Makita LXT BL1850 Battery Case 18V-21V - 5 MOSFET BMS, 10 x 18650 (5S2P)

Upgraded version: a different class of electronics

This is not the same case you saw a year ago. We have fully revised the model, and the biggest change is inside. Instead of a typical budget board, this unit ships with a BMS built on 5 power MOSFETs (3010KS, 30V / 110A die rating, TO-252 package). The board is manufactured by Wuyue Electronics (五月电子), part number 0026004.

In practice this means 30-40A continuous current and up to 60A peak. A drill under load, an angle grinder, garden tools - this board keeps working where cheap 3-MOSFET clones trip on the first serious effort.

Cell balancing - something budget clones simply lack

Cell balancing is handled by six power resistors (sealed under protective compound) - a passive balancing scheme. This matters enormously in a ten-cell pack: without balancing, cells drift apart in voltage over time, one starts sagging, and the whole pack degrades. With balancing, charge stays even across all strings and the pack lasts far longer.

There is also an NTC thermal sensor on a separate lead. This gives you genuine thermal protection: if the pack overheats under load or during charging, the board cuts the circuit. Combined with overcharge, over-discharge and short-circuit protection, that is a complete safety package for both your cells and your tool.

4-LED charge indicator included

A separate indicator board with 4 LEDs: 25% / 50% / 75% / 100%. It slots into the dedicated position in the case, and the contacts solder to the output terminals. The included scale sticker goes over the black plastic insert - the result looks factory-made, not homebrew.

No more guessing how much charge is left. Press the button, read the level.

5.5x2.1 mm jack: charge without a dock

The board exposes a standard 5.5x2.1 mm DC jack. You can charge the pack directly from an ordinary 21V adapter, with no Makita charging station required. For most users this solves charging entirely - adapters are cheap and available in any electronics shop.

Mechanically, the case is fully compatible with the Makita LXT (BL1850) standard - it mounts on genuine Makita tools and on every Chinese clone built to that standard, including FOX EXPERT tools.

Choosing your 18650 cells

The layout is 5S2P: five groups in series, two cells in parallel per group. That yields 18V nominal / 21V maximum (5 x 4.2V) - the same standard as original Makita 18V packs.

Pack capacity equals double the capacity of a single cell:

Matching cells to your application:

• Drills, impact drivers, high-torque tools - go for high-drain cells: 25R, HG2, VTC6. Here raw capacity matters less than the ability to deliver current instantly. Two 25R cells in parallel supply up to 40A, exactly what this board is designed for.
• Garden tools, trimmers, work lights, moderate loads - high-capacity cells like MJ1 or 30Q are the better fit. Longer runtime, modest peak draw.
• All-round choice - Samsung 30Q or LG HG2. A solid compromise between capacity and current delivery that suits almost any tool.

Important: all 10 cells must be the same model, from the same batch, and at the same charge level before assembly. Never mix different cells or old with new - that will ruin the pack.

Complete kit - nothing else to buy

Everything needed for a build from scratch:

• Case (upper and lower halves, black)
• 10-cell 18650 holder cassette
• 5S2P BMS board, 5 MOSFETs, with thermal sensor
• Charge indicator board (4 LEDs)
• Nickel busbar strips: 4 + 2 pcs
• Screws: 4 white (board) + 4 black (case)
• Insulation pads: 2 pcs
• Indicator scale sticker
• Spring and red locking latch
• Plastic insert for the indicator

All you need to add is a spot welder for the nickel strips (or a soldering iron if you are experienced with cells) and 10 x 18650 batteries.

Who this case is for

• DIY builders and hobbyists - assembling a 6 Ah pack from quality cells costs noticeably less than a branded battery, and often outperforms it.
• Repair shops - bring dead Makita and clone batteries back to life: swap the cells, and the electronics here beat the factory board.
• FOX EXPERT and Makita-clone tool owners - a spare battery for your tool at a sensible price.
• Wholesale: retailers and resellers - a steady-demand product with tiered pricing from 3 units.

Specifications