# Justfog Q16 Pro Plus, four voltages and two coils taken apart > The Justfog Q16 Pro Plus taken apart, 3.5 to 4.4 V settings, 1.2 and 1.6 ohm coils, wattage worked out, filling and the UK 2 ml tank rule. Four small LEDs, one adjustment button and no screen. The **Justfog Q16 Pro Plus** never shows the power it sends to its coil, and retail listings copy a wattage table without saying where it comes from. For a journal that reads every coil through Ohm's law, that silence raises a question. How many watts does a 1.6 ohm coil really get on the first setting? And why does the same LED not give the same result from one coil to the next? ## The Justfog Q16 Pro Plus sets a voltage, not a wattage The **Justfog Q16 Pro Plus** pairs a built-in 1500 mAh battery with a tube-style tank for a tight mouth-to-lung draw. Its button does not pick watts but one of four voltage settings, 3.5, 3.8, 4.1 and 4.4 V. The power then follows from the value of the coil screwed in, 1.2 or 1.6 ohm. Every figure in this article comes from the specification Justfog publishes, which places this kit in a line that began in 2015. The original Q16 was followed by the Q16 Pro in 2019, the Q16 FF in 2022 and this Pro Plus in 2024. Its advertised constant voltage function holds the chosen setting until the battery runs flat. ## The four Justfog Q16 Pro Plus settings run through Ohm's law The manufacturer publishes a table of wattages per setting and per coil. The journal rebuilt it from the voltage alone, since that is what the device fixes. Ohm's law gives power as the square of the voltage divided by the resistance, and current as the voltage divided by the resistance. | Setting | 1.2 ohm, stated | 1.2 ohm, worked out | 1.6 ohm, stated | 1.6 ohm, worked out | |---|---|---|---|---| | 3.5 V | 10 W | 10.2 W, 2.9 A | 8 W | 7.7 W, 2.2 A | | 3.8 V | 12 W | 12.0 W, 3.2 A | 9 W | 9.0 W, 2.4 A | | 4.1 V | 14 W | 14.0 W, 3.4 A | 11 W | 10.5 W, 2.6 A | | 4.4 V | 16 W | 16.1 W, 3.7 A | 12 W | 12.1 W, 2.8 A | ### What the manufacturer's table rounds off On the 1.2 ohm coil, the maths and the table agree to within a tenth. On the 1.6 ohm coil, two settings are rounded up. The first gives 7.7 W rather than 8 W, the third 10.5 W rather than 11 W. The gap is small, but it is a reminder that the wattage on a listing is only a consequence. A coil whose real value drifts from its nominal one will also change the power at the same voltage. That reasoning is set out in our article on [Ohm's law and battery safety with rebuildables](/uk/ohms-law-rebuildables-battery-safety/). ### Modest current, raised voltage At under 4 A on the highest setting, the Q16 Pro Plus stays far from the current drawn by a sub-ohm build. What sets it apart lies elsewhere. A fully charged lithium cell gives about 4.2 V, so the 4.4 V setting needs the circuit to lift the voltage above that of the battery. ## 1.2 or 1.6 ohm, picking your coil Both values cover a tight draw, but not over the same range. The 1.2 ohm spans 10 to 16 W across the four settings, the 1.6 ohm roughly 8 to 12 W. On the same LED, the 1.2 ohm always receives a third more power. The box holds a single coil, a 1.6 ohm cotton head, according to the kit contents the manufacturer lists. Some shop listings still show both values in the box. It is worth checking the contents before counting on a spare 1.2 ohm. The 1.6 ohm suits anyone after the tightest draw and lower liquid use. The 1.2 ohm, warmer on the same setting, produces more vapour. Innokin's Zenith coils come in the same two values, with their own ranges, set out in our piece on [Zenith coils read through Ohm's law](/uk/innokin-zenith-coils-ohms-law/). ## Fitting the coil and filling the tank The tank on the Justfog Q16 Pro Plus does not come apart like a pod. The coil sits in from below and liquid goes in through a side slot that a twist opens or closes. Three steps deserve some care. ### A coil screwed in under the tank Separate the bottom part of the tank, attach the coil to that base, then screw the whole assembly back under the tank. The manufacturer stresses one point, the tank must be firmly closed before it goes back on the