4iiii Power Meters

ANT+, Bluetooth Smart, and Getting Everything Talking

Connectivity is one area where 4iiii keeps things simple. Every current model broadcasts simultaneously over both ANT+ and Bluetooth Smart (BLE), which means you're not choosing between your head unit and your training app - you can run both at once. Pairing with a Garmin Edge is straightforward via the ANT+ sensor menu; Wahoo ELEMNT and Hammerhead Karoo pick it up just as cleanly, either over ANT+ or BLE depending on your preference. Most riders stick with ANT+ for their head unit and reserve BLE for a phone or secondary device.

For indoor training, the dual-band setup means Zwift, TrainerRoad, and Wahoo SYSTM all see the power meter without fuss. If you're running a smart trainer alongside it, you can use the 4iiii as your primary power source and pipe that data directly into your platform of choice - useful if you trust the crank measurement more than your trainer's own calibration. The 4iiii app (iOS and Android) handles firmware updates, lets you check battery status before you head out, and is where you'll go to configure advanced settings. It's not glamorous, but it works reliably, which is all you really want from a companion app. Compared to options like Stages power meters or Favero power meters, 4iiii's connectivity stack is competitive and well-supported across firmware updates.

Battery Life, Cold Weather, and Why Active Temperature Compensation Matters

Eight hundred hours is a big number. To put it in context, if you're riding ten hours a week through a UK winter, you're looking at roughly 80 weeks before you need to crack open a CR2032 - and those batteries cost pennies. That buffer matters more than it might seem, because cold temperatures cause battery voltage to drop even when charge remains, which can trigger false low-battery warnings or, in worst cases, cause a pod to cut out mid-ride. A February morning in the Yorkshire Dales or on the exposed roads above Merthyr Tydfil will find the limits of a less capable unit quickly.

This is where active temperature compensation earns its keep. The 4iiii Precision 3+ monitors temperature changes in real time and adjusts its strain gauge readings accordingly, maintaining that +/- 1% accuracy as you go from a warm garage into freezing air. Without it, the thermal expansion and contraction of the crank arm material would introduce drift into your power figures - subtle, but enough to skew interval targets if you're training to tight zones. It's the kind of thing that only becomes obvious when you compare data across rides in very different temperatures and wonder why your FTP seems to fluctuate. Road salt and grit accumulation around the non-drive side is another UK-specific concern; the sealed pod design keeps ingress out, and the IPX7 rating means full waterproofing to one metre depth, so winter road spray isn't something you need to think about. For riders also considering Garmin power meters or Quarq power meters, 4iiii's temperature compensation and battery longevity make a strong case in this price bracket.

Installing a 4iiii: The AAA Battery Clearance Check

Before you buy, do one thing: hold a standard AAA battery against your left chainstay where the crank arm passes closest to the frame. If the gap is tighter than that, a 4iiii pod may not clear. This is the most common fitment issue, and it's easier to check in the garage than to discover on delivery. Most modern road frames with standard crank positions are fine, but some aero framesets and older compact chainstay designs cut it close. When in doubt, check 4iiii's online compatibility tool with your specific frame and crank combination.

Installation itself is clean. The 4iiii left-sided power meter arrives as a complete crank arm with the pod already bonded and calibrated from the factory, so you're not dealing with DIY gluing or alignment. Swap your existing left arm, torque to the manufacturer spec (typically 12 - 14 Nm for Shimano), and you're done. The pod sits low-profile against the arm - it doesn't snag on shoes during pedalling strokes, and it doesn't add the kind of bulk that feels odd on the bike. Setting up a 4iiii power meter takes most riders under twenty minutes on their first attempt. The IPX7 rating does the rest: road grit, deep puddle spray, jet washing from a reasonable distance - the sealed enclosure handles it without drama. If you're running dual-sided, the same logic applies to the right-hand pod, and the combined unit gives you full left/right balance data for those who want to track pedalling asymmetry over time. Worth pairing with a reliable Garmin head unit to make full use of the balance metrics.

One practical note on the 4iiii battery life question that comes up regularly: the CR2032 is a standard coin cell available in any supermarket or chemist. Keep a spare in your saddle bag over winter and you'll never be caught short. Checking the battery percentage via the 4iiii app before a long ride takes seconds and removes any uncertainty.