JK BMS Password: Default Codes, Change and Reset Guide

A JK BMS password is actually two separate codes. The Bluetooth (connection) password lets the app talk to the BMS. The settings password lets you change parameters. The factory default on most units is 1234 for Bluetooth and 123456 for settings, but check your own manual, because batches and firmware differ.

The two codes a JK BMS uses

Many "password not working" problems come from mixing these up.

The two are independent. Changing one does not change the other. The app asks for the settings password when you open the parameter pages, which is where the "verify password" prompt comes from. Defaults are reported in the JK manual, on the JK shop pages and in many DIY Solar Forum threads. They are not guaranteed for every batch, so treat them as the first thing to try, not a promise.

Passwords and the browser connection

When you connect from the browser with the JK Preset Studio editor, there is no password prompt. The link uses the same JK02 Bluetooth protocol as the app, and in our tests on firmware 19 the BMS accepted reads and writes without either code: the JK app checks the codes itself. One report on an older V15 firmware says writes stopped after the settings password was changed, so this may differ on your unit. See the Bluetooth guide for the whole routine.

This also means the codes are not real security against someone within Bluetooth range. Keep the BMS connected to a monitor or switch Bluetooth off if that matters for your installation.

How to change the passwords

The exact menu names change between app versions, so look for the equivalents on your screen.

1. Connect to the BMS with the current Bluetooth password.
2. Open the settings area and enter the current settings password when asked.
3. Find the password options (the app has entries for the connection password and for the settings password).
4. Enter the old code, then the new one, and confirm.
5. Disconnect and reconnect to test the new Bluetooth password. Reopen the parameter screen to test the new settings password.

Use a short code of letters and digits. The BMS stores each code in a 16 character field, and plain ASCII is the safest choice. Write the new codes down somewhere other than the phone.

JK BMS password not working

Try these in order.

• Wrong code type. The pairing prompt wants the Bluetooth password. The parameter screen wants the settings password. Try 1234 on the first and 123456 on the second.
• Typing issues. Check caps lock and auto-capitalization on the phone keyboard. Passwords may be case sensitive. Watch for a trailing space.
• Changed earlier. If someone else set up the battery, the defaults no longer apply.
• App version. A very old or very new app can behave differently from your firmware. Update the app, or try the version recommended by the seller.
• Firmware differences. Some users on the DIY Solar Forum have reportedly had password trouble after the V19 firmware update. If the problem started right after an update, say so when you contact support.
• Stale app data. Some users report that clearing the app data and reinstalling lets the default settings password work again. This only resets the app side, so it will not help if the code was changed inside the BMS.

JK BMS forgot password: realistic options

There is no universal backdoor, and nobody should promise you one. Here is what is realistic.

1. Contact the seller or JK support with the BMS serial number. The serial is in the app under the About or device info page. JK support has reportedly offered a temporary password based on the serial number for owners who forgot their code, through its after-sales service pages. Availability and the exact procedure depend on your firmware and the support channel, so check the current support page rather than trusting an old forum post.
2. Look for a backup. If you exported your settings earlier, the .jkcfg file may contain the codes. See the next section.
3. Ask the seller about a reset procedure for your hardware version. Some versions have one, many do not.

Do not buy "unlock tools" from random sellers. A BMS that controls a battery bank is not the place for untrusted firmware or dongles.

Passwords inside the .jkcfg file

The exported .jkcfg is a 600 byte copy of two BMS frames. The second frame, the device info frame, has two ASCII fields of 16 characters each: the device passcode (the Bluetooth password) and the setup passcode (the settings password). So an exported file can contain both codes in plain text.

What this means for you:

• Treat an exported file like a password. Do not post it on a forum or send it to a stranger without checking it.
• Before sharing, clear both fields in the file, or replace them with throwaway codes. Do not share a file that holds your real codes.
• In JK Preset Studio, these are normal editable fields on the Device tab, not read-only ones. Model, serial number, hardware and software version are read-only there, but both passcodes can be edited, and only the edited bytes change when you export. The checksums are fixed automatically.

Importing a file may also write the codes stored in it back to the BMS. This is unverified. To be safe, check the codes in the file before you import, so you do not lock yourself out with a code you do not remember. Clear them before sharing the file. For the full backup and import routine, see export and import JK BMS settings. Once you can open the parameter screen, the LiFePO4 settings guide is a good next step.

FAQ

Is the JK BMS password the same as the Bluetooth PIN?

Not exactly. The connection password the app asks for is the BMS "device passcode". It is separate from the settings password. Your phone's own Bluetooth pairing, if it asks for one, is handled by the phone.

Does a firmware update reset the password?

It should not, but some users have reported password problems after updates. Export your settings before updating, and note both codes.

Can I read the password from the file?

Yes, if the file holds the codes in the device info frame, they are stored as plain text. Open the file in the editor and look at the Device tab to see what it contains.

Should I change the default codes?

Yes, if others can reach the battery. Anyone near the BMS with a phone can try 1234 and 123456.

Connect your BMS or open your .jkcfg in the editor to check which codes it holds before you share a file or import it.