Battery falling off a cliff (Bangle.js 2)

I've had my Bangle.js 2 since the Kickstarter and also wrote the Stardate Clock watchface for it. And I've been very happy with it so far. In the beginning, the battery was usually good for almost a week, which was great, even with Power On on twist (well, when driving a bike that came on too often so I had to temporarily turn it off). When turning on GPS, it had significant shorter battery lifetime of course, but even then it would be good for significant trips (though i didn't do that to often).
That said, with time, the battery lifetime became somewhat shorter, but still very decent, lasting multiple days, I think 2-3 months ago it was down to about 2 days or a bit over that. But then, suddenly, about a month ago, battery lifetime fell off a cliff and now even with settings set in a way that the backlight usually doesn't turn on at all any more, I barely can get it to last from when I get up until I go to bed, often not even that long.
And it's definitely a battery issue, as it completely acts like weak batteries usually do - e.g. even if full, when the backlight comes on, it immediately drops to less than half and when backlight is off, it goes up again.

Is there anything I can do to repair it in a reasonable way? Or is the best way to recover to get a new watch?

Hey,
Despite owning a new one this concerns me as well since I would like to be able to replace the battery eventually if this happens to me.

I don't know if you already saw the disassembly video of the watch, it is pretty straight forward. However it doesn't look like the battery is anything close to plug and play and might require some soldering skills to replace. In this picture you can see on the top right where I assume the leads of the battery to solder into. So if you are comfortable with a soldering iron this might be the way to go, assuming you can find a suitable replacement battery.

I would say it is reasonable, but I have not found a guide to replace the battery yet, might be a chance to create one.

All that being said, this is what I found and how I would go about it (disassemble, desolder, resolder new battery, reassemble, hopefully be happy) but I have no personal experience so take my take with a grain of salt.

Hi!

I have three suggestions.

Have you tried the battery calibration option under settings->utils? (The Power Manager app can also be used to calibrate battery automatically)

Try compacting the storage. Probably won't help - but doesn't hurt either.

Have you tried factory resetting the watch (do a backup first!) to see if it behaves better after that. It could be that code somewhere got messed up at some point or there is a bug in some app.

Edit: Maybe you find this conversation interesting: https://forum.espruino.com/conversations­/385629/

Hi - sorry to hear this. When you say the battery doesn't last, does the watch actually turn off, or is it just that the battery meter reads zero? If it's the reading, the calibration @Ganblejs mentioned may help.

But as you mention the battery meter dropping down substantially with the backlight on, that does sound like a battery issue - however it's quite surprising. It's not like I've had a great deal of issues with the battery failing in people's watches, and they shouldn't - recharging once a week the battery should last for years before there's any hugely noticeable drop in life.

As mentioned, you can get inside (see that video) and replace the battery but it's hard work, requires soldering, and will probably mess with the water resistance unless you're very careful glueing the screen back on.

All I can say really is what I've said to others who've had the watch fail after over a year - I can't replace on warranty but I'm happy to give you a 50% discount on a new one.

... but even if you're replacing it or trying to get inside it'd be worth doing a backup via the app loader, and if you're doing that you might as well completely erase it, ensure firmware is up to date, and see if that increases the battery life

The worst thing you can do to a battery is leave it flat or fully charged for an extended period of time. ( I hope that is not a myth ) Is it possible you did this often to it?

When speaking about Lithium ion batteries (and most others except lead acid probably) that is true. They are most comfortable between 20-80% of charge. A full charge can usually not even be reached by you because manufacturers of the devices makes sure that when the percentage reads 100% its not actually 100% internally (that could be a myth too, after all apple has a feature where they charge your iPhone up to 80% during the night and then to 100% shortly before your alarm rings in the morning to avoid having it at 100% charge for too long). I don't know of that is the case with the bangle, so it might be a good idea to unplug it at around 80%.

I don't know enough about the science behind it to explain it, but AFAIK the duration doesn't matter either. Fully charging or flattening it in both cases isn't ideal for LiIon batteries and should be avoided.

It is related to heat and stress, so yes time(duration) is a factor, on top of the discharge cycles*.

it might be a good idea to unplug it at around 80%

I wonder if there can be an app written to stop charging at a custom % (I've had laptops and tablets which have this--you specify a % like 70 for example, and even if you keep the device plugged in, the charge never goes above 70).

Just to answer some things that came up, the watch goes completely off when I don't charge it and the battery widget shows it going empty (after I guess about 15h now, without any backlight being active). I also already have done an erase and reinstall cycle (everything is up to date anyhow) to make sure the issue isn't something bad there - but then, the battery widget going down a lot (from green to red) when backlight comes on and then coming back up significantly again when it's off again is pretty much a giveaway that the battery is weak and dying. And I have never left it flat or fully charged for long, I just used it normally and recharged when it was nearing being empty - and had it on my arm at all times during the day, even keeping it out of any significant chance of getting wet, so basically nothing out of the ordinary.
It sounds to me - as I feared - that disassembly and replacing the battery is rather complicated and a level above what I am able to do, so @Gordon I may just come back to you on that discount offer (I actually fully expected that I would have to buy a full-price new one).
Also, it's good to know that this isn't a common issue and I just may have had bad luck with this battery.

