Gaming DSi battery life is suddenly terrible

[banjo2]

About a week or two ago, my DSi battery life suddenly became terrible. I used to get hours on a single charge, but now it only lasted 00:13:15 sitting on wifiboot, and similar times during gameplay.
I don't think I overcharged it, and I haven't messed with the battery.
I did remove it to clean the contacts with IPA, didn't seem to help.
As far as I can tell, the battery is not bulging or leaking.

Anyone have any ideas as to what might be going on?

 

[CMDreamer]

[...]

Anyone have any ideas as to what might be going on?

Batteries don't last for ever, even being Nintendo ones, sadly... if your DSi battery is the one that came brand new with the console, then its at least 10 years old, and that's way too much more time if compared with other products/brands, that don't even last a year.

 

[KleinesSinchen]

Did you try the obvious?

• Another battery in the same DSi
• Same battery in another DSi

This way you will easily see if it is just a bad battery.
=============

No idea (didn't search) if there are cheap devices for checking Li-ion battery capacity.


I have seen batteries go bad from one moment to the next, with all common chemistries: Nickel based, lead-acid and Li-ion.

 

[banjo2]

Batteries don't last for ever, even being Nintendo ones, sadly... if your DSi battery is the one that came brand new with the console, then its at least 10 years old, and that's way too much more time if compared with other products/brands, that don't even last a year.

Yeah, it's just very strange how it went from hours to less than 20 minutes
It is the one that came with the system, but it wasn't really a new system. As far as I can tell, it was reshelled.

Did you try the obvious?

• Another battery in the same DSi
• Same battery in another DSi

I switched the batteries, and it's... Behaving normally?

It's seemingly fine when they're swapped, but I soon get a red LED when they are set the way they were.
Maybe it's just inconsistent, I don't know. It's very strange.

To detail, the problematic one is the one that came with the system when I came into ownership of it (see above), the one from the other system was bought online after I had overcharged the original. It doesn't have battery life as good as either of the other two, in their prime that is.

---
Left is the problematic/original, right is the other/bought online one

Comparing the two, it does seem like the original has a slight bulge to it, but maybe that's just how it was made?

 

[FAST6191]

It is a fairly common failure mode -- most batteries are made up of several cells series wound to make a useful voltage level for running a device. Quite often then one cell (usually the one next to the positive) is the one that goes, and it then only holds a little charge* before it drops out, and that means even if the other two are still basically full they can't make the minimum voltage the main device expects (to say nothing of potential internal resistance issues). Many times I have recovered a laptop or tool battery by replacing one of the broken 18650 cells with a suitable replacement, however here it is probably a custom shape part of a custom shape battery.
There are things the makers of such devices can do to lessen the issues but they cost money and the cheap and cheerful way lasts comfortably longer than the warranty/likely useful lifetime of the device so I tend not to see it even on things where the batteries for a device cost more than the whole DSi would have at its priciest.

*also tends to mean the battery will appear to charge up very rapidly too.