Need a 3.7V to 5V 4A step-up converter circuit design to power up Raspberry Pi3

Thread Starter

raiz

Joined Oct 5, 2016
11
Hi all,

I am planing to develop a portable device using Raspberry Pi 3. Since, it is a portable device, I need to power the Pi-3 using batteries (18650 or Lipo batteries). My issue here is, I am unable to find a proper circuit diagram which will output 5V 3 to 4A of current, because you need minimum of 2.5A to operate the raspberry pi3.

I tried many power bank circuits which is available on Ali-Express and eBay. Also tried other modules such as buck/boost converter, Step-up converter's. But none of those modules were able to deliver the required output for the raspberry pi, although the ratings of these modules appeared to be 3 to 4 amps.

Can someone please guide me through or find me a proper solution for this issue.

Thanks in advance.
Raiz
 

Papabravo

Joined Feb 24, 2006
12,383
5V times 4A is 20 Watts. Assume 80% efficiency, so 20 Watts out requires 25 watts input power. 25 Watts from a 3.7 Volts will require 6.76 Amperes. How long do you think your battery will last when supplying that much current? Assuming you don't melt or weld something.
 

Thread Starter

raiz

Joined Oct 5, 2016
11
Something like this? Cheaper to buy off-the-shelf than to build.
Hi Alec, Thanks for you reply on this. I have purchased a similar module.

Vin = 3v-35v
Vout = 3v-35v

I just purchased it from a local radioshak shop. I haven't tried it yet. However I will let you know the feedback later.

step-up convertor.jpg
 

Papabravo

Joined Feb 24, 2006
12,383
I tried similar power bank modules, which has got 2 USB ports, one with 1A, and other 2.4A. However, these modules were not able to keep the raspberry pi alive.
Could you offer some additional details on why this was the case?
 

Thread Starter

raiz

Joined Oct 5, 2016
11
Could you offer some additional details on why this was the case?
I am not sure why it is not working properly. However, the Pi will boot till where you get its own IP address (I am using Raspbian OS) and then it starts from the beginning, it’s more like it is rebooting itself without going into the GUI mode. The Pi works fine when I use a Samsung adaptor as the power source, which has got 5v and 2A output.
 

Papabravo

Joined Feb 24, 2006
12,383
I am not sure why it is not working properly. However, the Pi will boot till where you get its own IP address (I am using Raspbian OS) and then it starts from the beginning, it’s more like it is rebooting itself without going into the GUI mode. The Pi works fine when I use a Samsung adapter as the power source, which has got 5v and 2A output.
It sounds like what we call a brownout. This is a temporary dip in the supply voltage that is seen by the processor on the Vdd pin. The usual response of a processor to a brownout is to do a power on RESET. If the battery is the input to a DC-DC converter and the output has a step increase in required current, this has a ripple effect on the DC-DC converter which causes a momentary drop in the output voltage. This inability to deal with load transients is a characteristic flaw of poorly designed DC-DC converters. This was especially noticeable in the development of early hard disk drives; when you try to start a spindle motor it can require 3-4 times the running current to start the spindle moving. The +12 V supply would come up smartly under light load, the spindle would start to move, then the +12V supply would fall to it's knees and not even bother to stop there.
 

Thread Starter

raiz

Joined Oct 5, 2016
11
It sounds like what we call a brownout. This is a temporary dip in the supply voltage that is seen by the processor on the Vdd pin. The usual response of a processor to a brownout is to do a power on RESET. If the battery is the input to a DC-DC converter and the output has a step increase in required current, this has a ripple effect on the DC-DC converter which causes a momentary drop in the output voltage. This inability to deal with load transients is a characteristic flaw of poorly designed DC-DC converters. This was especially noticeable in the development of early hard disk drives; when you try to start a spindle motor it can require 3-4 times the running current to start the spindle moving. The +12 V supply would come up smartly under light load, the spindle would start to move, then the +12V supply would fall to it's knees and not even bother to stop there.
Thank you very much for the information. How do I overcome this situation? Is there a proper circuit diagram where I can create for this project?

