Replacing the Coin Cell Battery in the Dell Latitude E6400

It was probably time to replace the BIOS battery in my Dell Latitude E6400 laptop. It’s a coin cell, a CR2032, a button cell, probably the RTC battery for the real-time chip, and sometimes called a CMOS battery even if that’s not the technology inside it.

Possible symptoms were showing. The time, when I had set it to local time in the Setup or BIOS, which was necessary when I deprived the laptop of both AC and DC power at the same time, would revert to GMT until I got a network connection to the Internet and even then it might take a while; and once it went back to local time, reverted to GMT, and came back to local again. Then some keyboard keys intermittently stopped working, the same ones each time. For each of those, the likeliest advice I saw online was to replace the battery. Possibly, the battery was becoming less tolerant of heat, and I wouldn’t be able to keep it cool enough most of the time.

I examined the battery, but it wasn’t bulging. However, it is over eleven years old. I think that’s a while, and might explain the problems.

I won’t recount the basic procedure here. You can find that online, from Dell. I’ll add to it.

Although Dell refers to it as a coin cell battery, it’s really a module that includes the battery. The battery is wrapped in soft plastic (which happens to be blue). Inside the wrapper, the battery has two small metal strips attached to it, perhaps glued but possibly attached with rivets or something like that, one on each side of the battery. The edge of the battery has a smooth ring; I don’t know if it’s an insulator. The module has three-conductor wiring to a connector. (Why three is a puzzle. Maybe they really thought it could leak power and could need grounding.) The module is glued to the place where it rests; the glue has a consistency that reminds me of chewing gum, but it’s small and not a problem for a finger.

After I removed the module from the laptop (Dell’s instructions say how), I used a razor to cut the wrapper away, cutting from the open end (not the wire end) and along the edge of the battery (be careful not to scratch the battery). I did not cut it away entirely but enough to peel the wrapper from both sides. That exposed the metal strips on the battery. I want to sandwich a replacement battery between the strips and hope they can be forced by the soft wrapper to rest firmly on the replacement, even though I don’t have suitable conductive glue.

I could peel the ends of the strips with my fingernail, but not far, and a tiny flat-bladed screwdriver did not make further progress; nor did a bent-tip ice pick (I guess you could call it an ice pick). I tried pulling on the peeled end with pliers, but it wasn’t giving way. Maybe that’s not glue. I could break the connections to the strips, but there’s no point to that.

I reassembled the whole. The wrapper being cut is not critical to reinstallation. I did have difficulty getting the module to lie flat enough; I think it’s still a little high, but not so much as to keep the case bottom from being reattached with the captive screw tightened. The bottom is not quite as tight as it should be, but it’s close enough.

I started shopping for a replacement module. Even from the original equipment manufacturer (OEM), it’s cheap enough. The off-brand modules are not much cheaper, so I may as well get the OEM one, and maybe a spare.

I hope the old battery still likes me, and will work a while longer. So far, it is.

Progress Note: I used the old battery daily for about two more weeks, including through warm- and cold-reboots. Sometimes, if I changed the main battery without AC power but rapidly enough, taking only a few seconds between batteries being in place, Setup nonetheless remembered the current date and time.

I’ve now replaced the CR2032 battery module with a new Dell one. For some reason I couldn’t figure out, the bottom panel on the laptop is not completely flush in position, but it is tight enough and I’ve been using the laptop since then.