Answering a number of questions will allow the determination of what the BMS is required to handle. Since the BMS is there to integrate between several systems these need to be outlined within your application to make sure you have the correct components to provide the necessary protection and operating functionality.
Here is a guide on how you can outline your hardware requirements.
Battery Pack: What type of cell are you planning to use to make a battery pack?
Outline the following:
- Manufacturer and Model
- Packaging format (18650, 26650, Pouch, Prismatic, other).
- Chemistry and Nominal Voltage
- Cell Capacity (typically in Ah)
- If known, operating voltage range Min / Max
- If known, operating temperature range Min / Max
- New / Recycled Cells
- If Recycled
- What was their original application (i.e. Vehicle, Laptop, etc.)
- Age, shelf life when fabricated
- Kilometres travelled, to indicate the accumulated kWh Charge/Discharge thus far.
Battery Pack Configuration: How do you plan to configure the cells into a pack?
- Number of cell strings
- Number of cells in series
- Number of cells in parallel
- Proposed cell monitors if known to this configuration
- Do you have individual cell fusing?
- What is the cell string fusing rating?
- With several strings, what is each string protection rating?
Charger / Inverter: What Charger / Inverter are you connecting your batteries to?
- Manufacture / Model of Charger
- Manufacture / Model of Load / Discharge of Inverter
- Is the Charger / Inverter integrated into one (1) unit or separate components
- Does the Charger have a Communication Port? If so, do you have the Communication Protocol that is used?
- Does the Load / Discharge equipment (i.e. inverter) have a Communication Port? If so do you have the Communication Protocol that is used?
- Peak Charging / Discharge Currents
- Continuous Charging / Discharge Currents
- Peak Voltage that will be measured from the Battery Pack
- What is the minimum voltage required to run the inverter/charger?
- Will this be directly linked to a vehicle alternator (or Dynamo)?
Do you want to know the SoC%
State of Charge ( aka. Fuel Gauge ) helps determine the operating condition and requires additional Shunt hardware.
- Peak Charging / Discharge Current
- Continuous Charging / Discharge Current
- Peak Voltage that will be Measured from the Battery Pack
- Where in the Circuit will the Shunt be Installed (Typically near the Negative Terminal)?
Protection Requirement: What protection is required?
- Will you be using a Circuit Breaker?
- If using a Circuit Breaker to the battery will this have a Remote Trip Function?
- What is the rated current for the circuit breaker (dual pole positive/negative)?
- Are there Contactors / Relays to Protect the Battery if required?
- Mechanical Disconnect, of which there are several types - Momentary (trigger) / or Latching (pulse), Latching Contactor or Normal Contactor?
- Accessory Coil Voltage 5v / 12v / 24v / 48v? or other,
- Is there a need for the Precharge Circuit?
- Are there any Permanent Accessory Circuits connected to the Battery that continue to Supply Power, even when the Critical Circuit Breakers have been Disengaged?
Cell Environment: What environment will the cell be used?
- Stationary (fixed) or mobile (vehicle)
- If mobile what is the accessory voltage? (i.e. 12v)
Connectivity
Will this be linked to The Network to have Internet access via Wi-Fi?
The typical connection is via WiFi. USB is there to do the initial commissioning and firmware update - and should not be left connected to the computer in normal operation.