# Schematic battery rescue for 9V battery

In my project I am using a 9V battery so I can read and compare the voltage to lower threshold value which is normally 5V (operation voltage level typically for Arduino). So if the voltage goes lower 5.00V it should activate theoretically rescue 5V battery.

V1: 9V Battery
VCC-Arduino output pin#8 (5V to trigger up IRLU014)
R1 and R2: voltage divider=4.90 Output
V2: 5Vbattery 1350mAh

It looks like great on multisim everything is working perfectly. I am not sure how good is it in real life…

``````/*************************************************************************
VOLTAGE DIVIDER R2(1.220kOhm)-GND  R1(1.000kOhm)+9V  V2=V1*(R1+R2)/R2
/************************************************************************/

const int BATpin=A2;
float BATVoltDiv=0;
float BATVoltInit=0;
int samples=15;

void setup(){

/********************************************************
BAT PIN CONFIGURATION
/********************************************************/

pinMode(BATpin, INPUT);
}

for(int i=0; i<=samples; i++){
BATVoltInit=BATVoltDiv*(1.000+1.220)/1.000-1.45; //Correction 1.45
}
}
``````

Where is the loop) function ?

Sorry my sketch was too big, so this is only a part. the loop is just after setup(){}

Hi,

Can you please post a COMPLETE copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?

Not a multisim or fritzy diagram thanks.
What will the 9V battery be powering?
What is the application?

Thanks… Tom…

the circuit is attached just after my post...

Hi,

the circuit is attached just after my post..

Sorry they are not schematics, they are a simulator graphic.

You need to show batteries, arduino, switching components, other components.

Have you built the circuit in real life?
Do you have it working with controller and code?

Tom....

Sorry for that. Let’s fix it.

To describe briefly Arduino application (it set’s via bluetooth Time with RTC module, and transmits voltage from a 9V battery, Time, Electromagnetic Field from both antennas, and able to activate another battery 5V if 9V gets < 5.00V - here I am).

A drawing:

http://s7.postimg.org/56ukjmrdn/Slide1.jpg

That isn't any better, but I see 2 problems already.

1. when the rescue battery is engaged the stronger battery will try to charge the weaker battery.

2. the RAW pin goes through the arduino's voltage regulator which will drop a volt or so.
You need 7v to 12v when supplying power via the RAW pin.

if you wish to use a 5v battery it needs to connect to Vcc which bypasses the regulator.
and yes #1 above still applies

Oh! Thank you a lot for this information. I was in doubt about this connection. You projected some light on it! Thank you.

Nick2012Future:
I am not sure how good is it in real life…

~2k2 across a 9volt battery (4mA) will drain it in less than 4days.
Leo…

Wawa:
~2k2 across a 9volt battery (4mA) will drain it in less than 4days.
Leo..

No-no this is not a question I have a rescue battery connected as the same that can be activated when a voltage drop is above the limit 5.00V.

I rode that RAW is about 7-12V is that people saying, In my case, I am using Arduino mini pro 5V (very happy with that: works pretty stable with majority of modules). I tested 5V on RAW pin and it works as well. I able to detect bluetooth module with my cellphone, not with my computer. But it's already something : ))

Nick2012Future:
I tested 5V on RAW pin and it works as well.

Sure it will work for a while. but the strain will soon kill it.

Hutkikz:
Sure it will work for a while. but the strain will soon kill it.

Very impressive!

I notices an interesting fact that the USB battery rescue pack (works with cellphone Samsung) is shutting down its power port to absolute 0V (I think that its due to small current output 40mA which should be close to 1A as specifications says). It works for I wile and suddenly 0V. Is there any way to make this battery work a "little bit longer" - I mean for the rest of the time.

Nick2012Future:
Very impressive!

Not sure what you mean here, but maybe this person's experience demonstrates the concept better

pmhassin

I have had two of these things fail on me in the last few weeks. I have mine connected to 5.2 V on the RAW pin. It works fine for awhile, then the Arduino just go bad. Anyone else have this problem????!!!

kevink

You’re going to need more than 5.2V for the RAW pin. The RAW pin uses a regulator, which has a dropout voltage of ~1.7V. This means the board is only getting 3.5V, which is not enough. If you have to use the 5.2V supply I would suggest you get the 3.3V version.
Another option would be to regulate to 5V outside of the board and connect to any VCC pin.

I think that its due to small current output 40mA which should be close to 1A as specifications says

the spec means that up to 1A may be safely drawn from it. with only 40 mA it should last much longer. as far as why it would suddenly go to 0v sounds like it may be defective.

Hutkikz:
Not sure what you mean here, but maybe this person's experience demonstrates the concept better

Maybe I should write differently, I mean Hutkikz is giving new glance over things.

Thank you Hutkikz! That took me a while to figure out how to connect the Rescue battery, because it's refusing to work after some seconds (as you said due to small output current which is 40mA on VCC pin). And I learned here that we can't use 5.2V on RAW pin. I figured out how to satisfy the battery and the board at the same time, so I connected the rescue battery on VCC and RAW pin and I noticed that current increased to 100mA at 100mA the battery is not trying to shutting down.