Temperature limitation

The BMS has implemented temperature limitations for the battery and the BMS itself.

info

• Before continuing, make sure, that all temperature sensor readings are correct and configured.
• All mentioned variables are located in folder /driver/temp/.

More about protection and limitation

Protection

The BMS ports are turned off when any temperature sensor reading is above its max value (or under min). To turn the ports back on, the temperature must be below the max value and the user must switch back on the BMS.

If the ports are turned off due to the temperature limitation, the BMS will enter PROTECT state and log the reason into protectLog:

• Value 0x0400 (Overtemp on TS inputs) - a battery TS input crossed max - marginMax or min + marginMin
• Value 0x0200 (Overtemp of the switch) - an internal switch sensor (switchptc, mcu) crossed its max threshold

If a balancer sensor (balmcu, ptcBal) is overtemperature, the ports stay on - only balancing is paused (balState bit 2).

Limitation

For each temperature sensor, you can configure the limitation. For the build-in temperature sensors, you can not configure the max parameter.

When the sensor reading enters the dec zone, the available current is linearly reduced (see how the limiter works) and the corresponding bit is set in the limit word - bit 1 for internal BMS sensors, bits 2 and 4 for battery TS inputs.

Parameter	Description
max	Maximum temperature for the sensor. If the sensor reading is above this value BMS enter PROTECT state.
marginMax	Area with no power.
decMax	Area with reduced power.
marginMin	Area with no power.
decMin	Area with reduced power.
min	Minimum temperature for the sensor. If the sensor reading is below this value BMS enter PROTECT state.

tip

• First, configure the max parameter, after that tune the limitation parameters
• The limitation can be configured even for sensors with ohm reading. Only the limitation parameters will be in ohms too.

note

Battery TS input min/max limits apply to discharging (DSC port). The limits for charging are configured separately - see below.

Charging temperature limits

Battery cells usually have a much narrower allowed temperature range for charging than for discharging. Each battery TS input therefore has a second, independent set of limits that applies only to the charge direction (CHG port and regen).

Parameter	Description
maxChg	Maximum battery temperature for charging.
marginMaxChg	Area below maxChg with no charging power. Sets limit bit 2048.
decMaxChg	Area with linearly reduced charging power. Sets limit bit 2048.
marginMinChg	Area above minChg with no charging power. Sets limit bit 1024.
decMinChg	Area with linearly reduced charging power. Sets limit bit 1024.
minChg	Minimum battery temperature for charging.

When a charger is connected and any battery TS input reading is above maxChg - marginMaxChg or below minChg + marginMinChg, the BMS enters the CHG_OVERTEMP state - the CHG port is blocked, but the DSC port stays available. The BMS does not enter PROTECT in this case, and charging resumes automatically once the battery temperature returns into the allowed range.