Load Shedding and Battery Life

What is the relationship between load shedding and battery life?

An AGM Battery offers approximately 260 cycles at 100% discharge.

Ordinarily, this would equate to 1 discharge per week. The battery would have a lifespan of +/- 5 years. Of course, this is under perfect conditions (temperature, charge voltage etc.) The minimal weekly interval between discharges allows the battery or battery bank to fully recharge before the next discharge occurs.

Any new AGM battery needs to be charged for 24 hours before it is used. When installing a new battery or battery bank during a period of load shedding, a full charge does not occur and this impacts the capacity of the battery.

Load Shedding and discharging to 100%

Under stage 2 load shedding conditions, over 1 week there will be about 11 outages and therefore 11 discharges. Often, the batteries or battery banks have not fully charged before the next round of load shedding. This will result in deterioration of the battery.

Taking the above into consideration, if we have 2 weeks of Stage 2 Load Shedding, 5-6 months worth of the battery’s cycles will have been used up during this time.

During these 2 weeks, the batteries will not have been fully charged and this will further diminish their life expectancy. With insufficient breaks to allow full recharging of the batteries, approximately 8 months worth of battery cycles will effectively be utilized. This degrades the battery capacity even more.

Stager 4 has 50% more outages.

Please also note that most UPS systems only cut off when the battery is discharged to 10.5v (200% discharge) This will further deplete the battery’s life cycles.

**2022 has already had 1166 hours of load shedding** (as of 14th July 2022).

If having 2 hours of load shedding at a time, this equates to over 550 cycles of the battery.

2021 had 1169 hours of load shedding, 2020 had 859 hours and 2019 had a total of 530 hours of load shedding. (Source CSIR).

Keep in mind, an average battery has approximately 260 full cycles under IDEAL conditions! It is no wonder that the batteries do not last. They were not intended to be used under such trying conditions.