Hi All
Just charged a bank of 3 lithium 200Ah batteries (in parallel - total 600Ah) - for first time.
Set the charger to be in absorption for 2 hours - as per manual.
See pictures showing BMV and the 3 batteries - these screen shots were taken 2 minutes before end of absorption (2 hours). I was expecting to see all batteries at 14.20 - but they are all below this.
Does this look OK ?
Thanks
Tim
The cell voltages look OK, especially if it's first time you are charging the batteries.
How are the batteries wired in parallel? With or without busbars?
Thanks Seb71
Wired in parallel - all wires same length - all +ve and -ve going to a Victron Lynx Power-In.
Started the multiplus at a very low 10A after installing the VE.Bus BMS Assistant. Then increased to 20A after about 10 minutes - then increased to 30A after another 5 minutes - and left it there (30A) for remainder of charge.
In total the batteries spent about 4 hours in bulk at 30A. Then - 2 hours in absorption.
Yes - I will increase settings in Multiplus to much higher - when I use in anger.
I left it at (low) 30A during this first charge - as I was watching the V rise steadily - in just 4 hours it left bulk and went to absorption. My logic is 4hours x 30A = 120A was pushed in to 600Ah bank - which is only 40A per battery = which indicated the batteries came about 80% full from factory.
Sound about right to you ? Or, do you think the batteries have not charged fully - my original worry ? On delivery the batteries were showing 13.28v (3.32v per cell).
At 3.53V-3.55V, your cells are (were) very close to full. LiFePO4 cells should not be charged above 3.6V.
At the end of the charge (starting from about 3.45V), the LiFePO4 cell voltage increases rapidly when charging. There is not much energy between 3.5V and 3.6V.
By charging the battery bank with a lower current, the BMS has more time to balance the cells (top balance).
Ideally, after a few charge-discharge cycles, you will have all cells with the same voltage when fully charged.
The BMS always balances the cells at the top end. It aims to bring all cells with the same voltage when fully charged.
Even when the cells are well balanced (at the top), depending on how well matched the cells are from the factory, you might have some smaller or bigger cell voltage differences when the battery is empty or close to empty.
You have to account for that when you set the inverter cut off voltage.
