Greetings,
When connecting batteries in parallel like this, it is important to ensure that they have an equal state of charge at the time they are being connected. One should also use cells of the same size, brand, model, age, etc.
When connected in parallel, batteries will tend to charge and discharge evenly, unless there are significant differences in the resistance of the wiring running to each cell, or major differences in the characteristics of the batteries used. The parallel connection naturally solves some of the problems that come from series connection, and in many ways is much simpler. There is little or no need to worry about charge flowing from one battery into another once they are connected, as long as the wiring resistance to each is more or less identical, stays intact, and similar cells are used.
It would probably be bad for example, if a person were to connect 7 fully-charged cells in parallel, and then try to add an 8th that was completely discharged. In this case, there would be a large transfer of charge, which might exceed the charge rate limits of the discharged cell and cause damage. Again, this is most likely to happen at the time of assembly. It could also occur later if, for example, a poor connection would cause one of the batteries to be disconnected for a time while the rest of the bank was charged or discharged.
Because of the size of the batteries being used here, I would suggest that it might be a good idea to provide over-current protection per-battery in order to protect against this sort of situation. It is possible that this sort of protection has already been built into the cells themselves, but this is not guaranteed. If you would provide a link to documentation for the specific lithium batteries you plan to use, I would be better able to offer suggestions for suitable fuses.
Please be aware that lithium batteries of this scale should be treated with great care. A battery bank of the kind described could make a length of 12AWG wire glow like a light bulb filament, and you wouldn’t want to be near it if it ever catches fire…