By Paul Cairns, M.A.Sc., Executive Director, SMARTNet Alliance
Have you heard about the Solar Cell Phone Challenge initiated by Darcy Whyte, inventorArtist? It was launched at Green Drinks Ottawa in January 2017. The challenge: Power your cell phone with nothing but solar power! (i.e. get it off the grid!).
I personally love this challenge. It is a GREAT way to learn about solar/storage, how it may affect your habits, and what to expect when going off the grid, all for less than a $100 investment (much cheaper than spending $30,000 for panels on your roof if you ask me).
I’ve had my cell phone off the grid for 10 weeks now without:
- having to turn off my cell phone (other than restarting it for updates);
- having it die; and,
- having to plug it (or my external batteries) into the grid ONCE.
It was actually much easier than I thought it would be. It just took a little bit of research and about a week of trial and error (I DID have to plug into the grid once during my first week due to not understanding how to manage my batteries, but haven’t since).
This article is meant to save you some of the headaches I had to go through and teach you how you can get YOUR cell phone off the grid and do it SUCCESSFULLY!
Let’s get started!
1) The Equipment – Portable solar panel(s) and external battery packs
When I started the challenge, it was January in Ottawa. The first 10 days were completely overcast with snowstorms. It was rough! So I wanted to make sure that I would SUCCEED. To do that I bought two 16 W portable solar panels and two 15600 mAh portable batteries on Amazon.
The cost for all four was ~$150 (CAD), but I would say I went a little overkill and YOU could do it with one panel and two external batteries (total ~$100 CAD) without having to change your habits significantly. If you wanted to go DIE HARD you COULD do it with one panel and one external battery. I would also research other options. This is what was available at the time, but there are always new and better products coming out on the market and if you CAN get a larger panel (18-20W) and/or a larger battery I would recommend it.
2) The Setup – Charge Batteries and Install Panels in South Facing Window
One mistake I made when I first got the external batteries was that I started using them right AWAY. This is a NO-NO (and why I had to plug them into the grid in my first week to reset the level reader). Read the instructions CAREFULLY, but what I was SUPPOSED to do, was put them on to charge (you can cheat a little and use the grid for your first top up). If you don’t fully charge them the first time it will affect the level reader memory and tell you it's fully charged when it isn’t. So READ THE INSTRUCTIONS and charge them fully to start. Once your external batteries are charged fully you can install the panels.
I hung my panels up in a southward* facing window vertically as shown in the photo below. That’s all you really need to do, just make sure that the window gets the most sun and try to hang them as close to the window as you can, this will ensure that you get as much sunlight as possible. The tops of my windows were shady pretty well the entire day because of the roof overhang so I hung them closer to the bottom. Another tip is to try and hang them horizontally (see the other example below). It’s a little trickier but it works. All in all, set it up so that it gets AS MUCH SUNLIGHT AS POSSIBLE. SIMPLE!
*Note: if you don’t have a southward facing window your next best option is west followed by east and north as an absolute last resort.
Solar panels: vertical set-up and horizontal set-up:
3) About Battery Management – Keep All Batteries Between 40% and 90% full if they are Li-ion
That was the easy part. Now for the MOST CRITICAL aspect. BATTERY MANAGEMENT. This is where the knowledge bombs are going to get dropped. It is EXTREMELY IMPORTANT that you know what kind of batteries your battery pack and cell phone have because this will affect the recommended Depth of Discharge (DoD) and the number of Cycles. NiCad batteries last longest if you cycle them through a 100%DoD. Lead acid and Li-ion batteries, however, prefer a 60% DoD (i.e. only let them get to 40% capacity) and a recharge capacity of 80%. For those who want the details, you can find them here, but to make it short and sweet, the best DoD/cycle ratio, and thus battery lifetime, occurs when you cycle between 40% and 80% capacity for Li-ion. You WILL want to recharge to 100% every few weeks. To play it safe you can just always charge up to 100% if you want. The real point is, don’t let your batteries (cell phone or battery pack) get below 40% without recharging them if you can avoid it. This is really quite easy if you keep your battery pack on you during the day. In short, you want to always be “topping up your batteries” whenever you can.
This is where most people have issues. Because of our old NiCad laptop days, we were trained to let our laptop FULLY DISCHARGE before recharging it because it would reduce its MEMORY. This is not the case ANYMORE. Li-ion batteries are different. They actually prefer being topped up and DON’T have CHEMICAL MEMORY. Also, you can leave them PLUGGED IN ALL THE TIME and it will not AFFECT the battery life. The one habit that will have to change is not to let your cell phone die anymore. Instead, run it down to 40% and top it up.
4) What your Day Will Look Like and Other Useful Tips
So how does this translate into your day to day? First things first, if your cell phone doesn’t display the charge % in the top, go into your settings and turn that feature on. Knowledge is power, and you ALWAYS want to know what level your cell phone battery is at. If you can make it through the day without going below 40% on your cell phone, perfect! Leave your external battery pack at home plugged into your solar panels and then charge up your cell phone at night. If not, you will need two battery packs, one that is on the solar panels charging/topping up (not allowing IT to go below 40% if possible), and the other one with you during the day so you can top up your phone while out and about.
If your phone is a BATTERY HOG, evaluate your usage, you may be able to extend battery life for the day by simply reducing the brightness of your screen, turning off data when you’re not using it, or even just using “power saver” mode on your phone’s settings. If you don’t want to change your habits AT ALL, go buy an extra panel and battery pack. But it’s cheaper to make these small changes - REDUCE, REUSE then RECYCLE.
For those who use their cell phone for an alarm clock and don’t turn it off at night, my phone has “EXTREME POWER SAVER MODE”, yours probably does too. USE IT, it's awesome, it allows you to receive phone calls, text messages, e-mails, and yes, your alarm will stay on and it won’t use anything more than about 3% of your battery capacity over the entire night! For those who don’t need their cell phone when they sleep, you can simply turn it off (I don’t have to do this).
If you really want to get energy conscious and try to get off grid for as little as possible, you can use EXTREME POWER SAVER MODE during the day, the only thing that you won’t receive are Facebook and Twitter updates, so if you’re addicted to social media you can turn off extreme power saver mode a couple of times a day and get all your notifications at once.
5) How to survive consecutive days without the sun
If you find that you get 10 or 15 days in a row overcast things might get a little tough. Don’t sweat it, though, even on overcast days your solar panels WILL PRODUCE power, just not enough to top your batteries up as quickly. If you ever get yourself into this kind of a jam, this is where you can use your 40% reserve (assuming that you kept your battery pack above 40% as previously mentioned). Only run your cell phone below 40% when you ABSOLUTELY HAVE NO OTHER OPTION. You want to keep that 40% reserve on your cell phone for when you get lost in the desert or something.
If the overcast is SUPER BAD EVERY DAY (highly unlikely) and you just can’t top up your battery packs at all, then I would resort to EXTREME POWER SAVER MODE during the day and turn it off at night. Running your cell phone from 100% on EXTREME POWER SAVER mode will take 10 days in itself. You may have to do this MAYBE ONCE in a year.
If you really can’t manage, there’s always the grid, but TRY to use it as an ABSOLUTE LAST RESORT. If you HAVE to use it, don’t worry, you’ve still cut your grid dependence by 99% so good on ya! Learn what you did wrong, and figure out how you can avoid it in the future. NOBODY’S PERFECT.
Well that’s it! Good luck to you all! And most importantly HAVE FUN! This is a really hands-on way to learn about solar and prepare yourself for the future ahead!
Paul Cairns, M.A.Sc.