question

First thing you will need is a BMS that will not only monitor the cell group voltages but also send a signal if a cell group goes over 3.6v. This signal needs to trigger a timer that will switch a relay open and hold it open for the length of time you set on the timer.

The relay com goes to battery positive via a fuse and the relay N/O goes to the non inverting VE direct cable (available from Victron) and plugs into the VE direct port on the MPPT controller. This will stop the charging from the MPPT controller and protect the cell groups (and therefore the battery itself) from cell damage due to over voltage charging.

The time set for the charging to stop depends on how long it takes the high voltage cell group to settle to a lower voltage, min 1 minute, max what ever you want but watch that the load does not pull the battery down too far while the charging is stopped.

Settings, bulk/absorption 14v, absorption time as short a it will let you and float between 13.65 and 17.5v, at least until you add the BMV 712 or Smart shunt, then you can network the MPPT to the BMV and the battery voltage will be more accurate at the MPPT controller, then revert to the 13.65v float.

Rebulk, 0.5v until you get a BMV networked to the controller, after that, 0.1v to 0.2v, this is the voltage drop below the float voltage that the controller will revert to absorption voltage and go through the absorption time again. If you see this happening too often and the cell balance starts to go out causing a lot of over voltage cell group charging stops, set the rebulk voltage to a higher amount.

Get a single cell 3.65v charger from one of the sellers of chinese stuff, and top up the lowest voltage cell group when a cell group apparts to be setting the over voltage trigger too often.

If you want a more detailed explanation, just ask, I'm more than happy to expand anything I might have brushed over.

My wife has added a lot of lithium battery info on her website t1lithium.com.au hope this doesn't contravene any forum rules by adding her website .... I'm just the unpaid slave :lol:

T1 Terry

Regarding the pack voltage I want to set the max pack voltage at about 58.1V (4.15V per parallel module) and the min voltage to 51.1V (3.65V per parallel module) as I need the battery to last.

I will also use 2 Chinese BMS in series connectable via Bluetooth then via a dongle to a Raspberry PI.

I'm unclear what BlueSolar MPPT controller will do after the battery is fully charged.