I’d like to thank everyone for their comments on their experience installing the replacement module. It helped me avoid issues I wouldn’t have been aware of without your warnings. I thought it might be useful to others if I documented the process I used to avoid damaging the battery holder.
Before starting the replacement process, I measured the dimensions of my RTC battery and the replacement module with calipers. The replacement module was slightly smaller than the battery in both thickness and diameter (by about 0.1 mm). This might suggest that the replacement module should fit more easily into the holder. However, their side profiles differed: the RTC module was cylindrical, whereas the RTC battery had an angled bottom edge.
This difference became significant during insertion because the components slide into the holder at an angle, impacting the fit. When inserting the RTC battery, a gap appeared between the top and the lip of the holder.
This was not the case with the original replacement module. Its 90-degree bottom corner increased the effective height of the module during insertion. As seen below, there was no gap between the top of the module and the holder’s lip; instead, the module was higher than the lip and did not fit under the retaining fingers.
I reasoned that adding a small angle to the bottom of the replacement module would allow it to fit under the top lip fingers. This modification would reduce strain on the fragile fingers and lower the risk of damaging the holder. I used a diamond knife sharpener to sand one edge on the bottom side of the replacement module, creating a slight angle. This edge was then inserted first into the holder. Note: When sanding, I ensured the gold coating on the side of the cylinder that makes contact with the electrode remained intact.
After this modification, the replacement module fit under the fingers, and I was able to gently complete the insertion using a SIM Eject tool without damaging the holder. The sanded corner did not affect the final fit once the replacement module was fully inserted.
