maxtherabbit
Veteran Member
No, the battery is not dead.
When the power is on, the RTC keeps good time (tested with checkit). When the power is off, the clock just freezes and doesn't advance. CMOS settings are never lost. I realize that these are the exact symptoms of a weak battery, but the 4xAA external battery pack I'm using still shows 6.5V open circuit voltage.
The board is a Shuttle 12MHz 286 board based on the VLSI 100 chipset. It is almost identical in layout and design to this comically overpriced Biostar:
https://www.ebay.com/itm/BIOSTAR-MB-1212V-VLSI-AT-MOTHERBOARD-W-286-12MHZ-CPU-1MB-RAM/123543534170
When I first acquired this system a couple of years ago, I removed the onboard rechargeable battery before it leaked, so battery damage is not a factor. I then fitted it with the external battery box and it has been working reliably ever since, keeping good time. About a month ago I noticed the RTC had stopped working during power off. I am using 4x Energizer lithium AA batteries, which I recently learned have an open circuit voltage slightly above 1.5V. I am slightly concerned that 4 of them in series was just enough above 6V to over volt something and damage it over time. I don't think the RTC chip itself is damaged, since it still keeps perfect time on main power. I measured the Vdd pin of the RTC when the system power was off and the battery was connected and got 2.4V, which explains why the thing isn't ticking since it requires a minimum of 3V.
Any thoughts?
When the power is on, the RTC keeps good time (tested with checkit). When the power is off, the clock just freezes and doesn't advance. CMOS settings are never lost. I realize that these are the exact symptoms of a weak battery, but the 4xAA external battery pack I'm using still shows 6.5V open circuit voltage.
The board is a Shuttle 12MHz 286 board based on the VLSI 100 chipset. It is almost identical in layout and design to this comically overpriced Biostar:
https://www.ebay.com/itm/BIOSTAR-MB-1212V-VLSI-AT-MOTHERBOARD-W-286-12MHZ-CPU-1MB-RAM/123543534170
When I first acquired this system a couple of years ago, I removed the onboard rechargeable battery before it leaked, so battery damage is not a factor. I then fitted it with the external battery box and it has been working reliably ever since, keeping good time. About a month ago I noticed the RTC had stopped working during power off. I am using 4x Energizer lithium AA batteries, which I recently learned have an open circuit voltage slightly above 1.5V. I am slightly concerned that 4 of them in series was just enough above 6V to over volt something and damage it over time. I don't think the RTC chip itself is damaged, since it still keeps perfect time on main power. I measured the Vdd pin of the RTC when the system power was off and the battery was connected and got 2.4V, which explains why the thing isn't ticking since it requires a minimum of 3V.
Any thoughts?