Cycleops Powercal

GGBiker

I've been thinking about getting a powertap hub based power meter recently, sadly I will get castrated if I spend that sort of money at the moment!

I thought I had checked all the possible options until last night I came across the Cycleops Powercal (same company who make the Powertap). This is a recently launched heart rate monitor based power meter, or more accurately a power estimator. It is simply a heart rate chest strap that sends an Ant+ signal for HR and also for power to a compatible head unit (e.g. a Garmin/Bryton or other GPS unit).

It is based on the fact that there is a correlation between HR and power output. It is obviously not a simple relationship, in fact the calculation involves an algorithm that looks at the heart rate and also the rate of change of the heart rate. Apparently it will show a low/zero output when you stop pedalling at the top of a hill for example, despite the fact that your HR is hitting 180.

I can't find any reviews of this from the usual suspects online (bikeradar, cycling weekly etc), the only reviews seem to be from independent riders. Some of them have plotted data from the powercal vs. data recorded simultaneously from their Powertap power meter and it seems the correlation is really very good, certainly a reasonable fit when the data is smoothed with e.g. a 30 second average for power output. With a second by second tracking it is less useful (but I have heard that power meters also spit out erratic numbers if monitored in this sort of time frame also).

The benefit of this over HR alone is that it doesn't lag as much as HR in measuring effort (can be a few minutes for HR to rise or settle with change actual power output) so it is much more useful for training in power output zones.
It is also interesting to know your approx. power output. Strava gives an estimate of this also but I'm guessing this system/algorithm may be better than that (plus you can see it whilst riding).

Many of the experiments carried out by reviewers seem to indicate that the Powercal is within a few % of the accurate Powertap data, which is obviously very impressive for £75 (versus £675 for a current Powertap installed in a wheel. It is also super portable between bikes and even activities (e.g. running/sports).

Has anyone any first hand experience of the Powercal? I wonder why it seems to be flying under the radar?

rozzer32

If you really want to measure power then get a powermeter.

GGBiker

Bit of a stupid answer unless you're paying....

fish156

DC Rainmaker review.

GGBiker

Yeah, that's one of the reviews I read, very thorough and overall positive if you accept the limitations.

Most people who criticise it seem to think that it is too simplistic, assuming that it matches a certain power output to a given HR, but it is more complex and takes account of the rate of change of HR which seems to allow it to predict power for people of varying weights and fitness levels.

Just wondered why there is little interest in this given that a lot of people would love a power meter but can't afford it. Personally I'm looking forward to the day when power meters are common and cheap like GPS or bike computers. It's bound to come as the technology does not seem to be that complex relative to the price.

The following are also useful

http://bikehabit.blogspot.co.uk/2012/07/cycleops-powercal-versus-quarq-is.html

http://teamrodrigo.com/2012/07/20/ridin ... -powercal/

The table below shows Powercal (average power 175w)



And for Powertap (average power 165w):


Below is a comparison of trace from Powercal (red) vs Powertap (blue), looks close.

rozzer32

GGBiker wrote:

Bit of a stupid answer unless you're paying....

Ask stupid questions you get stupid answers.

If you want to measure your power then get something that actually measures your power i.e powertap, srm etc

Until then just stick with heart rate.

GGBiker

Rude, aggressive and ignorant all in one, quite an achievement!

If you have nothing constructive to add why not just keep out of it?

If you have any experience of the Powercal or comments on the data/experiments conducted by the reviewers mentioned then by all means pitch in.

jezzpalmer

GGBiker wrote:

The table below shows Powercal (average power 175w)



And for Powertap (average power 165w):


Below is a comparison of trace from Powercal (red) vs Powertap (blue), looks close.

Not really close, if you look at the other attributes it looks like a different ride or completely different riding strategy.
VAM (rate of climb) is double, cadence is 50 less, speed is different.

Personally I think you'd be wasting your time/money with something like this.

rozzer32

http://www.bikeradar.com/forums/viewtopic.php?f=40011&t=12891420&p=18004900&hilit=powercal#p18004900

Another thread on it, basically come to the conclusion it's a waste of money which is very true.

It gives you a power value for when you're coasting. It would give you a power value for when you were hoovering.

Like I said before if you want to measure power then save your money and actually buy something that measures power.

GGBiker

What if I want a reasonable estimate of power at 10% of the price of a power meter? Should I then buy the Powercal? Or if I want to enhance training by having a better metric than HR alone but don't have the cash for a Powertap?

The link you posted is just another collection of ignorant viewpoints from people who fail to understand that the Powercal doesn't simply map HR to power. It uses the rate of change of power to arrive at the power number.

Unfortunately most people do not understand the first derivative hence the general ignorance over the methodology of this. Can you discuss the data in any meaningful way that indicates an understanding of it?

The reviews out there comparing Powercal to Powertap are largely favourable, perhaps you would realise this if you'd read them? Or perhaps you tried but couldn't grasp the information?

