Thanks for reply. It’s reading 38.5 so is that not good?
Is that after you take it off charge Trevor?
Could be that some cell groups are well out of balance. If so, what happens is that the BMS ceases charging any cells as soon as one group reaches 4.2v. This means the low cell groups never get properly charged, so the overall battery voltage is lower than it should be. On the road, the battery will shut down after a quite short range when the BMS detects that any group has reached the low voltage cut off point.
I had this problem, a while back after a long winter lay up, but in my case the charged voltage of the whole battery was higher than yours, and only one group was low - and it was really pretty far down. It is just possible that in your case, you have a couple or several groups that are low.
The solution I found was discovered after charging the battery to cut off, as normal, opening the battery case and using the multi meter to test and note the voltage of each parallel cell group. I had to solder tags onto the low group and individually charge that group with a 4.2v, lithium charger. This solved it, though that group does lose a wee bit of voltage vis a vis the others over time.