Our System
Goal Zero Yeti 400 Watt Hour Battery
What does 400 Watt Hour mean?
A “watt hour” is a measure of energy usage or storage. With one watt hour of energy stored in a battery, a light bulb pulling 1 watt could run for an hour, a 2 watt bulb for 30 minutes, and a 3 watt bulb for around 20 minutes. With 100 watt hours stored we could run a thing that pulls 100 watts for one hour, or a thing that pulls 1 watt for 100 hours. Our battery holds 400 watt hours.
Computer Batteries and Consumption
My MacBook air has a 50 watt hour battery. So with our Yeti 400 battery full, I can charge my laptop zero to full around 8 times. It’s important to remember though, that computer power consumption is variable. This is why computer batteries sometimes last 10 hours, sometimes 2. If the computer is doing complex tasks, such as playing videos, its energy consumption will be far greater than if it were running a note taking program.
Lets take watching a video on Youtube for example. The computer may pull 20 watts from its battery, to power all the pixels and do the computation for the video to play. If this were the case, we could watch video for around just under 3 hours given a 50 watt hour battery. Every hour we would draw 20 watt hours, 20 watt hours times 3 is 60 watt hours. Running our note taking app, it may only pull 5 watts from the computer's internal battery. Thus allowing us to take notes for 10 hours on a full 50 watt hour battery.
Goal Zero Boulder 30 Watt Solar Panel
What does a 30 watt solar panel do?
Our solar panel is rated to 30 watts. Meaning, in perfect conditions, it can harvest a maximum of 30 watts. The most we normally see on sunny days is around 25 watts. Dust on the panel, atmospheric density, length of the cable, and many other factors influence the efficiency of the panel. So if we have the panel positioned optimally for solar collection, we can expect to generate around 25 watts per hour. In 4 hours we store around 100 watt hours of power in our battery. So to fill the battery from empty to full or 0 to 400 watt hours, we would need the panel in the direct sun for around 16 hours.
Daily usage
We use the battery to charge laptops, iPads, phones, lights, Anker battery, speaker, camera batteries, lasers and more. We don't use an electric fridge*, blender, coffee maker, or water boiler.
If we're working in town, we charge our computers wherever we're working. This way we don't have to be as diligent keeping up with the battery.
On days we spend several hours working on our computers in the Scamp, we can be more intentional with energy collection, thus offsetting our increased usage.
Sometimes the battery gets low from watching movies, editing videos, playing video games and cloudy days. If we need to catch the battery's charge up, we put the battery in the car to charge as we drive. We don’t do this often, though, because we don’t want to put more strain than is necessary on the electrical system of the Scoop.
Modular Batteries
Most of our devices have an internal battery of their own. This increases our collective battery bank significantly, and prevents us from having a bunch of things plugged into the main battery all of the time.
Another aspect of modularity within our solar setup is the panel and battery combo. The fact that they're portable allows for us to place them in the sun as far from the Scamp as needed.
Modularly Powered Devices
Biolite BaseLantern
Biolite CampStove (generates power of its own when we cook)
Computers
Bose Speaker
Camera batteries
Anker Battery
iPhones
Headlamps
Charge Optimization
It’s best to charge other batteries when the main battery is at full capacity. Because when the battery is full, the panel’s energy input is wasted. When the battery is full we plug in a laptop or other device with internal battery, so we can store power beyond the capacity of our main battery.
Future Computers & Efficiency
If our laptops were capable of running on DC power, we could plug them directly into the solar panel, making the system more efficient. But since there is not a DC cord for our Mac’s, we have to use the battery’s inverter. If we had a computer which could be powered with USB-C like the “new MacBook”, we could plug directly into the panel, relinquishing the power wasted inverting DC to AC.
Final thoughts
This 400 watt hour setup works great for us. People often scoff at our small power reserve, but it's rarely an issue. Solar power seems daunting initially, but the best way I've found to understand it is through personal usage.
Did I miss anything you'd like to see answered? Please comment below. <3