kunalgupta
Posts: 13
Joined: Wed Feb 07, 2018 7:33 am

RPi Power supply (battery) with protection circuit

Wed Feb 07, 2018 7:41 am

I need to power my RPi using a battery with a battery protection circuit. Please suggest something!

wh7qq
Posts: 930
Joined: Thu Oct 09, 2014 2:50 am

Re: RPi Power supply (battery) with protection circuit

Wed Feb 07, 2018 9:28 pm

You need to specifiy physical size and form factor and which RPi you are using with what accessories (total current requirement) as well as how long you expect it to run. Nobody can answer your question as written.
Sent by WH7QQ from an RPi3/Raspbian/pixel desktop.

MaxK1
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Re: RPi Power supply (battery) with protection circuit

Wed Feb 07, 2018 11:10 pm

Look into "Powerbanks" - but you need to figure out your desired run-time, what the expected load is, etc,
You are in a maze of twisty little passages, all alike.
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kunalgupta
Posts: 13
Joined: Wed Feb 07, 2018 7:33 am

Re: RPi Power supply (battery) with protection circuit

Thu Feb 08, 2018 9:17 am

I'm using Raspberry Pi 3 B model. Things I need to power are as following :
1. Wireless keyboard and mouse ( shouldn't be a problem)
2. 2.4 inch touch display using SPI
3. Arduino pro mini connected to RPi using I2C
4. L293D Motor driver along with 2 motors if possible
5. PiCamera & Microphone
It should run for an hour or two necessarily. Any ideas?

Will any of these work? Link : https://www.alibaba.com/products/7.4v_l ... ction.html

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davidcoton
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Re: RPi Power supply (battery) with protection circuit

Thu Feb 08, 2018 9:54 am

That battery by itself will NOT work. There is no protection, no voltage regulation, and no charging circuit.

Go back to your list of parts. For each one (including the Pi), work out the peak and average current it requires, and the voltage (especially for the motors).

The peak current will have an impact on the selection of components and wiring, so that the whole thing works safely without catching fire.
The average current allows for how much work the device does -- again, especially the motors, are they running all the time or just for a few seconds during the run.
The voltage allows us to ensure that the system can supply each part with what it needs, and also to convert the current consuption to power(W) and thus to energy(Wh), which in turn determines battery size.
"If it ain't broke, fix it until it is."
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wh7qq
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Joined: Thu Oct 09, 2014 2:50 am

Re: RPi Power supply (battery) with protection circuit

Fri Feb 09, 2018 7:49 pm

And don't dismiss the wireless keyboard and mouse in your calculations. My logitech wireless mouse and wired keyboard draw 0.12 A so not to be ignored even though they "shouldn't be a problem". As far as the link you posted, that is a lot of different batteries with different shapes, sizes and electrical characteristics. You must do the research and come to your own conclusions as to what you want/need. You also need to consider how you are going to recharge. LiPo's require careful cycling and recharge control for maximum life and safety. We can point you in a direction but we cannot, or certainly should not, engineer your project for you.
Sent by WH7QQ from an RPi3/Raspbian/pixel desktop.

kunalgupta
Posts: 13
Joined: Wed Feb 07, 2018 7:33 am

Re: RPi Power supply (battery) with protection circuit

Tue May 15, 2018 10:57 am

I'm sorry for a reply this late. I was working on a different project. Now I'm back onto it, but I don't know whether u guys will reply.
wh7qq wrote:
Fri Feb 09, 2018 7:49 pm
And don't dismiss the wireless keyboard and mouse in your calculations. My logitech wireless mouse and wired keyboard draw 0.12 A so not to be ignored even though they "shouldn't be a problem".
I was planning to use both keyboard and mouse via a single usb dongle, only current consumed will be by the dongle. That is why I said shouldn't be a problem.
As far as the link you posted, that is a lot of different batteries with different shapes, sizes and electrical characteristics. You must do the research and come to your own conclusions as to what you want/need.

I did research quite a while and found the batteries which can fulfill my need of running two motors along with the Pi, Atmega and two motor drivers for about an hour.

You also need to consider how you are going to recharge. LiPo's require careful cycling and recharge control for maximum life and safety.
I'm using a Li-ion battery of 7.4V (a couple of 3.7V of 2500 mAh each (actual capacity is around 1000 mAh (chinese batteries)) ) and stepping it down to 5.1V via a LM39302 voltage regulator (also tried it with a Buck converter). The only problem I'm left with is the battery protection and charging part. For charging part, I looked at the TP4056 but it is only for charging a single 3.7V battery. If I've to use 7.4V, then I must charge both the batteries in a balanced way (balanced charging) and plus I also have to implement load sharing i.e. should work even while charging.
However for battery protection, I did reverse engineering of one of the circuits in market.
ic.jpg
ic.jpg (148.05 KiB) Viewed 142 times
Any ideas if this circuit will work?

We can point you in a direction but we cannot, or certainly should not, engineer your project for you.
Thank you for that.

kunalgupta
Posts: 13
Joined: Wed Feb 07, 2018 7:33 am

Re: RPi Power supply (battery) with protection circuit

Tue May 15, 2018 11:46 am

davidcoton wrote:
Thu Feb 08, 2018 9:54 am
That battery by itself will NOT work. There is no protection, no voltage regulation, and no charging circuit.
Please refer to my reply to wh7qq. USing LM39302 for regulation. Posted the battery protection circuit as well.
Please help with me with a circuit for balanced charging of two 3.7V li-ion batteries in series.
Go back to your list of parts. For each one (including the Pi), work out the peak and average current it requires, and the voltage (especially for the motors).
1. RPi 3 B : 0.5 A ideally, 0.7A avg, 1A peak
2. Wireless keyboard and mouse : 80 mA peak, 50 mA avg (may be less but not more)
3. 3.5 inch touch display : 150 mA peak, 140 mA avg
4. Atmega328p : 100 mA peak, 50 mA avg
5. Two Motor drivers : 2.5 mA peak, 2.2 mA avg
6. PiCamera & Microphone : 10-20 mA peak, 5 mA avg
7. Motors (running directly through battery voltage (7.4V)) : 150 mA each, 1 A stall
Avg adds up to 1.1 Amps and peak adds up to 2.35 Amps
The peak current will have an impact on the selection of components and wiring, so that the whole thing works safely without catching fire.
The average current allows for how much work the device does -- again, especially the motors, are they running all the time or just for a few seconds during the run.
The voltage allows us to ensure that the system can supply each part with what it needs, and also to convert the current consuption to power(W) and thus to energy(Wh), which in turn determines battery size.
Yeah I don't want anything to catch fire as I'm using chinese Li-ion batteries, can't trust them. Any suggestions on how to calculate the rest of the things you mentioned?

boyoh
Posts: 1125
Joined: Fri Nov 23, 2012 3:30 pm
Location: Selby. North Yorkshire .UK

Re: RPi Power supply (battery) with protection circuit

Wed May 16, 2018 7:43 pm

I'm getting very confused as to your answers to the project proposals given to you

You are asking witch battery is suitable for your project

Your answered was you have already chosen the battery .

AS for protection I would , I would add some current limiting on the battery out/put
to give circuit protection ,in the event of a fault (Short )

Do some research as type of charger that will will charge your battery type.

If you are waiting for some one to design a compleat circuit for you
that will not be don
BoyOh ( Selby, North Yorkshire.UK)
Some Times Right Some Times Wrong

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