Makita LTX Digital Interface

Makita LTX batteries (18 V tool batteries) use a proprietary one-wire digital interface that allows querying battery details, assessing health, and unlocking locked batteries.

Access the interface via the yellow auxiliary connector on the battery.

Overview

Makita LTX batteries feature a proprietary, undocumented digital interface. Official chargers like the DC18RC and diagnostic tools like the BTC04 use this communication channel.[web:1][web:2]

Community reverse-engineering has produced affordable DIY diagnostic tools.

Hardware Interface

The 1-Wire interface uses the yellow 7-pin connector. Source cables from AliExpress.

Required pins (2nd from each side):

Key notes:

• Standard connectors have 6 connected pins (1 missing)
• Enable = pin next to missing pin
• 1-Wire = 2nd pin from opposite side
• Voltage: 5 V recommended (3.3 V possible but unstable)
• Remaining pins: unknown function (typically cut)

Complete protocol reference: makita-lxt-protocol

1-Wire Protocol

Standard Dallas 1-Wire (16.3 kbps):

• Open-drain bus with 4.7 kΩ pull-up (3-5 V)
• Master reset: 480 µs low → slaves presence: 60-240 µs low
• Bit timing: 60 µs slots (logic 1 = release, 0 = hold low)

Communication Sequence

1. Reset (500 µs low)
2. Presence (550-650 µs low from battery)
3. Command: cc + command bytes (ex: cc d7 0e 02 = temp)
4. Response: data bytes + 0x06 terminator

Source: makita-lxt-protocol repo

Example: cc d7 0e 02 → 9d 0b 06

Battery Commands

Batteries use different BMS generations with varying command sets.

Universal Commands

All types support:

• Battery type
• Capacity
• Failure codes
• Cycle count

Details

Specific Commands

Reading battery information such as cell voltages, temperature, charge level, and battery health indicators requires different commands based on battery type.

Type Detection

Follow [BTC04] probing sequence:

Issue Specific Commands

Once you know the battery type, you can use supported commands from the table below.

Notes:

• Types 0,2,3 terminate with 0x06
• All data: little-endian

Calculated Values

The official Makita diagnostic tool BTC04 calculates indicators from the raw values:

State-of-Charge

Scale of 0-7:

  ratio = charge_level / capacity / 2880

  if ratio == 0:
    sof = 0
  elif ratio < 10:
    sof = 1
  else:
    sof = min(ratio / 10, 7)

Overdischarge percentage

Calculated like this:

  if overdischarge_count > 0 and cycle_count > 0:
    p = 4 + 100 * overdischarge_count / cycle_count
  else:
    p = 0

Overload percentage

Calculated as follows:

  if sum(counters) > 0 and cycle_count > 0:
    p = 4 + 100 * sum(counters) / cycle_count
  else:
    p = 0

Health

For batteries of type 0, a pre-calculated health value can be queried and is then scaled like this:

ratio = health / capacity
if ratio > 80:
  h = 4
else:
  h = ratio / 10 - 5

For all other battery types, a health value is calculated like this:

  f_ol = max(overload - 29, 0)
  f_od = max(35 - overdischarge, 0)
  dmg = cycles + cycles * (f_ol + f_od) / 32
  scale = 1000 if capacity in (26, 28, 40, 50) else 600
  h = 4 - dmg / scale

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