USB mobile device charger to power arduino. Safe ?

Hi, I have an external lithium-ion battery pack made to recharge mobile devices. That battery pack itself is recharged when connected to a computer with USB port and once unplugged from the PC it's able to recharge mobile phones.

I tried to plug the USB cable of my arduino into the USB port of the battery pack and the arduino did worked but I'd like to know if this is something I can do long term or if I could damage the arduino using that battery pack.

Also I'd like to know how long the arduino could run with a 3400mAH battery. The label say that it output 5.5V.

-- Frédéric

As long as its only putting out 5V your fine.

The label say that it output 5.5V

5.5V is pushing it a bit. I would be careful or get a small loss regulator (if that's what they're called) to keep it at 5V

Mowcius

Also I'd like to know how long the arduino could run with a 3400mAH battery

It depends on how much current it takes from those batteries (and you can measure the current with an ammeter). For example, if your whole Arduino-based device takes 34mA, the batteries will last, theoretically, 100 hours (3,400mAh / 34mA).

You really need to check the voltage with a voltmeter to confirm it's 5.5vdc or less.... Remember, the total rating of a battery is not available for use - even with a LiOn battery I'd expect less than 75% use.... Realistically expect a bit over 50 hrs of useful battery life.

Ken H.

Hi,

thank you very much for your replies. I think I will buy a multi meter.

-- Frédéric

5.5V is pushing it a bit. I would be careful or get a small loss regulator (if that's what they're called) to keep it at 5V

wire a standard silicon diode in series with the + side to drop 0.7 volts off, and your good

and no, its a Low Drop Out (LDO) regulator

Low Drop Out (LDO) regulator

Knew it was somethunk like that :P

Hi, googling for USB voltage… the max. by its standard is 5.25V.
From the ATmega328 datasheet its rated max is 5.5V.
So, I think your board/CPU is safe.

From the topics and discussions I have read the majority of concern is about the low/minimum voltage and the total current draw.

And, here is what I know from experience, the Arduino core software EATS batteries. A recent toy of mine is a simple binary clock, a 9v PP3 died in less than 24 hours! The main loop is running at 100% all the time.

I am experimenting with a delay2() function using timer2 and compare-A interrupt (gives less jitter than overflow) and… set_sleep_mode(SLEEP_MODE_EXT_STANDBY). This all works and my clock keeps time correctly. I have not yet measured the power saving as I was about to move on to PRR – Power Reduction Register - to turn off unused parts of the chip (I’ll try using macros in avr/power.h). Finally I will increase the system clock prescaler reducing the system clock from 16Mhz to 1Mhz (or as much as I can). This allows the timer2 to remain in sleep longer, this means delay2()'s precision will be under 1ms (but its accuracy will remain the same!!). I also believe the overall power consumption is reduced by slowing the clock. Then, a final step may be to lower the supply voltage to the ATmega to 3.3V (requires the system clock =<8Mhz) I may buy a clone like Seeeduino (switchable supply voltage 3.3V or 5V) or Freeduino SB (powerdown of FT232 USB-Serial chip) to avoid soldering and take advantage of their hardware power saving modifications to complement the software changes I am working on.

I am going to look at the recent posting of DuinOS.

Hope this gives you some ideas.