Tuesday, December 18, 2007

Polar S725 - Battery Replacement

I have a love hate relationship with my Polar S725 cycling computer and heart rate monitor. Overall it's been a great product, but there
have been a few times which I've though about chucking it in the
river. The first problem appeared not long after I first installed it
on my bike. The heart rate readings would jump from normal all the
way up to 200-225 bpm. If my heart was beating that fast there would
be serious problems.. This problem seemed to go away all by itself,
or was caused by some sort of interference in my neighborhood. Who
knows maybe there was some old guy sending high frequency RF signals
into space trying to make contact with aliens?

The second problem was the speedometer. My bike originally had ITM
wing shaped handlebars to which the Polar handlebar mount did not fit
very well. So I purchased a small Velcro strap device that would
allow you to mount the Polar watch unit on the stem instead of the
handlebars. This worked ok, and was a good solution for getting the
watch unit off the bars, but that's when the speedometer readings
started getting wacky. It seems the signal would drop off, and I'd
have no data for speed / distance for much of a ride. I'm a bit of a
techno geek so I love to analyze the numbers after each ride. With
half of the data missing it was almost useless. I contacted Polar and
they recommended I move the watch unit back onto the handlebars. By
using the stem mount there was enough interference between the speed
sensor mounted on the right fork blade and the watch unit that was
causing the erratic readings. So I got some extra long zip ties and
somehow got the Polar watch mount to work on my wing shaped bars. It
wasn't the best, but it worked. I had to push the mount really close
to the stem and somehow use two different length zip ties. The other
change I made was to the speed sensor. I did a bit of research and
found out that you can increase the signal strength by switching a
jumper (similar to a hard drive jumper) on the circuit board. So, I
opened up the speed sensor with a long very small screw driver,
replaced the battery, and switched the jumper. Voila. My speed
sensor has been rock solid ever since. The only drawback to this was
that sometimes when I'd ride alongside my buddy who also had a Polar,
my speed signal would interrupt his and his watch would pause. That's
not a problem any more because he lost his Polar head unit on the
Leesville Gap Road Race last year. Now he has a PowerTap SL 2.4
wireless, nice!

My most recent headache with this Polar S725 was downloading the data
from the wrist unit to the PC. Polar uses an infrared interface from
the watch unit to the PC. In my case, I have the Polar USB IRDA
receiver. This has been a bit finicky at times. Getting the watch
lined up just right so the infrared signal transmits successfully
seems to be key. When the watch memory was full I would download the
data. Over time this became more and more of a problem. The watch
didn't seem to be sending the signal to the PC, or the transmission
would start then just stop about 1/2 way through. I finally figured
out that you can send one file at a time to the PC, but this was a bit
more time consuming. I finally contacted Polar regarding this issue.
They seemed to know right away that this was a sign that the battery
needed to be replaced in my wrist unit. I'd had this S725 for about
2.5 years now and this was the original battery. The documentation
states that the battery should last 1.5 - 2 years under normal use.
So I figured it was time to send it in for a battery replacement.
Polar recommends that you send the watch in to an authorized service
center. So I boxed up my wrist unit, heart rate monitor strap &
transmitter and sent it off. I got it back in about 7-10 days as
promised. They replaced the battery in both the wrist unit and the
heart rate transmitter, and sold me a new strap as well. Much to my
surprise the data on the watch was still there when I got it back.
This worked out good as I was able to test the infrared download
immediately. It worked perfectly. So, if you are having trouble with
your infrared connection, it's time to replace your battery, no doubt.
It would be cool if the wrist unit has some sort of low battery
warning indicator to warn you it was time to replace it. Other than
the infrared downloading, everything else worked just fine.

One other note, though not a problem, to be aware of. I recently
added the cadence sensor to my bike to record my pedal rpm's. This
was an easy install and works great. The one thing to be aware of is
that since the wrist unit is now recording one more piece of data,
your memory will fill up faster. You will have to download the data
more frequently. I think this is actually good, since you are more
likely to remember each ride or workout you've done. If you wait to
long to download the data you're likely to forget, now where did I
ride on 10/23/2007? Another good reason to keep a cycling diary!

I've been very happy with Polar's customer service. They generally
respond to email inquires in 1-2 days. So far their help has been
very good and solved my problems. My one wish is that they would use
a standard USB hard wired connection instead of the funky infrared
wireless for downloading data.

tags: polar hrm s725 heart rate monitor cycling computer speedometer
cadence sensor
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