Eskom Load Shedding Effects on VRLA Batteries

After Eskom’s systematic load shedding schedules announcement some questions have arisen about the impact on VRLA batteries. The expected autonomy of your system is calculated at 100% load, therefore, in a normal standby application when the load is less than 100% for example 50% the expected autonomy will be extended up to double in terms of time. However, CSB battery series HR, HRL, GP, GPL, MU, MSJ, MSV, UPS and TPL are designed for today’s stable grid standby applications; Eskom’s load shedding schedules propose daily blackouts in a range of up to 4 hours. The reality is that it could be shorter, longer and with frequencies from twice per day up to every 3 days or more, additionally the time period for this situation to reach an end is unknown. This daily load shedding condition represents a cyclic application and premature capacity loss can be expected, leading to early battery replacement.

Premature capacity loss effects due to Load Shedding conditions:

  1. Number of Discharges:
    • Under current Eskom Load Shedding situations the application is not a standby but cyclic cycle. When a Standby design VRLA battery is used under such conditions, it is expected to have premature capacity loss leading to a reduction on your battery bank autonomy in a short period of time until it fails, this is, under Eskom load shedding conditions, unavoidable for any standby AGM VRLA battery.
  2. Insufficient recharge:
    • A battery in normal conditions needs to be overcharged in a range of 5 to 10 percent, a standby application requires around 72 hours to reach this stage after a deep discharge; therefore, under current Eskom Load Shedding conditions with daily discharge if the battery bank is exposed to deep discharges the battery bank will not be fully recharged when the next load shedding occurs next day and so on, leading to a fast autonomy loss (2 to 5 days), due to insufficient recharge and plate crystallization which might damage the battery permanently.
  3. Deep discharges:
    • Battery series HR and HRL are specifically designed for 90 minutes, under Eskom load shedding scheme of 4 hours the blocks will be exposed to a very deep discharge which lead to a slow and long recharge need of +72hr, which under current Eskom situation cannot be achieved, leading to premature capacity loss.
  4. Temperature:
    • Battery life will be reduced by half for each 10°C above the battery designed temperature; in the event of a load shedding a battery room cooling system without an automatic re-start system might leave the batteries working under a high temperature environment which have an impact over the battery design life.

In order to reduce the risk of power loss without notice, the use of a battery monitoring system can help to predict when the system needs a longer recharge, equalization or replacement. CSB Battery EVX series has been designed with a higher cyclic capability, however the charger set up needs to be re-defined to a higher charging voltage as well as a higher end of discharge voltage which some equipment might not be able to do.

As a consequence, of the current Load Shedding situation early battery replacement can be expected.

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