Arduino is in power_down_mode 23:50 min.. and 10 min awake with full power
so that means 0.11 Ah .. 2.44 Ah per day...
I have good price for solar kit
20W solar panel 12 V
5 Amps regulator
7.5 Ah battery
now .. would that works (would battery be charged over day) and it would last at least 2 days without sun (cloudy or rain)? or should i extend power to 15 Ah?
That depends entirely on where you live, what's the weather and how you position your solar panel, but yes, a 20W panel could conceivably charge a 7,5Ah 12V battery over the course of one sunny summer day.
Although I wouldn't count on it for those cloudy winter days, on higher (and lower for the down unders) geographical locations.
Consider going barebones instead of using a Mega. That should drop the power consumption significantly.
So during the 10 minutes it uses 300mA, and asleep it uses 100mA.
If you would use an energy efficient (Pololu) switching 5volt DC/DC converter between 12volt battery and Arduino instead of the inbuild lineair regulator.
Then those currents will be halved.
A 20watt panel, on an average location, average light, will produce about 5-6Ah over the day.
Enough to recharge an almost flat 7.5Ah battery.
A lead-acid battery should not be discharged more than 20-40%, unless it's a deep cycle battery.
Yes, I would use a 15Ah battery, or a use 30-40Ah car battery if that's possible.
Leo..
Your board does not use 100 mAh. It uses 100mA, or 100mAh per hour.
Mmm, barebones mega is a pain in the ass, since the 2560 isn't available in DIP package (though if he can fit it into a 1284, that one is available in pdip, which means you can easily make a barebones).
As for the matter of battery sizing... that's an oversized solar panel, so you should probably be able to get enough power to easily charge the battery if there's sun (note - you do need to have proper electronics to handle the charging - I'll assume you do. There's a ton of information on this if you don't).
What is a "5 amps regulator"?
What voltage is the battery? Usually they spec batteries based on the total of all cells in the battery, so that's 7,500 mAh @ ~3.7v. You will likely need a DC-DC converter, unless you're using a power-bank type battery that has one in it and outputs 5v already. In this case, you'll need to adjust your battery estimates appropriately, considering the efficienct of the converter (probably 90-95% - even the chinese crap ones are surprisingly good). So 1mAh from 5v = ~1.5 mAh from battery. Also, batteries always best-case their battery life numbers or flat out lie, particularly if they're imports (I have some "4000mAh" 18650's that have a measured capacity of ~800mAh)
I think what he's saying is it pulls 100mA when turned off, 300mA when on? That's how I interpreted it, anyway.
DrAzzy.
The OP has a 12volt solar panel kit.
I assume that comes with a solar regulator and a 12volt battery.
You DO need regulation when you use an oversized panel on a small battery.
7.5Ah batteries are almost always the sealed type, and they loose their electrolyte very fast when kept on more than 13.6volt. A 12v panel can produce >17v unloaded.
What is important regarding DC/DC converters is their idling current.
Some have very low efficiency, worse than a lineair regulator, when very little current is drawn.
Best to use a small one. e.g.