I wonder if there can be an app written to stop charging at a custom %

@parasquid It's not possible without having a BLE enabled wall socket or similar, but there is an app that will buzz to warn you I think.

But as I said it's not something you should not have to worry about. I just checked and the charge circuitry itself does not overcharge and sticks at 4.2v. Given the battery really isn't stressed at all and doesn't experience high temperatures, from what I can see, charging every 10 days you could expect that after 10 years you'd still have more than 80% capacity left.

Obviously my usage pattern isn't very normal, but I haven't noticed any I have here that have noticeably lost battery life. The only times I have, it's been due to software issues.

@KaiRo yes, you might expect the battery level to show a drop with the backlight/GPS on normally, but maybe in the 10% range - not what you're seeing. It does seem like you've been a bit unlucky with yours.

I am also having the same issue. I have exposed the watch to harsh temperatures and I use the GPS everyday so I normally need to charge it every 3 days. However I accidentally ran the GPS until the the device died and now it won't even last 24 hours.

I will try calibrating the battery to see if it fixes the issue.

However I accidentally ran the GPS until the the device died and now it won't even last 24 hours.

That could be a contributing factor. @Gordon Can we determine at what voltage the circuitry cuts out?

So I tried a battery calibration and it didn't help. I took a look at the battery graph on the banglejs app and it was fairly constant up until recently.

How do I replace the battery? Is it even possible?

Can we determine at what voltage the circuitry cuts out?

I did do some tests a while ago but I forget exactly. I think it's actually around 3v - the Bangle doesn't use a switching regulator so it turns off before any of the components start to suffer from the lower voltage. The voltage that'd end up causing damage to the battery is way lower than that.

@user156610 could you maybe try backing up your watch contents using the App Loader, then doing just a standard factory reset and see what the battery life is like? It's even possible that you had stuff working fine and then some app had an update that suddenly increased its power draw.

Or... it's also possible that when you ran the GPS you were logging, that filled up all the Bangle's available memory and now it's spending far more CPU time trying to find free space to write data.

How do I replace the battery? Is it even possible?

There is a video at https://www.espruino.com/Bangle.js2+Disa­ssembly but it's not at all easy to do since you have to heat up the display to soften the glue on it. Replacing the battery is possible with some work but it should be a last resort

I will back up my data and do a reset to see what happens. I have a feeling that its the battery but you never know.

Also, today my alarm went off but it was fairly weak. Could a failing battery lead to weak vibration? Could that be a sign of low voltage?

hi, thx to your video this is the way i opened my P8, instead of using atc1411's brute force.
however, as i dont have a professional heater,

i put my P8 on a metal disc, then float it on fresh boiled water.
as you mentioned you want the heater to be <100 oC, around 90 oC,
that's almost exactly to the setup i mentioned.

for about 5mins warm up, i then easily disassemble my P8.*

btw, since i may further disassemble other watches and glue back,
could you provide some info on how to glue it back?
what is the glue used? can i buy individually?
i saw your discussion else, thanks
https://forum.espruino.com/comments/1705­3109/

thank you.

*ps, my P8 is almost bricked so i haven't tested if this temp will ruin the LCD.
my SWD tools haven't come back so my P8 is still a brick.

Could a failing battery lead to weak vibration?

I think it's unlikely - I haven't really noticed any change in vibration strength based on how much battery voltage there is.

Is it possible that you've had your Bangle.js under water for a while? Low battery life and weak motor vibration could be symptoms that it's got damp inside

If I open it up how do I put it back together? Also does anyone know if there is a compatible replacement battery? I looked at just replacing it but its kind of expensive just to dispose of.

Once it's open you have to glue it back together (probably a silicone based glue is best) but yes, it's not really designed to be opened.

We don't stock replacement batteries but the battery itself is a XK302627 (which means a 3 x 26 x 27mm) any LiPo you can get that's that size or smaller will work.

My Bangle 2 is now just entering its third year, and I currently get around 50 hours on a single charge. Might have to swap to the backup Bangle I purchased alongside it. I would replace the battery were it not so fiddly a process (and tricky to find one) -- was burned by my experience trying to replace a Pebble Round battery a few years ago. Yikes.

I'm at around 70 hours so far after the initial charge (with 25% left) and a lot of tinkering because it's new. I guess I have too much set to active - Always on display, GPS via Phone, HRM @ 3min (had it at continous for some hours). I'd like to get it as far to the 40 days as possible. I guess a week is possible and that's my goal. You guys are crushing this dream haha

The always on display and GPS via phone shouldn't use any noticeable power, but:

• Definitely ensure 'wake on twist' is off
  
• If you can make do with HRM every 10 minutes that'll help too
  
• Be careful about your choice of clock face. If it shows seconds it'll kill your battery. Some faces are better than others too (although it's very hard for us to test/quantify each one I'm afraid)
  

Makes sense :)

Need to think about the wake on twist. Can't really decide for or against, ha

After charging this morning I only lost 4% today. That's quite impressive <3

That's great! Out of interest, what changes did you make?