I have an EV conversion I've done with a 62kwh leaf pack.
Are you using it in the original configuration ,..355v, 168 ah ?
If so, your 400 a draw ,( < 2.5 C ) , is well within its designed performance.
Those cells are claimed to be an “improved” version of the original Leaf cells, which, according US Department of ENERGY study, those original 54Ah packs could provide up to 240A continuous or over 540A short time on pulse, (10+C discharge),..so it should be reasonable to expect similar or better capability from the cells in your pack.
HOWEVER,..im sure you are aware that test results , and daily use are very different situations, and that one of the issues with Leaf packs is lack of active cooling which would be desirable in high discharge situations, so some caution is advised !
But, drawing 3-4C, ( 650a) should be feasible, at least for short periods.
Unless you can find some reliable data from other users who have tested the pack at higher discharges, (400+a), you might want to monitor internal pack temperatures , voltage sag, etc etc to be sure nothing nasty is happening.
How far above that number is safe?
..? ..that depends on your definition of safe, and what your risk threshold is !
Some people do not think any Lithium pack is “safe” , even when just sitting unused !
