DS1287 question

[alank2]

I've got a DS1287 with an internal lithium cell that is dead.  There are many guides on fixing these.  I drilled it to expose the two battery contacts and disconnected the negative side from the internal lithium coin cell.  Then if I hook up a CR2032 to it I am surprised to find it consuming 12mA which seems way too high.  I'm not sure what the internal battery is, but I doubt it has the 225 mAH that the cr2032 does and at 12mA it would be dead in 18 hours or so.  The spec says it should last 10 years with the internal coin cell!  I'm guessing it would normally be in the 2.5 uA or lower category?

[Greybeard]

Have you removed the old cell?

[Ian.M]

Alan *SAID* he disconnected its negative side.
However I'm wondering if there's any possibility its got two coin cells in parallel, and he's only disconnected one?

Check with a small strong magnet to confirm there is only one cell, (as parallel cells would usually be side by side, not stacked), then take a very close look at where you drilled the negative connection - maybe there's a wisp of metal still shorting the break.

[alank2]

All the guides show disconnecting the old cell by severing the connection on pin 13 and that is definitely cut.  I think there is only one cell and from the pictures I saw it looked like the legs were bent upwards, but I could try drilling out the solder and doing more testing.

[retiredfeline]

If you can measure any voltage at all between those IC pins with nothing else wired to them, the internal (single) lithium cell isn't disconnected.

[alank2]

It is 0V between the two pins for the IC, but this IC has an issue.  Connecting a 2032 to those pins and it is back as 12mA.  I drilled another DS1287 I have and it doesn't have that issue.

[alank2]

Still working on these.  The one that doesn't have the high current still doesn't work right with a new cell connected to it.  I've got a couple of nice CR2032 battery holders so I am going to try my luck at the other two DS1287's that say their battery is depleted, but I'm going to dremel them a bit more slowly to see what I can do. I've also got two DS1872's that report their internal battery still good (register D has bit 7 set).  One question I have for anyone who has ever put a new battery in one of these is - did register D bit 7 come back after the new battery?  Should that happen?