No one has confirmed for sure what the message is since the only people with access to the canbus definition are constrained by NDA. However, we are reasonably certain this message (5bc) is the "Charge Status Signal" described in the service manual transmitted from the EV/HEV to the TCU. We know it's units to be energy with nominal value of 80 watt_hours. It does not seem to be super accurate, though, with at least +/-10% variation. Despite this variation, it remains the best indicator of the available energy in the battery. None-the-less 10% error is a bit annoying when trying to figure out how many miles you have remaining. This is why we are trying to understand it better. In my chart I show that, for the simple scenario of a charge, I am able to much better compute the charge in the battery by monitoring the current and voltage into the battery and integrating the power over time. The reason I think the Leaf doesn't just do the same is this is much harder to do accurately when driving where charge moves in and out of the battery quite frequently - each time adding a little more error to the computation.
I have compiled everything I am aware of that we have reverse-engineered about the evcan and carcan busses here
(don't forget to look at the tabs at the bottom of the spreadsheet).