# Calculation for power consumption

#### j3r

Joined Jan 9, 2011
15
I want to power a device using solar panel. The device's manual stated
Recommended power supply 24 W, 24 VDC
Power consumption 15 W maximum

Obviously i need a 24W solar panel. However i'm kinda of confuse as with Ampere Hour.

For example, i want to let me device run for 1 day 24 hours on 24Volts @ 1A.

How do i calculate the required power?

P = V*I

I'm missing the duration. Hmmmmm.

#### kubeek

Joined Sep 20, 2005
5,776
Power is instanteneous. Energy is based on time x power.
So over 24 hours your device consumes 24x24x1 Wh = 0.576kWh.

#### j3r

Joined Jan 9, 2011
15
Thanks for the reply. Sorry, i missed out some information.

Between the device and the panel lies a battery management system. Connected to the battery management system are 2 batteries total having 28.8V (14.4V each)

I wanted to have the solar panel which can be connected to the battery management system so that it can charge the batteries. However i'm confuse which to choose.

There's a 32Watt one, 60 watt one...........

Many thanks!

#### kubeek

Joined Sep 20, 2005
5,776
It shouldn´t matter, it will only take longer to charge the batteries with smaller-wattage panel. Also the Ah rating of the batteries is another factor in how long will it take to charge them.