Whilst running the battery down this evening the discharge rate fell suddenly from 3.6kW to 1.7kW and it's been stuck there since - see this graph:
This hasn't happened before, I know that charge rates are limited when it's cold but I didn't think the same applied to discharge. Does anyone have any ideas?
If its not a stuck power level setting and this is on discharge only (so low temp does not apply) then I'd hazard a guess you have a cell going low voltage in your battery which the BMS will see and reduce rate.
I'd suggest using a 3rd party app like: https://play.google.com/store/apps/details?id=uk.rubikcube.invertermonitor&hl=en_GB and click on the battery bar at the bottom to monitor the 16x cell voltages.
Is it a 9.5 pack by any chance? Seem to be common issues with cell 5, 9, 13 on those.
Any that differ massively is what your looking for.
So it charged overnight and it seems like it's working ok again this morning...
Yes, it is a 9.5. I downloaded that app (thanks for the rec) and this is the current state-of-play:
They all seem pretty close, apart from Cell #1 - but I don't know what the normal range of values should be and whether this is outside what it should be.
This is our second battery, the first had to be replaced because of cell mis-alignment, is this a common problem?