JK Preset Studio

Change JK BMS Settings over Bluetooth in Your Browser

You can change JK BMS settings over Bluetooth straight from a browser, without the JK app and without exporting a file. Open the JK Preset Studio editor in Chrome or Edge, press Connect BMS and pick your BMS. The editor reads every setting, lets you change it with presets and checks, and writes the result back one setting at a time, reading the BMS back after each step.

What you need

  • A browser with Web Bluetooth. Chrome or Edge on Windows, macOS, ChromeOS or Android. Firefox, Safari and every browser on iPhone and iPad do not have it. On those, use the .jkcfg file workflow instead.
  • The JK app closed. The BMS accepts one Bluetooth connection at a time. If the app or another monitor (an ESP32 with esphome, for example) is connected, the BMS does not show up or drops the link.
  • A JK BMS with the JK02 protocol. We tested a JK-PB2A16S20P (firmware 19.26) and a JK-B2A8S20P (firmware 19.25). Other JK boards with firmware 19 use the same protocol.
  • Range. Stay within a few metres of the BMS. A metal battery cabinet shortens the range a lot.

Connect and read the settings

  1. Open the home page and press Connect BMS.
  2. The browser shows a list of nearby devices. JK boards usually advertise their serial number or a name starting with JK. Pick yours.
  3. The editor reads two frames from the BMS: one with all settings and one with device information. The BMS beeps once when it sends the settings.
  4. The editor opens with your values, the model, hardware and firmware version.

These two frames are exactly what the JK app saves in a .jkcfg file. You can download them as a file at any time, which makes a good backup before you change anything.

Which settings your model has

Not every JK BMS has every function. The settings frame always contains all fields, even for features the board lacks: an 8S B2A board without heating still reports a heating start temperature. So right after connecting, the editor asks the BMS directly. It writes the current value of each optional setting back, which changes nothing, and the BMS answers for every one: accepted, or "this model has no such setting".

Settings the BMS lacks are marked Not on this BMS. They stay visible but cannot be edited, presets leave them alone and they are not validated. On our JK-B2A8S20P this covered float voltage (RFV), charging float mode, heating, precharge, the PCL module, the port switch and the CAN and UART2 protocols. The result is stored in your browser for that BMS, so the next connection is instant.

Edit and apply a preset

Every parameter has a short explanation, a recommended range for your cell chemistry and a link to sources. You can:

  • change single values, for example OVP or the balance start voltage;
  • apply a ready preset for LiFePO4, NMC or LTO and then adjust it;
  • check the parameter reference for what each field does.

The editor checks dependent values as you type, for example that OVPR stays below SOC-100% voltage and that stays below RCV. Errors block writing; warnings only inform you.

Write and verify

Press Write to BMS. The dialog shows the plan before anything is sent: how many steps, which settings in each step, and which edited settings are skipped. Download the backup offered there first.

The firmware checks every written value against what the BMS holds at that moment, so the same final values can fail in one order and pass in another. The editor splits your changes into steps that are safe in any order. After each step it reads the BMS back and compares every value.

The BMS answers each write with a result code. If it refuses a value because it clashes with another setting, writing stops at once and the editor shows which setting failed and what the BMS holds now. If a setting turns out to be missing on your model, it is skipped and listed. Nothing fails silently.

One detail we found on real hardware: a write sent the instant after a read can be dropped without any answer. The editor waits briefly after every read and resends a write once if no answer comes.

When a file is still better

  • Your browser or phone has no Web Bluetooth.
  • You want a long-term backup or to keep several configurations side by side.
  • You prepare settings before the pack is assembled, or send them to someone else.

The export and import guide covers that workflow. If an import fails with "Sending failure", see the Sending failure guide.

Common mistakes

  • Leaving the JK app open, so the BMS never appears in the list.
  • Writing without a backup. Download the current settings first.
  • Expecting every setting to change on every model. Check the Not on this BMS marks.
  • Writing values for another chemistry. Start from the LiFePO4 settings guide or the right preset.

FAQ

Do I need the BMS password to write over Bluetooth?

In our tests the BMS accepted writes without a passcode; the JK app checks the password itself. One report on an older V15 firmware says writes stopped working after the settings password was changed, so results may vary.

Is it safe?

The editor writes only what you changed, in a safe order, and checks every value afterwards. Wrong values can still damage cells, so compare them with your cell datasheet and keep the backup.

Does anything leave my computer?

No. The browser talks to the BMS directly. Settings are never uploaded.

Why does the BMS beep?

The BMS beeps when it is asked for its settings. The editor asks once on connect and once after each write step.

Connect your BMS and see your current settings in a minute.

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