coil connected, that should be enough to work with.
 
  • #18
zach_wildmind said:
I more don't have the skills/knowledge for that.. I am more doing a project to keep myself busy/hobby. I'm a young man who gets ideas of how to possibly help people and then try to pursue it...
Fair enough. You can learn at least something by just randomly wrapping a bunch of wire around a nail and attaching a battery. Odds are good you'll run your batteries dead quickly, but that's a small price to pay.
 
  • Like
Likes davenn
  • #19
sophiecentaur said:
It is worth while trying to get somewhere near the 'best' performance from anything you are making - for yourself or others. It's a simple matter of finding the diameter of the wire first and estimating the length that you used for the coil. I can help you to find what the resistance of that coil is. We can then decide, on the basis of that, whether it's better to use more or fewer turns of wire. If you could also measure the battery volts with and without the coil connected, that should be enough to work with.
I have 20 meteres of wire, 22 gauge and the volts is 1.6V
 
  • #20
zach_wildmind said:
Well it's to build an electromagnet... But I need a lot of amps.
you have a little misunderstanding about current. Current isn't something you supply, it is something that is "drawn" from a PSU ( batteries etc)
and it will depend on the resistance of the load ( circuit) in this case your coil

So measure the resistance of your 20 metres of 22 gauge wire. it may be around 1 Ohm, 2 Ohms at most
After initial experiments ... you should consider increasing that to 2 or 3 times that length and possibly dropping to 26 or 28 gauge

Amps = Volts / Resistance
Amps = 1.6V / 2 Ohms
Amps = 0.8 A

several AA batteries in parallel will handle that current for a short while but as @russ_watters said, they won't last long

cheers
Dave
 
  • Like
Likes 256bits and sophiecentaur
  • #21
davenn said:
you have a little misunderstanding about current. Current isn't something you supply, it is something that is "drawn" from a PSU ( batteries etc)
and it will depend on the resistance of the load ( circuit) in this case your coil

So measure the resistance of your 20 metres of 22 gauge wire. it may be around 1 Ohm, 2 Ohms at most
After initial experiments ... you should consider increasing that to 2 or 3 times that length and possibly dropping to 26 or 28 gauge

Amps = Volts / Resistance
Amps = 1.6V / 2 Ohms
Amps = 0.8 A

several AA batteries in parallel will handle that current for a short while but as @russ_watters said, they won't last long

cheers
Dave
ohh ok that makes sense, i will try this thank you!
 
  • Like
Likes sophiecentaur and davenn
  • #22
sophiecentaur said:
finding the diameter of the wire firs
zach_wildmind said:
22 gauge
I think it was mentioned that telephone wire was being used for the wrap.
That is a fairly thick wire, and.
That has a fairly thick plastic insulation making for a "loose" linking of the magnetic flux and the iron core, for the outer layers of wrap.
I would bet that after a few layers of wrap, a lot of the flux is not contributing to the magnetization of the core.
Better to use an wire that can be wrapped around the core in a dense bundle.
Look at some of the wrappings for motors, speakers, relays that use a thinner varnish or enamel as insulation.

davenn said:
possibly dropping to 26 or 28 gauge
Maybe even thinner wire and more wrap - 38 gauge - after all, its NI ( ampere-turns ) that gives rise to the magnetomotive force.
https://www.britannica.com/science/magnetic-circuit#ref235761
More N--> More ohms --> less I --> batteries last longer, for the same NI.
 
  • Like
Likes davenn and sophiecentaur
  • #23
256bits said:
That has a fairly thick plastic insulation making for a "loose" linking of the magnetic flux
Most electromagnets use multiple layers but the wire that's used is enamelled. That packs the turns in much more densely. With enamelled wire, it's much easier to wind neatly, which helps performance.
 
