Lithium-ion battery

How to build a Li-ion battery pack with panasonic 18650 cells 3100mah A

• Report rights infringement
• published: 08 Jul 2014
• views: 125251

In this video, I show you how I recycled my old Lithium ion battery pack and reused the cell balancing circuit board. The original pack used standard 18650 Li-ion cells and had a capacity of 10 AH at 29.4 V. Since this pack did not conveniently allow me to change broken 18650 cells with new ones, I decided to build my own design. This pack is going to have about 37 AH at 29.2 V and can get me on my electric bike more than 80 Km of range. All the 84 cells which I am going to use can be checked and replace in less than ten minutes. I first started this project with some cheap cells from China which were labeled to hold up to 4600 mah. However, as it turned out, it was no more than a terrible scam. They had no more than 1200 mah. I only managed to get 34 km of range out of them. Therefor I went back to the dealer and complained. Luckily, he wanted to get rid of me as quietly as possible and kindly helped me to get the original Panasonic 18650 3100 mah cells from Japan. Since I designed the positive connectors for nipples, the Panasonic 18650 cells are flat on the top. I had to redesign the pack a little. After that, charging the battery pack went just fine and my first trip was very impressive. First 16 km each cell discharged 0.17 V, the second 17 km they discharged 0.14 V each. Maximum charge for each cell is 4.2 Volts, whereas I do charge them to 4.17 V. The minimum cutoff on my setup is at 3.42 Volts. On 0.14 V of discharge I can go an average of 16 km. 4.17 V maximum charge - 3.42 minimum charge, leaves my with 0.75 V. After going five times 16 Km, there is still 0.05 V per cell left. Recharging the battery pack takes about 8 hours. The charger goes perfectly through all three different charging speeds. It stays in the fastest for up to 4 hours than goes into the second for another 1.5 hours and stays in the slowest till the cells are full. It then turns off. All cells are charged this way at a maximum of 650 mah, which is good. The Panasonic lab tests promise 500 life cycles. This however are lab conditions. I am very optimistic that my setup will meet these conditions now most of the time, and therefor provide me with the promised 500 charging cycles. This should leave me with 40 000 Km and about 3.5 years before the pack goes down to 80 to 90% of it's original capacity. I know the positive connection is a little sub optimal. I should have made the top Plexiglas 0.5 centimeters thinner and have 7 separate tops like the ones I use now, but with the copper plates and nipples. Now I have to use two copper-plates cause I haven't thought it all the way through. I will change this when I have time. For now, everything works very perfectly. This is a good weekend project.