# DIY - Polar T61 transmitter battery replacement



## serpico7 (Jul 11, 2006)

The battery in my T61-coded transmitter was fading. Rather than send it back to Polar and pay for a new one, I decided to replace it myself. It's only $40 or so to replace, but I was annoyed that Polar had made these non-user servicable in terms of battery replacement. To their credit, they now give customers the choice - sealed (like the T61) or user servicable (Wearlink).

There is a guide on the net for older transmitters (https://www.smallbattery.company.or...attery.company.org.uk/sbc_tips_and _faqs.htm), but the T61 is a bit different, so I figured I'd post my DIY job.

Apologies for the low-res pics, but my digi-cam is being serviced, so these were taken with my cellphone.

I cut out the center oval that had the Polar logo on it with an x-acto knife - this was quite tedious as the molded plastic does not cut easily and I was careful not to let the blade poke through and hit the circuit board. After removing the oval, it looked like this:









Much to my dismay, my cutout did not allow full access to the battery. Sick of using the x-acto knife, I pulled out the Dremel, which cut through the plastic like a hot knife through butter. Now I could get at the battery:









Fortunately, the battery was not soldered to the connectors (older transmitters used soldered leads), so no soldering iron or wires or leads needed! Pulled out the battery, which is a CR2354 3V lithium battery. Turns out Radio Shack doesn't have this battery or an equivalent, though they did have the battery used by the old Polar transmitters. Ordered one online, which should be here in a few days. 









Since my transmitter works intermittently with the old battery, I decided to keep the old battery in there until the new one arrives. I didn't want to bother replacing the cut out plastic (I suppose you could use some waterproof caulk and reseal it, but I don't use my HRM in the water), so I used a rolled up piece of electrical tape to ensure that the connectors press down on the battery.









Finally, I wrapped the center of the transmitter in electrical tape. When the new battery arrives, and whenever I need to replace the battery in the future, I can just remove the tape, replace the battery and tape the transmitter back up.


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## filtersweep (Feb 4, 2004)

If you would have used duct tape, you would have a classic thread in the making.


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## zooog (Mar 18, 2002)

As long as it works....


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## serpico7 (Jul 11, 2006)

filtersweep said:


> If you would have used duct tape, you would have a classic thread in the making.


Good point. When I receive the new battery, I'll have to remove the electrical tape anyway, and I'll rewrap with duct tape. And post the pic of course!


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## serpico7 (Jul 11, 2006)

I'll be damned - while waiting for the new battery, I went riding today with the taped-up transmitter using the old battery and my heart rate was picked up perfectly. Now it could be that this is just a good day in a very spotty last 2 weeks for the transmitter. Or maybe that extra bit of rolled-up tape is causing the battery contacts to make a better connection to the battery than the molded plastic did? I'll keep using it until the battery fades, then pop in the new battery.


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