Dying battery with no wear (only 25% usable)

[Cloppy]

I started to notice that my battery bar estimate was constantly going down when it reached 6 hours. I thought that it was only because the program was “calibrating” my usage.

Once it reached 4.5 hours, I thought something weird was going on so I did a clean install of W10 CU, that was around july when the tablet was 5-6 months old.

I had performed the thermal mod, had a custom power saving profile which limited the processor speed to about 800MHz, very low screen backlight, I was also using XTU to lower the CPU and GPU voltage as well as limiting a lot the turbo state (both in Watts and seconds). So I thought I should be getting about 8 hours of battery instead of 4.5!

I started investigating and found that charging via USB-C (innergie 45W adapter) while powered down (and with 0% battery) resulted only a charge of about 1050mAh at 19.6V (measured using the satechi monitor). That’s about 20580 mWh, while the battery reports to the OS a full charge capacity of 38000 mWh (even though it advertised capacity is around 33000mWh IIRC).

So I blamed the USB-C charger and went back to the supplied charger, but nothing changed (except that the original charger was now using less power (7-9W) during charge than what I initially measured (22W), and it was slower. Note that when I got the USB-C charger, both took around the same time to fully recharge the battery (2 hours), although at that point I was already experiencing the run time estimate going lower and lower.

I tried monitoring the battery voltage while charging it, both in Windows (using BatteryInfoView and BatteryMon) and Linux and there was a weird thing in all my tests: the battery voltage never reached 8.4V, the stated maximum voltage, (and what you would expect for a 2-Cell LiFePO4 or Li-Ion battery, 2*4.2V). Besides that, the battery informed it was over when it was above 7.0V (while I would expect it to report it at 6.0V, perhaps 6.4V…).

So… I kept using the tablet, about 1 hour a day and now… I have a fantastic battery that lasts only for 2 hours. It charges to 500mAh (9800mWh, 25%), stops charging at about 7.5V IIRC and it shuts down at 7.0V).

Does anybody know what’s the cause of this? I have a 11 years old laptop with only some 15% battery wear, but it charges until the maximum voltage so this must be something very different.

[Algorithm]

That is worrying indeed.  Is there no method of resetting this (Maybe disconnecting battery as well?)  then charging again?

[Cloppy]

Not that I know. I’ve tried several load/unload cycles to no avail.

I’m thinking of opening the tablet to inspect for any kind of damage (will take pics).

[Cloppy]

I opened the tablet and unplugged/plugged back again the battery, but nothing has changed. I’ll post pics later in case someone is able to spot something, but it looks OK to me.

[chee5y]

It sounds like I have a similar issue. Can somebody tell me where I can find a replacment battery?

[Cloppy]

I’ve plotted a graph of a recent discharge loop (until 17%). Note that the battery voltage suddenly drops as soon as I unplug the charger cable, which doesn’t make too much sense to me. And then, the voltage oscillates and even climbs from 96% to 76%!!!

 

@chee5y It’s the same battery as the i7 book. I found a replacement some weeks ago but it was just 2 wires. I recall reading someone who said that Cube sells them for around $50. Do you have the same symptoms as I do? When did you order the tablet? (Mine’s from January).

I’m also considering getting the anker usb-c powerbank, but I don’t know if it will compatible and also if the tablet or the battery will eventually die out.

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[chee5y]

@Cloppy Have ordered mine in march and didn’t opened it for modding or so. Warranty is given but the time it will took for repair and maybe customs duty again. A replacement battery would be the best way in my opinion. Isn’t there some kind of protection board between the battery and pcb ? Where did you find a replacement and which tool did you use to graph you battery ? Would be nice to compare ours.

[Author]

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