I recently switched to a dynamic energy contract, and therefor enabled DESS in trade mode on my ESS system consisting of a MultiPlus II 5000 and a DIY battery. However, the system would not charge the battery, despite hours with very low rates. The energy graph would show Grid to Battery forecasts of up to 2 kWh for a number of hours, but they would not lead to battery charging.
After checking all settings multiple times, I finally discovered a silly mistake in my DESS settings: I had specified the battery capacity in Ah (315) instead of kWh (16)! After correcting this, DESS starting charging the battery.
But I was wondering why the large value for the battery capacity would block charging altogether and it appears that it is caused by the truncation of target SOC percentages as calculated by DESS. A battery capacity of 315 kWh with a maximum charge rate of in my case 2 kW results in a maximum SOC increase of 0.63% per hour. When the target SOC delta calculations are performed as integers, the result will always be zero.
I’m not sure if it is possible to use fractional target percentages or perhaps target Ah numbers, but it would be nice if at least the calculation of the target SOC percentages could use fractional numbers internally to allow the propagation of a truncation error to the next hour. This would make the schedule more accurate, especially for systems with a large battery and relatively low charge/discharge limits.