Can Old Batteries Be Used for Solar Power Storage?

When considering the repurposing of batteries for solar power storage, the first impulse might be to recycle old batteries. After all, why not utilize something that is already present and could potentially reduce waste? However, using old batteries for solar power storage presents significant challenges that make it a suboptimal solution. This article will explore why this idea is generally not advisable and discuss the potential repurposing of old lithium-ion batteries from cars as solar storage.

Challenges with Using Old Batteries for Solar Power Storage

The term 'old battery' typically refers to a battery that has lost a substantial portion of its original capacity. Even more concerning are batteries that have failed entirely, such as those that are shorted and unable to hold or pass electricity effectively. This makes it crucial to understand the inherent limitations of old batteries before considering their use in solar systems.

Automotive Batteries vs. Solar Storage Batteries

Automotive batteries, whether for electric vehicles (EVs) or internal combustion engine (ICE) vehicles, are designed to provide a substantial amount of current for short periods. This is ideal for starting an engine but not for long-term energy storage. These batteries typically discharge only a small fraction of their capacity when used to start an engine. However, when subjected to deep and frequent discharges, as often occurs in off-grid solar installations, they rapidly lose capacity and become less effective as storage devices.

Repurposing Old Lithium-Ion Batteries from Cars

Thankfully, it is possible to repurpose old lithium-ion batteries from cars for solar storage applications. These batteries, despite being 'worn down' to a reduced capacity, still retain a significant amount of their original energy storage capability. For instance, a lithium-ion battery that has been reduced to a capacity equivalent to only 300km of driving in a car can still store sufficient solar-generated power for most households overnight.

Households do not require nearly the energy that would drive a car 600km. Therefore, even a battery that has been reduced to 300km drive range can provide ample power to meet most household energy demands at night. However, as the battery continues to deteriorate, reaching a point where it can only drive 100km, it becomes impractical for household storage and would need to be recycled. This is because the remaining capacity is insufficient to meet energy demands.

Energy Intensity and Usage Considerations

Motor vehicles, whether electric or ICE, are highly energy-intensive, using thousands of times more energy to travel a given distance than a bicycle or even an e-bike. For example, if you need to travel 1km, walking 10km, riding a bicycle 30km, and using an e-bike for the final distance, a car would be the most inefficient option unless you are traveling beyond the city limits or carrying bulky items including passengers.

Conclusion

While repurposing old lithium-ion batteries from cars for solar storage can be a viable option, it is crucial to recognize the limitations and challenges involved. For optimal performance and efficiency, it is best to use batteries specifically designed for solar energy storage. However, for those with existing old car batteries that need a second life, repurposing them could be a practical and environmentally friendly option, provided they are still capable of meeting the energy storage needs of a household.