Power2Spare has large, brushless fans for keeping the Opus BT-C3100s cool while you are processing cells. They cut the cycle time down vs the stock fans and work even better on the 1,000 mAh setting. The mod is simple, but I did have issues. Also shows test results.
⚡️DIY Powerwall Project – ep4 – Opus BT-C3100 Fan Mod & Test (2019)