A small update to this post. We ran across a great deal on solar panels and have upgraded the system for the RV. We picked up a pallet of 230 watt panels that were rejected on a large installation for minor visual flaws. We tested each panel for voltage and current and each panel meets and usually exceeds the manufacturers specifications. Most are in storage until we need them but we kept 2 and added them to the RV system. Just 2 panels has increased our system by 8 times!
We now run laptops, charge gadgets, charge tool batteries, use our blender and vacuum cleaner during the day with no worries! The old panels are now charging a secondary battery that is powering LED work lights for the construction site. You can read about details on the system below in the original post…
This is a repeat of a tweet from last summer but I thought I would add it to the blog just the same! In an effort to get used to the idea of living offgrid and working with a solar system, we converted our construction trailer (a.k.a. RV) to a solar system and doubled the capacity.
The images below show you the modification to the original battery system in the RV. I replaced the original battery and added a second to bring the capacity up to about 180 amp/hours. Using a Rubbermaid container I made a box to house the second battery and a power inverter. It sits under the RV itself and has a 110V power outlet. We use the outlet to run our hand vacuum cleaner, charge laptops, IPhones, power tools etc. I also changed every light in the camper from incandescent to LED. This reduced the lighting draw down to about a tenth of what it was with the incandescent bulbs. Overall the new system meets all of our needs for now but we may bump it up as we move ahead with construction.
With deep cycle batteries it is recommended to always keep your batteries above 80%. This will maximize the life span of the batteries. This means that the batteries should never drop below 10.5 volts or so (max is around 13.2 volts). To help regulate this and avoid battery damage I also added a voltage/current meter to the system. This meter is proving very valuable in other ways as we can now see what each appliance or device is drawing and adjust what we use when to maximize our stored power.
The batteries are charged by 3 small 25 watt solar panels. The panels are outputting 24 volts so we always have enough headroom to the charge controller to supply a consistent charge voltage even on overcast days. Since solar panels are not 100% efficient and the sun doesn’t always shine I calculate the solar panel output at about 75%. So with this in mind we can now refer to our meter to get an idea of how long we can run things. For example, if I run our vacuum cleaner for 1 hour straight I will pull 5 amps out of our battery system. This will take a little over 2 hours of sun to re-charge. Here is the math in case you’re interested (P=VA 75 watt panel at 75% is 56 watts divided by 24 volts is 2.33 amps per hour of charging if the sun is shining the entire time). So you can see it is easy to drain the system if you do not monitor it and manage your power use. The power usage adds up quickly when we are running a water pump, charging IPhones and laptops and running the electronics of our propane fridge.
Two or three overcast days could be an issue. Luckily we also have a generator to quickly charge the system if we run into problems. Another option is to add more panels which we plan to do this year. I’ll try to add to this post when I upgrade the system some more.
Feel free to add comments or ask questions using the comments section below the post.