I haven't seen any how to's on replacing the battery in a polar HRM watch. This is how I changed the battery in my HRM, yours may look different on the inside. It will take around 5-10 minutes depending on how fast you work.

Mine uses a CR2032 battery that cost $3.99 from Walgreens

Here's my HRM waiting for the battery replacement


I used a #0 Phillips head screwdriver to remove the 4 screws on the back cover, when you remove the cover, this is what you will see. There is a very small spring that is just setting there, make sure it doesn't fall onto the floor.


Now, carefully pry the innards out of it, they are just setting in there and will look like this when they are removed.


Around the outside edges are a bunch of little snaps. Carefully pry them up to separate the cage thingy from the rest of the electronics. I used a very small flathead screwdriver to separate the pieces. Keep track of the direction that they came apart so you don't put it back together wrong


Next carefully slide the cage section apart, this will allow you get access to the battery to easily remove it. Pay attention to which side is positive and which is negative.


Now reassemble in the opposite order you took it apart.

...but doing it yourself destroys the waterproofing seal and voids the warranty doesn't it?

Just keep in mind this will void the 2 year warranty and will most likely no longer be water resistant.

Mine's already 3 years old or so and it never sees rain so I'm not worried. Although I don't see how it makes it no longer water resistant.

you could probably reseal it with some wax.
My F6 died on me on Sat. but it was about 4 yrs old. I'll probably tear into it this weekend.

I replaced the battery in my Polar 720 last summer. I don't recall the battery type, except it was one that most shops (Radio Shack, big box stores) do not stock. Fortunately, a local battery specialty shop did. Turns out the watch battery compartment has a bevel in it that fits real Panasonicbrand batteries but not generics with the same part number. Watch was well out of warranty and I'll take my chances on rain; if it ever goes "swimming", I'm in BIG trouble.

The second photo from the top shows a "rubber" moisture seal. When the back it put back in place, it will seal out moisture once again.

Is there not a second battery in a chest strap sensor? I do not have a Polar HRM, but I believe the chest strap battery is more difficult to change.

Rather than using wax to seal an HRM not only from rain, but also from perspiration or humidity, silicone gasket sealant woud be a good choice.

I changed mine a few years ago. The back plate has a rubber gasket that has to be put back in it's groove. It should be just as waterproof as when new. I haven't tried a dunk test, though.

I'm still using the original strap, and it's battery is sealed in. I guess I'll be sending it in when it fails.

How is the battery sealed into the chest strap, if you can tell? Is the case welded along a seam so that opening the battery case means breaking plastic? I remember that someone found a way to get that thing open and change the battery, although any warranty against moisture coming in was long gone.

It seems the fees on getting the battery changed by a factory representative can be expensive enough that some folks just buy a new HRM when the time comes.

I do not have a Polar, but have a Sigma BC-2006 I like a lot. All of its batteries are made to be changed by the user. "O" rings are used for the seals. Just twist a battery cover to the release position and let it fall out in your hand. Put in a new battery and twist the battery cover until it locks.

I specifically did not buy a Polar because of the lack of user-replaceable batteries. I've also got a Sigma HRM that I've used for 3 years with many battery changes.

Once the back was off as in the second photo, couldn't the little tab/contact be lightly lifted and the battery removed?