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Energy storage is in a place now where it has gained strong traction with some utility companies and as a complement to renewable energy. But for storage to gain true widespread adoption at the commercial level, warranty coverage needs to be vastly improved. Here’s how we can do it.

The typical warranty offered for a large-scale energy storage system is based on cycles, or a round of discharging and recharging the batteries of the storage system. For most lithium-ion battery systems, the warranty that companies offer is in the range of several thousand cycles depending on how the systems are used, the charge and discharge rates of the systems, the ambient temperature the systems are being operated in, and other factors. But measuring energy storage system usage in charge and discharge cycles (and basing the system warranty on these cycles) really doesn’t make much sense. Furthermore, there is no easy or reliable way to do this accurately.

The car warranty analogy

Imagine that car warranties were based on how many times you start your car rather than on mileage measured by the car’s odometer. Knowing how many times the car has been started doesn’t really give you any useful information about how far and how fast the car has actually been driven and how much wear and tear should be expected on the engine and other components of the car. It certainly does not give you any of the other useful information offered by popular services like Carfax, which can give you a more complete history of things like accidents, the number of owners, service history, flood damage, structural damage, etc. Simply knowing how many times a car has been started would tell you none of those things, just like knowing how many times a battery storage unit has been cycled gives you very little information about how the system was actually used, the system’s present state of health, or its resale value.

The energy storage industry needs to view warranty coverage more like the automobile industry does.

The entire idea of measuring battery life in cycles was created in a lab setting for individual battery cells where all conditions and uses are controlled, but real world usage varies greatly from the conditions and battery cells that are tested in labs. The familiar electric utility billing meter would be a far more accurate and reliable way to measure how a storage system is being used. Such meters are easy to read and verify plus they are closely related to the actual purpose of energy storage systems, i.e., the buying and selling of electricity. Energy is bought and sold in kilowatt-hours and is measured by electric utility billing meters, not cycles.  

Battery odometer measures usage

The use of a battery odometer would be far more useful to accurately measure the real life usage of battery energy storage systems than cycles just as a car odometer is a better measure of a car’s usage than the number of times it has been started. This is the approach we’ve taken at Powin Energy with our patented bp-OS.

Software incorporated into an energy storage system typically measures three key factors that affect the life of a battery: charge and discharge rate, battery cell voltages, and battery cell temperatures. In Powin’s systems, these three key factors are continually monitored and recorded every few seconds by the bp-OS and are used to calculate battery usage with a value that increases whenever the battery is being charged or discharged (very similar to how an automobile’s odometer increases whenever the automobile is being driven). This battery odometer allows an energy storage system user to monitor in real time how a particular application of the energy storage system is impacting the battery life and the battery warranty. Currently, if something malfunctions in an energy storage system, how does the manufacturer know if the problem lies with how the system integrator installed the system or if the end user has not operated it properly, or if a battery cell or other piece of equipment simply failed? Better data that records how a storage system is used makes it easy to determine if an issue was the manufacturer’s, integrator’s, or customer’s fault.

Data-driven conclusions

Where this starts to get really interesting for the industry is if software like Powin Energy’s bp-OS logs all of this data in all deployed energy storage. Then, you’ll be able to see very specifically how batteries from numerous manufacturers perform, how certain energy applications impact battery life, what effect different balancing methods have on the lifespan of batteries, how competing battery chemistries perform in an apples-to-apples comparison, and other data-driven conclusions. Right now, this data does not exist for our industry. All the information on stationary storage performance that the industry has - and that current warranty and insurance coverage is based on - has all been compiled in lab settings.

Energy storage is on the cusp of becoming mainstream and it will certainly have a very large role to play in renewable energy installation targets and reaching carbon reduction goals. But one critical step on the way there is making sure these high-value assets are properly covered by better warranties and insurance.

Written by Virgil Beaston, Senior Vice President & Chief Technology Officer, Powin Energy

Labels: Powin,energy storage,batteries,warranties,solar power,backup

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