question

A couple of things.

I don't recall BSL supporting mixed battery sizes in parallel. Has this changed and what does their support say?

You shouldn't be adjusting the BMS, that is not (was not, anyway) permitted for users/installers.

The 55V and 54.8V for float should work and it will generate voltage warnings, most new fixed voltage packs will, which is why they should be left on charge for a while.

I see they have added mucking with DVCC to some guides, this isn't meant as a permanent solution, especially not lowering the charge voltage - it is meant to help with balancing issues.

Historically, BSL is very slow to balance, but you have mixed models, and that won't help.

Their Pace BMS wasn't bright on a good day normally.

And good luck with their support, it used to aspire to be terrible.

Thanks @nickdb ... Both battery's are the same model / capacity (did I make a typo?)

I've appeared to have found their sweet spot at 55v, even though the documentation of the BSL 100Ah rack models (LFP48-100E) list the charge voltage from 55v to 56.3v to 56.8v depending on which .PDF you read. I'm still bewildered by the +0.5v BMS offset however.

I've heard they arrive from the factory way out of balance, outside normal expectations, but one would expect at least the BMS to have some basic parameters correct, even if just to avoid them being annoyed by unnecessary customer enquiries.

I've also heard their passive balancing is very lazy and not working properly 'out of the box', so was hoping someone may have found a better (and quicker) way to top balance them.... Although I seem to have done it eventually. Just the pack voltage deviation that is upsetting my charge curve and sending the higher of the two battery’s into cell delta hell at some point.

Unfortunately there is no bulk/abs/float in setups with ESS configuration, which is how my Multiplus (in parallel with grid) is setup to interact with the grid / house loads.

What did you think of the parameter changes in the BMS ? Would you find it strange having the protection kick in at such a high cell voltage ? And BEFORE the alarm ?

Cheers :)