Sscience news: A home in Farmingdale, New York has created an entire power system from more than 650 salvaged laptop batteries. This system has been providing uninterrupted electricity to this house since 2016.
The system was built without the help of any big company or expensive materials and uses reused lithium-ion and solar panels. This shows that it is possible to store electricity for long periods of time at low cost. This system is working continuously even after almost 10 years without any cell replacement or battery failure.
How was the system created?
The main part of this power system is 18650 lithium-ion cells that were extracted from old laptop batteries. The person who made it separated each battery pack by hand and after testing, organized them into small packs with a capacity of 100 AH. Depending on the capacity, 51 to 80 cells were mixed together in each pack.
electrical connections
Emphasis was laid on making the system reliable. All battery packs were connected with 1.5 mm copper wires and copper was chosen because it conducts electricity well and is easy to connect. To ensure equal flow of electricity in all the cells, the length of the bus bar was kept the same. This entire battery arrangement is housed in a separate garden shed about 50 meters away from the main house.
How is the system charged?
To charge these battery packs, the system uses 24 solar panels installed on the roof. The capacity of each panel is 440 watts, which together produces more than 10.5 kilowatts of electricity. This power passes through a Victron MPPT 100/50 charge controller, a 3 KVA Victron inverter and a 24V-to-12V voltage converter. These devices provide electricity directly to the house without connecting to the municipal grid.
Is it sustainable?
Unlike most self-made electrical setups, this system has remained completely safe despite being used daily for 9 years. There has been no thermal event in it, neither has there been a fire nor have the batteries swelled. This success is due to carefully designed battery packs that constantly balance the voltage and prevent the battery from over-discharging.
How was the initial test?
When the initial tests of the system were conducted, it was found that the speed of power dissipation in different sized packs was not the same. One night when electricity was being supplied to 2 refrigerators and other small loads in the house, there was a sudden drop in the voltage of the system. The voltage of some packs remained at 3.3 V while the voltage of other packs dropped below 2 V. Due to this, there was a risk of long-term damage to the cells.
What was the reason for the problem and what is the solution?
Upon investigation it was found that the defect was due to difference in pack size. The pack with fewer cells was draining its power faster and reaching cutoff voltage sooner than the larger packs. This problem was fixed by adding more cells to the underperforming packs and rebalancing the entire system. With this change, the ability to store electricity became stable and the problem of premature voltage drop was stopped.