Victron bms 12/200 Battery Management System

The bms 12/200 from victron Energy (mpn bms012201000) is an efficient battery management system (bms) specially designed for installation in vehicles and boats. The 12/200 bms is exclusively suitable for operation withvictron Energy 12.8 volt lithium iron phosphate batteries (also called LiFePO4 or lfe).

The lithium iron phosphate (LiFePO4 or lfp) battery is the safest of the regular lithium iron battery types. The nominal voltage of an lfp cell is 3.2 v (lead-acid: 2 v/cell). A 12.8 v lfp battery therefore consists of 4 cells connected in series and a 25.6 v battery consists of 8 cells connected in series.

Reasons for the need for a battery management system (bms):

• An lfp battery will be damaged if the voltage applied to the cell drops to a value below 2.5 v.
• An lfp battery will be damaged if the voltage applied to the cell rises to a value above 4.2 v. Lead-acid batteries can also be damaged in some circumstances if they are discharged too deeply or overcharged, but this usually does not happen immediately. A lead-acid battery will recover from a deep discharge even if it has been left in a discharged state for several days or even weeks (depending on the battery type and brand).
• The cells of an lfp battery do not automatically equalize at the end of the charge cycle. The cells in a battery are never 100% equal. for this reason, some cells are fully charged or discharged earlier than others when cycling. These differences become more pronounced if the cells are not equalized from time to time. In a lead-acid battery, a small current continues to flow even when one or more cells are fully charged (the main effect of this current is the splitting of water into hydrogen and oxygen). With the help of this current, the other cells, whose state of charge is lagging behind, are also charged, thus balancing the state of charge of all cells. However, the current flowing through an lfp cell when it is fully charged is virtually zero. Less charged cells are not fully charged for this reason. The difference between the individual cells can become so extremely large over time that, although the total voltage of the battery is within the limits, some cells are destroyed due to overvoltage or undervoltage.

Conclusion: A LiFePO4 battery must therefore be protected by a bms that actively balances the individual cells and thus prevents under- or overvoltage.

task coverage by the bms 12/200 during installation in the mobile sector.

This is what the power port ab (input for the alternator or battery charger) of the bms 12/200 does

1. The first task of the power port ab is to prevent the load connected to the lfp battery from discharging the starter battery. This function is similar to that of a Cyrix battery coupler or an argo FET battery isolator. Current can only flow to the lfp battery if the input voltage (= voltage at the starter battery) exceeds the value of 13 v.
2. No current can flow from the lfp battery back to the starter battery. This prevents possible damage to the lfp due to excessive discharge.
3. excessive input voltages and transients are regulated down to a safe level.
4. The charging current is reduced to a safe level in case of cell imbalance or overheating.
5. The input current is electronically limited to approximately 80% of the ab fuse rating. A 50 a fuse therefore limits the input current to 40 a Choosing the right fuse therefore entails the following:
6. 1. The lfp battery is protected from too high a charging current (important in the case of a low capacity lfp battery).
   2. The alternator is protected from overload in case of a lfp battery bank with a high capacity (most 12 v). AC generators overheat and fail if they operate at maximum output power for more than 15 minutes).
   3. The charging current is limited so that the current carrying capacity of the wiring is not exceeded The maximum rating of the fuse is 100 a (which limits the charging current to approximately 80 a).

This is what the power port lb (output/input load/battery charger) of the bms 12/200 can do

1. maximum current in both directions: 200 a uninterruptible
2. Peak discharge current electronically limited to 400 a.
3. Blocking battery discharge whenever the weakest cell drops below 3 v.
4. The charge current is reduced to a safe level in case of cell imbalance or overheating.

Scope of delivery:

1x victron Energy bms012201000 12/200
1x instruction manual