Some homeowners may be able to spend between $5,000 – $20,000 on a solar power system to avoid load shedding, but for most of us looking for cheap solutions, an inexpensive UPS (uninterrupted power supply) backup system is the most accessible (and temporary) way to keep electrical appliances running for a few hours while the power is out.
With a wide range of mostly inexpensive products on the market, from a few hundred rand to a hundred thousand rand, it’s important to make choices that meet our energy needs and are based on good information.
“You need to know how much power the appliance you want to fix uses. Usually, you wouldn’t need to know that, but because of the energy situation we’re in, we all need to understand what these numbers mean “Kinesh Chetty, who used to run the Maxx Solar academy in Johannesburg and is an energy consultant who specialises in solar (PV) energy systems, says this.
Below, he explains the difference between watts, volts, and amps, which are three ways that retailers often measure the amount of energy that UPS backup batteries can hold.
What’s up?
Chetty says that even though the science might sound hard, one of the easiest ways for the average person to choose the right UPS backup system is to know how much power each appliance uses.
On the back of a typical flat-screen TV, for example, there is a small sticker with a nameplate rating that tells you things like the voltage and the watts. On a typical 49-inch smart TV, the label might say that it uses 100 watts of power.
In practise, this means that the TV only needs a little bit less than 100 watts of power. So, if a person wanted a UPS backup to power just the TV for 4.5 hours of Stage 6 load shedding, they would multiply 100 watts by 4.5 hours to get an idea of how much energy they would need from the UPS, which in this case would be about 450wh (watt hours).
Another user might be looking for backup power for 2.5 hours during Stage 4 daytime load shedding so they can stay connected to their Wi-Fi and maybe charge their laptop and phone.
Chetty tells them to use the same formula here by adding up the power ratings on the different appliances they plan to plug into the UPS and multiplying that number by the number of hours they think they will need power. Then you have to make sure that the UPS has enough watt hours.
If there are no watts, maths will be used.
But not all appliances will show the number of watts they use. Some devices, like routers and smartphones, that use little energy will only have measurements for volts (V) and amps (A). In that case, one more calculation will be needed.
To get the watts measurement, you just need to multiply the voltage by the amps measurement. As was said above, check twice to see if the UPS’s watt output is enough for what you need.
For instance, if you turn a 2017 MacBook Pro on its side, you’ll see that it can handle up to 20 volts and 4.3 amps. Add these two numbers together to get 86 watt hours. So, you can be sure that is the most energy the computer will use, even though it will usually use a little less.
Some UPS units will only show the milli-Amp hours (mAH) units. Even though this is a bit more technical, 1 Amp Hour is the same as 1,000 mAh. So, even though that cheap USB may sound impressive when it says it has 8,000 mAh, remember that is only eight amp hours, and multiply that by the voltage it says it has.
For example, the standard iPhone 13 has a 3,227 mAh battery (3.2 amps). The voltage of the battery is said to be 3.8 volts. When you multiply 3.8 volts by 3.2 amps, you get about 12.16 watt hours. You can also just Google the watt hour rating if you don’t want to do the math.
If you needed enough power to charge an iPhone, keep a MacBook Pro laptop plugged in, and run a typical router that uses 7 wh of power, you would add the 86wh of the laptop to the 12.16wh of the iPhone and the 7wh of the router, for a total of 105.16wh. Over a period of two and a half hours, these three appliances would use up to 263 watts (wh).
A small UPS that can be bought at a local store for R1,900 is said to have a 57wh capacity. In this situation, this wouldn’t be enough for all three, but if you charged the laptop before the power went out, it would be enough to charge the phone and keep the router running.
Since the phone would probably take about an hour to fully charge, you would have even more watt hours to keep the router running since the phone won’t be plugged in for the whole 2.5 hours.
Lithium batteries are better than lead ones.
Most of the time, UPS systems with lead batteries are cheaper to buy. But lithium batteries lose the same amount of power throughout the charging cycle, while lead batteries lose a lot less power the longer they are charged.
So, while it might only take an hour to fully charge the iPhone from a lithium battery-powered UPS, the rate at which it charges slows down as the lead battery loses power, which could add more hours to the charging time as the battery starts to go flat.
Also, when it comes to how long they last, lead batteries have about half the life of lithium batteries.
Chetty says this: “The thing about lead acid batteries is that even though 12 volts times 100 amp hours looks like we have 1,200 watt hours, we don’t actually have 1,200 hours because you don’t want to damage the units by using more than 50 percent of the battery. So, what you really have is more like 600 watt hours.”
Spend a little more because it will last longer.
“There is a bit of a gold rush going on right now. There are a lot of useless things on the market “When we show Chetty some of the cheaper options from a well-known online store, he says, “That’s interesting.”
“They might keep your modem running for a few hours, but in a year, they’ll be so used up that you’ll have to replace them. It’s like putting a piece of tape over a volcano that’s erupting “he says.
Maverick Life showed Chetty a few options under R10,000. He said that the more reliable ones would have lithium batteries instead of lead batteries and would also show the wattage in a clear way.
He recommends that people buy the ones that say “lithium” and “watt hours” right on them instead of trying to figure out different unit measurements that might be confusing.
