Batteries mounted in parallel. Amps wont add !

Thread Starter

Yuseph

Joined Jun 8, 2020
45
20200728_210243.jpg
Hey guys,

I dont understand. Its the simplest thing to do and i cant do it.
I cant combine amps.
i tried different possibilities. Only one worked.
Its only when i combine an ac adapter set at 6v and 4 aa batteries (6v) that it seems to works. And thats only when the multimeter is plugged on the adapter side.
Strangely with the multimeter connected on the batteries side amps wont combine.
I then tried 4 aa batteries in parallel with 4 other aa batteries. Multimeter placed on 4 different positions. Didnt succeed either.
Not only it doesnt combine but it loses amp.
I want to specify that i never inverted polarities.
I cant believe im stuck on sth like that.
 

dl324

Joined Mar 30, 2015
11,282
Whats funny is it gets worse when i switch adapter connectors and the batteries connectors. I get a negative result.
Have no clue what you're trying to show us. I see a meter, a bulb, and some leads connected to things out of the frame.

Schematics would be more helpful.
 

Papabravo

Joined Feb 24, 2006
14,244
That makes two of us that have asked for a schematic diagram. When do you think the TS will get the hint?

EDIT:
Here is a simulation of two 6V battery packs with different internal resistances engaging in current hogging. This is expected behavior. You do not get the maximum current from both battery packs when you connect them in parallel. What you get is what the lamp and the internal resistance of the battery packs will allow. Notice that one of the battery packs is providing most of the current for this 0.8 watt bulb.

LampDemo.png

I hope that my interpretation of the drawing is what the TS intended.
Yeah I know are exceeding the spec on the bulb. What do you want for a sim I just threw together.
 
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Thread Starter

Yuseph

Joined Jun 8, 2020
45
Can you guys put two batteries together and a multimeter in series and have the amps double ? Because it seems impossible with 1,5v batteries
 

Papabravo

Joined Feb 24, 2006
14,244
Can you guys put two batteries together and a multimeter in series and have the amps double ? Because it seems impossible with 1,5v batteries
No. You can't do that. It doesn't work that way -- as you have discovered it is impossible.
You can pull twice as much current from any number of batteries if you put two identical loads in parallel.
If the batteries have different internal resistances then one of the batteries will supply most of the current.
 

crutschow

Joined Mar 14, 2008
25,267
I think you have a misunderstanding about current in a circuit.

Battery current is determined by the battery load and battery voltage, not the number of cells in parallel.
If you had a fixed load and two identical batteries in parallel, then each cell will carry half the load.
That's why two batteries in parallel can deliver twice the current of one battery, for a rated battery current.
 

dl324

Joined Mar 30, 2015
11,282
Ive read the parallel article. It doesnt help.
Look all cells are identical. I dont understand.
You're still not helping us help you.

Is the light bulb always the load? What is it's nominal operating voltage?

When you connect batteries in parallel, you increase the total current capacity, but, are you changing the load to draw more current?

BTW, your "identical" batteries aren't identical.

Another thing you need to consider is the shunt resistance of your meter. That changes depending on the range the meter is on and that can affect circuit operation. It's much better to put a small resistor in the circuit and measure the voltage drop across it. This would be particularly helpful if you wanted to measure the current coming from each battery.

EDIT:
battery.jpg
If you connect the batteries and load as shown, you can calculate the current from each battery and through the load by measuring the voltage drop across the appropriate 0.1 ohm resistor.
 
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jpanhalt

Joined Jan 18, 2008
10,095
That parallel setup of 4 cells that you show comes nowhere near ensuring the batteries -- all of them -- are connected in parallel. Why do you think real holders use springs?
 

WBahn

Joined Mar 31, 2012
26,068
Can you guys put two batteries together and a multimeter in series and have the amps double ? Because it seems impossible with 1,5v batteries
You seem to be thinking that if you connect a lightbulb to a single battery and the result is 100 mA of current that if you put a second identical battery in parallel with the first that now you will have 200 mA of current in the lightbulb.

It doesn't work that way. The load determines how much current it will take at a particular supply voltage and any supply that can deliver that voltage and at least that much current will only provide that much current.

Assuming ideal batteries, what you would see is that with one battery that battery is delivering 100 mA to the bulb, but with two batteries in parallel each battery is delivering 50 mA to the bulb and if you put 100 batteries in parallel then each battery would be delivering 1 mA of current. So the currents from the batteries do add.
 

sparky 1

Joined Nov 3, 2018
301
Your drawing skills will really help you. The schematic drawings that you make will also be neat and detailed.
Let the load = 1k Ohms for convenience 3V 3mA or 1.5V 1.5mA when switched
measuring voltage across R1. measuring amperage by opening the circuit between S1 and R1 inserting ammeter between.
series battery.JPG
 
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