Does the battery in the Garmin Edge 500 get better with age?
When I started using mine in late February of this year, a 2 hour ride would drain the battery to about 94% or so.
Lately, after downloading data from my rides, the Edge still sows 100% charge, even after rides in excess of 2 1/2 hours.

Is this normal, or am I seeing something goofy?
I guess I will keep charging times to a minimum and see if successive rides show a drain.

Anybody else experience this?

In my experience the battery life depends on what the data recording setting is on. If you use the Garmin Smart Record the battery will last longer. Also the number of rides you can have on the 500 will increase because the files are smaller.

The battery should lose capacity as it ages, but I've also heard they have a break in period and it takes several charge cycles before it reaches full capacity. I don't know.

I'd bet it's not fully charged after three hours of use. I get about 20 hours out of my Edge (800) and by extension I'd guess yours is still very full, but not 100 %.

I have put about 5 hours on it in the last 2 days, with only as much charging time as yesterday's download required.
After today's ride, the Edge shows 98%.
At least I know that it will register a drop.
After about 10 minutes on the USB, it is showing 100%

Well, I put almost 12 hours on the Edge 500 in 2 days, and it STILL shows 100%
I believe that something is a bit wonky...............
Or, I have the best battery ever made.

Maybe yours came with the optional solar charging unit

How to Prolong Lithium-based Batteries - Battery University

And all the BU-808 and BU-809 pages should tell you all you need to know about the batteries in your Garmin.

Congrats on your slow draining battery. I have also noted that the Edge 500 battery will continue operating for quite a while when the battery needs charging. While riding with cadence, heartrate, and speed sensors, plus course navigation, my older Edge 500 unit operated for about 45 minutes with the "battery low" annunciation on. The screen then blanked. However, all data was saved and I successfully downloaded some fast times to Garmin Connect.

Out of the box, I could do a metric century in 5% of the battery on my 500. Now, several hundred charge cycles later, it will use ~20% of it's charge in a 3 hour ride. However, the discharge "display" is not linear-- it's something like the fuel gauge in a Toyota. I could use it for 2 hours and it would still show 100% charge. Use it for 6-7 hours, and the charge would show between 50-60%. After that, it was close to 10% per hour.

Lithium batteries definitely don't get better with age, and once you pass ~300 charge cycles, they really start to taper off.

I've got well over 500 hours on my 500, and a 2-3 hour ride takes the battery down to ~ 94%.

It's tough to know the level li-ion batteries so the meter is an estimate based on how the battery behaved in the past. It's calibration can get messed up causing it to read incorrectly. One thing to try is leave it on until the unit shuts off by its self and then fully charge it. This can reset the meter calibration. If the meter is showing low prematurely, you try the same thing. This will sometimes reset the meter calibration. The unit will shut off before draining the battery low enough to damage it. In general, of course, it's best not to routinely let the battery get that low. You'll get the most use out of Li-ion batteries by keeping them cycled between ~95% and ~50%.

Heads up: the 100% charge after hours and hours of use is totally normal (in my experience). And then it will precipitously drop to 4% - Low Batt warning, out of nowhere. I carry a Gomadic charger and mount my Garmin in such a way that I can access the port and plug it in while riding.

I have a feeling this has to do with "overcharging" i.e. leaving it plugged in while it's stuck at 99% "Charging". Only when it is very close to dead does it reach 100% and then say "Complete".

As a randonneur who uses GPS for navigation, having my Garmin on and working is super crucial. I get anywhere from 16-18hrs usually on a full battery, and then it can charge back up fairly quickly with the Gomadic. However, when I say "full battery", I mean I drained it to 0% on purpose, and then charged it to 100% Complete the night before. I used to do this regularly, but have gotten a bit lazier with it now that I know I can plug the Gomadic charger while riding.

My battery charge will go down a little bit. But I have done two (club)metric centuries in the last two years. That took me 6Hrs.+. Only because I unintentionally deviated from the planned route(there were routes for 100, 65, 50, 30, and 25, depending on what a cyclist was capable of). So, Instead of going 65mi., I would go 70mi.. My battery charge didn't go down below 80% for each metric century. Last years was in Shepherdstown, WV, and 2014 was in the Clarke County, VA. Shepherdstown is hillier than Clarke County.

I upload(and recharge) it every day that I go out on a ride. I don't leave it on the charger for hours.

Just FYI mine started showing 100 percent charge all the time unless it is really low. When u download your ride does it say charging or charge complete. Mine will say charging until it is charged obviously but it also says 100 percent unless it is really low.

So I performed the discharge cycle til the level reached 4%.
Recharged, and all was fine for a while.
Then, the old 100% charge would show after a several hour ride.
Discharged again.All is OK.
Something I have noticed: when charging from my computer's USB port in rear of computer, like
after downloading the ride data, the Garmin just shows a screen saying "Charging" and gives the % of charge.
When using a wall-pack power supply, the unit powers up like it was in use on the bike, displaying ride data, and stays that way til I turn the unit off. Then, it displays the "Charging" screen.
What is different between the 2 methods ??
Is using the wall pack P/S better??

Mine seems to drain slowly, too.

Good to see folks still have and use their Edge 500s.

It kinda keeps my interest level in riding up................

I didnt pay attention to the battery last night. I will report back Saturday!