I've been asked to look into this for a company that has done this already, and sees demand for many more if it can be solved. They are using NMC cells, which have a lower voltage characteristic, so the BMS learns a lower capacity that is actually present.
Also, these are 93 Ah cells, and I read somewhere that the limit on this value (or perhaps reporting of this value, it wasn't clear) is limited to 60 Ah.
With 30 km on the GOM, the lowest cell voltage was 3.825 V, meaning that there is still roughly 50% capacity left.
I'd certainly be happy if the BMS will eventually learn a higher capacity, perhaps even something approaching actual capacity, but it doesn't seem likely.
The proper way to solve this would be to modify the BMS to take into consideration the characteristics of the new cells and their initial capacity, but that option doesn't seem open to us. I patch solar inverter firmware, so I'd be prepared to try this, but getting the image to analyse and patch is the problem.
It was pointed out to me that we may have to change the current reported on the CAN bus to other ECUs to prevent other problems. I intend to try a gadget soon that should allow a reduction of measured current by 10-50% (adjustable). I hope that the 10% figure will be noticeable as a range improvement, and if it affects other systems, a 10% change should be noticeable, but hopefully not damaging.
If the digital adjustment is necessary, it would be nice to also adjust the GOM figure, a la Leafs. But I've not seen a CAN Id for the GOM display. Anyone seen one?