I also tried so called "Lithium Battery Expansion Board For Raspberry PI 3" (see below link) but unfortunately it couldn't turn on raspberry pi as well. I think I have tried almost all the options other than the one that I purchased today.

http://www.banggood.com/V1_0-Lithium-Battery-Expansion-Board-For-Cellphone-Raspberry-Pi-3-Model-B-Pi-2B-B-p-1059297.html
 

Papabravo

Joined Feb 24, 2006
12,383
The first thing I would do is check to see if the RPi will run from a standard power supply connected to the mains. The next thing I would try is to see if you can create a suitable "5V Battery" from which you can run the device directly without needing a DC-DC converter. In this case a "5V Battery" could be something like a 12V automotive battery with a linear regulator. You should know what current draw the RPi will take so you can properly heatsink the 5V regulator. You could also use 4 "D" cell batteries with a linear regulator for a smaller heatsink requirement. Lastly you should be able to find a commercial DC-DC converter that will work for you from the battery configuration of your choice.
 

Thread Starter

raiz

Joined Oct 5, 2016
11
You do know that it is inadvisable to charge and discharge a LI-ion cell at the rate on the label. You might want to check out Battery University before you waste your time and money and end up with a pile of scrap for the landfill.

http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries
It sounds like what we call a brownout. This is a temporary dip in the supply voltage that is seen by the processor on the Vdd pin. The usual response of a processor to a brownout is to do a power on RESET. If the battery is the input to a DC-DC converter and the output has a step increase in required current, this has a ripple effect on the DC-DC converter which causes a momentary drop in the output voltage. This inability to deal with load transients is a characteristic flaw of poorly designed DC-DC converters. This was especially noticeable in the development of early hard disk drives; when you try to start a spindle motor it can require 3-4 times the running current to start the spindle moving. The +12 V supply would come up smartly under light load, the spindle would start to move, then the +12V supply would fall to it's knees and not even bother to stop there.
I tried a similar module, which I have posted earlier today. Actually I am bit disappointing with its performance. Again, when I changed the voltage to 5.1 and connected the raspberry pi. The moment I connected the Pi, the 7 segment display on the circuit started to wobble up and down. It will got to 4.5, 4 and come back to 5.1V. I think it is about what "Papabravo" explained to me before about ripple and stuff. The output doesn't supply a stable voltage or current to the load.

I forgot to mention one point. I tried a step-down (I tried circuit diagram on the web, using a breadboard) converter last week. The circuit requires minimum of 7 to 8 volts as input to run the raspberry Pi. However, it was a successful attempt, but I had to connect the batteries in series mode, therefore I wont be able to keep the pi up and running for a longer period of time, unlike a parallel connection.

Basically, to give you an idea about this project: There will be an enclosure for this device, which will be the exact size of the raspberry Pi. So the dept of the this enclosure is slightly lengthy (maximum 2.5inch). That is because, I am planing to have a small cooling fan to keep the pi processor cool as well as the batteries and other circuitry designs with in this enclosure along with the pi.

Papabravo - Thanks for the above ideas. I will look into this information you shared with me. However, my goal is to power up the raspberry pi using 18650 or Lipo batteries, since it is going to be a portable device. If it is not a portable device the automotive batteries would have been really handy, in that case as you mentioned before, I just need to use a regulator IC based on the output voltage/current of the load, or use a step-down circuit. I really appreciate your ideas on this. But I do have few more questions....

Where can I find 5V batteries? (I have been looking for these types of batteries every since I started to work on this project)
Can I find rechargeable 4 D cell batteries? (If so, I need to find a way to charge them as well as run the raspberry pi at the same time)
Where can I find commercial DC-DC converter ?

Thanks
 

Papabravo

Joined Feb 24, 2006
12,383
I tried a similar module, which I have posted earlier today. Actually I am bit disappointing with its performance. Again, when I changed the voltage to 5.1 and connected the raspberry pi. The moment I connected the Pi, the 7 segment display on the circuit started to wobble up and down. It will got to 4.5, 4 and come back to 5.1V. I think it is about what "Papabravo" explained to me before about ripple and stuff. The output doesn't supply a stable voltage or current to the load.

I forgot to mention one point. I tried a step-down (I tried circuit diagram on the web, using a breadboard) converter last week. The circuit requires minimum of 7 to 8 volts as input to run the raspberry Pi. However, it was a successful attempt, but I had to connect the batteries in series mode, therefore I wont be able to keep the pi up and running for a longer period of time, unlike a parallel connection.

