Voltage or Current problem

[benjaminpeere]

Hello everyone,

I am in trouble because of a vlotage of current problem, I think it is most a voltage problem.

Let me explain, 

I have a NRF51DK that I programmed to work with a stepper motor, a nema 17 (https://www.pololu.com/product/2267)

I made the code to make it work in Bluetooth, so I am able to make it turn in one and other direction.

Everything works perfectly when I power the circuit with the usb cable plug to the nrf51dk, event if  I plug 4 AAA batteries of 1.5V each

But I wanted to make it better and use a rechargeable battery,  I made some research and as the stepper motor that I use only require 2.8V and 1.68A to work, I choosed this Li Ion battery (www.tinytronics.nl/.../samsung-18650-li-ion-batterij-2600mah-5.2a-icr18650-26j) that deliver 3.6V and 2600mAh with 5.2A for it's maximum delivery performance, so I was sure it was right because it deliver more power than necessary and the voltage is not too low.

But it doesn't work with this battery, I didn't changed the circuit, I tried with the 3 possibilities and only this battery doesn't work, I tried with another one because I bought 2 of them, and still the same problem, and the batteries are both full charged.

My first thought was it was a voltage problem but I Don't hink because the stepper motor require only 2.8V.

Also the same problem happens if I use a nrf51822 that only requires 3.6V (this is why I choosed this battery because the futur is to use the nrf51822 and it is easier to use the good voltage)

Also I am using this driver to control the motor : www.pololu.com/.../MP6500_r1.0.pdf

Thanks for your reply and your help!

[Jared]

Hi

• I'm not sure I fully understand the connection. Is the nRF51 DK connected to the same node as the driver? Could you possibly provide a schematic of the design?
• If they are connected to the same node, it might be that the motor temporarily sinks more current than the battery can provide for both the nRF51 DK and the motor simultaneously. 
• What exactly happens when you run your application? Do you manage to start the DK? Could you try to only initialize the motor and not drive it and see if the battery is able to provide power to the DK and the idle motor.

But it doesn't work with this battery, I didn't changed the circuit, I tried with the 3 possibilities and only this battery doesn't work, I tried with another one because I bought 2 of them, and still the same problem, and the batteries are both full charged.

This sentence is unclear for me. Did it work with the 2 other batteries you had? If it did It would indicate that it is a problem with the battery and not the connection. 

Jared 

[AmbystomaLabs]

In addition to the points Jared made you have another serious problem if you hooked up that battery up directly to the nRF51, Lithium Ion batteries are 3.6volt nominal, they are NOT 3.6volts max.  They are charged to either 4.1 or 4.2 volts to get their full mAh capacity.  Fully charged these batteries will easily burn out an nRF51.