battery. To separate the two, it advises holding the bottom of the tank securely. ### A side slot opened by a twist To fill, turn the top part to the right until a horizontal slot appears. Liquid goes in through that slot, then a turn to the left closes the tank and limits leaks. The manufacturer asks you not to fill beyond 80% of capacity. ### Five minutes before the first puff A new coil should be left to soak for five minutes with the tank filled before any press of the button. Drawing on cotton that is still dry can damage the coil. Spitting or a burnt taste then calls for the same diagnosis as on a rebuildable, covered in our article on [the spitting coil and burnt taste](/uk/spitting-coil-burnt-taste-diagnosis/). ## The 3 ml tank and the UK 2 ml limit The manufacturer's specification gives the tank a capacity of 3.0 ml. In the UK, refillable tanks placed on the market are limited to 2 ml, and nicotine e-liquid is sold in bottles of no more than 10 ml at a strength of up to 20 mg/ml. Justfog's page on its European product notifications does not list this model, and no 2 ml version appears there. Before buying, the capacity actually printed on the packaging is the figure to go by. None of this changes the electrical picture, which depends only on voltage and coil resistance. ## Airflow, battery and protections Airflow is set by a sliding control at the base of the tank. The manufacturer advises against closing it completely, as strong suction can cause leaks and overheating. The battery charges over USB-C from a 5 V, 1 A charger or higher, and Justfog rules out fast chargers. It also recommends a first full charge to 100% before use. The electronics cut the power on a short circuit, overcharge, over-discharge, over-voltage while charging or overheating. Overall, the kit stands 126.4 mm tall and weighs 77.7 g. The battery alone weighs 56.2 g for 21 x 28.5 x 70.1 mm, the tank 21.5 g for an 18 mm diameter. ## Related reading - [Wicking cotton, choosing it and fitting it properly](/uk/wicking-cotton-choosing-fitting/) - [Ohm's law and rebuildables, vaping safely with cells](/uk/ohms-law-rebuildables-battery-safety/) ## FAQ Five answers drawn from the questions buyers of the Q16 range tend to ask. ### Which e-liquid suits the Q16 Pro Plus? The manufacturer sets no ratio. Coils of 1.2 and 1.6 ohm on a tight draw generally cope better with a liquid that leans on propylene glycol, which is thinner, than with one heavy in glycerine. ### Why will my Q16 Pro Plus not switch on? The device turns on and off with four presses of the button within two seconds. If it stays silent, a protection may have cut the power after a short circuit or overheating, or the battery may be flat. ### How do I read the battery level? The button LED changes colour. It stays white from 100 to 65%, turns blue from 65 to 30% and goes red below 30%. ### How does it differ from the Q16 FF? Justfog compares them directly. The Q16 FF has a 1.9 ml tank and a 900 mAh battery, the Q16 Pro Plus 3.0 ml and 1500 mAh. ### Which finishes does the Q16 Pro Plus come in? Justfog shows it in three colours, black, silver and gold. The battery combines anodised aluminium and polycarbonate, while the tank pairs PCTG with anodised aluminium and chrome-plated brass. ## The Justfog Q16 Pro Plus, a kit that speaks in volts The Q16 Pro Plus does not hide its power, it simply expresses it in volts. Four settings from 3.5 to 4.4 V and two coil values are enough to work it out, give or take two roundings on the 1.6 ohm. Three findings stand out from that reading. On the same setting the 1.2 ohm gets a third more power, the box supplies only a 1.6 ohm, and the 3 ml the manufacturer states runs into the 2 ml UK limit. To choose a setting on the **Justfog Q16 Pro Plus**, start from the coil screwed in rather than the LED that lights up, a habit that serves just as well on any device with adjustable voltage. Editorial content for adult readers only. Vaping products can contain nicotine, a substance that causes addiction. Nicotine vaping products are not for sale to anyone under 18 in the UK. This article is not a buying recommendation.