Basically, to give you an idea about this project: There will be an enclosure for this device, which will be the exact size of the raspberry Pi. So the dept of the this enclosure is slightly lengthy (maximum 2.5inch). That is because, I am planing to have a small cooling fan to keep the pi processor cool as well as the batteries and other circuitry designs with in this enclosure along with the pi.

Papabravo - Thanks for the above ideas. I will look into this information you shared with me. However, my goal is to power up the raspberry pi using 18650 or Lipo batteries, since it is going to be a portable device. If it is not a portable device the automotive batteries would have been really handy, in that case as you mentioned before, I just need to use a regulator IC based on the output voltage/current of the load, or use a step-down circuit. I really appreciate your ideas on this. But I do have few more questions....

Where can I find 5V batteries? (I have been looking for these types of batteries every since I started to work on this project)
Can I find rechargeable 4 D cell batteries? (If so, I need to find a way to charge them as well as run the raspberry pi at the same time)
Where can I find commercial DC-DC converter ?

Thanks
The reason I put "5V Battery" in quotation marks is because I know of no single unit that can provide that exact voltage with say a 10% tolerance so that you will not exceed the chip manufacturer's specifications. This is a place where you have some leeway. If you can find a combination of batteries that will work for you at some voltage between the upper and lower limits of the device that should be an optimal solution. If you feel you have to use a DC-DC converter then you must research their specifications and query the manufacturers about their behavior in the presence of "load transients". Whatever your hear from them you should remember the words of president Reagan to: "Trust, but verify". Good luck with your project.

Your search for components should start with a broad spectrum distributor like Digi-Key. They have selection tools that will narrow your search to manufacturers according to specifications and more importantly price. If you just search for specifications alone you might be shocked by the prices. It is best to have it all in one place.

http://www.digikey.com/
 
I am not sure why it is not working properly. However, the Pi will boot till where you get its own IP address (I am using Raspbian OS) and then it starts from the beginning, it’s more like it is rebooting itself without going into the GUI mode. The Pi works fine when I use a Samsung adaptor as the power source, which has got 5v and 2A output.
This happened to me when i tries running RPI B3 with internal screen and camera attached. Screen would flicker and eventually reboot. Screen had it's own UBC connection, so i would connect 2.4A to RPi and 1A tot he screen. Worked great after that.
 

Thread Starter

raiz

Joined Oct 5, 2016
11
This happened to me when i tries running RPI B3 with internal screen and camera attached. Screen would flicker and eventually reboot. Screen had it's own UBC connection, so i would connect 2.4A to RPi and 1A tot he screen. Worked great after that.
I haven't connected anything to the Pi.
 

Thread Starter

raiz

Joined Oct 5, 2016
11
The reason I put "5V Battery" in quotation marks is because I know of no single unit that can provide that exact voltage with say a 10% tolerance so that you will not exceed the chip manufacturer's specifications. This is a place where you have some leeway. If you can find a combination of batteries that will work for you at some voltage between the upper and lower limits of the device that should be an optimal solution. If you feel you have to use a DC-DC converter then you must research their specifications and query the manufacturers about their behavior in the presence of "load transients". Whatever your hear from them you should remember the words of president Reagan to: "Trust, but verify". Good luck with your project.

Your search for components should start with a broad spectrum distributor like Digi-Key. They have selection tools that will narrow your search to manufacturers according to specifications and more importantly price. If you just search for specifications alone you might be shocked by the prices. It is best to have it all in one place.

http://www.digikey.com/
Thank you very much for your thinformation again. I have alre contacted people at Digikey site. Will keep you posted. :)
 

Thread Starter

raiz

Joined Oct 5, 2016
11
Something like this? Cheaper to buy off-the-shelf than to build.
Hi guys, thank you very much for your help and guidance. I manage to power the Pi using the above attached module, which Alec initially asked me to use. The problem was with the battery. Therefore, I replaced the battery with two Samsung mobile phone batteries (3.7v norminal, 3200mAh x 2) and they are connected parallel. I was able to run the raspberry pi 3 more than 5.5 hours, by connecting these two batteries to the module, which I think is a successful attempt. I have attached an image for your reference but “please ignore my messy environment”. :)

I do have another problem with charging these two batteries. I will open a new post for that.
 

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