JK BMS Firmware: V15 vs V19 and How to Update Safely
JK BMS firmware is tied to the hardware generation: a V15 board runs V15 firmware and a V19 board runs V19 firmware, and you cannot turn one into the other with an update. You update firmware with the JK PC software over a wired connection, not over Bluetooth. Back up your settings first, use only a file made for your exact hardware, and update only when you need a fix or a feature, because a failed update can leave the board unusable.
How to read your hardware and software version
Every JK board reports two versions:
- Hardware version, such as 19H or 15A. The number is the generation; the letter is the board variant.
- Software version, such as 19.25 or 19.26. The first part matches the hardware generation, the second part is the firmware release.
The JK app shows both in the device info. JK Preset Studio shows them too, right after you connect over Bluetooth, together with the model, the serial number and the uptime. Write them down before you look for firmware.
V11, V15 and V19: what changed
JK's own comparison of V11 and V15 lists the upgrades of V15:
| Feature | V11 | V15 |
|---|---|---|
| Temperature sensors | 2 | 4 |
| Heating | on some boards | on all boards |
| CAN and RS485 | one or the other | both at the same time |
| Alarm functions | no | yes |
| Parallel operation | no | yes |
For V15 against V19 there is no official table. What owners report, and what we saw ourselves:
- Ports. On PB boards, V19 has a working RS232 port on the communication board; on V15 that port is reported as not connected. V19 also adds a separate UART port next to the display connector.
- Heating logic. Owners report that heating behaves differently before and after firmware 19.05.
- Settings values. Some settings are stored differently. On a JK-PB2A16S20P with software 19.26 the short circuit delay is stored as 5, and a settings file from an older board with 1500 is refused. The OCP and SCP guide has the details.
- Missing settings. Even within V19, boards differ: a JK-B2A8S20P with hardware 19H refuses float voltage, heating and precharge time because it lacks those functions.
The practical result: a settings file from a V15 board often fails on a V19 board with a Sending failure. Write settings one by one instead of importing a file across generations, as the Sending failure guide explains.
How to update JK BMS firmware
The official procedure for PB inverter boards uses the PC software:
- Back up your settings. Read the BMS and save a
.jkcfgfile, as the export and import guide shows. Firmware updates can reset settings. - Connect by cable. Use the USB to RJ45 cable from JK (RS485 or RS232, depending on the board) and select the right port in the PC software.
- Make the BMS a slave. JK requires the device address to be other than 0 during the update, and the BMS must not talk to another master. Set the DIP switch and disconnect parallel links.
- Upgrade. In the PC software open the menu at the top right, choose Upgrade Firmware, select the file and press Start Upgrade. The update is complete when the progress bar ends.
- Check and restore. Confirm the new software version, then compare your settings with the backup and write back what changed.
Standard boards such as the B2A series are updated with the JK BMS Monitor PC software through an RS485 to USB adapter. Ask your seller which adapter fits your board before you buy one.
Forced upgrade and recovery
If the normal upgrade refuses a file, JK has a Forced Upgrade option. It needs an authorization code from the manufacturer, which exists to stop you from flashing a file meant for other hardware. If an update fails, JK's steps are: repeat the forced upgrade; keep the activation or display switch pressed; press and release the RST button; wait for the progress bar to finish.
Be careful with firmware files from cloud links and forums. There is no public, signed release channel, and at least one file shared as a new version turned out to be a test build without working firmware.
Should you update at all?
Update when a specific fix or feature matters to you: a bug in inverter communication, a heating change, a setting your firmware lacks. If the BMS works and protects your cells, the risk of a failed update usually outweighs the benefit.
FAQ
Can I update a JK BMS over Bluetooth?
No. Firmware updates use the JK PC software over a cable. The phone app and Bluetooth tools read and write settings only.
Can I turn a V15 BMS into a V19 BMS with firmware?
No. The version follows the hardware generation. V19 firmware is not meant for V15 boards, and flashing the wrong file can brick the board.
Will a firmware update erase my settings?
It can. Save a backup file before updating and compare the settings afterwards.
Connect your BMS to see its hardware and software version and save a backup before you update.
Related guides
- JK BMS Model Numbers Explained: B2A8S20P, PB2A16S20P and MoreDecode any JK BMS model name: series, balance current, cell count and current rating, plus the -H, -HC and -R suffixes and what they mean for heating, CAN and RS485.
- Export and Import JK BMS Settings: The .jkcfg File GuideHow to export and import JK BMS settings with the app, what the .jkcfg file contains, why hand edits break it, and how to edit it safely in your browser.
- JK BMS Sending failure: Causes and Step-by-Step FixJK BMS Sending failure on import? See why the firmware rejects settings (voltage chains, write order, SCP delay) and how to fix it step by step.
- JK BMS Overcurrent Protection Settings: OCP and SCP GuideJK BMS overcurrent protection settings explained: charge and discharge OCP limits, delays, recovery times and SCP, with ranges and sizing for inverters.