Third Party > Repairing and Upgrading Rockbox Capable Players

Sansa clip zip not charging after battery replacement


Hi. I have a clip zip that has been in daily use for some years now (actually by my wife) and the battery had got very tired.
I discovered that these are very hard to buy now (none on ebay at the moment) and the new Sport model cannot support rockbox.
So I got a new battery off ebay, checked the vids for how to get in without breaking stuff and did the swap. Simple enough - I am experienced at this sort of thing.
However it became clear after a couple of days that the new battery was not charging. It powered the machine for quite a few hours as it discharged and the battery level measurement seems to work fine (the little scale said it was nearly full, and now says it's empty).
On inserting the power lead the charging icon in the top RH corner flashes once but that's it. leaving it in for hours does not change the battery indicator. The cell is at 3.63V which is of course fairly flat for a lipo and presumably around the low-batt cut-off voltage for the device. The info screen says 8% (after leaving it plugged in for 24hrs).

So I guess my question is can I get any debug from the software about why it it not charging. What does it check? How does it enable charge? Which bit of the circuit is responsible?

It is possible that this issue is nothing to do with the battery swap. I also put an SD card in for the 1st time ever a few days before the bat swap. It turned out that something was amiss there because with that in, when the device was powered it got _really_ hot after a few minutes. Apparently the microSD was sucking a huge amount of current and it got to 50C or so. It took a few hours to notice this so the poor box was sat being really hot for at least a couple of hours. Taking the SD card out made that problem go away, but I guess it's possible that some component has got tired from this. If I put the microSD back in now it still gets hot, showing that the PSU for that is still working.
Again how is the SD power related to the charging power? Is it on the same 3.3V circuit as the main device power?

A schematic would be great, or details of where to look in the codebase for the charge control would be great.

I'll try charging the batt separately just to check it does in fact charge normally, and I could put the old one back in and see if that behaves differently. Any other suggestions to work out what's going on?

I guess it's possible that the thermistor in the new pack is different from the old one in some important way. but it was advertised as a direct replacement so should be right.

Oh and if it matters my rockbox version is 3.13, which is probably from years ago.

1st check the thermistor lead isn't swapped
I could see it being common w/ ground and swapping ground and still work for powering the device
or common with positive and swapped with positive...

check continuity between the thermistor and ground or thermistor and positive to figure out the way its wired
checking voltage between the 3 should show a lower voltage between the thermistor and the opposite lead (pos or gnd)

try disconnecting the thermistor completely
if that fails hook up old pack common and thermistor

We have control over set points for the charging chip but its pretty independent of our control beyond start and stop levels we can choose


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