I'm really glad that I was able to help. If you want to keep the size and weight down, please consider an R/C Li-Po battery and charger, as your power source. It's hard to beat their energy density. You can feed your boost converter with the output connector, and use the balancing connector for recharging. A 3S or 4S, 2200mAHr Li-Po would power your tester for several hours continuously. The "T-Plug" in the example is called a "Deans Connector". Other common connectors are called EC-3, and XT-60. I think that they all can handle around 60A, so no issue there. The balancing connectors, that fit into the chargers, are JST XH connectors. Looking forward to seeing pics of your prototype.