Reusing e-bike batteries for powering homes

Reusing e-bike batteries for powering homes

The issues of resource usage and efficiency are becoming increasingly important within the energy storage industry.

The energy provider WEMAG from Schwerin, located in the German state of Mecklenburg-Vorpommern, is taking on these challenges by turning used batteries from electric bicycles into energy storage for photovoltaic (PV) systems. Known by the brand name of ReeVOLT!, this energy storage solution comes with its own innovative fi nancial model for customers.

We have identified two reasons why homeowners rarely add energy storage, explains Jost Broichmann, Sales Manager at ReeVOLT!. On the one hand, entry level storage systems often cost more than 10,000 plus installation costs, and on the other hand, clients are worried about battery failure. The latter reason, especially, discourages many customers. Many batteries currently sold have a warranty time of 5 to a maximum of 10 years. If the batteries are irreparably damaged after the warranty period has expired, the entire investment is lost.

These two problems have been addressed by the ReeVOLT! model from WEMAG. For one, the energy storage system based on used batteries is signifi cantly less expensive than a model made up of new batteries, because lithium batteries alone make up roughly half of all costs associated with storing energy. For another, WEMAG counters the warranty expiration problem by offering the energy storage model as a rental instead of a system that has to be purchased.

We are sitting on a renewable raw material source

The ReeVOLT! storage system has 16 e-bike batteries from Swiss pedelecs, which together have a capacity of up to 5 kWh. If one of the batteries has too little capacity or is defective, it is simply replaced by mail. This way the customer profits from a low entry price and any risk associated with the batteries falls on the manufacturer. The storage system has a manufacturer suggested retail price of 7,100 including installation by a local electrician.

The battery rental price, as estimated by WEMAG, is around 20 per month. After 20 years, the total cost amounts to approximately 11,000. This is roughly equivalent to the cost of a comparable energy storage system that is currently available on the market. However, the advantage is that, unlike other solutions, this storage system can be operated on a battery exchange program that ensures top functioning batteries.

The replacement of batteries is guaranteed by the energy provider for the next 20 years because the battery supplier biketec has a large quantity of used batteries available, meaning there is access to a renewable source of raw materials, according to Broichmann. Naturally, this business model only works economically with used batteries, explains Broichmann, revealing where the batteries come from. The Swiss e-bike producer biketec from Huttwil in Canton Bern makes thousands of ebikes available each year for rental programs. The batteries, made by Panasonic, usually have a remaining capacity of 80% at the time they are returned. This makes them suitable for mobile use only in flat countrysides. This is why the Swiss remove these batteries after they are returned and put the e-bikes back on the market with new batteries.

Batteries are waiting to be used a second time

Meanwhile, tens of thousands of batteries have been collected. They are awaiting their second use, because the raw materials used for them are still too valuable to simply be recycled. In their second life, the batteries used in conjunction with a PV system can cover about half of the energy needs of a single family home.

This gives our customers the opportunity to produce their own electricity more ecologically, because reusing batteries conserves resources, reduces waste and lowers costs, remarks Broichmann. The idea has potential: According to an estimate of the German two-wheeler industrys association, ZIV, around 1 million e-bikes are sold in Europe each year. Another advantage is the usage of separate batteries, which increases their safety.

Each battery pack has its own battery management system and several protection features, such as surge protection and thermal safety features. In addition, a so-called meta-battery management system supervises the entire system. If one of the battery packs fails, the system still operates properly. The storage system also allows the temporarily removal of single batteries during operation for powering an e-bike or other electrical devices.

The life expectancy of the used batteries is estimated by the manufacturer to be more than 5 years. Using 16 batteries together, results in the individual cells having a significantly lower workload than if they were individually used in an electric bicycle. If the system falls below the guaranteed minimum capacity of 2.5 kWh, individual batteries are replaced. The energy storage system shows any defective batteries on its status display and upon request it can also forward this information directly.

The batteries can be automatically re-ordered in future, whenever the performance starts to decline. The customer can easily exchange the batteries themselves. The energy storage is integrated as a single phase system into the alternating current circuit and is connected to the house wiring through a grid and plant protection box.

The purpose of the box is to synchronize the frequency of the rotating field with the frequency of the storage system after, for example, a power outage. This is because the energy storage system has its own uninterruptible power supply (UPS) and can continue to partially supply energy to the house during a power outage. Apart from the economic and ecological benefits, this is another important selling point.

Source: ees International

SMART GRID Bulletin March 2018

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