We cant tell because we dont know what size it is. 20cells with 300a is huuuge.. thats 15a per cell. Beware that higher current just slightest resistance in the busbar Will cause the cells closest to the connection to have higher load. Up to 30a Id wrongly done.
What is the size of that bar? Do you going to run The oposite om the other Side? And what Wire do you Connect the cells with? (You cannot have cell level fuses on that high current. It wont work)
As daromer pointed out above, due to bar resistance, you should have the lugs at opposite ends of the pack to get more even resistance & cell load distribution.
Take it this is for a short term use, eg < 1 hour run time & shorter cell life is accepted?
Also, the cells are likely to get warm (at least) when loaded hard like this.
Don't have a spot welder at the moment, so I will be soldering the connections to the cells.
I will derating the inverter a bit to protect the battery until we are able to build another battery to share the load.
Also thought about making them into 4x 75ah batteries and string them together. Balancing would be hard though unless I could inter connect them or separate BMS for each.
Tried a 4p16s1p similar to the pcb layouts people have been making. Draw 58amps for 15mins cells handled no problem but when charging @ 8amps got to 3.5v and cells went all out of balance by 250mv 3.43v to 3.68v pack closest to +ve side was lowest voltage. Would it be due to resistance in the connections?