FNIRSI HS-03 Cordless Soldering Iron

FNIRSI HS-03 Cordless Soldering Iron

The FNIRSI HS-03 is a cordless soldering iron for UK makers who need to solder away from the bench — on-site repairs, field work, or anywhere a mains socket isn’t handy. It runs on a 2600mAh 18650 lithium cell, heats from cold to working temperature in 7 seconds, and covers 100°C to 450°C with PID-controlled precision. At 134g it’s light enough to use one-handed for extended sessions.

• 7-second heat-up — working temperature from cold before you’ve picked up the solder
• 100–450°C range — handles leaded solder, lead-free, and fine SMD work
• 2600mAh replaceable 18650 cell — swap the battery instead of waiting to recharge
• Corded + cordless dual mode — run from a USB-C power bank or mains adapter when the battery runs low
• 1°F precision control — fine-tune temperature exactly, not in 5° or 10° steps
• Advanced PID stability — temperature holds steady under load, not just at idle
• Smart auto-sleep — reduces tip wear when the iron sits idle
• 12-month Kunkune warranty — covered if it fails in normal use

How fast does the FNIRSI HS-03 heat up?

The HS-03 reaches working temperature in 7 seconds from cold. The 10W ceramic heating element draws power efficiently from the 5V USB-C input, so you’re not waiting around — pick it up, press the button, and it’s ready by the time you’ve positioned your work.

Recovery after a cold joint is equally fast, keeping throughput high when you’re working through a board with many joints.

Is the battery replaceable on the HS-03?

Yes — the HS-03 uses a standard 18650 lithium cell that you can swap out in seconds. Most cordless soldering irons use sealed, fixed batteries that are dead when discharged. The HS-03 lets you carry a spare 18650 and keep working without any downtime.

The iron also runs in corded mode via USB-C, so a power bank or laptop charger keeps it going indefinitely when you don’t have a spare cell to hand.

Can the HS-03 be used while plugged in via USB-C?

Yes. Dual mode means you can run the HS-03 from any 5V USB-C source — a power bank, a mains USB-C charger, or a laptop port — without needing the battery at all. Switch between corded and cordless on the fly depending on where you’re working.

This makes it practical at the bench as a lightweight daily-use iron as well as a portable field tool.

How accurate is the temperature control?

The HS-03 adjusts temperature in 1°F increments with PID feedback that corrects for load drop in real time. Most budget cordless irons offer coarse presets with no closed-loop control — the tip temperature drifts when you touch solder. The PID loop on the HS-03 keeps the tip stable under continuous use, which matters for SMD work where overheating pads lifts them.

Five quick-adjust levels let you jump between common temperatures fast; the fine 1°F control lets you dial in exactly when precision matters.

What tips are compatible with the FNIRSI HS-03?

The HS-03 uses F210-series tips. The iron ships with a K-tip (chisel), an I-tip (fine point), and an IS-tip (angled fine), so most common soldering tasks are covered out of the box. F210 tips are the standard for FNIRSI pen-style irons and replacements are available separately.

Will the tip oxidise quickly?

The auto-sleep system reduces heating power when the iron sits idle, cutting the main cause of tip oxidation — sustained heat without flux to protect the surface. Keep the tip tinned between sessions and wipe on a brass-wool cleaner (not a wet sponge, which thermal-shocks the tip) and an F210 tip will last through many hours of regular use.

Best for

On-site PCB repair, field electronics work, Arduino and ESP32 prototyping, SMD rework on tight boards, guitar pedal builds, 3D printer wiring repairs, drone and RC electronics, loft and under-floor cable terminations, repair tech work away from the bench, school and college electronics courses, and hobbyist builds where you want to solder away from the mains.

What’s In The Box

• FNIRSI HS-03 cordless soldering iron with 2600mAh 18650 battery fitted
• K-tip (chisel)
• I-tip (fine point)
• IS-tip (angled fine point)
• Pen cap
• Screwdriver (for tip changes)
• USB-C cable
• Storage box

Why Kunkune

Shipped from our Oxfordshire warehouse via Royal Mail 1–2 day delivery. 12-month warranty on all FNIRSI products — if the HS-03 fails in normal use, we’ll replace it. 60-day returns. No drama.

Frequently Asked Questions — FNIRSI HS-03

Does the FNIRSI HS-03 work while charging?

Yes. In dual mode, the HS-03 runs from any 5V USB-C power source — power bank, mains adaptor, or laptop — so you can use it indefinitely while connected, with no need for the battery to be charged first.

What battery does the FNIRSI HS-03 use?

A standard 18650 lithium-ion cell rated at 2600mAh. The battery is removable — you can carry a spare and swap it in seconds rather than waiting for a recharge cycle.

What tip standard does the HS-03 use?

F210-series tips. The iron ships with three tips (K, I, and IS profiles). Replacement F210 tips are available separately.

How do I change temperature on the HS-03?

Press the button to cycle through 5 quick-adjust temperature presets. For fine adjustment, hold the button to enter 1°F increment mode and dial to your exact target. The 0.96″ IPS screen shows current and set temperature at all times.

Is the FNIRSI HS-03 good for SMD soldering?

Yes. The PID controller holds tip temperature stable under load, which is what matters for SMD work — a tip that droops when it touches a pad causes cold joints and risks lifting pads. Pair it with the I-tip or IS-tip (both included) for fine SMD work.

Does the auto-sleep turn the iron off completely?

No — auto-sleep reduces power to protect the tip and conserve battery, but the iron remains warm. A short press wakes it back to your set temperature instantly.