Dallas Nonvolatile Ram Chips - Battery Surgery

[edpalmer42]

With regard to your NVRAM chips, the life of the battery is very much dependant upon the use that the equipment has had. Dallas state 10 years minimum. That would be storage conditions, no power applied. If a piece of equipment is powered and running, the NVRAM battery is not providing power and so its capacity is preserved except for natural discharge due to chemistry. More good news is that the lithium cell is actually charged at a very low current via the diode that connects it to the supply rail. Reverse current leakage of the diode is the cause of this and it is an aid to battery life in 24/7 powered equipment as it counters the natural discharge rate of the cells chemistry. I have tested 25 year old kit that was used 24/7 and the original lithium battery was still over 3.0V 

I don't have any info on the history of this unit, but it has an part number on it that identifies it as part of a spares kit for a big Agilent semiconductor manufacturing system.  That might suggest that it has had very little usage.  OTOH, the number of dings and scuffs on the cover suggest that it's been well used.  I'd still like to check those battery voltages, but I don't think I'll risk it for now.

Ed

[vaualbus]

Could do inside the unit photo so anybody know how this equipment is?

[edpalmer42]

Could do inside the unit photo so anybody know how this equipment is?

I was in such a hurry to get things back together that I forgot to take pictures.   

Most of it is easy to get at, but the main board is a pain to get out so that's not going to happen.  In the next few days I'll post a new thread for just the teardown.

Ed