Test from the FSA Powerbox power sensor

Reliable and well built, the FSA Powerbox power meter has not failed during the 1 km of test that we inflicted on him at the end of this winter. Beyond his performances, he especially helped us at the start of this season to perfect our training and approach the first deadlines in good shape.

By Sylvain Pigeau – Photos: SP 3bikes

No more pre-release calibrations, at the risk of having wacky data. Also no more tedious maintenance for a simple battery failure. Today, power sensors are very easy to use, reliable and precise, while being more affordable.

But it is always difficult to venture into very scientific territory. What to do? What more can be said about a sensor whose accuracy is estimated at plus or minus 3%. For ordinary mortals and the vast majority of cyclists, this margin is not even sensitive to training, in the short or long term. Unless you evolve with a sensor that would give mind-boggling data from one month to the next or from one season to another (because of the temperature differences), It is very difficult to tell the difference between two models. And for a simple reason: comparing two power sensors (each with their degree of uncertainty as to the precision of their data) can only be done by taking a third sensor as a reference, which is also imprecise.

The Powerbox did not give us this kind of bad surprises. It must be said that the device from the Taiwanese brand FSA is in fact not unknown, since it is the German Power 2 Max sensor (used for example by the Movistar riders, Alejandro Valverde in the lead).

In February and March, in the Parisian cold, the humidity of the Bretagor the dry air of the South of France, no anomalies were detected and the measurements were found to be stable and accurate, and in line with our past references. We're not going to give you a 2-watt estimate, that would be ridiculous. But you can see below how we did it. Even with a battery at the end of its life, quickly replaced. The lifespan of the latter (CR 2450) is given for 400 hours of use (around 12 km). In our case, the sensor had already been used.

The battery life (CR 2450) is given for 400 hours of use (approximately 12 km).

The Powerbox in practice

Lightweight (733 g with 53×39 chainrings), with rigid carbon cranks with UD finish, our test model above all demonstrated strength in precision and reliability.

Once installed, the connection was made immediately with our ANT+ devices, both on the Garmin 520 Plus, that on the Wahoo smart trainer. The Powerbox is also Bluetooth ready and therefore compatible with smartphones in particular.

We naturally find the traditional power measurements (immediate, maximum or average), but also the right leg – left leg balance.

The cranks are made of UD carbon, the axle is made of aluminum to the BB386EVO standard and the chainrings, compatible with Shimano and Sram 11v, are CNC machined. Finally, on the availability side, The new version offers a range of five crank lengths and three chainring combinations (in four arms). So everyone can find something for them.

That's it for the technical side and all that remains is to specify the price: €1, a bit high for this type of equipment, which tends to become more affordable under €249. But to save some money, it is possible to switch to the version with aluminum cranks, at €699 (announced at 921 g against 733, weight verified by us, for the carbon model).

Avoid overtraining

But what did the Powerbox bring us? In order to prepare for the long-distance triathlon season, the aim was above all to "redo the basics", rather than to practice advanced exercises.

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On the menu therefore, basic endurance, long outings in Negative Split (at a progressive pace), a few long series at I4 and two so-called “Gimenez” exercises.

> READ ALSO : Focus on the so-called Gimenez session

Once reassured on the first outings, on the consistency of the values ​​displayed for the average power (around 180 watts average on our outings in general), the work could begin with outings containing the repetition of bumps, long and regular, as in the Arrée mountains in Bretagno, or on the routes du Tanneron, on the Côte-d'Azur.

At the start of the cycle, at the beginning of February, the longest climbs (regular slopes of 2 to 5% for around 3 km), on the Monts d'Arrée, had gone to around 230 watts on average (for 59 kg). For a time gain of around 10% (observed on the Strava segments), a month later, we noted an increase of around 5 watts on the averages. Consistent with a "body" found, without having particularly "hit it". Here, the Powerbox played its role to the full, without any drift or crazy measurements, despite the bad weather and somewhat mistreated equipment.

Because the challenge was there, especially in a period where climatic conditions hinder fragile organisms from practicing high intensities. We left that to those carried out in the pool (three one-hour sessions per week) and on foot (about two walking sessions per week, only one of which contained short VMA type exercises).

By combining the sessions, with swimming and running in particular, the use of the power sensor took on its full meaning.

By combining the sessions, with swimming and running in particular, the use of the power sensor took on its full meaning.

During the big weeks, both in terms of swimming and running sessions, we noticed a slight drop in average power on some bike rides that were nevertheless "simple" and without too much elevation gain (always between 500 and 1 m approximately), around 000 watts. A sign that it was necessary to ease off, when conversely, on light weeks (around 165 hours of weekly sport), it was possible to spend the same rides at more than 10 watts.

> READ ALSO : How to gain Watts

In the case of these cross-training sessions, and in the absence of competitions to gauge ourselves, the use of the sensor helped us a lot. It is also useful during exceptional weather phenomena. So we don't forget this outing at the end of February in Bretagne, where, having left with the West wind, we found ourselves with more than 210 watts on average on the way there. For less than 150 on the way back…

Alpe d'Huez as a standard measure

And as the idea was to tester, it was possible to do it on the climb of Alpe d'Huez, via the BKool application. 1 h, at I3, for about 230 watts, we were pretty much "on target", even in virtual. Especially given the period (end of February) and the kilometers accumulated since the 1^er December (3). Here too, the Powerbox did not move and by setting the Garmin to the "power over 500 seconds" indication, the exercise was rather comfortable.

Reliable, precise and very simple to operate, the Powerbox has therefore largely won us over. Guaranteed for 2 years, it does not require calibration and remains very easy to synchronize. In terms of price, it remains placed compared to the competition. But it is true that today, for this type of equipment, we would ask for an additional effort from the brands, such as almost systematically going below the 1 euro mark.