Just curious. The BMS can charge individual batteries (balancing) and can shut-off the entire battery via the BMS circuit board. All the batteries are connected together via the bus bars, and are connected to the inverter, or grid or generator. I don't think there is any circuits/electronics inside any of the 16 LifePo4 batteries, so how does a BMS control the power flow to individual batteries. Since they are all wired together and the balance lead is attached to the bus bar, even if you flow more juice to 1 battery via the balance leads, wouldn't that also flow through the bus bars into the other batteries? Scratching my head on this one.
How does a BMS control each battery?
- Thread starter wsaharem
- Start date
Ampster
Renewable Energy Hobbyist
A passive BMS uses resistance to shunt current from a cell that has higher voltage than the others. That lowers the voltage of that cell..
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Yeah, they dont really balance like you are thinking.
They burn off voltage to the cells with the highest readings.
You can also buy an active balancer that takes energy from the hot cells and pushes it to the low cells.
They burn off voltage to the cells with the highest readings.
You can also buy an active balancer that takes energy from the hot cells and pushes it to the low cells.
FilterGuy
Solar Engineering Consultant - EG4 and Consumers
First some terminology.
The BMS manages a set of cells. A battery is a set of Cells.
Now to answer your question: There are two types of balance circuits
Passive balancing
A passive balance system will watch all the cells and drain current (via the balance leads) across a resistor. This energy is lost to heat, but it forces the cell that is 'ahead' of the others to a lower state of charge. These systems typically have a fairly low balance current. Typically 500mA or less. Some of them are lower than 100ma. These systems can struggle to keep a high-capacity bank of LiFePO4 cells in balance.
Active Balancing.
An active balance circuit will take energy from the high-voltage cells and move it to the low-voltage cells. There are a couple of different ways of doing this. They all lose some energy to heat, but they are more efficient than passive balancing. More important than efficiency is the fact that these systems are typically much higher balance current. A small one is rated at 1A, but some of them go up to 10A.
The BMS manages a set of cells. A battery is a set of Cells.
Now to answer your question: There are two types of balance circuits
Passive balancing
A passive balance system will watch all the cells and drain current (via the balance leads) across a resistor. This energy is lost to heat, but it forces the cell that is 'ahead' of the others to a lower state of charge. These systems typically have a fairly low balance current. Typically 500mA or less. Some of them are lower than 100ma. These systems can struggle to keep a high-capacity bank of LiFePO4 cells in balance.
Active Balancing.
An active balance circuit will take energy from the high-voltage cells and move it to the low-voltage cells. There are a couple of different ways of doing this. They all lose some energy to heat, but they are more efficient than passive balancing. More important than efficiency is the fact that these systems are typically much higher balance current. A small one is rated at 1A, but some of them go up to 10A.
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