We have used vanadium redox batteries in our project for years now, they are very reliable and stable. No maintenance is required because of their durability. The cell balancing is difficult to perform manually, so we use an automatic balancing method which works well enough. Sometimes the auto balancing feature doesn't work properly and needs manual intervention. If you need cost effective energy storage that is easy to manage and maintain, vanadium redox batteries will be your best choice. They are good solution for power storage applications where long life, reliability and safety are critical.