You say it gives a power output when coasting? The reviews indicate that it doesn't, it uses the pattern and rate of change in HR to identify when you are not pedalling and shows a zero output.
As for hoovering, guess what, when you're hoovering you are doing work and hence have a power output! Is that really news to you? If you attached a strain gauge from a power meter to your Hoover and pushed it around it would also show a power output!

Looks like the Powercal is going to die of ignorance more than anything else.

Hanners

a guy in my club has one he used to hire a powertap for the winter his reaction is that its not realy a power output measure, its no good for short intervals, but ok for ftp work but if your doing 2 x 20 mins youll get more use out of a hrm.

SPOC

Great piece of kit for the price IMHO.

Have ridden half a dozen times recently with my mate who has a traditional powertap linked to his 705 and the 'powercal' to his 910 on the same ride.

The powercal has come within 3-4 watts on 1-3 hour rides each time, bar one where it was 9 watts under what the powertap put out as an average for the ride.

I was hugely skepitcal at first, but ordered one off ebay for about 60 quid from America. Came over the weekend, 2 rides so far, very pleased with it.

For the long rides, when I want a pretty good overall average at KJ used/ calories burnt, I figured why not? I needed a new heart rate strap anyway for my Garmin and that's 25 around about for a soft rate one anyway, so thought what the hell.

For the average cyclist who likes to train, does the odd sportive, maybe a bit of racing, for a pretty low cost in the grand scheme of things, worth a go.

It obviously doesn't calculate power in real terms, but must have enough data built in all the algorithms from 10,000s of rides from different riders etc. to make a very close guess.

Until I saw it in action, I probably wouldn't have given it the time of day myself.

GGBiker

Interesting, thanks for sharing, I plan to use it for measuring average power over long rides and on long steady efforts such as long climbs. May also try to work out threshold power. If it is accurate to within even 10 watts it will suffice for my use, 3-4 watts is as accurate as a proper power meter !

SPOC

GGBiker wrote:

Interesting, thanks for sharing, I plan to use it for measuring average power over long rides and on long steady efforts such as long climbs. May also try to work out threshold power. If it is accurate to within even 10 watts it will suffice for my use, 3-4 watts is as accurate as a proper power meter !

If your main aim is for longer rides, it's perfect for that within it's limitations.

Don't let people on here put you off, especially ones who don't actually own it. I am very much in the camp for proper power meters if you can afford it or you want to take your training very seriously.

But for 95% of other people who just want to get a bit better and have some extra data, absolutely nothing wrong with this bit of kit.

As I say, I'll think you'll find most people who have bought this been refreshingly surprised at how accurate the average power came out over a long distance compared to a normal powertap.

stueys

The issue I have with the powercal is that it makes no logical sense to me how it can work. Heart rate is a lagging indicator of effort. Your heart rate would vary dependent on how much coffee you had drunk, how tired you were, whether you had trained heavily the day before, how fit you were, etc, etc. All of which would make no difference to the power output at that point of time. How can it possibly be accurate

danowat

Stueys wrote:

How can it possibly be accurate

It's not, and it never will be, anyone who uses a power meter and a HRM will see that very quickly, sometimes there is a correlation, sometimes there isn't, it's just not as straight forward as the makers would like you to believe.

If you want to use power, get a power meter, if you want to use HR, use HR, the powercal is not doing anything that you can't really do yourself by guestimating from HR data.

Save your money for a power meter.

rozzer32

Finally some people talking sense.

GGBiker

Stueys wrote:

The issue I have with the powercal is that it makes no logical sense to me how it can work. Heart rate is a lagging indicator of effort. Your heart rate would vary dependent on how much coffee you had drunk, how tired you were, whether you had trained heavily the day before, how fit you were, etc, etc. All of which would make no difference to the power output at that point of time. How can it possibly be accurate

I'm pretty sure you don't know how an aeroplane works, or antibiotics or a water treatment plant. I take it you don't believe in those either and don't use them?

The answer is that it looks at the rate of change of HR, I.e. the acceleration/deceleration of the heart rate, not just simply the heart rate alone. Does the evidence from people running the powercal alongside a power meter and getting differences of 3 watts over a long ride not carry any weight for you? How much more convincing do you need? It does lag but only really for a few seconds versus a power meter.

dewaynef

Thanks GGBiker and SPOC for your efforts to encourage substantive dialogue on the PowerCal. I really appreciate it. By the way, I bought one.

mellowmiles

so,,,, how did we get on with the powercal?!
I'm also thinking of getting a powercal. I'm in the odd position of already actually having a power meter for the winter bike and hence not sure need another for the sunday/summer bike as well. It is a also a campy rather than a shimano so can't just chop and change wheels.
I've thought of the various permutations and keep wondering about the powercal. plan is to use for pacing on hills in sportives and maybe in for duathlons. I thought perhaps i'd get a reference point or 2 using the PT then that might work. the info is mixed. it appears great post ride analysis but not for my needs like pacing from what people say. i wonder if those on here whom have used it feel differently?
would be nice if vector came out with the single pedal thingymagic that would solve all my problems!! other than the fact i still use spd pedals...