Just an update. Going purely on the display bars (the 1st of which I think we have established goes out at 48v, here are my findings:
Yesterday I did a moderately hilly 36 miles. Some distance from the end the 1st bar momentarily flickered out, only to return for the remainder of the trip - including some hills. Recharged when I got home.
This morning I did 37 miles, probably with less hills, but still hilly. Today I was really finding it hard going, I think I am overdoing it as not cycling fit - my legs felt like concrete. Anyway, being very lazy on the last couple of hundred feet, the 1st bar flickered as I was practically turning into my drive.
I actually think my 10ah battery maybe not quite 10ah given the 50g cells used but close enough so let's ignore that. Looks like the voltage goes off a cliff shortly after 4000mah at around 3.3v which I suspect the lvc is?
Looking at an average discharge rate of 2a (per cell string), 54v to 48v delivers ~4000mAh(2000mAh per cell). Then the remainder of the battery delivers another ~4000mAh until 3.3v.
This was all based off cell discharge graphs I found on the interweb.
Realistically 5000mAh isn't achievable with the cells and getting to 4800mAh you are down to 2.4v per cell.
So roughly speaking the 1st bar gives 4Ah and the remaining gives 4Ah with a very linear discharge resulting in a usable 8Ah.
The 1st bar (goes out at 48v) gives ~200wh so at 37 miles that's 5.5 wh a mile.
The remainder of the battery should give ~180wh (due to lower voltage) so I might expect no more than 32 miles out of that.I will need to test the theory (have not felt confident enough to embark on a long ride with a half depleted battery yet) but I think 60+ miles is achievable for me in my surroundings, possibly approaching 70 miles, but no more. I expect that to be somewhat less in the colder months, although it was cold yesterday evening with a heavy frost. Playing it safe, I think 50 miles range is the maximum I would consider in these parts. That's quite good imo, but I guess I need to test the theory out in the real world as I made a lot of assumptions and there are a lot of variables.
Realistically I am unlikely to want to go much further than 50miles in a trip - and today I was definitely regretting the last detour and wishing I'd headed towards home sooner. The 10ah bag battery is a good size for my needs.
Early on I had gotten 50+ miles and down to 3 bars so the achievable range is proving remarkably consistent.