Hi!
Can you please tell me how does the system ensure that two batteries in series will mostly be the same voltage if connected to form a 48v system? I know that a competitor has a low current connection between these batteries and actively balances these out. How does that work with Victron?
Our smart LFP batteries have individual cell balancing. Each cell in each battery will be balanced individually. No midpoint balancing is needed for these batteries.
Yes they will stay equal when connected in series. This is because each cell, within the battery, will be equal after cell balancing is finished. Cell balancing only happens when you are charging the battery. An individual 24V LFP battery contains 8 cells in series, and a 12.8V LPF contains 4 cells in series.
The rebalancing process is complete when the charge current has dropped even further, and all cells are 3.55V.
Hi Margreet,
IIRC, the smart LFPs use active balancing. The task is to transfer charge from high voltage cells to low voltage ones, until all the cells have equal voltage.
And then what.
Does the balancing circuit pass charging current from battery positive to battery negative if all cells have the same voltage during the absorption stage?
If not, we may have a problem.
The fully charged cells won't pass current, and if the balancing circuit doesn't provide a bypass, charging current drops to a very low level.
But the other battery wired in series, could comprise cells from a different batch, with higher self discharge.
How can this inferior battery balance its cells if its terminal voltage can't reach absorption level, because the other battery is ahead in the charging curve, sitting at a higher voltage up to 15V or 3.75Vpc.
And when the balanced battery hits 15V, it turns off the charger via BMS, denying the inferior battery its much needed charge. In the end, after an x number of cycles, you have a single or more cells in the inferior battery being deeply discharged.
