How much hours Arduino survive with a 12v 1.2Ah battery

hi , i want know how much hours an arduino uno can still on while is powered by a battery with 12v 1.2Ah , since the consumption is : Power = 5v * 46.5mA = 232.5mW Thanks ...

Is this an academic exercise, or do you want to get the maximum run-time from your battery? If the latter, you can do better than heating up the environment pointlessly with a linear regulator.

per example i want have my arduino like a watering system , and i want the arduino always on and i want to have a battery to power the arduino the maximum possible , and i want know hou much hours the arduino can endure ...

Approx 25 hours, obtained by dividing the batteries AH rating 1200 by 46. But this is an extremely inefficient way of running an Arduino from a battery. Most of the batteries energy is wasted.

My ideia is : Arduino watering system , powered by a 12v 1.2Ah battery and thr battery is charged by a solar panel ( 12v 1.5W ) what do you think ?

Well, at 46mA, the Arduino is using about 0.5W from the battery. The solar cell only makes the claimed 1.5W in perfect conditions (midday in Australia) so you should count on it making only 1W for 8-12 hours per day. Lower when you are further from the equator or in winter time or in an area that gets lots of clouds.

So the solar cell will be making somewhat less than 0.5watt-days per day, but the Arduino consumes 0.5watt-days every day. It's simply not powerful enough, although it is close.

The other part of the equation is: how much power does the other stuff attached to the Arduino use? You haven't said how much power that uses per day.

I will need see the power per day so ...i know i use Ethernet and a relay board

Nonetheless, I find it really interesting that, for experts like you, it seems to be difficult to convert a Fritzing diagram like mine in your head to a schematic.

So you have to add the current that they take to the basic Arduino current.

Note AWOL’s post #1. You can buy very cheap (<£1) switching regulators which will be more than twice as efficient as a linear regulator in converting 12v to 5v

look at eg

http://www.ebay.co.uk/sch/sis.html?_nkw=10x+Mini-360+DC-DC+4.75V-23V+to+1V-17V+Buck+Converter+Step+Down+Power+supply&_id=122087412850&&_trksid=p2057872.m2749.l2658

And since the arduino will spend most of it’s time doing nothing, check out on this forum Nick Gammon’s comprehensive guide to reducing power consumption.

Plus turn off everything you’re not using until you need it . And use latching relays.

I bet you could get the power consumption down to <1mA average if you tried.

Allan

brunofmc: hi , i want know how much hours an arduino uno can still on while is powered by a battery with 12v 1.2Ah , since the consumption is : Power = 5v * 46.5mA = 232.5mW Thanks ...

If you use a Uno board with all SMD parts, or a Mini/Nano, you will find they use about half the power of a Dip board.

mauried: Approx 25 hours, obtained by dividing the batteries AH rating 1200 by 46. But this is an extremely inefficient way of running an Arduino from a battery. Most of the batteries energy is wasted.

With a DC-DC converter you might get about 50 hours.

With a real-world 1.2Ah battery after a few months or years you'll have maybe 0.7Ah as capacity drops with age and use - the 1.2 figure is for a new freshly charged battery.

If this is a lead-acid battery and you abuse it by over-discharge, even once, its capacity will drop like a stone...

If you need micropower, consider a board without a USB-serial chip, then you can use sleep-mode and get dramatic reductions in consumption.

Switching is nice, but not the main screw to turn here, I guess. Lets rather talk about what the Arduino needs to monitor, how often it has to do something, etc. I just set up a door switch with power hog ESP8266 that is expected to run multiple month on a 18650 LiPo

Where will the power to operate the delay and solenoid valve come from and how long per hour/day will each be energised.