Something I’ve not seen discussed here recently (or often) is having an energy/battery back-up. I think it’s probably fairly common for folks to have a UPS type backup for short outages. But what about hours or days? A couple of months ago we had a tornado pass through our area which had a direct hit on the main office of our local electric co-op and just a few miles away another hit on an electrical substation. I was one of the lucky ones and only lost power for 3 days. Others were out for many more days. It’s not uncommon in our area to have a short, multi-hour outage once a month and longer, day-long outage a couple times a year, usually due to severe storms with strong winds.
I’ve got a UPS for my MacMini that ensures a safe shut-down but for longer outages I decided I wanted a bit more and thought I’d share what I’ve come up with and what it will do for me in the case of day-long or multi-day power loss.
My budget was between $500 and $1000. The goal was to be able to power a few lights in the evening, keep the internet on and keep my iPad and iPhone charged and to do this for 2-3 days and with careful use perhaps 4 days. I use a well so this would not get me water, cooking, heating or cooling. The initial goal was just creating a base level comfort of lights in the evening and access to the internet and computing with the iPad and iPhone.
After a bit of research I decided to go with the Bluetti EB70 which sells for between $500 and $600. Currently $600.
At around 650 usable watt hours this backup will let me power a 6 watt string light, 10 watt bulb, 5 watt hotspot, 15 watt small table-top fan for a total of 36 watts per hour. At 5 hours a day that’s 180 WH per day, so 2 days is 360 WH used. So that leaves just under 300 WH for charging the iPad and iPhone. Three full iPad Pro charges would be around 120 WH and two full iPhone charges would be around 24 WH. That leaves just around 150 WH.
So, two days would be pretty doable. With more careful use I could probably stretch to three days.
One of the considerations in this kind of battery back-up is charge cycles. I went with the Bluetti because they are Lithium Phosphate cells which mean 2500 cycles compared to Lithium-ion which is are likely in the 700 cycle range.
In thinking about how many watts this category of device can output at any given moment, it’s important to note they’re usually 800 watts or less so no high energy device… no microwaves, coffee makers, etc. But it can handle quite a few low energy devices (up to 800 watts for this particular unit). So, if I only needed power for a day I could not only run a couple lights and charge my iPhone/iPad but my smallish energy efficient fridge only pulls around 40 watts so I could also run that for a few hours. Or, I could run my smallish TV, AppleTV, 2 HomePods.
In testing my set-up I plugged in several lights, the small fan, AppleTV, TV, 2 HomePods. I ran the lights during the afternoon and in the evening added the TV, AppleTV, AirPort Extreme and HomePods for 2 hours. That full load, all attached to a power strip, is only about 100 watts, so, not much, not even close to the 800 watt capacity. In addition to the 4 standard AC plugs, there are also 2 100 watt USB C ports, USB A, and a spot on top for wireless charging of a phone.
These units can be charged up via a standard wall outlet in 3-4 hours, a car takes several hours more or a solar panel. I opted to also get a 200 watt rigid solar panel
What does the solar panel get me in practical terms? The Bluetti EB70 will only take in about 150 watts from this panel which means on a sunny day it will fully recharge in 5-6 hours. This changes though based on cloud cover and time of year/angle of sun. They will, assuming at least a few hours of sun, give me indefinite (though still carefully moderated) power supply of 650 WH per day.
This panel cost around $220. I also added an extra 50 feet of cable so that I can charge without moving the battery so that’s additional cost. It’s just plug and play. I securely attached the panels to my south facing porch, plugged the cable in and ran that into my tiny house and plugged it into the Bluetti. 10 minutes.
Solar charging on a mostly clear winter day, around 2pm, 131 watts from the sun.
There are other solar panel options including portable folding panels. Bluetti offers two different folding panel options geared towards mobile use, both at significantly higher cost than rigid panels from other companies. As I expect to use this primarily at my tiny house I chose a rigid panel for lower cost.
My last consideration for a future change is that at some point I’ll need to replace my 2012 MacMini. I’d previously planned to replace it with another MacMini but now plan to replace it with a MacBook Air. The reason being that my general set-up is that the Mac shares internet: Hotspot to Mac via Wi-Fi which shares via Ethernet to the AirportExtreme which then shares to all my other devices via Wi-Fi. The MacBook Air would be a better solution during a power outage as it would not affect the internet at all even if some of the HomeKit devices would be offline. The hubs and a few lights would just continue with no affect at all.
Anyone else have additional energy back-up?