To illustrate why this battery size would be sufficient, Berrow provided the estimated consumption of a set of key appliances that could run during load-shedding for four hours, the maximum length of an outage during stage 6:<\/p>\n
- \n
- 10 x 5W LED bulbs x 4 hours = 200Wh<\/b><\/span><\/li>\n
- 1 x 160W TV x 4 hours =\u00a0 640Wh<\/b><\/span><\/li>\n
- 1 x 150W Fridge Freezer x 4 hours =\u00a0600Wh<\/b><\/li>\n
- 1 x 10W Modem x 4 hours =\u00a040Wh<\/b><\/li>\n
- 1 x 45W Laptop Charger x 4 hours =\u00a0180Wh<\/b><\/li>\n
- Total = 1,660Wh or 1.66kWh<\/b><\/li>\n<\/ul>\n
Berrow said a common misconception among consumers was that they could draw the same amount of power as the peak capacity of a battery without running out of juice.<\/p>\n
The kWh capacity does not refer to the amount of power you can drain in an hour, but rather in total.<\/p>\n
Using the battery’s maximum capacity for an hour will mean you drain its total capacity.<\/p>\n
In addition, Berrow said a battery’s depth of discharge (DoD) meant it might only be able to safely consume a certain portion of its capacity.<\/p>\n
The DoD specifies how much a battery can be safely depleted without damaging its long-term health.<\/p>\n
“If you have a 5kWh battery with a depth of discharge of 80%, the usable capacity is 4kWh,” she said.<\/p>\n
“To be safe, we recommend slightly oversizing a battery bank to ensure the consumer has extra backup to get them through stage 6 load-shedding.”<\/p>\n
![\"\"](\"https:\/\/mybroadband.co.za\/news\/wp-content\/uploads\/2023\/08\/Pylontech-5kWh-battery-.jpg\")
PylonTech 4.8kWh battery<\/p><\/div>\n
AWPower’s Christiaan Hattingh said although a household with fairly conservative electricity consumption could get away with a 5kWh pack, he recommended 10kWh for those who wish to be less fussy about their consumption.<\/p>\n
Hohm Energy public relations head Matthew Cruise concurred with this.<\/p>\n
“A battery rated at 5kWh should provide a seamless experience for avoiding load shedding for a three- or four-bedroom household for two hours,” Cruise said.<\/p>\n
“To last the 4 hours of load shedding experienced in stage 6, a minimum of a 10kWh battery is recommended.”<\/p>\n
Rubicon Energy and Mobility director Greg Blandford said for accurate and tailored recommendations, consumers must consult with a professional in the field of home energy systems or a solar\/battery installer.<\/p>\n
“They can perform an on-site assessment and help you choose the right battery size and backup solution for your specific needs and budget,” he said.<\/p>\n
Battery size should only be the starting point.<\/p>\n
![\"\"](\"https:\/\/mybroadband.co.za\/news\/wp-content\/uploads\/2023\/08\/Backup-power-installation.jpg\")
<\/p>\nAlthough a 5kWh capacity would be enough to carry you through load-shedding, the recharge and discharge capabilities of the battery are also important.<\/p>\n
Blandford said to determine this, consumers should look out for the battery’s C-rating.<\/p>\n
“The C-rating of a lithium battery refers to its charge and discharge rate capabilities in relation to its capacity,” Blandford said.<\/p>\n
“It’s a way to express how quickly a battery can be charged or discharged relative to its capacity.”<\/p>\n
“A battery with a higher C rating can handle higher charge and discharge currents relative to its capacity.”<\/p>\n
For example, a 5kWh battery with a 1C rating can charge and discharge at 5kW, meaning it can return to full capacity in an hour.<\/p>\n
One with a 0.2C rating can only charge and discharge at 20% of its rated capacity \u2014 or 1kW.<\/p>\n
The latter will take roughly four to five hours to recharge, depending on how deeply it was depleted.<\/p>\n
“It’s important to choose a battery with an appropriate C rating for your application to ensure that it can handle the power demands without becoming overly stressed or overheating.”<\/p>\n
Battery chemistries<\/h2>\n
Another important specification is the battery’s chemistry, which can significantly affect its performance characteristics.<\/p>\n
While many consumers might now be aware that lithium batteries should be vastly preferred over lead acid types, there can also be differences in the chemistries of lithium batteries themselves.<\/p>\n
Blandford explained that the two main types of lithium batteries are lithium-ion (Li-ion) and lithium-metal.<\/p>\n
“Within each category, there are different variations based on the specific chemistry and materials used,” Blandford said.<\/p>\n
Li-ion batteries are the most common rechargeable batteries used in portable electronics, electric vehicles (EVs), and more.<\/p>\n
They are known for their high energy density and relatively low self-discharge rate. The different variations of Li-ion batteries include:<\/p>\n
Lithium Cobalt Oxide (LiCoO2 or LCO)<\/strong><\/h3>\n
Commonly used in consumer electronics, these batteries offer high energy density but can be prone to thermal runaway and reduced lifespan.<\/p>\n
Lithium Iron Phosphate (LiFePO4 or LFP)<\/strong><\/h3>\n
These batteries are known for their improved safety, longer cycle life, and better performance at colder temperatures.<\/p>\n
“They have lower energy density compared to other Li-ion chemistries,” Blandford said.<\/p>\n
“These are most commonly used for residential energy storage systems.”<\/p>\n
Lithium titanate (Li4Ti5O12), often abbreviated as LTO<\/strong><\/h3>\n
A specific type of lithium-ion battery technology that offers distinct advantages compared to the aformentioned lithium-ion chemistries.<\/p>\n
These batteries have a rapid charge time, long cycle life, wide temperature range, and low discharge rates.<\/p>\n
“Often referred to as supercapacitor batteries, they are more costly than traditional lithium iron batteries,” Blandford said. They are not commonly available in South Africa.<\/p>\n
Cycle life and warranties<\/h2>\n
Two final important attributes are cycle life and warranties, which are often linked.<\/p>\n
Many batteries come with 10-year manufacturer warranties that will provide the customer with a free replacement if the battery’s retained capacity drops below a certain threshold sooner than it was designed to do.<\/p>\n
However, this will only apply if the battery was installed correctly and cycled fewer times at its DoD than its warranty covers.<\/p>\n
Generally, manufacturers of lithium-ion batteries offer 70% capacity retention after ten years over 6,000 cycles at 80% DoD.<\/p>\n
One noteworthy exception is Tesla’s Powerwall, which the company says will retain at least 70% of its original capacity after ten years with unlimited cycles up to 100% DoD of its 13.5kWh useable capacity.<\/p>\n
- 1 x 160W TV x 4 hours =\u00a0 640Wh<\/b><\/span><\/li>\n
![\"\"](\"https:\/\/mybroadband.co.za\/news\/wp-content\/uploads\/2022\/10\/Tesla-Powerwalls_Shutterstock_headline.jpg\")