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SELF-DISCHARGE

WHAT DOES THIS MEAN?

Self-discharge refers to self-running electrochemical processes which cause batteries (accumulators) to discharge more or less quickly, even if no electrical consumers are connected.

The speed of self-discharge determines which part of the originally stored charge quantity (capacity) can still be used after storage. Self-discharge is one of the most important characteristics of batteries or accumulators.

What does the rate of self-discharge depend on?

The rate of self-discharge depends on the ambient temperature, type of battery and battery technology. Self-discharge is considerably increased at temperatures above +55°C. Batteries can reach or even exceeded these temperatures when left in storage rooms during hot summers. The same goes for batteries installed in vehicles, especially in the engine compartment and in hot ambient temperatures. However, you shouldn’t underestimate how hot it can get in the glove compartment or boot during the height of summer either.

 

Store battery in a cool place

Low temperatures are perfect for storing batteries as the electrochemical processes responsible for self-discharge are greatly slowed.

Here is a brief example: An AGM battery stored at 0°C will hold up to 90% of its capacity (nominal capacity) for approx. 6 months. If this same battery is stored at +40°C, it loses approx. 50% of its capacity within 4 months! Batteries installed in the vehicle are further discharged by having a lot of electrical consumers (air conditioning, sound system, …), in extreme cases this can even be to the point of deep discharge.

What do I need to know about the battery in the vehicle?

 

  • Always install batteries with the highest possible voltage in the vehicle, never install batteries with a voltage below 12.5V!

 

Banner tip: Especially in the case of irregular driving profiles, equalisation charging with an external charger twice a year can (significantly) extend the life of a battery.

What should be observed when storing batteries?

 

Optimal storage conditions are

  • in a cool (between 0° and +25° C), dry place
  • Keep out of direct sunlight 
  • Make sure the battery surface and terminals are clean
  • The battery must be immediately recharged at the latest when an open-circuit voltage of 12.5V is reached.