# How to determine the Solar-panel power requirement battery

I'm having a problem calculating the rated power requirement for my solar panel project. The panel will charge a battery that will power a 'micro' water pump.

The power requirement for the pump is .827 Watts (very small, I know, it's in the project requirements).

Can I use a deep cycle battery with this size?

My motor consumes 1 watt at 40rpm 6v, based in Ireland (weather and sunlight hours).

• What is the anticipated duty-cycle for your pump (i.e. how many hrs/day of 0.827W power demand)? Commented Feb 16, 2016 at 14:28
• Sunshine hours - 4th hart top ine. Dublin is 4-5 hrs/day over mid summer and under 1 hour/day over 3 months in winter, Panel and battery must be sized accordingly. Std lead acid use only top 50% od capacity for longer life. gaisma.com/en/location/dublin.html Commented Feb 16, 2016 at 15:17

## 2 Answers

First you need to know the amount of daily working hours of the motor. How many days do you plan to run it without sun ( cloudy days)? Even deep cicle batteries suffer from deep discharge. Put in your calculations that you shouldn't discharge frequently the battery, no more than 30% ( for depp c. battery) THe solar panel should be able to charge the battery on sunny days. So make the calculations for the solar panel depending where you live. Use this for the calculations. http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php#

Battery required:

Motor is consuming 1 Watt of electricity at 6V. (W=V*I) then I=166mA

if you use 6V 1000mAH battery your motor will run approx 6 hours with one full charge battery.

Solar panel:

You can use solar panel to around 12V(technically 7V would be nice but depending upon the sun light it will be charging battery only in full sun light)

If you are using 12V 100mA solar panel and assuming sun light is available to charge battery for 6 hours per days. it will take 1.5 days to full charge the battery.

• I think you dropped a decimal point. Commented Feb 16, 2016 at 15:51