  • Like
Likes 256bits
  • #24
256bits said:
I think it was mentioned that telephone wire was being used for the wrap.
That is a fairly thick wire, and.
That has a fairly thick plastic insulation making for a "loose" linking of the magnetic flux and the iron core, for the outer layers of wrap.
I would bet that after a few layers of wrap, a lot of the flux is not contributing to the magnetization of the core.
Better to use an wire that can be wrapped around the core in a dense bundle.
Look at some of the wrappings for motors, speakers, relays that use a thinner varnish or enamel as insulation.Maybe even thinner wire and more wrap - 38 gauge - after all, its NI ( ampere-turns ) that gives rise to the magnetomotive force.
https://www.britannica.com/science/magnetic-circuit#ref235761
More N--> More ohms --> less I --> batteries last longer, for the same NI.
Oh wow ok, I shall look to find some then
 
  • #25
As others have pointed out, you need only a set of nominal resistances to measure voltage, while you need a set of energy-depleting loads to measure amperage.

Resistors, in the sense of electronic components, are in general of negligible load once their resistance is overcome by adequate voltage, while ampere-measured loads, in the sense of objects that perform work, are ultimately heaters, and substantially deplete the power of a battery.

Please read the warnings and directions before verifying that your multimeter can display a/c 110v-125v when you insert the probes into a wall socket. To verify that the outlet can supply more than 15a, you need a 15a load -- for example, you can plug two or three 1500w heaters into a power strip that has a 15a breaker, turn them on, and watch the resultant current draw trip the breaker. Your multimeter alone can't tell you what that tells you.

On a car battery label, along with voltage, you can see ratings for such values as steady amps, peak or cold cranking amps, and total amp-hours. To run a 1000 watt microwave oven from a 12v battery, for a few minutes at a time, you'd want to see ratings in the hundreds of amps, and you'd want at least a few tens of amp hours to not run the battery down too soon. Cell phone batteries are similarly rated, but the results are usually reported primarily in terms of standby and in-use time.

To accurately determine the energy and power storage and transmission capacities of a battery set requires a more sophisticated testing apparatus set than the one you presented, which is fine for testing voltage, but insufficient for testing whether the battery can adequately supply your contemplated electromagnet.
 
Last edited:

1. Why am I getting a reading of 0.3 Amps when connecting AA batteries in parallel?

When connecting batteries in parallel, the current in the circuit is divided among the batteries. This means that each battery is supplying a portion of the total current. In the case of AA batteries, the maximum current they can provide is typically around 0.3 Amps. So, when connecting multiple AA batteries in parallel, the total current will be limited to 0.3 Amps.

2. Does connecting batteries in parallel affect their overall voltage?

When connecting batteries in parallel, their voltages are not affected. This is because the positive terminals are connected to each other and the negative terminals are also connected to each other, creating a circuit with the same voltage as one battery. However, the overall capacity of the batteries will increase, as more batteries are providing energy to the circuit.

3. Can I increase the current by connecting more batteries in parallel?

Yes, connecting more batteries in parallel will increase the overall current in the circuit. However, it is important to note that the maximum current will still be limited by the highest current rating of the individual batteries. So, if you are using AA batteries with a maximum current of 0.3 Amps, connecting more batteries in parallel will not increase the maximum current beyond 0.3 Amps.

4. Will connecting batteries in parallel make them last longer?

No, connecting batteries in parallel will not make them last longer. While the overall capacity of the batteries will increase, the rate at which they discharge will also increase. This means that the batteries will still last the same amount of time as one battery would on its own, but they will be able to provide more energy during that time.

5. Is it safe to connect batteries in parallel?

Yes, it is generally safe to connect batteries in parallel. However, it is important to make sure that the batteries being connected have the same voltage and current ratings. If different types of batteries are connected in parallel, it can lead to imbalances in the circuit and potentially damage the batteries. It is also important to use caution when connecting batteries to avoid short circuits or electrical shocks.

Similar threads

  • Electrical Engineering
Replies
9
Views
2K
  • Other Physics Topics
Replies
11
Views
3K
  • General Engineering
Replies
1
Views
2K
  • DIY Projects
Replies
15
Views
2K
  • DIY Projects
Replies
31
Views
5K
  • Electrical Engineering
Replies
16
Views
2K
  • Electrical Engineering
Replies
6
Views
2K
  • Introductory Physics Homework Help
Replies
7
Views
2K
Replies
16
Views
2K
Replies
6
Views
3K
Back
Top