Hello,
is it possible to NEVER exceed 28 V on this battery ? Charge controller will be 100/50 smart.
Devices on the load side of the battery can survive max 28v, so I wonder in an offgrid system,
the internal BMS can do cell balancing, if charging-voltage is 28V @ max. , it ´s ok the the battery will never reach soc above 85 %.
Load will be approx. 2kw for max 2 hours.
greets rudi
Which Victron lithium battery.
If it is the Smart Lithium then it needs 28.8V to balance, if it is the NG Lithium then it needs 28.4V to balance. These numbers are given in the manuals. Charging to 28.0V will get the cells to around 99% SOC. You will need to charge to the full voltage at least once per month to balance the batteries. The manuals suggest the amount of time spent in absorption at the charging voltages depending on the type of use.
According to the Lithium Smart Battery Manual charge voltage can range from 28v to 28.8v.
With the note that the battery has to spend at least 2 hours a month in absorption to balance the cells.
28v hard limit? No.
Should a load cut out in absorption, or the sun poke it’s head out there can be a brief moment of overvoltage.
How sure are you that your loads can never exceed 28 volts?
Ok, then I have to choose other way, reducing the 28.xx V with one or two 70A Si-diodes in series to lower the load voltage down to 27V or whatever.
Loads will be model-rc chargers, which are limited to Vin(max) 28V.
Or system will be build with 12/14V circuits, and 3-4 Victron Stepups in parallel to get enough current in the 25V section.
Thanks in advance.
Do not forget that the Victron Lithium Smart or NG batteries do not have an internal BMS when you come to charge them, or you need to buy a BMS.
You could set your charger to 27.4V absorption, 27.0V float and once every month when your RC equipment is disconnected put the voltage up to the full 28.8V.