Recently, I've had trouble keeping up my pace on my bicycles. I like to have a target to chase.. and that just isn't there without a bike computer.
Everyone who's installed a bike computer, knows the pain of calibrating them, and then keeping their batteries fresh, and recording information off of them.. and well.. it sucks. That's where fancy bike computers like Garmin's Edge series come into play. By being GPS based, they calibrate versus satellites instead of wheel revolutions. Garmin also puts a barometer on them so the can reasonably track single foot elevation changes, which GPS is a little less good at.
Since GPS doesn't work in tunnels, and on the bike trainer, Garmin also allows the use of a wheel speed and cadance sensor. So it's useful, even when the bike isn't moving.
Suffice it to say, the Garmin 305 is a heck of a device. And being six years old now, is cheap on the used market. I found mine on craigslist, and picked it up for $55. The seller didn't mention what was wrong with it.
The Garmin 305 series has the battery, speaker, and USB port as part of the back cover. The two halves are glued together. But instead of using a wiring harness, they used spring terminals to bring the electrical connections from one side to the other. This is not a high quality coil spring, guide, and plunger setup. It's some bent copper tabs that press on a PCB. Those are affected by inertia, and vibration.
The following isn't my image.. my hands were to busy doing the repair job to take shots of the guts of my garmin.
There's essentially no bulk capacitive value on the mainboard. This means as soon as any power is removed, the whole shebang shut s down.
This means surgery. The accepted method of repairing this is to get some jumper wires, and solder the battery directly to the mainboard. Which is what I did Friday evening. I took the GPS for a bike ride on sunday, and the thing didn't shut off at all.
Here are the links I used for reference:
And.. while we're at it, here's how the rest of my garmin looks post surgery.
Darned thing almost looks like new.