Voltage Drop Issue When Powering Project with Batteries

Using Arduino Project Guidance
1

I’m using two polymer batteries (nominal voltage 3.7 V each) connected in parallel, which should give me about 7.4 V at the input. After that, I’m using an LM2596 module to step down the voltage to 5 V. The project includes 6 N20 geared motors, an Arduino Mega 2560 Mini, and a DRV8833 motor driver. When I connect the batteries, the voltage at the output of the regulator drops to 2 V, and the project stops working.

Interestingly, everything works fine when using a power supply. What could be the problem, and how can I solve it? Could it be due to insufficient current from the batteries, internal resistance, or something else? I would appreciate any help and advice!

Additionally, I have some lithium batteries, as well as both step-down and step-up modules if that could help solve the issue.

2

Do you mean in series? The positive of one battery connected to the negative of the other.

image
image1610×980 83.1 KB

I’m using an LM2596

That can only supply a maximum of 2A of current. You may need a larger buck.

Interestingly, everything works fine when using a power supply.

Is the power supply connected to the buck or directly to the DRV8833?

3

What are the amperage ratings on the batteries? 100ma?
What is the amp rating of the power supply? 1A?

Edit: You did check the voltage with a voltmeter, correct? If jim_p is correct, you may have only half the voltage you think you have.

4

Yes, of course, just as shown in the photo

that the power supply is connected to the microcontroller and separately to the driver, and GND joint

5

One polymer battery 2000mah

Can you please explain this point, I checked the volt, how can it go down twice

6

Batteries fully charged?

7

Then as I said, it probably because the buck cannot supply enough current.
Those N20 motors can draw over 1A each.

Connect the power supply to the buck instead of the batteries and see what happens.

8

Yes, both were charged, but after connecting to the project, one of them dropped sharply by 1.4 volts

9

Bad battery? Major voltage drop under load indicates it isn't holding a charge.

10

If it has protection circuit it may be cutting off because you are drawing to much current.
See post #7

11

So it's enough just to connect the 5 V 2 A power supply to the input of the step-down converter, and then use this converter to provide 5 V at the output and connect the project to this output? Did I understand correctly?

12

No, I thought you had a higher voltage supply.
Then either the batteries are bad, or the buck can't supply enough current.

You said you had other batteries, why not try them.

13

I tried the same thing with the help of lithiph batteries, the result was the same, I thought maybe the capacity was not enough, and connected 2 lithium batteries and increased the current to 5 volts, but the result is the same, I made exactly the same scheme but with 4 polymer batteries, the result is the same

14

If one bad battery, that could cause your problem. Not only does a bad battery not provide the rated current, but can become resistive, limiting the current of the other good battery.

15

Two completely different batteries?
What is the mAh rating of these different batteries

16

Tell me which scheme is better for my case, connect 2 polymer batteries in parallel and get about 3.8 volts 4000 mah to increase them to 5 volts

Or

Connect 2 polymer batteries in series and get about 7.4 volts 2000 mah lower them to 5 volts

17

I'd pick series. Buck is normally more efficient than boost.

1 Like
18

Never connect batteries in parallel!

If two new batteries did not work, then, as I said before your buck probably can't supply enough current, it's limited to 2A

Do you have a 12V supply?

1 Like
19

I just disconnected from the converter and two polymer batteries show 3.86 volts,

Please tell me what should I do now?

20

Yes, I have a 12-volt 2 amp power supply unit