Possible to calibrate battery?

[AZImmortal]

I haven't used my e260 in about a year and earlier today I decided to start using it again. I charged it for most of the morning but I can't seem to get Rockbox to report anything higher than a 94% charge even after I leave it charging for a while. I'm currently running the battery bench plugin to see what kind of shape the battery is in. In the meantime, is there some way to calibrate how Rockbox reads the battery's capacity?

[JSP62]

Have you tried running the Sansa until the battery dies, then recharge?

[WalkGood]

I’ve never found a battery icon meter on small devices to be 100% accurate other than laptop ones which are fairly accurate. I view them more as a guide to give one an idea of how much power you have left. Have you tried to update to the latest rockbox build to see it it makes a difference? That said, it’s nice you can still get e200 batteries http://www.buy.com/pr/product.aspx?s...lerid=15743316 My e260 is really old and it's still running fairly well on original battery.

[saratoga]

Originally Posted by AZImmortal

In the meantime, is there some way to calibrate how Rockbox reads the battery's capacity?

Yes, the percentages are taken from this table:

http://git.rockbox.org/?p=rockbox.gi...f12498;hb=HEAD

You can do a battery bench in rockbox, and then pull out the 0, 10,..100% values from that and insert them into the table above then compile your own build.

[AZImmortal]

Originally Posted by JSP62

Have you tried running the Sansa until the battery dies, then recharge?

That's partially why I was running the battery bench. I'm currently recharging it now after running it down overnight.

Originally Posted by WalkGood

I’ve never found a battery icon meter on small devices to be 100% accurate other than laptop ones which are fairly accurate. I view them more as a guide to give one an idea of how much power you have left. Have you tried to update to the latest rockbox build to see it it makes a difference? That said, it’s nice you can still get e200 batteries http://www.buy.com/pr/product.aspx?s...lerid=15743316 My e260 is really old and it's still running fairly well on original battery.

I know that battery meters are never 100% accurate, which is why I wanted to know how to calibrate it myself. I updated to the current build before I tried to fully charge the battery the first time.

Originally Posted by saratoga

Yes, the percentages are taken from this table:

http://git.rockbox.org/?p=rockbox.gi...f12498;hb=HEAD

You can do a battery bench in rockbox, and then pull out the 0, 10,..100% values from that and insert them into the table above then compile your own build.

I've never tried to compile a build before so this might be beyond me. I was hoping that there was a text file of some sort in the compiled build that I could easily edit. Thanks for the tip though.

The battery bench says that it lasted 13 hours and 34 minutes before dying, which from what I understand is fairly low (I've seen benches in the 18-20 hour range). I did turn on the screen a few times to see how it was doing, but I'm guessing that it wouldn't have made a tremendous difference. Hopefully running the battery down will help.

[WalkGood]

Originally Posted by AZImmortal

... The battery bench says that it lasted 13 hours and 34 minutes before dying, which from what I understand is fairly low (I've seen benches in the 18-20 hour range). I did turn on the screen a few times to see how it was doing, but I'm guessing that it wouldn't have made a tremendous difference. Hopefully running the battery down will help.

How old is the battery? I'm probably not getting much more than that on my old battery but that's fine w/me. I doubt turning on the screen a few times made a big difference ...

[AZImmortal]

I've had the player since 2006 or 2007 and I've never changed the battery. I wasn't sure if 13 hours was abnormally low for a battery this old, but if that's about what you're getting, then I guess I'll just live with it. Regarding turning on the screen while testing the runtime, the Rockbox wiki (http://www.rockbox.org/wiki/BatteryRuntime) has this to say:

The best method for determining if the device is still on (if this cannot be determined by looking at it) is to listen briefly at the headphones. Pressing a button will light up the backlight and this is a considerable power use.

I'm not sure how much of an effect me turning on the screen had, but I might try benching the battery a few more times without turning on the screen to see what happens. The battery is fully charged now and Rockbox is reporting a 100% charge.

[saratoga]

Originally Posted by AZImmortal

I've had the player since 2006 or 2007 and I've never changed the battery. I wasn't sure if 13 hours was abnormally low for a battery this old, but if that's about what you're getting, then I guess I'll just live with it. Regarding turning on the screen while testing the runtime, the Rockbox wiki (http://www.rockbox.org/wiki/BatteryRuntime) has this to say:


I'm not sure how much of an effect me turning on the screen had, but I might try benching the battery a few more times without turning on the screen to see what happens.

5-6 years is quite old for a battery. When they're new you'll probably get 20-22 hours IIRC. But 13 isn't too bad given the age. Probably also why the battery meter is inaccurate, the battery's voltage doesn't go as high as mine did when it was new and I made that calibration in the source.

[saratoga]

I guess you could also try replacing the battery:

http://www.amazon.com/Li-Ion-Replace.../dp/B001RW4ZSI

[AZImmortal]

13 hours is probably good enough for me. I was just mostly concerned with having an accurate meter (or at least more accurate).

Regarding my last post about Rockbox reporting a 100% charge, the 100% came after I fully charged on the official firmware and then rebooted into Rockbox. I left it charging on Rockbox a little longer (maybe 30 min) before starting the next battery benchmark and I noticed that Rockbox was now reporting a 90% charge. Seems odd that the reported charge went down even though it was left on the charger. Anyways, I'm doing my second battery bench right now so hopefully I'll have some increased battery capacity to show for it.

[Pennhaven]

I've had two different batteries in my e280, and no matter how long I charge it the Rockbox meter never hits 100%. 94% - 96% is about it. Could be a quirk with Rockbox on the e2_0 series or with some of the batteries. I wouldn't worry about it since you're getting 13 hours of play time which is great for a battery that old. The beauty of this player is you can easily replace the battery though when you do need to. A "feature" all consumer electronic devices should offer, I might add.

[AZImmortal]

Yeah, the playing duration isn't a concern for me because 13 hours is plenty (my latest battery bench said 14:15). I just wanted to be able to tell when I was actually running low on battery because the current battery calibration is wildly inaccurate for my battery, not just at full charge, but throughout the runtime. Here are a few examples from the benchmark (runtime, reported percentage remaining, and reported runtime remaining):

3:30, 58%, 14:30 remaining
7:00, 18%, 4:30 remaining
10:30, 8%, 2:00 remaining

I picked these because they represent roughly 25%, 50%, and 75% of the way into the 14 hour benchmark, and as you can see, the percentage remaining isn't even close (the benchmark actually reports the last "10%" lasting the final four hours of the benchmark, which is almost 30% of the actual runtime). The reported runtime remaining is somewhat more accurate, but it's still not close. I'm in no way blaming Rockbox or its developers for this because I know that battery behavior changes over time. I just wish that there was some way to calibrate the battery ourselves without having to compile our own build (feature request saratoga?).

[saratoga]

Its been on my to do list for 5 years now. Not sure I'll ever find time though since its not something that really has any impact on me.

[AZImmortal]

That's understandable. If you ever do find the time though then I'd very much appreciate it, even if it's just being able to enter a min and max voltage like you can do with CHDK (http://chdk.wikia.com/wiki/CHDK).