My laptop has a 100 watt DC to DC power supply. The other night I streamed several movies in a row, until way too late. I have a RC watt meter inline on the power cord. The laptop alone consumed 42.96 amp hours in about 8 hours*. I was running the sound through my stereo. That and my 12v fridge and my fans/lights used up another 23 AH. My battery monitor claimed to be down 62AH when I shut down the laptop.
At 3pm the next day my single group31 battery had been held at 14.9v for 3 hours. My amp hour counting battery monitor indicated 100%, but it lies.
I have 198 watts if Solar. This time of year, it is almost always more than enough to get the battery to 97% or higher.
In wintertime, it is not, and I am at 32'N in a sunny climate.
Streaming a movie at full brightness is about 4.5 amps, the meter goes from 4.2 to 4.8amps
Typing this right now is 2.4 amps, bouncing from 1.7 to 3.3 with a rare 4.8 reading
There is about 10 feet of 10 gauge wire from the fuse block to the Anderson powerpole which feeds my DC to DC laptop power supply, so voltage readings on the watt meter are 0.5v or more, less than actual battery voltage. The watts the laptop pulls is accurate, but the voltage drop knocks off accuracy on the amp hours displayed.
If you need 9 hours of laptop use daily, the solar you require is More than me. The variable is how much the laptop actually draws in how you are going to use it. Huge variables exist in different laptops. Cycling the laptop's battery is wasteful, unless you know you will be able to charge it when you have an excess of solar, or are driving, or get to plug it into the grid. When I am charging my laptop's depleted battery and using it at the same time, I have seen 8.9 amps consumption, and the DC to DC converter does get warm.
http://www.amazon.com/GT-Power-Analyzer-Consumption-Performance/dp/B00C1BZSYO
* these are not 100% accurate, I'd say 88% to 97% depending on the load. Light loads are less accurate, and It cannot read loads under ~0.1 amp
They only come with 12 awg aluminum wires. I replaced this with 8 AWG wire right to circuit board and have 45 amp anderson powerpole connectors, and it can now pass 40 amps for hours without heating up excessively. Accuracy also improved.
Please don't try and pass 40 amps through these consistently with the provided 12awg aluminum wire. I'd say not more than ~20 amps continuously with it. The 130 amp claim is only for short bursts.
These only measure current flow in one direction. There is a source side and a load side. So it either measures amp flow out of the battery, or into the battery. One could wire in two and do some math and use them as a battery monitor in some smaller setups.( keep that ~20 amp limit in mind unless you modify it with fatter wire) They only count to 64 amps hours before reverting to 0.
