Explanation:

This is a Samsung tablet from 2014, currently has LineageOS 18.1 (Android 11), the last it can get. Since it's unused I did a little experiment until I find someone who will use it. Today I have found so here is the post.

After charging it to 100%, I disabled Wi-Fi connection, put it on battery saving mode and it's been on for more than 2 months. Battery is still in good condition after all these years I guess. :)

Impressive!!!!!!

Wow, 2 months? How big is the battery!?

Looks like the current version of Accubattery works on Android 7!

If you install it and then do a full charge cycle (15%-100%) it can determine battery health by how much power is required for that charge cycle.

It's not perfect, but I've found it pretty effective at predicting my run times over the last 10 years/half a dozen different phones.

I'd even upgrade this from mildly interesting to interesting!

I don't understand the graph. Why does it have spikes up and down and why, despite being at 13%, it shows roughly 75%?

It's not that surrpisingly, they doesn't use it at all and the rom is Lineage;

i once remove all google bullshit from a shitty 80€ phone and used it as server for a discord bot, it would last roughly a week per charge, it also had a version of android that was way too heavy for such a cheap phone, if i had installed Lineage and an older version (android 7?) It would've lasted way more probably

It probably cannot measure correctly because this is an unexpected usage. Correct place is the bottom of it obviously. The screenshot just coincided with the upper side of the spike.

Apparently 8220 mAh o.0

Don't know the size though.

Actually maybe can try this before handing the tablet over. Though it would take another 2 months so maybe not . :)

Yeah, not having anything Google related surely increase the battery health. Also mental health.

Hey, battery technician here.
You see, what happened here is that the hungry little caterpillar has entered the digital age and I don't know what the hell is going on here.

Yo I think your tablet is sick or something

So it started out at 50%?

This doesn't make any sense for me, except if it was plugged in and the battery is dying over time 😋

I think it cannot show the whole graph, maybe the only one month part is here.

That still doesn't make any sense IMO.

nice

My guess (I don't know if this is actually right) is that the battery is showing a lower charge while under load. So when it wakes up to do it's little periodic checks/activity (could be trying to fetch updates, could be scans, could be cleanup, idk) it draws additional power and the old battery can only support that load for so long.

Explanation based on theory as I understand it:
Using an analogy, batteries aren't a cup full of electricity that just gets sipped or dumped, they're closer to a water balloon with a little valve. The system may only use a little water at a time, but the "battery full" percent is the measure of how much pressure is in the balloon to push the water out. So when the valve is mostly closed (phone is idling) the pressure is pretty normal, slowly dropping. But as batteries age when you open the valve further you start to realize the battery can't actually push out the pressure you need (the balloon has stretched out). The pressure drops, to the levels it would be at if the balloon was brand new, but almost drained. The valve closes more as the device demands less power, and it seems like the expected pressure returns to normal, because the balloon can handle that lower pressure demand.

In short "New battery almost dead under load = old battery mostly charged but under load" but "new battery charged with no load = old battery charged with no load" which is why you see the slingshotting on the battery graph.

I think its more of a sensor issue. Not too surprising given the age.

I placed on charge my iPod Touch 2G and it awoke, had been surviving on its old ass battery for about 45 days

If it's functional as a reader that's fine I think. You can also turn it into a some kind of server though Android 2.2 is really old and you won't likely to find apps from F-Droid for it.

Schrödinger battery

Decently sized, impressive runtime for that capacity.

Damn new tablets get good battery life. Older model ones the only can go to 1 month standby