JK BMS Model Numbers Explained: B2A8S20P, PB2A16S20P and More

A JK BMS model name looks cryptic, but it follows a pattern. JK-B2A8S20P, JK-PB2A16S20P and JK-B2A24S15P each tell you the product line, the balance current, the maximum cell count and the continuous current rating. JK does not publish an official decoder, so what follows is the pattern that matches the spec sheets and the shop listings. Check the spec sheet of your exact unit before you rely on a number.

The pattern

Take JK-PB2A16S20P apart:

Part	Example	Meaning
JK	JK	Brand (Jikong, Chengdu)
Series	PB	Product line: B, PB, BD and others
Balance current	2A	Active balancer current
Cell count	16S	Maximum number of cells in series
Current rating	20P	Continuous current in tens of amps: 20P = 200 A
Suffix	-H, -HC, -R	Optional features of a variant

So JK-B2A8S20P is a B-series board with a 2 A balancer, up to 8 cells and 200 A. JK-B2A24S15P is a 2 A balancer for up to 24 cells at 150 A. JK-PB2A16S20P is the inverter BMS for up to 16 cells at 200 A.

The series

B: the classic smart BMS with an active balancer and Bluetooth. Common for vans, boats, e-bikes and DIY packs. Lower-numbered versions have few or no communication ports.
PB: the "inverter BMS" for home storage. It adds CAN and RS485 ports for the inverter, a parallel RS485 port, a 4-bit DIP switch for the pack address, dry contacts, a heating output, a 1000-event log and LED SOC indicators. See the inverter communication guide.
BD: smaller boards with a lighter balancer. Here the balance figure is read differently: BD6A means 0.6 A, not 6 A, and BD4A is 0.4 A.

Board revisions inside a series also matter. The device info page in the app shows a hardware version (for example 19H) and a software version (for example 19.25). V19 firmware changed some value formats, such as the short circuit delay, so a setting copied from a V15 board may not fit a V19 one.

The balance current

The number before the A is the balancer current: 1A, 2A, or 0.4A and 0.6A on BD boards. Active balancing moves energy from the highest cell to the lowest, so a 2 A balancer corrects a drift about twice as fast as a 1 A one. For packs from 100 Ah up, 2 A is the usual choice. The balance settings guide explains when the balancer runs.

Cell count

The S figure is the maximum. A board marked 8S runs 4 to 8 cells, 16S runs 7 or 8 up to 16, and 24S runs 8 to 24. The exact minimum depends on the board, because the BMS needs a minimum pack voltage to power itself. Set the Cell Count setting to your real number of cells: a mismatch raises the "cell count does not match" alarm and makes the voltage protections wrong.

Current rating

The P figure times ten is the continuous current: 10P = 100 A, 15P = 150 A, 20P = 200 A, 30P = 300 A. Peak and short circuit current are higher and listed in the spec. Choose a board rated above the largest continuous current your inverter or motor draws, with some margin for heat. A 3 kW inverter on a 24 V pack already draws about 125 A at full load, before conversion losses.

JK Preset Studio uses this figure. When you apply a ready preset, its current limits are capped at the rating read from the model name, so a 100 A board never gets a 200 A limit. The OCP and SCP guide covers how to set the limits below the rating.

Suffixes

Suffix	Seen on	What sellers list
-H	B-series	Heating pad output
-HC	B-series	Heating pad output and CAN port
-R or R	B-series	RS485 port only

The letters are not used consistently. Some listings write HS where others write HC for the same board. Read the feature list, not only the suffix.

Same model, different features

Two boards with the same name can still differ. We probed a JK-B2A8S20P on hardware 19H and firmware 19.25: it refused writes to RFV, charging float mode, RCV and RFV time, precharge time, the PCL switch, heating and the heating temperatures, the port mode and the CAN and UART2 protocol numbers. The settings frame still carried values for all of them, so the app may show settings the board cannot use.

The browser editor checks this for you. After it connects, it tries each optional setting by writing back its current value, which changes nothing. Settings the BMS does not have are marked "Not on this BMS" and left out of presets and writes. For a .jkcfg file from a known model, they get a softer "Maybe not on this BMS" hint.

Which one to buy

12 V or 24 V van, boat or e-bike pack: a B-series 8S board, 1 A or 2 A balancer, current rating above your inverter or motor.
48 V home storage with a hybrid inverter: a PB-series board, because the inverter needs CAN or RS485 and parallel packs need addresses.
Cold location: a board with a heating output, plus a pad. See the temperature and heating guide.

Whatever you choose, start from the LiFePO4 settings guide once it is wired.