M48T18-150PC1 Timekeeper

[BobW777]

I have a circuit card that uses the M48T18-150PC1 Timekeeper SRAM, and the battery died. I replaced the part but the settings did not save once power was cycled. A second part was used with the same result. Looking at the date stamp, (412) tells me I'm possibly at the limit of the battery's life. I tried measuring the voltage (Vcc to Vss), but have no reading at all. The replacement units integrity are questionable, so I'm wondering if I'm measuring something wrong. Is there a latch I'm not aware of that prevents me from measuring this voltage? Any help would be appreciated. In the meantime, I have placed an order for new parts hoping this will solve my problem.

Regards,

Bob

[Peter BENSCH · Accepted solution]

Welcome @BobW777, to the community!

In the M48T18-150PC1, the battery and crystal are moulded in so that the battery voltage cannot be measured externally due to missing connections. The only option is to replace the Timekeeper completely.

As far as the date code is concerned, it is given as YWW, where Y stands for the last digit of the year of manufacture and WW for the calendar week. M48T18-150PC1 has been manufactured since 1999, so 4 can (currently) stand for 2004, 2014 or 2024. If you can rule out 2024, only the years 2004 and 2014 remain, both of which are longer ago than the battery has a service life.

Hope that helps?

Regards
/Peter

[BobW777]

Peter,

Thank you for that invaluable information. We've been dealing with this issue over the last year, while everything drops off at the same time. Ironically, the replacement pieces supplied to us came from the original batches of materials, so it would make sense that they are beyond their life span.

Now that we know that there is no viable way to perform a measurement on them, we can assume anything coming in will be dead on arrival, with the exception of new factory purchases.

Thanks for the info.

Cheers,

Bob