South Africans making big battery mistakes
South Africans with backup power batteries should avoid keeping them fully charged for long periods as this can degrade their long-term health or cause inaccuracies in battery level readings.
With load-shedding suspended for over half a year, many people with backup power systems might keep their batteries at full charge for prolonged periods.
The mistake is likely most common among those who do not pair their batteries with self-generation like solar power. These can include those with power trolleys and portable power stations.
For these users, depleting the battery instead of using the grid seems to offer no apparent benefit, as they won’t be able to charge their batteries without paying for the electricity.
However, due to the chemistry of lithium-ion batteries, it is best to at least partially discharge them every few days.
Solar power company AWPower has told MyBroadband that its customers were often apprehensive about discharging their batteries deeply, even if they could be recharged with self-generated power.
A part of this concern might have developed from the many years of consumer experience with lead-acid and gel batteries, neither of which were designed for a deep depth of discharge (DoD).
The rated DoD on a lead-acid battery is typically 50%, meaning users should consume only half its full capacity.
If the discharge goes deeper, it can severely shorten the total lifecycles of the battery.
However, the chemistry of lithium-ion batteries, the most common type of modern backup battery, typically supports DoDs of 80%, 90%, or even 100% for premium packs like Tesla’s Powerwall.
Either out of a lack of knowledge or an over-abundance of caution, consumers are potentially keeping their batteries fully charged to protect their long-term useability when that might be doing the exact opposite.
AWPower managing director Christiaan Hattingh explained that keeping these batteries at 100% capacity could make the cells go into a type of voltage overcharge.
That can cause issues with the battery level calibration, resulting in the battery displaying the incorrect state-of-charge (SoC), making it difficult to manage consumption.
“Modern lithium-ion batteries want to be cycled because of their chemistry and the way battery management systems work,” Hattingh said.
“Those that don’t want to use their batteries because they’re feeling like they are putting kilometres or mileage in their expensive batteries, should just discharge and charge them by 2% to 5% and recharge.”
“It’s a little bit of discharge and charge but enough to keep the batteries healthy in terms of voltage.”
Hattingh advised people with home-integrated batteries who lack the technical expertise to contact an electrician to help them set their inverter to regularly use small amounts of power from the battery.
Those with non-integrated systems like standalone power trolleys or portable power stations can simply plug a few appliances into them and run them for a couple of minutes before charging them up again.
Charging to 100% is also a bad idea when switching off and storing backup batteries while load-shedding is suspended.
If you plan to keep the battery dormant for a long time, many manufacturers recommend discharging it to between 50% and 60% before putting it away.
The battery should also be recharged to full capacity every three or six months, discharged to its rated DoD and then recharged back to 50% to 60% SoC before being stored again.
This practice will ensure that the battery does not reach too low a state of charge from self-discharge while also avoiding the higher SoC levels where lithium-ion movement is more restricted.