That is, by itself, correct. But the DESS scheduler does already account for these losses by means of the round trip efficiency factor. Unfortunately the default value thereof seems much too optimistic at 90% whereas 80% to 83% reflects actual losses much better. Our system is set to 81% which allows setting battery cost to zero (0ct) to maximize active trading without the scheduler planning to sell at a loss. Depending on your battery costs write off philosophy you can then add back in a few cents to run the batteries less hard but I fully concur with dognose that the best strategy, after having made the financially irrational business decision to buy/build an DESS (trade) system in the first place, is to see the batteries as a sunk cost investment and therefore the least bad strategy becoming to run them as hard as possible as long as the heat losses wont actually lead to net costs.
TL;DR DESS, with all its flaws as they are, still works best when all key parameters are set reflect actual system performance values as good as possible. Not correcting the efficiency factor itself is a recepy for increased complications and less control over DESS behavior and performance.
PS, I will [EDIT: not share, thanks to Sarowe1990] my efficiency excel sheet for those interested. I reverse engineered the exact way in which the DESS scheduler calculates the delta SoC% per quarter or per hour based on the maximum grid and battery power limits. It is a plain no frills no scripting sheet, so it should not be too complicated to find the fill in cells you need to adjust for your own system (hint: different colors) and all formulas can be seen by un-hiding the intermediate columns. I won’t provide much help with it but if you really get stuck, say so in reply to this msg and I might get back to you in DM.
See also here: DESS charges only 1-2 minutes per quarter due to hourly SOC target communicated every 15 minutes - #46 by UpCycleElectric