Hi, everybody. I am building a little autonomous car using arduino nano V3.0. I have two smart phone batteries, and I am going to use those as my power. I have a DC motor with L293D chip, an ultrasonic distance sensor, 3 LED lights and my arduino board in my car. The cell phone batteries are 3.7 volts each,so total 7.4v. One is 1700 mAh, the other one is 1520 mAh. I can power the board by using pin 27, which is labeled by '5v'. But it has some weird behaviors. For instance, the sensor stops working. Actually, I don't know if it stops or not. I can hear it clicking, but it just can't measure the distance. When i switch to pin 30, which is the vin one. The whole thing doesn't work at all. So am I using the wrong pins or i just can't use these batteries as my power? Does the ground pin matter, because there are 2 ground pins on both sides of nano, I am kinda confused when using it.
can you teach me how to connect it? Thanks.
Don't use cell phone batteries . PERIOD. It's a long story but the short version is they are made for VERY LOW POWER CIRCUITRY.
Most of the stuff you described does not begin to fall into that category and the L293 IS JUST PLAIN CRAZY to try to run from a cell phone battery. It's so crazy I won't even talk about it . Just forget it .PERIOD. Get some RC batteries , or just one. Get a 2S 2200mAhr
battery, 25C to 40C. Make sure to use a Lipo charger. If you don't want to use Lipo's then use NiCad. They're heavier but don't have
some of the hazards that Lipos have. Ask around and you'll find out what I am talking about. Just to put it into perspective. If for some reason you weren't paying attention and accidently shorted the leads of a Lipo battery, it would burst into flames instantly,
just like that , every time. I acidently punctured one with my pocket knife trying to separate two of the cells and it burst into flames right in my hand. Yes, I dropped it like a hot potato. and it scorched the parking lot asphalt. That's Lipo's for you.
really appreciate your reply. But can you explain to me why not use cell phone batteries to power my car? I was thinking it was a pretty good idea, because I just had two batteries that were unused, and cell phone batteries are small, portable. I even have cleared the middle of the car for holding the batteries. My car is really not that big, It is just 15cm * 8cm * I don't know the height yet. Are there any ways that I can make use of those cell phones batteries?
Thanks.
I told you it was complicated. Now you want to get into the internal resistance of a cell phone battery compare to other batteries,
like C or D batteries. Do you know what internal resistance is ? Do you know the relationship between current and resistance as defined by Ohm's Law (E= I x R, P= I x E ) ?
Ok, you asked for it: don't say I didn't warn you..
Long story short: If the internal resistance is too high , then I = E/R < I (motor[min]) (The current is equal to the voltage devided by the resistance. In the case of the cell phone battery, the result of this calculation is a value of current that is below the minimum current necessary to drive the motor of the car. It might work for a second or two but I would be surprised if you are not loading the battery down so much that the voltage drops to almost zero until you disconnect the load. Did you try monitoring the battery voltage when you try to power everything from the battery ? Does the battery voltage drop drastically when you connect the motor and everything else ?